1
|
Carroll AS, Park SB, Lin CSY, Taylor MS, Kwok F, Simon NG, Reilly MM, Kiernan MC, Vucic S. Axonal excitability as an early biomarker of nerve involvement in hereditary transthyretin amyloidosis. Clin Neurophysiol 2024; 159:81-95. [PMID: 38377648 DOI: 10.1016/j.clinph.2024.01.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 12/26/2023] [Accepted: 01/22/2024] [Indexed: 02/22/2024]
Abstract
OBJECTIVES The treatment of hereditary transthyretin amyloidosis polyneuropathy (ATTRv-PN) has been revolutionised by genetic therapies, with dramatic improvements in patient outcomes. Whilst the optimal timing of treatment initiation remains unknown, early treatment is desirable. Consequently, the aim of the study was to develop biomarkers of early nerve dysfunction in ATTRv-PN. METHODS Ulnar motor and sensory axonal excitability studies were prospectively undertaken on 22 patients with pathogenic hereditary transthyretin amyloid (ATTRv) gene variants, 12 with large fibre neuropathy (LF+) and 10 without (LF-), with results compared to age- and sex-matched healthy controls. RESULTS In motor axons we identified a continuum of change from healthy controls, to LF- and LF+ ATTRv with progressive reduction in hyperpolarising threshold electrotonus (TEh40(10-20 ms): p = 0.04, TEh40(20-40 ms): p = 0.01 and TEh40(90-10 ms): p = 0.01), suggestive of membrane depolarisation. In sensory axons lower levels of subexcitability were observed on single (SubEx) and double pulse (SubEx2) recovery cycle testing in LF+ (SubEx: p = 0.015, SubEx2: p = 0.015, RC(2-1): p = 0.04) suggesting reduced nodal slow potassium conductance, which promotes sensory hyperexcitability, paraesthesia and pain. There were no differences in sensory or motor excitability parameters when comparing different ATTRv variants. CONCLUSIONS These progressive changes seen across the disease spectrum in ATTRv-PN suggest that axonal excitability has utility to identify early and progressive nerve dysfunction in ATTRv, regardless of genotype. SIGNIFICANCE Axonal excitability is a promising early biomarker of nerve dysfunction in ATTRv-PN.
Collapse
Affiliation(s)
- Antonia S Carroll
- Brain and Mind Centre, Faculty of Medicine and Health, Translational Research Collective University of Sydney, and Department of Neurology, Royal Prince Alfred Hospital, Sydney, Australia; Westmead Amyloidosis Centre, Westmead Hospital, University of Sydney, Sydney, Australia; Centre for Neuromuscular Disease, Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK.
| | - Susanna B Park
- Brain and Mind Centre, Faculty of Medicine and Health, School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Cindy S Y Lin
- Brain and Mind Centre, Faculty of Medicine and Health, Translational Research Collective University of Sydney, and Department of Neurology, Royal Prince Alfred Hospital, Sydney, Australia
| | - Mark S Taylor
- Westmead Amyloidosis Centre, Westmead Hospital, University of Sydney, Sydney, Australia
| | - Fiona Kwok
- Westmead Amyloidosis Centre, Westmead Hospital, University of Sydney, Sydney, Australia
| | - Neil G Simon
- Faculty of Medicine and Health Sciences, Macquarie University, Sydney, Australia
| | - Mary M Reilly
- Centre for Neuromuscular Disease, Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, London, UK
| | - Matthew C Kiernan
- Brain and Mind Centre, Faculty of Medicine and Health, Translational Research Collective University of Sydney, and Department of Neurology, Royal Prince Alfred Hospital, Sydney, Australia
| | - Steve Vucic
- Brain and Nerve Centre, Concord Hospital, University of Sydney, Sydney, Australia
| |
Collapse
|
2
|
Li T, Kandula T, Cohn RJ, Kiernan MC, Park SB, Farrar MA. Prospective assessment of vincristine-induced peripheral neuropathy in paediatric acute lymphoblastic leukemia. Clin Neurophysiol 2023; 154:157-168. [PMID: 37633123 DOI: 10.1016/j.clinph.2023.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 07/30/2023] [Accepted: 08/02/2023] [Indexed: 08/28/2023]
Abstract
OBJECTIVE Vincristine is a mainstay treatment for paediatric cancers, particularly acute lymphoblastic leukemia (ALL), with common toxicity including vincristine-induced peripheral neuropathy (VIPN). The present study comprehensively assessed VIPN outcomes in patients receiving vincristine treatment for ALL. METHODS Children diagnosed with ALL commencing vincristine treatment were prospectively evaluated (baseline, post-induction, pre-reinduction, post-reinduction, follow-up). VIPN was examined clinically using the Balis sensory/motor scale, neurophysiologically using axonal excitability techniques and quality-of-life using Pediatric Quality of Life Inventory. RESULTS Thirty-one patients were recruited to this study (age = 6.8 ± 4.4; 61.3% female). Incidence of motor VIPN (motor Balis grade > 0) symptoms were higher than sensory VIPN (sensory Balis grade > 0) at post-induction (92.0% vs 36.0%) and post-reinduction (81.8% vs 22.7%) vincristine treatment. Neurophysiological assessment also demonstrated greater change in motor axonal excitability parameters compared to sensory parameters including changes in depolarising threshold electrotonus (P < 0.0125), superexcitability and subexcitability parameters (all P < 0.0125). Follow-up assessment demonstrated persisting VIPN symptoms with reduced quality-of-life scores compared to baseline. CONCLUSIONS Clinical and neurophysiological evaluation of VIPN suggests vincristine produces a motor-prominent sensorimotor neuropathy in children which persisted at follow-up. SIGNIFICANCE VIPN signs and symptoms develop early in the treatment course, in line with axonal excitability profiles. Early detection of significant nerve changes may support timely implementation of neuroprotection strategies.
Collapse
Affiliation(s)
- Tiffany Li
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Tejaswi Kandula
- Department of Neurology, Sydney Children's Hospital, Sydney, New South Wales, Australia; Discipline of Paediatrics and Child Health, School of Clinical Medicine, UNSW Medicine and Health, UNSW Sydney, New South Wales, Australia
| | - Richard J Cohn
- Kids Cancer Centre, Sydney Children's Hospital, New South Wales, Australia; Discipline of Paediatrics and Child Health, School of Clinical Medicine, UNSW Medicine and Health, UNSW Sydney, New South Wales, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Susanna B Park
- Faculty of Medicine and Health, School of Medical Sciences, University of Sydney, Sydney, New South Wales, Australia.
| | - Michelle A Farrar
- Department of Neurology, Sydney Children's Hospital, Sydney, New South Wales, Australia; Discipline of Paediatrics and Child Health, School of Clinical Medicine, UNSW Medicine and Health, UNSW Sydney, New South Wales, Australia
| |
Collapse
|
3
|
McGarr GW, Cheung SS. Effects of sensory nerve blockade on cutaneous microvascular responses to ischemia-reperfusion injury. Microvasc Res 2022; 144:104422. [PMID: 35970407 DOI: 10.1016/j.mvr.2022.104422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 08/10/2022] [Accepted: 08/10/2022] [Indexed: 10/31/2022]
Abstract
OBJECTIVE Examine the effects of sensory nerve blockade on cutaneous post-occlusive reactive hyperemia (PORH) and local thermal hyperemia (LTH) following prolonged upper limb ischemia. MATERIALS AND METHODS In nine males [28 years (standard deviation:6)], volar forearm skin blood flux normalized to maximum vasodilation (%SkBFmax) was assessed at control (CTRL) and sensory nerve blockade (EMLA) treated sites during the PORH response following 20-min of complete arm ischemia and during rapid LTH (33-42 °C, 1 °C·20 s-1, held for ~30-min + 20-min at 44 °C) before and after ischemia-reperfusion (IR) injury. RESULTS EMLA increased mean [95 % confidence-interval] PORH amplitude by 21%SkBFmax ([9,33]; p = 0.003), delayed time to peak by 111 s ([40,182]; p = 0.007) and increased area under the curve by 19,462%SkBFmax·s ([11,346,27,579]; p < 0.001) compared to CTRL. For LTH, EMLA delayed onset time by 76 s ([46,106]; p < 0.001) Pre-IR and by 46 s ([27,65]; p < 0.001) Post-IR compared to CTRL. Post-IR onset time was delayed for CTRL by 26 s ([8,43]; p = 0.007), but was not different for EMLA (p > 0.050) compared to Pre-IR. EMLA delayed time to initial peak by 24 s ([4,43]; p = 0.022, Main time effect) and it attenuated the initial peak by 27%SkBFmax ([12,43]; p = 0.002) Pre-IR and by 16%SkBFmax ([3,29]; p = 0.020) post-IR compared to CTRL. Post-IR, the initial peak was not different for CTRL (p > 0.050), but it was increased by 16%SkBFmax ([5,26]; p = 0.005) for EMLA compared to Pre-IR. Neither EMLA nor IR altered the steady-state heating plateau (all p > 0.050). CONCLUSION For the current model of IR injury, sensory nerves appear to have a negligible influence on the LTH response in non-glabrous forearm skin once vasodilation has been initiated.
Collapse
Affiliation(s)
- Gregory W McGarr
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Stephen S Cheung
- Environmental Ergonomics Laboratory, Department of Kinesiology, Brock University, St. Catharines, ON, Canada.
| |
Collapse
|
4
|
Carroll AS, Howells J, Lin CS, Park SB, Simon N, Reilly MM, Vucic S, Kiernan MC. Differences in nerve excitability properties across upper limb sensory and motor axons. Clin Neurophysiol 2021; 136:138-149. [DOI: 10.1016/j.clinph.2021.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 11/16/2021] [Accepted: 12/07/2021] [Indexed: 11/24/2022]
|
5
|
Nalbant M, Ümit Yemişci O, Özen S, Tezcan Ş. Ultrasonographic and electrophysiological outcomes of carpal tunnel syndrome treated with low-level laser therapy: A double-blind, prospective, randomized, sham-controlled study. Arch Rheumatol 2021; 37:19-30. [PMID: 35949869 PMCID: PMC9326377 DOI: 10.46497/archrheumatol.2022.8605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 04/30/2021] [Indexed: 11/29/2022] Open
Abstract
Objectives
The aim of this study was to investigate the therapeutic effects of low-level laser therapy (LLLT) on clinical, ultrasonographic (US), and electrophysiological findings in carpal tunnel syndrome (CTS). Patients and methods
Between January 2015 and August 2015, 42 patients (7 males, 35 females; mean age: 50.4±8.7 years; range, 32 to 65 years) with mild-to-moderate CTS were randomly assigned to one of two groups: active LLLT (therapy group, n=22) 0.8 J/painful point and sham LLLT groups (n=20). Both groups wore neutral wrist orthoses. The patients were evaluated before and after 15 sessions of therapy (670 nm, 4 J/session over the carpal tunnel). Follow-up parameters included the Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) Symptom Severity Scale (SSS), Functional Status Scale (FSS), nerve conduction studies and US evaluation of the median nerve cross-sectional area (CSA), vascularization (via power Doppler), flattening ratio (FR), and palmar bowing of the flexor retinaculum. Results
Nocturnal paresthesia improved in both groups; however, pain and patients with a positive Phalen’s test reduced only in the therapy group (p=0.031). The FSS and SSS scores also improved only in the therapy group (p<0.001). Electrophysiologically, median sensory nerve conduction velocities showed a significant improvement only in the therapy group (p=0.002). The CSA, FR, and vascularization of the median nerve showed a significant improvement in the therapy group alone (p<0.001, p=0.048, and p=0.021, respectively). Conclusion
Improvements in the signs and symptoms of CTS and hand function, the improvements in sensory nerve conduction studies, and reduction in median nerve CSA, FR and vascularity in the LLLT group can be attributed to the anti-inflammatory and analgesic effects of LLLT. This study provides new US data demonstrating efficacy of LLLT along with a clinical and electrophysiological improvement. The LLLT seems to be an easily applied, non-invasive treatment option.
Collapse
Affiliation(s)
- Merve Nalbant
- Department of Rheumatology, Mersin University Faculty of Medicine, Mersin, Turkey
| | - Oya Ümit Yemişci
- Department of Physical Medicine and Rehabilitation, Başkent University Faculty of Medicine, Ankara, Turkey
| | - Selin Özen
- Department of Physical Medicine and Rehabilitation, Başkent University Faculty of Medicine, Ankara, Turkey
| | - Şehnaz Tezcan
- Department of Radiology, Koru Hospital, Ankara, Turkey
| |
Collapse
|
6
|
Excitability of motor and sensory axons in multifocal motor neuropathy. Clin Neurophysiol 2020; 131:2641-2650. [PMID: 32947198 DOI: 10.1016/j.clinph.2020.08.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Revised: 07/18/2020] [Accepted: 08/14/2020] [Indexed: 11/24/2022]
Abstract
OBJECTIVE To assess excitability differences between motor and sensory axons of affected nerves in patients with multifocal motor neuropathy (MMN). METHODS We performed motor and sensory excitability tests in affected median nerves of 20 MMN patients and in 20 age-matched normal subjects. CMAPs were recorded from the thenar and SNAPs from the 3rd digit. Clinical tests included assessment of muscle strength, two-point discrimination and joint position. RESULTS All MMN patients had weakness of the thenar muscle and normal sensory tests. Motor excitability testing in MMN showed an increased threshold for a 50% CMAP, increased rheobase, decreased stimulus-response slope, fanning-out of threshold electrotonus, decreased resting I/V slope, shortened refractory period, and more pronounced superexcitability. Sensory excitability testing in MMN revealed decreased accommodation half-time and S2-accommodation and less pronounced subexcitability. Mathematical modeling indicated increased Barrett-Barrett conductance for motor fibers and increase in internodal fast potassium conductance for sensory fibers. CONCLUSIONS Excitability findings in MMN suggest myelin sheath or paranodal seal involvement in motor fibers and, possibly, paranodal detachment in sensory fibers. SIGNIFICANCE Excitability properties of affected nerves in MMN differ between motor and sensory nerve fibers.
Collapse
|
7
|
Kandula T, Park SB, Carey KA, Lin CSY, Farrar MA. Peripheral nerve maturation and excitability properties from early childhood: Comparison of motor and sensory nerves. Clin Neurophysiol 2020; 131:2452-2459. [PMID: 32829292 DOI: 10.1016/j.clinph.2020.06.035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 06/11/2020] [Accepted: 06/28/2020] [Indexed: 10/23/2022]
Abstract
OBJECTIVE Understanding of maturational properties of sensory and motor axons is of central importance for determining the impact of nerve changes in health and in disease in children and young adults. METHODS This study investigated maturation of sensory axons using axonal excitability parameters of the median nerve in 47 children, adolescents and young adults (25 males, 22 females; age range 1-25 years) and compared them to concurrent motor studies. RESULTS The overall pattern of sensory maturation was similar to motor maturation demonstrating prolongation of the strength duration time constant (P < 0.001), reduction of hyperpolarising threshold electrotonus (P = 0.002), prolongation of accommodation half-time (P = 0.005), reduction in hyperpolarising current-threshold slope (P = 0.03), and a shift to the right of the refractory cycle curve (P < 0.001), reflecting changes in passive membrane properties and fast potassium channel conductances. Sensory axons, however, had a greater increase in strength duration time constant and more attenuated changes in depolarising threshold electrotonus and current-threshold parameters, attributable to a more depolarised resting membrane potential evident from early childhood and maintained in adults. Peak amplitude was established early in sensory axons whereas motor amplitude increased with age (P < 0.001), reflecting non-axonal motor unit changes. CONCLUSIONS Maturational trajectories of sensory and motor axons were broadly parallel in children and young adults, but sensory-motor differences were initiated early in maturation. SIGNIFICANCE Identifying the evolution of biophysical changes within and between sensory and motor axons through childhood and adolescence is fundamental to understanding developmental physiology and interpreting disease-related changes in immature nerves.
Collapse
Affiliation(s)
- Tejaswi Kandula
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, High Street, Randwick, NSW 2031, Australia; Department of Neurology, Sydney Children's Hospital, High Street, Randwick, NSW 2031, Australia
| | - Susanna B Park
- Brain and Mind Centre, Faculty of Medicine and Health, University of Sydney, 94 Mallett Street, Camperdown, NSW 2051, Australia
| | - Kate A Carey
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, High Street, Randwick, NSW 2031, Australia
| | - Cindy S-Y Lin
- Brain and Mind Centre, Faculty of Medicine and Health, University of Sydney, 94 Mallett Street, Camperdown, NSW 2051, Australia
| | - Michelle A Farrar
- School of Women's and Children's Health, UNSW Medicine, UNSW Sydney, High Street, Randwick, NSW 2031, Australia; Department of Neurology, Sydney Children's Hospital, High Street, Randwick, NSW 2031, Australia.
| |
Collapse
|
8
|
El-Hady AO, El Molla SSA, Ibrahim RA. Evaluation of axonal loss in ulnar sensory nerve fibers recorded from ring and little fingers secondary to idiopathic carpal tunnel syndrome in Egyptian patients. EGYPTIAN RHEUMATOLOGY AND REHABILITATION 2020. [DOI: 10.1186/s43166-020-00004-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
The association between carpal tunnel syndrome (CTS) and ulnar nerve entrapment is unclear, and the extra-median paresthesia in the ulnar nerve territory innervation in CTS is unexplained. Our purpose is to evaluate the neurophysiologic changes in ulnar nerve sensory fibers secondary to idiopathic CTS in comparison to normal subjects, and their relation to the severity of CTS.
Results
The difference between CTS and control hands regarding all parameters of ulnar motor nerve conduction studies (MNCS) was not statistically significant (p > 0.05). There was a statistically significant difference in all parameters of median sensory conduction study (SCS) and MNCS between CTS and control hands (p < 0.0001) except for conduction velocity and in all parameters of median and ulnar SCS recording digit 4 (D4) (p < 0.05). The mean value of abnormalities of ulnar SCS recording D4 and digit 5 (D5) was significantly higher in moderate and severe CTS hands (p < 0.05). There were significant negative correlations between median motor and sensory latency and ulnar sensory amplitude recording D4 and D5.
Conclusion
Ulnar sensory nerve abnormalities exist among CTS patients, which were more in moderate and severe grades. The drop in amplitude of ulnar nerve sensory response argues in favor of the possible impact of CTS on the ulnar nerve and did not indicate axonal deterioration of the ulnar nerve.
Collapse
|
9
|
Mendonca GV, Mouro M, Vila-Chã C, Pezarat-Correia P. Nerve conduction during acute blood-flow restriction with and without low-intensity exercise Nerve conduction and blood-flow restriction. Sci Rep 2020; 10:7380. [PMID: 32355236 PMCID: PMC7193597 DOI: 10.1038/s41598-020-64379-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 02/07/2020] [Indexed: 11/09/2022] Open
Abstract
Despite being apparently safe for most individuals, the impact of low intensity (LI) blood-flow restricted (BFR) exercise on nerve function and integrity is still obscure. We explored whether BFR (with and without exercise) alters the properties of nerve conduction measured at the level of the restricted limb. Thirteen healthy, young men (22.0 ± 1.7 years) were included in this study. Arterial occlusion pressure was taken at rest. Soleus M- and H-recruitment curves were constructed for all participants. H-wave latencies and amplitudes were obtained in three testing conditions (non-BFR vs. 60 vs. 80% BFR) at four different time points: [#1] non-restricted baseline, [#2] time control either with or without BFR, [#3] non-restricted pre-exercise, [#4] LI exercise either with or without BFR. Nerve conduction was estimated using the difference between the latency of H and M wave. BFR did not affect H-wave amplitude, either with or without exercise. The changes in the difference between H- and M-wave latency of over time were similar between all conditions (condition-by-time interaction: F = 0.7, p = 0.47). In conclusion, our data indicate that performing LI exercise with BFR, set at 60 or 80% BFR, does not exert a negative impact on sciatic-tibial nerve function. Thus, from a neurological standpoint, we provide preliminary evidence that LI BFR exercise may be regarded as a safe mode of resistance training in healthy young men.
Collapse
Affiliation(s)
- Goncalo V Mendonca
- Neuromuscular Research Lab, Faculdade de Motricidade Humana, Universidade de Lisboa, Estrada da Costa, 1499-002, Cruz Quebrada, Dafundo, Portugal. .,CIPER, Faculdade de Motricidade Humana, Universidade de Lisboa, Estrada da Costa, 1499-002, Cruz Quebrada, Dafundo, Portugal.
| | - Miguel Mouro
- Neuromuscular Research Lab, Faculdade de Motricidade Humana, Universidade de Lisboa, Estrada da Costa, 1499-002, Cruz Quebrada, Dafundo, Portugal
| | - Carolina Vila-Chã
- Polytechnic Institute of Guarda, Av. Dr. Francisco Sá Carneiro, n. 50, Guarda, 6300-559, Portugal.,Research Center in Sports Sciences, Health and Human Development (CIDESD), Vila-Real, Portugal
| | - Pedro Pezarat-Correia
- Neuromuscular Research Lab, Faculdade de Motricidade Humana, Universidade de Lisboa, Estrada da Costa, 1499-002, Cruz Quebrada, Dafundo, Portugal.,CIPER, Faculdade de Motricidade Humana, Universidade de Lisboa, Estrada da Costa, 1499-002, Cruz Quebrada, Dafundo, Portugal
| |
Collapse
|
10
|
Kiernan MC, Bostock H, Park SB, Kaji R, Krarup C, Krishnan AV, Kuwabara S, Lin CSY, Misawa S, Moldovan M, Sung J, Vucic S, Wainger BJ, Waxman S, Burke D. Measurement of axonal excitability: Consensus guidelines. Clin Neurophysiol 2019; 131:308-323. [PMID: 31471200 DOI: 10.1016/j.clinph.2019.07.023] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 07/17/2019] [Accepted: 07/24/2019] [Indexed: 12/12/2022]
Abstract
Measurement of axonal excitability provides an in vivo indication of the properties of the nerve membrane and of the ion channels expressed on these axons. Axonal excitability techniques have been utilised to investigate the pathophysiological mechanisms underlying neurological diseases. This document presents guidelines derived for such studies, based on a consensus of international experts, and highlights the potential difficulties when interpreting abnormalities in diseased axons. The present manuscript provides a state-of-the-art review of the findings of axonal excitability studies and their interpretation, in addition to suggesting guidelines for the optimal performance of excitability studies.
Collapse
Affiliation(s)
- Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia.
| | - Hugh Bostock
- UCL Queen Square Institute of Neurology, London WC1N 3BG, United Kingdom
| | - Susanna B Park
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
| | - Ryuji Kaji
- National Utano Hospital, 8-Narutaki Ondoyamacho, Ukyoku, Kyoto 616-8255, Japan
| | - Christian Krarup
- Department of Neuroscience, University of Copenhagen and Department of Clinical Neurophysiology, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Arun V Krishnan
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | - Satoshi Kuwabara
- Department of Neurology, Graduate School of Medicine, Chiba University, Japan
| | - Cindy Shin-Yi Lin
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
| | - Sonoko Misawa
- Department of Neurology, Graduate School of Medicine, Chiba University, Japan
| | - Mihai Moldovan
- Department of Neuroscience, University of Copenhagen and Department of Clinical Neurophysiology, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
| | - Jiaying Sung
- Taipei Medical University, Wanfang Hospital, Taipei, Taiwan
| | - Steve Vucic
- Department of Neurology, Westmead Hospital, Western Clinical School, University of Sydney, Australia
| | - Brian J Wainger
- Department of Neurology and Anesthesiology, Critical Care & Pain Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Stephen Waxman
- Department of Neurology, Yale Medical School, New Haven, CT 06510, USA; Neurorehabilitation Research Center, Veterans Affairs Hospital, West Haven, CT 06516, USA
| | - David Burke
- Brain and Mind Centre, University of Sydney and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney 2006, Australia
| |
Collapse
|
11
|
Relations between sensory symptoms, touch sensation, and sensory neurography in the assessment of the ulnar neuropathy at the elbow. Clin Neurophysiol 2019; 130:199-206. [DOI: 10.1016/j.clinph.2018.11.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 10/19/2018] [Accepted: 11/11/2018] [Indexed: 11/23/2022]
|
12
|
Ginanneschi F, Mondelli M, Cioncoloni D, Rossi A. Impact of carpal tunnel syndrome on ulnar nerve at wrist: Systematic review. J Electromyogr Kinesiol 2018; 40:32-38. [DOI: 10.1016/j.jelekin.2018.03.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 03/10/2018] [Accepted: 03/19/2018] [Indexed: 10/17/2022] Open
|
13
|
Kovalchuk MO, Franssen H, Van Schelven LJ, Sleutjes BTHM. Comparing excitability at 37°C versus at 20°C: Differences between motor and sensory axons. Muscle Nerve 2017; 57:574-580. [DOI: 10.1002/mus.25960] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/02/2017] [Indexed: 11/06/2022]
Affiliation(s)
- Maria O. Kovalchuk
- Department of Neurology and Neurosurgery, Brain Center Rudolf MagnusUniversity Medical Center UtrechtUtrecht The Netherlands
| | - Hessel Franssen
- Department of Neurology and Neurosurgery, Brain Center Rudolf MagnusUniversity Medical Center UtrechtUtrecht The Netherlands
| | - Leonard J. Van Schelven
- Department of Medical Technology and Clinical PhysicsUniversity Medical Center UtrechtUtrecht the Netherlands
| | - Boudewijn T. H. M. Sleutjes
- Department of Neurology and Neurosurgery, Brain Center Rudolf MagnusUniversity Medical Center UtrechtUtrecht The Netherlands
| |
Collapse
|
14
|
Weerasinghe D, Menon P, Vucic S. Hyperpolarization-activated cyclic-nucleotide-gated channels potentially modulate axonal excitability at different thresholds. J Neurophysiol 2017; 118:3044-3050. [PMID: 28904107 DOI: 10.1152/jn.00576.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 09/06/2017] [Accepted: 09/12/2017] [Indexed: 11/22/2022] Open
Abstract
Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels mediate differences in sensory and motor axonal excitability at different thresholds in animal models. Importantly, HCN channels are responsible for voltage-gated inward rectifying (Ih) currents activated during hyperpolarization. The Ih currents exert a crucial role in determining the resting membrane potential and have been implicated in a variety of neurological disorders, including neuropathic pain. In humans, differences in biophysical properties of motor and sensory axons at different thresholds remain to be elucidated and could provide crucial pathophysiological insights in peripheral neurological diseases. Consequently, the aim of this study was to characterize sensory and motor axonal function at different threshold. Median nerve motor and sensory axonal excitability studies were undertaken in 15 healthy subjects (45 studies in total). Tracking targets were set to 20, 40, and 60% of maximum for sensory and motor axons. Hyperpolarizing threshold electrotonus (TEh) at 90-100 ms was significantly increased in lower threshold sensory axons times (F = 11.195, P < 0.001). In motor axons, the hyperpolarizing current/threshold (I/V) gradient was significantly increased in lower threshold axons (F = 3.191, P < 0.05). The minimum I/V gradient was increased in lower threshold motor and sensory axons. In conclusion, variation in the kinetics of HCN isoforms could account for the findings in motor and sensory axons. Importantly, assessing the function of HCN channels in sensory and motor axons of different thresholds may provide insights into the pathophysiological processes underlying peripheral neurological diseases in humans, particularly focusing on the role of HCN channels with the potential of identifying novel treatment targets.NEW & NOTEWORTHY Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels, which underlie inward rectifying currents (Ih), appear to mediate differences in sensory and motor axonal properties. Inward rectifying currents are increased in lower threshold motor and sensory axons, although different HCN channel isoforms appear to underlie these changes. While faster activating HCN channels seem to underlie Ih changes in sensory axons, slower activating HCN isoforms appear to be mediating the differences in Ih conductances in motor axons of different thresholds. The differences in HCN gating properties could explain the predilection for dysfunction of sensory and motor axons in specific neurological diseases.
Collapse
Affiliation(s)
| | - Parvathi Menon
- Department of Neurology, Westmead Hospital, Sydney, Australia; and.,Westmead Clinical School, The University of Sydney, Sydney, Australia
| | - Steve Vucic
- Department of Neurology, Westmead Hospital, Sydney, Australia; and .,Westmead Clinical School, The University of Sydney, Sydney, Australia
| |
Collapse
|
15
|
Abstract
To gain insights into erythromelalgia disease pathophysiology, this study elucidated changes in peripheral axonal excitability and influences of temperature and mexiletine on axonal function. Erythromelalgia (EM) is a rare neurovascular disorder characterized by intermittent severe burning pain, erythema, and warmth in the extremities on heat stimuli. To investigate the underlying pathophysiology, peripheral axonal excitability studies were performed and changes with heating and therapy explored. Multiple excitability indices (stimulus–response curve, strength–duration time constant (SDTC), threshold electrotonus, and recovery cycle) were investigated in 23 (9 EMSCN9A+ and 14 EMSCN9A−) genetically characterized patients with EM stimulating median motor and sensory axons at the wrist. At rest, patients with EM showed a higher threshold and rheobase (P < 0.001) compared with controls. Threshold electrotonus and current–voltage relationships demonstrated greater changes of thresholds in both depolarizing and hyperpolarizing preconditioning electrotonus in both EM cohorts compared with controls in sensory axons (P < 0.005). When average temperature was raised from 31.5°C to 36.3°C in EMSCN9A+ patients, excitability changes showed depolarization, specifically SDTC significantly increased, in contrast to the effects of temperature previously established in healthy subjects (P < 0.05). With treatment, 4 EMSCN9A+ patients (4/9) reported improvement with mexiletine, associated with reduction in SDTC in motor and sensory axons. This is the first study of primary EM using threshold tracking techniques to demonstrate alterations in peripheral axonal membrane function. Taken together, these changes may be attributed to systemic neurovascular abnormalities in EM, with chronic postischaemic resting membrane potential hyperpolarization due to Na+/K+ pump overactivity. With heating, a trigger of acute symptoms, axonal depolarization developed, corresponding to acute axonal ischaemia. This study has provided novel insights into EM pathophysiology.
Collapse
|
16
|
Sung JY, Tani J, Chang TS, Lin CSY. Uncovering sensory axonal dysfunction in asymptomatic type 2 diabetic neuropathy. PLoS One 2017; 12:e0171223. [PMID: 28182728 PMCID: PMC5300160 DOI: 10.1371/journal.pone.0171223] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 01/17/2017] [Indexed: 12/02/2022] Open
Abstract
This study investigated sensory and motor nerve excitability properties to elucidate the development of diabetic neuropathy. A total of 109 type 2 diabetes patients were recruited, and 106 were analyzed. According to neuropathy severity, patients were categorized into G0, G1, and G2+3 groups using the total neuropathy score-reduced (TNSr). Patients in the G0 group were asymptomatic and had a TNSr score of 0. Sensory and motor nerve excitability data from diabetic patients were compared with data from 33 healthy controls. Clinical assessment, nerve conduction studies, and sensory and motor nerve excitability testing data were analyzed to determine axonal dysfunction in diabetic neuropathy. In the G0 group, sensory excitability testing revealed increased stimulus for the 50% sensory nerve action potential (P<0.05), shortened strength-duration time constant (P<0.01), increased superexcitability (P<0.01), decreased subexcitability (P<0.05), decreased accommodation to depolarizing current (P<0.01), and a trend of decreased accommodation to hyperpolarizing current in threshold electrotonus. All the changes progressed into G1 (TNSr 1–8) and G2+3 (TNSr 9–24) groups. In contrast, motor excitability only had significantly increased stimulus for the 50% compound motor nerve action potential (P<0.01) in the G0 group. This study revealed that the development of axonal dysfunction in sensory axons occurred prior to and in a different fashion from motor axons. Additionally, sensory nerve excitability tests can detect axonal dysfunction even in asymptomatic patients. These insights further our understanding of diabetic neuropathy and enable the early detection of sensory axonal abnormalities, which may provide a basis for neuroprotective therapeutic approaches.
Collapse
Affiliation(s)
- Jia-Ying Sung
- Department of Neurology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.,Department of Neurology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Jowy Tani
- Department of Neurology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan.,Ph.D. Program for Neural Regenerative Medicine, College of Medical Science and Technology, Taipei Medical University and National Health Research Institutes
| | - Tsui-San Chang
- Department of Neurology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Cindy Shin-Yi Lin
- Neural Regenerative Medicine, College of Medical Science and Technology, Taipei Medical University and National Health Research Institutes.,Translational Neuroscience, Department of Physiology, School of Medicine Science, Faculty of Medicine, University of New South Wales, Sydney, Australia
| |
Collapse
|
17
|
Howells J, Bostock H, Burke D. Accommodation to hyperpolarization of human axons assessed in the frequency domain. J Neurophysiol 2016; 116:322-35. [PMID: 27098023 DOI: 10.1152/jn.00019.2016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 04/18/2016] [Indexed: 11/22/2022] Open
Abstract
Human axons in vivo were subjected to subthreshold currents with a threshold impedance amplitude profile to allow the use of frequency domain techniques to determine the propensity for resonant behavior and to clarify the relative contributions of different ion channels to their low-frequency responsiveness. Twenty-four studies were performed on the motor and sensory axons of the median nerve in six subjects. The response to oscillatory currents was tested between direct current (DC) and 16 Hz. A resonant peak at ∼2-2.5 Hz was found in the response of hyperpolarized axons, but there was only a small broad response in axons at resting membrane potential (RMP). A mathematical model of axonal excitability developed using DC pulses provided a good fit to the frequency response for human axons and indicated that the hyperpolarization-activated current Ih and the slow potassium current IKs are principally responsible for the resonance. However, the results indicate that if axons are hyperpolarized by more than -60% of resting threshold, the only conductances that are appreciably active are Ih and the leak conductance, i.e., that the activity of these conductances can be studied in vivo virtually in isolation at hyperpolarized membrane potentials. Given that the leak conductance dampens resonance, it is suggested that the -60% hyperpolarization used here is optimal for Ih As expected, differences between the frequency responses of motor and sensory axons were present and best explained by reduced slow potassium conductance GKs, up-modulation of Ih, and increased persistent Na(+) current INaP (due to depolarization of RMP) in sensory axons.
Collapse
Affiliation(s)
- James Howells
- Brain & Mind Centre, The University of Sydney, Sydney, Australia;
| | - Hugh Bostock
- Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, United Kingdom; and
| | - David Burke
- Royal Prince Alfred Hospital and The University of Sydney, Sydney, Australia
| |
Collapse
|
18
|
Kwai NCG, Arnold R, Poynten AM, Howells J, Kiernan MC, Lin CSY, Krishnan AV. In vivo evidence of reduced nodal and paranodal conductances in type 1 diabetes. Clin Neurophysiol 2015; 127:1700-1706. [PMID: 26725257 DOI: 10.1016/j.clinph.2015.11.047] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 11/13/2015] [Accepted: 11/29/2015] [Indexed: 12/28/2022]
Abstract
OBJECTIVES Diabetic neuropathy is a debilitating complication of diabetes. Animal models of type 1 diabetes (T1DM) suggest that functional and structural changes, specifically axo-glial dysjunction, may contribute to neuropathy development. The present study sought to examine and characterise early sensory axonal function in T1DM patients in the absence of clinical neuropathy. METHODS Thirty patients with T1DM (15M:15F) without neuropathy underwent median nerve sensory and motor axonal excitability studies to examine axonal function. A verified mathematical model of human motor and sensory axons was used to elucidate the underlying causes of observed alterations. RESULTS Compared to controls (NC), T1DM patients demonstrated significant axonal excitability abnormalities in sensory and motor axons. These included marked reductions in sensory and motor subexcitability during the recovery cycle (T1DM 7.9 ± 0.4:10.4 ± 0.6%, NC 10.4 ± 0.7:15.4 ± 1.2%, P<0.01) and during hyperpolarizing threshold electrotonus at 10-20 ms (T1DM -75.5 ± 0.8:-69.7 ± 0.8%, NC -78.4 ± 1:-72.7 ± 0.9%, P<0.01). Mathematical modelling demonstrated that these changes were due to reduced nodal Na(+) currents, nodal/paranodal K(+) conductances and Na(+)/K(+) pump dysfunction, consistent with axo-glial dysjunction as outlined in animal models of T1DM. CONCLUSIONS The study provided support for the occurrence of early changes in nodal and paranodal conductances in patients with T1DM. SIGNIFICANCE These data indicate that axonal excitability techniques may detect early changes in diabetic patients, providing a window of opportunity for prophylactic intervention in T1DM.
Collapse
Affiliation(s)
- Natalie C G Kwai
- Prince of Wales Clinical School, The University of New South Wales, Sydney, Australia
| | - Ria Arnold
- Department of Pharmacology and Physiology, The University of New South Wales, Sydney, Australia
| | - Ann M Poynten
- Department of Endocrinology, Prince of Wales Hospital, Sydney, Australia
| | - James Howells
- Brain and Mind Centre, University of Sydney and Royal Prince Alfred Hospital, Sydney, Australia
| | - Matthew C Kiernan
- Brain and Mind Centre, University of Sydney and Royal Prince Alfred Hospital, Sydney, Australia
| | - Cindy S-Y Lin
- Department of Pharmacology and Physiology, The University of New South Wales, Sydney, Australia
| | - Arun V Krishnan
- Prince of Wales Clinical School, The University of New South Wales, Sydney, Australia.
| |
Collapse
|
19
|
Sung JY, Tani J, Park SB, Kiernan MC, Lin CSY. Early identification of 'acute-onset' chronic inflammatory demyelinating polyneuropathy. Brain 2014; 137:2155-63. [PMID: 24983276 DOI: 10.1093/brain/awu158] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Distinguishing patients with acute-onset chronic inflammatory demyelinating polyneuropathy from acute inflammatory demyelinating polyneuropathy prior to relapse is often challenging at the onset of their clinical presentation. In the present study, nerve excitability tests were used in conjunction with the clinical phenotype and disease staging, to differentiate between patients with acute-onset chronic inflammatory demyelinating polyneuropathy and patients with acute inflammatory demyelinating polyneuropathy at an early stage, with the aim to better guide treatment. Clinical assessment, staging and nerve excitability tests were undertaken on patients initially fulfilling the diagnostic criteria of acute inflammatory demyelinating polyneuropathy soon after symptom onset and their initial presentation. Patients were subsequently followed up for minimum of 12 months to determine if their clinical presentations were more consistent with acute-onset chronic inflammatory demyelinating polyneuropathy. Clinical severity as evaluated by Medical Research Council sum score and Hughes functional grading scale were not significantly different between the two cohorts. There was no difference between the time of onset of initial symptoms and nerve excitability test assessment between the two cohorts nor were there significant differences in conventional nerve conduction study parameters. However, nerve excitability test profiles obtained from patients with acute inflammatory demyelinating polyneuropathy demonstrated abnormalities in the recovery cycle of excitability, including significantly reduced superexcitability (P < 0.001) and prolonged relative refractory period (P < 0.01), without changes in threshold electrotonus. In contrast, in patients with acute-onset chronic inflammatory demyelinating polyneuropathy, a different pattern occurred with the recovery cycle shifted downward (increased superexcitability, P < 0.05; decreased subexcitability, P < 0.05) and increased threshold change in threshold electrotonus in both hyperpolarizing and depolarizing directions [depolarizing threshold electrotonus (90-100 ms) P < 0.005, hyperpolarizing threshold electrotonus (10-20 ms), P < 0.01, hyperpolarizing threshold electrotonus (90-100 ms), P < 0.05], perhaps suggesting early hyperpolarization. In addition, using excitability parameters superexcitability, subexcitability and hyperpolarizing threshold electrotonus (10-20 ms), the patients with acute inflammatory demyelinating polyneuropathy and acute-onset chronic inflammatory demyelinating polyneuropathy could be clearly separated into two non-overlapping groups. Studies of nerve excitability may be able to differentiate acute from acute-onset chronic inflammatory demyelinating polyneuropathy at an early stage. Characteristic nerve excitability parameter changes occur in early acute-onset chronic inflammatory demyelinating polyneuropathy, to match the clinical phenotype. Importantly, this pattern of change was strikingly different to that shown by patients with acute inflammatory demyelinating polyneuropathy, suggesting that nerve excitability techniques may be useful in distinguishing acute-onset chronic inflammatory demyelinating polyneuropathy from acute inflammatory demyelinating polyneuropathy at the initial stage.
Collapse
Affiliation(s)
- Jia-Ying Sung
- 1 Department of Neurology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan2 Department of Neurology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Jowy Tani
- 1 Department of Neurology, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
| | - Susanna B Park
- 3 Neuroscience Research Australia and Prince of Wales Clinical School, University of New South Wales, Australia
| | - Matthew C Kiernan
- 3 Neuroscience Research Australia and Prince of Wales Clinical School, University of New South Wales, Australia4 Brain and Mind Research Institute and Central Clinical School, University of Sydney, Sydney, Australia
| | - Cindy Shin-Yi Lin
- 5 School of Medical Sciences, Department of Physiology, Faculty of Medicine, University of New South Wales, Sydney, Australia
| |
Collapse
|
20
|
Franssen H. The Node of Ranvier in Multifocal Motor Neuropathy. J Clin Immunol 2014; 34 Suppl 1:S105-11. [DOI: 10.1007/s10875-014-0023-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 03/19/2014] [Indexed: 01/07/2023]
|
21
|
Nasu S, Misawa S, Nakaseko C, Shibuya K, Isose S, Sekiguchi Y, Mitsuma S, Ohmori S, Iwai Y, Beppu M, Shimizu N, Ohwada C, Takeda Y, Fujimaki Y, Kuwabara S. Bortezomib-induced neuropathy: Axonal membrane depolarization precedes development of neuropathy. Clin Neurophysiol 2014; 125:381-7. [DOI: 10.1016/j.clinph.2013.07.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2013] [Revised: 07/21/2013] [Accepted: 07/31/2013] [Indexed: 01/17/2023]
|
22
|
Uncini A, Notturno F, Capasso M. Natura Non Facit Saltusin Anti-Ganglioside Antibody-Mediated Neuropathies. Muscle Nerve 2013; 48:484-7. [DOI: 10.1002/mus.23881] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/15/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Antonino Uncini
- Department of Neuroscience and Imaging; University “G. d'Annunzio,”; Chieti-Pescara Italy
| | - Francesca Notturno
- Department of Neuroscience and Imaging; University “G. d'Annunzio,”; Chieti-Pescara Italy
| | - Margherita Capasso
- Department of Neuroscience and Imaging; University “G. d'Annunzio,”; Chieti-Pescara Italy
| |
Collapse
|
23
|
Hofmeijer J, Franssen H, van Schelven LJ, van Putten MJAM. Why are sensory axons more vulnerable for ischemia than motor axons? PLoS One 2013; 8:e67113. [PMID: 23840596 PMCID: PMC3688630 DOI: 10.1371/journal.pone.0067113] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2013] [Accepted: 05/14/2013] [Indexed: 12/23/2022] Open
Abstract
OBJECTIVE In common peripheral neuropathies, sensory symptoms usually prevail over motor symptoms. This predominance of sensory symptoms may result from higher sensitivity of sensory axons to ischemia. METHODS We measured median nerve compound sensory action potentials (CSAPs), compound muscle action potentials (CMAPs), and excitability indices in five healthy subjects during forearm ischemia lasting up to disappearance of both CSAPs and CMAPs. RESULTS ISCHEMIA INDUCED: (1) earlier disappearance of CSAPs than CMAPs (mean ± standard deviation 30±5 vs. 46±6 minutes), (2) initial changes compatible with axonal depolarization on excitability testing (decrease in threshold, increase in strength duration time constant (SDTC) and refractory period, and decrease in absolute superexcitability) which were all more prominent in sensory than in motor axons, and (3) a subsequent decrease of SDTC reflecting a decrease in persistent Na(+) conductance during continuing depolarisation. INTERPRETATION Our study shows that peripheral sensory axons are more vulnerable for ischemia than motor axons, with faster inexcitability during ischemia. Excitability studies during ischemia showed that this was associated with faster depolarization and faster persistent Na(+) channel inactivation in sensory than in motor axons. These findings might be attributed to differences in ion channel composition between sensory and motor axons and may contribute to the predominance of sensory over motor symptoms in common peripheral neuropathies.
Collapse
Affiliation(s)
- Jeannette Hofmeijer
- Clinical Neurophysiology, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.
| | | | | | | |
Collapse
|
24
|
Ng K, Kumar KR, Sue C, Burke D. Axonal excitability during ischemia in MELAS. Muscle Nerve 2013; 47:762-5. [PMID: 23553640 DOI: 10.1002/mus.23733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2012] [Indexed: 11/11/2022]
Abstract
INTRODUCTION In mitochondrial disease, it is likely that energy substrate depletion leads to paralysis of ATPase-dependent pumps, resulting in membrane depolarization. Axonal depolarization has been demonstrated in a crisis, but not in the resting state. We, therefore, stressed axons using ischemia to see if this would reveal abnormal responses, as occurs in diabetes mellitus. METHODS Excitability of median nerve axons at the wrist was studied in 13 patients with MELAS (6 with glucose intolerance) and 17 control subjects in response to ischemia due to inflation of a cuff around the arm for 10 min. RESULTS There were no significant differences in preischemic measures of axonal excitability or in the intra- and postischemic responses. CONCLUSIONS Although depolarization has been noted to occur spontaneously during a crisis, we could not demonstrate a defect of axonal ATP-dependent mechanisms. The mechanisms underlying axonal excitability and neuropathy in diabetes may not apply to MELAS.
Collapse
Affiliation(s)
- Karl Ng
- Department of Neurology and Clinical Neurophysiology, Royal North Shore Hospital, New South Wales, Australia.
| | | | | | | |
Collapse
|
25
|
Abstract
Multifocal motor neuropathy (MMN) is a rare disorder in which the symptoms are caused by persistent conduction block lesions. The mononeuropathy multiplex progresses over time with increasing axonal loss. The cause of the conduction blocks and axonal loss are not completely understood but immune mechanisms are involved and response to intravenous immunoglobulin has been established. The importance of MMN goes beyond its clinical incidence as the increasing understanding of the pathogenesis of this disorder has implications for other peripheral nerve diseases and for our knowledge of peripheral nerve biology.
Collapse
Affiliation(s)
- Ximena Arcila-Londono
- Department of Neurology, Wayne State University School of Medicine, Detroit, Michigan, USA
| | | |
Collapse
|
26
|
Crone C, Krarup C. Neurophysiological approach to disorders of peripheral nerve. HANDBOOK OF CLINICAL NEUROLOGY 2013; 115:81-114. [PMID: 23931776 DOI: 10.1016/b978-0-444-52902-2.00006-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Disorders of the peripheral nerve system (PNS) are heterogeneous and may involve motor fibers, sensory fibers, small myelinated and unmyelinated fibers and autonomic nerve fibers, with variable anatomical distribution (single nerves, several different nerves, symmetrical affection of all nerves, plexus, or root lesions). Furthermore pathological processes may result in either demyelination, axonal degeneration or both. In order to reach an exact diagnosis of any neuropathy electrophysiological studies are crucial to obtain information about these variables. Conventional electrophysiological methods including nerve conduction studies and electromyography used in the study of patients suspected of having a neuropathy and the significance of the findings are discussed in detail and more novel and experimental methods are mentioned. Diagnostic considerations are based on a flow chart classifying neuropathies into eight categories based on mode of onset, distribution, and electrophysiological findings, and the electrophysiological characteristics in each type of neuropathy are discussed.
Collapse
Affiliation(s)
- Clarissa Crone
- Department of Clinical Neurophysiology, Rigshospitalet and University of Copenhagen, Copenhagen, Denmark
| | | |
Collapse
|
27
|
Nodera H, Rutkove SB. Accommodation to hyperpolarizing currents: Differences between motor and sensory nerves in mice. Neurosci Lett 2012; 518:111-6. [DOI: 10.1016/j.neulet.2012.04.065] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Revised: 04/12/2012] [Accepted: 04/25/2012] [Indexed: 12/22/2022]
|
28
|
Uncini A. A common mechanism and a new categorization for anti-ganglioside antibody-mediated neuropathies. Exp Neurol 2012; 235:513-6. [DOI: 10.1016/j.expneurol.2012.03.023] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 03/24/2012] [Accepted: 03/29/2012] [Indexed: 11/30/2022]
|
29
|
Changes of the peripheral nerve excitability in vivo induced by the persistent Na+ current blocker ranolazine. Neurosci Lett 2012; 518:36-40. [DOI: 10.1016/j.neulet.2012.04.050] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Revised: 04/10/2012] [Accepted: 04/19/2012] [Indexed: 02/01/2023]
|
30
|
Uncini A, Kuwabara S. Electrodiagnostic criteria for Guillain-Barrè syndrome: a critical revision and the need for an update. Clin Neurophysiol 2012; 123:1487-95. [PMID: 22480600 DOI: 10.1016/j.clinph.2012.01.025] [Citation(s) in RCA: 163] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Revised: 01/02/2012] [Accepted: 01/05/2012] [Indexed: 10/28/2022]
Abstract
Electrophysiology plays a determinant role in Guillain-Barré syndrome (GBS) diagnosis, classification of the subtypes and in establishing prognosis. In the last three decades, different electrodiagnostic criteria sets have been proposed for acute inflammatory demyelinating neuropathy (AIDP), acute motor axonal neuropathy (AMAN) and acute motor and sensory axonal neuropathy (AMSAN). Criteria sets for AIDP varied for the parameters indicative of demyelination considered, for the cut-off limits and the number of required abnormalities (all a priori established) showing different sensitivities. Criteria sets for AMAN and AMSAN were proposed on the initial assumption that these subtypes were pathologically characterised by simple axonal degeneration. However, some AMAN patients show transient conduction block/slowing in intermediate and distal nerve segments, mimicking demyelination but without the development of abnormal temporal dispersion, named reversible conduction failure (RCF). The lack of distinction between RCF and demyelinating conduction block leads to fallaciously classify AMAN patients with RCF as AIDP or AMAN with axonal degeneration. Serial electrophysiological studies are mandatory for proper diagnosis of GBS subtypes, identification of pathophysiological mechanisms and prognosis. More reliable electrodiagnostic criteria should be devised to distinguish axonal and demyelinating subtypes of GBS, taking into consideration the RCF pattern and focussing on temporal dispersion.
Collapse
Affiliation(s)
- Antonino Uncini
- Department of Neuroscience and Imaging, University G. d'Annunzio, Chieti-Pescara, Italy.
| | | |
Collapse
|
31
|
Park SB, Lin CSY, Burke D, Kiernan MC. Activity-dependent conduction failure: molecular insights. J Peripher Nerv Syst 2012; 16:159-68. [PMID: 22003929 DOI: 10.1111/j.1529-8027.2011.00358.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Weakness and fatigue are commonly encountered symptoms in neurological disorders and significantly impair quality of life. In the case of motor axons, conduction block contributes to weakness and fatigue and may be associated with aberrant nerve activity including fasciculations and cramp. These symptoms result from dysfunction of the constituent channels and pumps of the axonal membrane. In critically conducting axons, impulse conduction can be impaired by the effects of activity or by other mechanisms that produce a significant shift in membrane potential. Conduction failure may be accentuated or relieved by maneuvers that manipulate the time course of the driving current, including the administration of agents that interfere with Na(+) channel function. In patients with inflammatory neuropathies, normal activity may be sufficient to precipitate conduction failure at sites of impaired function in multifocal motor neuropathy (MMN) and chronic inflammatory demyelinating polyneuropathy (CIDP). From a clinical perspective, these features are not assessed adequately by conventional neurophysiological techniques. As weakness and fatigue may only develop following activity or exertion, it is useful to assess the effects of impulse trains to determine the extent of conduction failure and the resulting symptoms in neurological patients. These techniques and the physiological mechanisms underlying the development of activity-dependent hyperpolarization will be critically appraised in this review, with a focus on demyelinating neuropathies, MMN and the neurodegenerative disease, and amyotrophic lateral sclerosis (ALS).
Collapse
Affiliation(s)
- Susanna B Park
- Prince of Wales Clinical School, University of New South Wales, Sydney, Australia
| | | | | | | |
Collapse
|
32
|
Howells J, Trevillion L, Bostock H, Burke D. The voltage dependence of I(h) in human myelinated axons. J Physiol 2012; 590:1625-40. [PMID: 22310314 DOI: 10.1113/jphysiol.2011.225573] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
HCN channels are responsible for I(h), a voltage-gated inwardly rectifying current activated by hyperpolarization. This current appears to be more active in human sensory axons than motor and may play a role in the determination of threshold. Differences in I(h) are likely to be responsible for the high variability in accommodation to hyperpolarization seen in different subjects. The aim of this study was to characterise this current in human axons, both motor and sensory. Recordings of multiple axonal excitability properties were performed in 10 subjects, with a focus on the changes in threshold evoked by longer and stronger hyperpolarizing currents than normally studied. The findings confirm that accommodation to hyperpolarization is greater in sensory than motor axons in all subjects, but the variability between subjects was greater than the modality difference. An existing model of motor axons was modified to take into account the behaviour seen with longer and stronger hyperpolarization, and a mathematical model of human sensory axons was developed based on the data collected. The differences in behaviour of sensory and motor axons and the differences between different subjects are best explained by modulation of the voltage dependence, along with a modest increase of expression of the underlying conductance of I(h). Accommodation to hyperpolarization for the mean sensory data is fitted well with a value of -94.2 mV for the mid-point of activation (V(0.5)) of I(h) as compared to -107.3 mV for the mean motor data. The variation in response to hyperpolarization between subjects is accounted for by varying this parameter for each modality (sensory: -89.2 to -104.2 mV; motor -87.3 to -127.3 mV). These voltage differences are within the range that has been described for physiological modulation of I(h) function. The presence of slowly activated I(h) isoforms on both motor and sensory axons was suggested by modelling a large internodal leak current and a masking of the Na(+)/K(+)-ATPase pump activity by a tonic depolarization. In addition to an increased activation of I(h), the modelling suggests that in sensory axons the nodal slow K(+) conductance is reduced, with consequent depolarization of resting membrane potential, and action potential of shorter duration.
Collapse
Affiliation(s)
- James Howells
- Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and The University of Sydney, Sydney, Australia.
| | | | | | | |
Collapse
|
33
|
|
34
|
Franssen H, Gebbink TA, Wokke JHJ, van den Berg LH, van Schelven LJ. Is cold paresis related to axonal depolarization? J Peripher Nerv Syst 2011; 15:227-37. [PMID: 21040145 DOI: 10.1111/j.1529-8027.2010.00275.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cold paresis may occur in multifocal motor neuropathy and lower motor neuron disease. It was proposed to reflect nerve lesions where axons are depolarized due to loss of Na/K-pump activity. In those circumstances, a further decrease in pump activity by cooling may induce extra depolarization, conduction block, and weakness. Evidence for this hypothesis is incomplete because it is unknown if cold induces depolarization in human motor axons and other factors may contribute to the symptoms. To solve these questions, we examined 10 normal subjects. At 37, 25, 20, and 15°C we assessed: excitability in the median nerve, decrement on 3-Hz stimulation, pulsed Doppler of a wrist artery, and thenar muscle strength. Cooling induced: (1) findings compatible with axonal depolarization on excitability testing (fanning-in of threshold electrotonus, steepened current threshold relation, increased refractory period, decreased super- and subexcitability), (2) decreased Doppler peak systolic velocity without causing ischemia, (3) decreased muscle strength and impaired muscle relaxation. Decrement tests and compound muscle action potential amplitude remained normal. The excitability findings induced by cooling were best explained by axonal depolarization due to the effect of temperature on Na/K-pump activity. The induced weakness may be explained not only by this mechanism but also by impaired muscle contraction.
Collapse
Affiliation(s)
- Hessel Franssen
- Department of Neurology, Neuromuscular Disease Group, Rudolf Magnus Institute for Neuroscience, University Medical Center Utrecht, The Netherlands.
| | | | | | | | | |
Collapse
|
35
|
Trevillion L, Howells J, Bostock H, Burke D. Properties of low-threshold motor axons in the human median nerve. J Physiol 2010; 588:2503-15. [PMID: 20478975 DOI: 10.1113/jphysiol.2010.190884] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
This study investigated the excitability and accommodative properties of low-threshold human motor axons to test whether these motor axons have greater expression of the persistent Na(+) conductance, I(NaP). Computer-controlled threshold tracking was used to study 22 single motor units and the data were compared with compound motor potentials of various amplitudes recorded in the same experimental session. Detailed comparisons were made between the single units and compound potentials that were 40% or 5% of maximal amplitude, the former because this is the compound potential size used in most threshold tracking studies of axonal excitability, the latter because this is the compound potential most likely to be composed entirely of motor axons with low thresholds to electrical recruitment. Measurements were made of the strength-duration relationship, threshold electrotonus, current-voltage relationship, recovery cycle and latent addition. The findings did not support a difference in I(NaP). Instead they pointed to greater activity of the hyperpolarization-activated inwardly rectifying current (I(h)) as the basis for low threshold to electrical recruitment in human motor axons. Computer modelling confirmed this finding, with a doubling of the hyperpolarization-activated conductance proving the best single parameter adjustment to fit the experimental data. We suggest that the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel(s) expressed on human motor axons may be active at rest and contribute to resting membrane potential.
Collapse
Affiliation(s)
- Louise Trevillion
- Institute of Clinical Neurosciences, Royal Prince Alfred Hospital and The University of Sydney, Sydney, Australia
| | | | | | | |
Collapse
|
36
|
Han SE, Boland RA, Krishnan AV, Vucic S, Lin CSY, Kiernan MC. Ischaemic sensitivity of axons in carpal tunnel syndrome. J Peripher Nerv Syst 2010; 14:190-200. [PMID: 19909483 DOI: 10.1111/j.1529-8027.2009.00231.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Although carpal tunnel syndrome (CTS) is the most common human entrapment neuropathy characterized by paraesthesiae and numbness with nocturnal exacerbation, the mechanisms underlying the generation of these symptoms remain unclear. Consequently, the aim of the present study was to investigate the relationship between changes in axonal excitability and the development of neurological symptoms in response to an ischaemic insult in CTS patients. Sensory and motor excitability were measured in 10 CTS patients and compared with 10 healthy controls, with participants asked to report symptom generation and intensity during the development of limb ischaemia. To induce ischaemia, a sphygmomanometer was inflated above the elbow and maintained at 200 mmHg for 10 min. During ischaemia there were decreases in axonal threshold, with less overall reduction in CTS patients when compared with controls. Associated with these differences in threshold, both sensory (p < 0.001) and motor (p < 0.05) refractoriness increased dramatically in CTS patients. This prominent increase in refractoriness was accompanied by a significant reduction in compound sensory action potentials and compound motor action potentials amplitudes for CTS patients when compared with controls (p < 0.05). These changes in axonal excitability resulted in a higher intensity of numbness and paraesthesiae reported by CTS patients during ischaemia. The present study has established differences in the nerve excitability and symptom development during ischaemia for patients with mild and moderate CTS, and may suggest that axons in the median nerve of CTS patients have an altered functional capacity to respond to an ischaemic insult, further contributing to nocturnal exacerbation of their symptoms.
Collapse
Affiliation(s)
- S Eric Han
- Prince of Wales Medical Research Institute & Prince of Wales Clinical School, University of New South Wales, Barker Street, Randwick NSW, Australia
| | | | | | | | | | | |
Collapse
|
37
|
Krishnan AV, Lin CSY, Park SB, Kiernan MC. Axonal ion channels from bench to bedside: a translational neuroscience perspective. Prog Neurobiol 2009; 89:288-313. [PMID: 19699774 DOI: 10.1016/j.pneurobio.2009.08.002] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Revised: 08/17/2009] [Accepted: 08/17/2009] [Indexed: 12/13/2022]
Abstract
Over recent decades, the development of specialised techniques such as patch clamping and site-directed mutagenesis have established the contribution of neuronal ion channel dysfunction to the pathophysiology of common neurological conditions including epilepsy, multiple sclerosis, spinal cord injury, peripheral neuropathy, episodic ataxia, amyotrophic lateral sclerosis and neuropathic pain. Recently, these insights from in vitro studies have been translated into the clinical realm. In keeping with this progress, novel clinical axonal excitability techniques have been developed to provide information related to the activity of a variety of ion channels, energy-dependent pumps and ion exchange processes activated during impulse conduction in peripheral axons. These non-invasive techniques have been extensively applied to the study of the biophysical properties of human peripheral nerves in vivo and have provided important insights into axonal ion channel function in health and disease. This review will provide a translational perspective, focusing on an overview of the investigational method, the clinical utility in assessing the biophysical basis of ectopic symptom generation in peripheral nerve disease and a review of the major findings of excitability studies in acquired and inherited neurological disease states.
Collapse
Affiliation(s)
- Arun V Krishnan
- Translational Neuroscience Facility, University of New South Wales, Randwick, Sydney, NSW, Australia
| | | | | | | |
Collapse
|
38
|
The Effect of Blood Flow on H-Reflex and Motor Responses in Adults With Type 2 Diabetes. J Clin Neurophysiol 2009; 26:201-6. [DOI: 10.1097/wnp.0b013e3181a768f3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
|
39
|
Short-term electrophysiological conduction change in median nerve fibres after carpal tunnel release. Clin Neurol Neurosurg 2008; 110:1025-30. [PMID: 18845386 DOI: 10.1016/j.clineuro.2008.07.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Revised: 07/01/2008] [Accepted: 07/15/2008] [Indexed: 02/07/2023]
Abstract
Standard electrophysiological techniques and analysis of the stimulus-response relationship (i.e., the input-output (I-O) curves) of the median nerve were performed in 16 patients with carpal tunnel syndrome (CTS) both prior to and 1 and 6 months after surgical decompression at the wrist. One month after carpal tunnel release (CTR), conduction in cutaneous and motor axons (i.e., sensory conduction velocity and distal motor latency) was found to be improved with respect to pre-surgical values, whereas motor action potentials and the motor I-O curve showed a decrease with respect to control values. This suggested reduced efficiency of axon recruitment following CTR. Six months after surgery, all parameters were significantly improved with respect to control values. The sensory and motor I-O curves suggested that the reduced motor fibre recruitment efficiency observed 1 month after CTR was due to changes in current density distributions under the surface stimulating electrode on the median nerve at the wrist. Slight transient compression (such as that due to post-surgical oedema) acting on median fibres located superficially within the nerve cannot be excluded, however. Since electrophysiological studies are an important, objective method of evaluating the outcome of surgical CTR, electrophysiologists must be aware of the possibility of reduced compound motor action potential (CMAP) in the first few months after surgery.
Collapse
|
40
|
Ginanneschi F, Milani P, Rossi A. Anomalies of ulnar nerve conduction in different carpal tunnel syndrome stages. Muscle Nerve 2008; 38:1155-60. [DOI: 10.1002/mus.21070] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
41
|
Han S, Boland RA, Krishnan AV, Vucic S, Lin CSY, Kiernan MC. Changes in human sensory axonal excitability induced by an ischaemic insult. Clin Neurophysiol 2008; 119:2054-63. [DOI: 10.1016/j.clinph.2008.04.295] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Revised: 04/09/2008] [Accepted: 04/11/2008] [Indexed: 11/26/2022]
|
42
|
Krishnan AV, Lin CSY, Park SB, Kiernan MC. Assessment of nerve excitability in toxic and metabolic neuropathies. J Peripher Nerv Syst 2008; 13:7-26. [DOI: 10.1111/j.1529-8027.2008.00155.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
43
|
Diatchenko L, Nackley AG, Tchivileva IE, Shabalina SA, Maixner W. Genetic architecture of human pain perception. Trends Genet 2007; 23:605-13. [PMID: 18023497 DOI: 10.1016/j.tig.2007.09.004] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Revised: 09/12/2007] [Accepted: 09/13/2007] [Indexed: 11/27/2022]
Abstract
Pain is emotionally detrimental and consciously avoided; however, it is absolutely crucial for our survival. Pain perception is one of the most complicated measurable traits because it is an aggregate of several phenotypes associated with peripheral and central nervous system dynamics, stress responsiveness and inflammatory state. As a complex trait, it is expected to have a polygenic nature shaped by environmental pressures. Here we discuss what is known about these contributing genetic variants, including recent discoveries that show a crucial role of voltage-gated sodium channel Nav1.7 in pain perception and how we can advance our understanding of the pain genetic network. We propose how both rare deleterious genetic variants and common genetic polymorphisms are mediators of human pain perception and clinical pain phenotypes.
Collapse
Affiliation(s)
- Luda Diatchenko
- Center for Neurosensory Disorders, University of North Carolina, 2190 Old Dental Building, Chapel Hill, NC 27599, USA.
| | | | | | | | | |
Collapse
|
44
|
Ginanneschi F, Dominici F, Milani P, Biasella A, Rossi A. Evidence of altered motor axon properties of the ulnar nerve in carpal tunnel syndrome. Clin Neurophysiol 2007; 118:1569-76. [PMID: 17475547 DOI: 10.1016/j.clinph.2007.03.024] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2007] [Revised: 03/20/2007] [Accepted: 03/22/2007] [Indexed: 12/31/2022]
Abstract
OBJECTIVE To analyse recruitment properties of ulnar nerve motor axons in 60 CTS patients with negative ulnar nerve electrodiagnostic tests. METHODS Recruitment properties of the ulnar nerve were studied by analysing the relationship between the intensity of electrical stimulation and the size of motor response, i.e. the stimulus-response curve. Parameters of the curve (threshold, slope and plateau) were compared with those of the corresponding curve of the median nerve and both with parameters of 30 control curves. RESULTS The ulnar nerve stimulus-response curve was strikingly abnormal and, except for severity, closely resembled that of the median nerve. The slope of the curve was significantly less than that of controls and decreased with increasing abnormalities of the median nerve. This suggested that the pathological process involving the ulnar nerve was contingent with the severity of median nerve involvement. CONCLUSIONS We propose that the ulnar nerve may be subject to compression in Guyon's canal as a consequence of high pressure in the carpal tunnel of CTS patients. SIGNIFICANCE Ectopic activity from ulnar axons may contribute to clinical spread of symptoms outside the median nerve territory in CTS. This does not exclude possible involvement of central plasticity mechanisms in producing extra-median symptoms in CTS patients.
Collapse
Affiliation(s)
- F Ginanneschi
- Clinical Neurophysiology Unit, Department of Neurological and Behavioural Sciences, University of Siena, Policlinico Le Scotte, Viale Bracci 2, Siena, Italy
| | | | | | | | | |
Collapse
|
45
|
Jankelowitz SK, McNulty PA, Burke D. Changes in measures of motor axon excitability with age. Clin Neurophysiol 2007; 118:1397-404. [PMID: 17452010 DOI: 10.1016/j.clinph.2007.02.025] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Revised: 02/19/2007] [Accepted: 02/21/2007] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Threshold tracking is a novel technique that permits examination of the excitability of human axons in vivo. Protocols have been validated for sensory and motor axons, but there are limited data on the changes in the excitability of motor axons with age. This study aimed to determine such changes from the third to the eighth decades. METHODS Sixty healthy subjects aged 22-79, 10 per decade, were studied using the TRONDXM4 protocol of the QTRAC threshold-tracking program to assess motor axon function. The median nerve was stimulated at the wrist and the compound muscle action potential was recorded from the thenar muscles. RESULTS There was an increase in threshold in elderly subjects, associated with a decrease in slope of the stimulus-response curves. Strength-duration time constant and threshold electrotonus to depolarising and hyperpolarising currents of up to 40% did not change significantly with aging. The current-threshold relationship was similar across all decades for subthreshold depolarising currents, but the slope of the current-threshold relationship was significantly steeper the older the subjects for hyperpolarising currents, particularly those greater than 40% of threshold. There was also a significant decrease in supernormality in the recovery cycle with increasing age. CONCLUSIONS The threshold of axons increases with age and the extent of supernormality decreases. There may also be greater inward rectification in motor axons, perhaps due to greater activity of I(H), the hyperpolarisation-activated conductance, though this is only significant with hyperpolarising currents greater than 40% of the threshold current. SIGNIFICANCE Many indices of axonal excitability, such as strength-duration time constant, the relative refractory period, late subnormality, threshold electrotonus and the depolarising side of the current-threshold relationship, do not change significantly with age. For other indices, age-related changes may be due to a combination of non-neural factors that alter current access to the node of Ranvier, changes in the axon and its myelination and, possibly, changes in channel activity and/or changes in extracellular [K(+)](o).
Collapse
Affiliation(s)
- S K Jankelowitz
- Institute of Clinical Neurosciences, University of Sydney and Royal Prince Alfred Hospital, Sydney, Australia.
| | | | | |
Collapse
|
46
|
Jankelowitz SK, Howells J, Burke D. Plasticity of inwardly rectifying conductances following a corticospinal lesion in human subjects. J Physiol 2007; 581:927-40. [PMID: 17363389 PMCID: PMC2170828 DOI: 10.1113/jphysiol.2006.123661] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
This study investigated whether there are changes in the excitability of motor axons in peripheral nerves of patients with corticospinal lesions, reflecting plasticity of the motoneuron due to altered descending drives and/or changes in afferent feedback. The excitability of motor and sensory axons in peripheral nerves of the affected limb of 11 patients with unilateral hemiparesis due to stroke was compared with that for the unaffected limbs and with data for 12 age-matched controls. There was significantly less accommodation to hyperpolarizing currents in motor axons on the affected side. There were small differences between the data for the unaffected side and that of the control subjects but these were not statistically significant. Other findings indicate that there was no change in resting membrane potential. There was no comparable alteration in the excitability of sensory axons. The changes in response of motor axons to hyperpolarizing currents could be reproduced in a computer model of the human motor axon by reducing the hyperpolarization-activated conductance, IH, by 30% and the quantitatively small leak conductance by 77%. The data for the uninvolved side matched the data for control subjects best when IH was increased. These findings are consistent with modulation of IH by activity. They demonstrate a change in the biophysical properties of motor axons not directly affected by the pathology and synaptically remote from the lesion, and have implications for 'trans-synaptic' changes in central nervous system pathways. In human subjects studies of motor axon properties may allow insight into processes affecting the motoneuron.
Collapse
Affiliation(s)
- Stacey K Jankelowitz
- Medical Foundation Building - K25, The University of Sydney, NSW 2006, Australia.
| | | | | |
Collapse
|
47
|
Trevillion L, Howells J, Burke D. Outwardly rectifying deflections in threshold electrotonus due to K+ conductances. J Physiol 2007; 580:685-96. [PMID: 17272346 PMCID: PMC2075549 DOI: 10.1113/jphysiol.2006.126003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
A transient decrease in excitability occurs regularly during the S1 phase of threshold electrotonus to depolarizing conditioning stimuli for sensory and, less frequently, motor axons. This has been attributed to the outwardly rectifying action of fast K(+) channels, at least in patients with demyelinating diseases. This study investigates the genesis of this notch in healthy axons. Threshold electrotonus was recorded for sensory and motor axons in the median nerve at the wrist in response to test stimuli of different width. The notch occurred more frequently the briefer the test stimulus, and more frequently in sensory studies. In studies on motor axons, the notch decreased in latency and increased in amplitude as the conditioning stimulus increased or the limb was cooled. Low-threshold axons displayed profound changes in strength-duration time constant even though the threshold electrotonus curves contained no detectable notch. When a 1.0 ms current was added to subthreshold conditioning stimuli to trigger EMG, the notch varied with the timing and intensity of the brief current pulse. This study finds no evidence for an outwardly rectifying deflection due to K(+) channels, other than the slow accommodation attributable to slow K(+) currents. In normal motor axons, a depolarization-induced notch during the S1 phase of threshold electrotonus is the result of the conditioning stimulus exceeding threshold for some axons. The notch is more apparent in sensory axons probably because of the lower slope of the stimulus-response curve and their longer strength-duration time constant rather than a difference in K(+) conductances. This may also explain the notch in demyelinating diseases.
Collapse
Affiliation(s)
- Louise Trevillion
- University of Sydney, Royal Prince Alfred Hospital, Sydney, NSW 2006, Australia
| | | | | |
Collapse
|
48
|
Ginanneschi F, Mondelli M, Dominici F, Rossi A. Changes in motor axon recruitment in the median nerve in mild carpal tunnel syndrome. Clin Neurophysiol 2006; 117:2467-72. [PMID: 16987705 DOI: 10.1016/j.clinph.2006.08.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Revised: 08/02/2006] [Accepted: 08/04/2006] [Indexed: 10/24/2022]
Abstract
OBJECTIVE To determine whether patients with mild carpal tunnel syndrome (CTS) and conventional electrodiagnostic evidence of selective involvement of sensory conduction show changes in motor axon recruitment in the median nerve. METHODS Wrist-to-abductor pollicis brevis (APB) motor axon conduction was studied by analysing the relationship between the intensity of electrical stimulation and the size of motor response (input-output curve) in 30 CTS patients with conventional electrodiagnostic evidence of selective involvement of sensory conduction. Parameters (threshold, slope and plateau) of input-output curves were compared with those obtained in 30 controls. RESULTS The slope of the input-output curve of CTS patients was less steep than that of controls. For stimulus intensity above M-wave threshold (MTh), fewer motor axons were recruited in patients than controls. CONCLUSIONS Motor fibres are affected in CTS when conventional electrodiagnostic tests show normal motor conduction. Altered recruitment of motor axons could mainly be due to impairment of energy-dependent processes which affect temporal dispersion of the compound volley or axonal conduction block. SIGNIFICANCE In mild CTS, motor fibres are more often affected than was originally thought. The sensitivity of wrist-to-APB motor conduction studies may be increased by using submaximal stimulus intensities.
Collapse
Affiliation(s)
- F Ginanneschi
- Unit of Clinical Neurophysiology, Department of Neurological and Behavioural Sciences, University of Siena, Italy
| | | | | | | |
Collapse
|
49
|
Nodera H, Kaji R. Nerve excitability testing and its clinical application to neuromuscular diseases. Clin Neurophysiol 2006; 117:1902-16. [PMID: 16631406 DOI: 10.1016/j.clinph.2006.01.018] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Revised: 01/16/2006] [Accepted: 01/23/2006] [Indexed: 11/22/2022]
Abstract
Non-invasive nerve excitability testing measures the membrane polarization, ion channel function and paranodal/internodal condition of peripheral nerves. This technique has been recently used for various neuromuscular disorders, such as pure motor conduction block in multifocal motor neuropathy, conduction block in carpal tunnel syndrome and Na(+) channel function disorders in diabetic neuropathy, to shed light on their pathophysiology. Here, we review the basics of ion channel functions and membrane properties that influence nerve excitability, the basic principles of nerve excitability testing and the reported findings in various disorders.
Collapse
Affiliation(s)
- Hiroyuki Nodera
- Department of Neurology, Graduate School of Medicine, Tokushima University, 2-50-1 Kuramoto, Tokushima 770-8503, Japan.
| | | |
Collapse
|
50
|
Moldovan M, Krarup C. Evaluation of Na+/K+ pump function following repetitive activity in mouse peripheral nerve. J Neurosci Methods 2006; 155:161-71. [PMID: 16466807 DOI: 10.1016/j.jneumeth.2005.12.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2005] [Revised: 11/02/2005] [Accepted: 12/19/2005] [Indexed: 10/25/2022]
Abstract
After conduction of prolonged trains of impulses the increased Na+/K+ pump activity leads to hyperpolarization. The aim of this study was to develop a mouse model to investigate the Na+/K+ pump function in peripheral nerve by measuring the decrease in excitability during activity-dependent hyperpolarization. Acute electrophysiological investigations were carried out in seven adult mice. Nerve excitability was evaluated by tracking the change in threshold current after 5 min of 100 Hz stimulation of the tibial nerve at ankle. We developed a threshold tracking system that allowed us to follow several excitability measures simultaneously from the evoked plantar compound muscle action potential (CMAP) and sciatic compound nerve action potential (CNAP). Three minutes after repetitive supramaximal stimulation maximal CMAP and CNAP amplitudes recovered but the threshold was increased approximately 40% for motor axons approximately 34% for axons generating CNAP. The threshold recovered with a rate of 3.8%/minute that was similar for nerve and motor responses. By tracking the effect of polarizing currents we found evidence of activity dependent hyperpolarization, and our data suggest that the observed threshold change after repetitive stimulation of the mouse tibial nerve is an indicator of the Na+/K+ pump function in vivo. Evaluation of activity-dependent hyperpolarization may be an important indicator of axonal ability to cope with Na+ load.
Collapse
Affiliation(s)
- Mihai Moldovan
- Division of Neurophysiology, Institute of Medical Physiology, Panum Institute, University of Copenhagen, Denmark
| | | |
Collapse
|