AAEM minimonograph #34: polyneuropathy: classification by nerve conduction studies and electromyography

The role of electrodiagnosis in focal neuropathies

Electrodiagnostic (EDX) testing plays an important role in confirming a mononeuropathy, localizing the site of nerve injury, defining the pathophysiology, and assessing the severity and prognosis. The combination of nerve conduction studies (NCS) and needle electromyography findings provides the necessary information to fully assess a nerve. The pattern of NCS abnormalities reflects the underlying pathophysiology, with focal slowing or conduction block in neuropraxic injuries and reduced amplitudes in axonotmetic injuries. Needle electromyography findings, including spontaneous activity and voluntary motor unit potential changes, complement the NCS findings and further characterize chronicity and degree of axon loss and reinnervation. EDX is used as an objective marker to follow the progression of a mononeuropathy over time.

Acupuncture improves chemotherapy-induced neuropathy explored by neurophysiological and clinical outcomes - The randomized, controlled, cross-over ACUCIN trial

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is recognized as the second commonest side effect after chemotherapy. Besides neurological deficits and pain, it is a potential reason for terminating chemotherapy. Effective curative treatments of neurodegeneration are lacking. Hitherto, no randomized controlled study used nerve conduction studies (NCS), the gold standard diagnostic tool for peripheral neuropathy, as the primary outcome parameter for evaluating acupuncture for CIPN, which can also measure structural changes.

METHODS

The study was carried out at the HanseMerkur Center for TCM at the University Medical Center, Hamburg-Eppendorf. Sixty patients with CIPN were included in the study after physical examination, subjective evaluation and quantitative evaluation by NCS. Subsequently, the patients were randomly assigned to Group 1 (30 patients), which received, in the first period, needle acupuncture and to Group 2 (30 patients), which was assigned to the waiting list in the first period. Group 1 received a standard 10-week bilateral treatment of ST34 (Liangqiu), EX-LE12 (Qiduan) and EX-LE8 (Bafeng). After 14 weeks, both groups were re-evaluated. Using a cross-over design, the patients of Group 2 received the same treatment procedure as Group 1 in the first period. Patients of Group 1 were assigned to the waiting list for the second period. After 28 weeks both groups were re-evaluated. Wilcoxon test was used as a pre-test to rule out carryover effects and to test for differences between acupuncture and the waiting list. Group assignment was not exposed to the statistician and the neurologist.

RESULTS

Sural sensory nerve amplitude, and sural nerve conduction velocity, were significantly improved (p < 0.01, effect size (f) 0.55 and 0.49) compared to measurements in the waiting period. Change of NCS of the tibial nerve did not significantly differ in group comparison. Patients reported subjective improvement during acupuncture treatment superior to the waiting period for burning pain, cramps, numbness, frequency of symptoms (all p < 0.01) and unsteadiness of gait (p < 0.05). On physical examination, blind walking, heel-to-toe walking, distal pallhypesthesia (both p < 0.01), and the neuropathy deficit score (p < 0.05) were significantly improved during acupuncture treatment compared to the waiting period.

CONCLUSION

Acupuncture can enhance structural regeneration in CIPN as measured by NCS, which is manifested in subjective improvement and neurological findings.

Sural Sensory Nerve Action Potential: A Study in Healthy Indian Subjects at Tertiary Care Center of North-West India

Objectives

This study was done to obtain the reference data for the sural SNAP amplitude and latency at distances of 14, 12, and 10 cm from the active recording electrode in Indian healthy subjects for different age groups.

Material and Methods

Two hundred forty-four healthy subjects (18-80 years) were included in this cross-sectional study. Subjects were divided into six groups according to age. Sural SNAP was recorded antidromically stimulating at three sites (14, 12, and 10 cm from the recording electrode). The quantitative variables were expressed as Mean ± SD/Median (IQR) and compared using t test/ANOVA. Transformed data for amplitude were analyzed with the use of paired t test. P < 0.05 was considered statistically significant. SPSS version 20.0 software was used for statistical analysis.

Results

Mean age of included subjects was 43.28 years. Maximum leg girth was at 14 cm. Analysis showed a significant difference in the leg girth at all three sites (P < 0.001). Sural SNAP latency at each stimulating site was compared in different age groups, no significant difference was found between groups (P = 0.19). Maximum amplitude was in the 18-30-years age group and amplitude was minimum in the 71-80-years age group (4.34 and 2.79, respectively). The difference in the amplitude recorded in the different age groups was found to be statistically different (P < 0.001). The difference in the amplitude recorded at each site was found to be statistically different (P < 0.001).

Conclusion

This is the first study with a large sample size (244 subjects) to provide age-stratified reference data for SNAP in the Indian population by using three sites of stimulation at distances of 14, 12, and 10 cm from the recording electrode. This study shows that sural SNAP amplitude varies with the age of the subject and distance from stimulation.

Approach to Neuropathic Pain

Neuropathic pain is a common chief complaint encountered by neurologists and primary care providers. It is caused by disorders involving the somatosensory nervous system. The clinical evaluation of neuropathic pain is challenging and requires a multifaceted systematic approach with an emphasis on a thorough history and physical examination to identify characteristic signs and symptoms. Ancillary laboratory investigations, targeted imaging, and electrodiagnostic studies further help identify underlying etiologies to guide specific treatments. Management of neuropathic pain encompasses treating the underlying pathology as well as symptomatic control with nonpharmacological, pharmacological, and interventional therapies. Here, we present an approach to help evaluate patients with neuropathic pain.

Differences in peripheral neuropathy in xeroderma pigmentosum complementation groups A and D as evaluated by nerve conduction studies

Background

Xeroderma pigmentosum (XP) is a rare autosomal recessive genetic disorder with defective DNA nucleotide excision repair and associated with a high frequency of skin cancer. Approximately 25% of patients develop progressive neurological degeneration. Complementation groups XP-A and XP-D are most frequently associated with neurological disorders.

Design/methods

This is a retrospective review of patients with XP who were evaluated at NIH from 1986 to 2015 and had nerve conduction studies (NCS). In the complementation groups with peripheral neuropathy, further comparisons of the NCS were made with audiological, brain imaging, neuropsychological assessments that were also performed on most of the patients. Limited neuropathology of XP-A and XP-D patients were examined..

Results

The 33 patients had NCS: XP-A (9 patients), XP-C (7 patients), XP-D (10 patients), XP-E (1 patient), XP-V (4 patients), and XP-unknown (2 patients). Peripheral neuropathy based on nerve conduction studies was documented only in two complementation groups: 78% (7/9) of XP-A patients had a sensorimotor neuropathy while 50% (5/10) of XP-D patients had a sensory neuropathy only. Analysis of sural sensory nerve amplitude in both complementation groups XP-A and XP-D correlated with sensorineural hearing loss (SNHL), MRI/CT severity, and Full-scale Intelligence Quotient (IQ). Analysis of fibular motor nerve amplitude in complementation XP-A correlated with SNHL and MRI/CT severity. Limited follow-up studies showed gradual loss of NCS responses compared to an earlier and more rapid progression of the hearing loss.

Conclusions

Despite similar brain imaging and audiological findings patients, XP-A and XP-D complementation groups differ in the type of neuropathy, sensorimotor versus sensory alone. A few cases suggest that sensorineural hearing loss may precede abnormal NCS in XP and therefore serve as valuable clinical indicators of XP patients that will later develop peripheral neuropathy.

Hereditary Transthyretin Amyloidosis- Clinical and Genetic Characteristics of a Multiracial South-East Asian Cohort in Singapore

BACKGROUND AND AIMS

Studies of hereditary transthyretin amyloidosis (ATTRv amyloidosis) in South-East Asia are underrepresented in the literature. We report the unique phenotypic and genetic characteristics of this disorder in a multiracial South-East Asian cohort.

METHODS

Patients with genetically proven ATTRv amyloidosis were identified over a 13-year period (2007-2020) at the National Neuroscience Institute, Singapore. Clinical, laboratory, genotypic and electrophysiological features were retrospectively reviewed.

RESULTS

29 patients comprising Chinese, Malay, Burmese, Vietnamese and Indonesians with ATTRv amyloidosis were identified. Somatic neuropathy was the most common initial presentation, followed by carpal tunnel syndrome, autonomic dysfunction and cardiac dysfunction. ATTR-A97S (p.Ala117Ser) was the most common variant found in 14 patients, constituting 66.7%of ethnic Chinese patients and 48.3%of the entire cohort. Five patients had early-onset disease (age < 50 years) with the following variants: ATTR-V30M (p.Val50Met), ATTR-G47A (p.Gly67Ala), ATTR-S50I (p.Ser70Ile) and ATTR-A97S (p.Ala117Ser); one patient with ATTR-A97S (p.Ala117Ser) had isolated unilateral carpal tunnel syndrome with amyloid deposits identified on histological examination of the transverse carpal ligament. All early-onset patients had a positive parental history; two patients, with ATTR-S50I (p.Ser70Ile) and ATTR-Ala97Ser (p.Ala117Ser) respectively, demonstrated anticipation with mother-to-daughter inheritance. Amongst the 24 patients with late-onset disease (age≥50 years), two patients had novel variants, ATTR-G66D (p.Glu86Asp) and ATTR-A81V (p.Ala101Val) that were confirmed to be pathogenic based on the histological identification of transthyretin amyloid. Other identified variants included ATTR-V30M (p.Val50Met), ATTR-R34T (p.Arg54Thr), ATTR-S50I (p.Ser70Ile), ATTR-H88R (p.His108Arg) and ATTR-A97S (p.Ala117Ser).

CONCLUSION

Our study further expands the genotypic and phenotypic knowledge regarding ATTRv amyloidosis.

Leprous Neuropathy: Observational Study Highlighting the Role of Electrophysiology in Early Diagnosis

Background  Worldwide leprosy is a common cause of peripheral neuropathy. Electrophysiology is underutilized in its diagnosis.

Objective  This study aims to evaluate the usefulness of electrophysiological study in the diagnosis of leprous neuropathy.

Materials and Methods  Clinical and electrophysiological abnormalities of 36 histopathology proven leprosy patients from January 2015 to January 2017 were studied.

Statistical Analysis  Proportions were compared by Chi-square test.

Results  Total patients were 36. Thirty-four patients had abnormal electrophysiology and 34 had neurological deficits like weakness, sensory changes, and thickening. By clinical examination, multiple nerve involvement (motor weakness, sensory changes, and nerve thickening) occurred in 29, single nerve in 5, and no nerve involvement in 2. With electrophysiology, multiple nerve involvement (mononeuritis multiplex) was present in 32, single nerve in 2, and normal conduction parameters in 2. From the 36 patients, a total of 1,008 nerves were subjected to clinical examination and 132 were picked up clinically as affected, (13.1%). Electrophysiological study was done in 504 nerves, and 215 were found to be involved, (43%). Nerve abnormality detected by electrophysiology is significantly higher than clinical detection. (Chi-square =164.4054; p = 0.0000). Clinically, the most commonly affected nerve was unar (27) and the least affected was median (2) nerve. Electrophysiology detected 69% of nerves with demyelination and 35% of nerves with axonal features (mosaic pattern).

Discussion  There was subclinical neuropathy with electroclinical dissociation, as evidenced by more abnormality in electrophysiology than clinical examination. The nerve involvement was mononeuritis or mononeuritis multiplex pattern, both clinically and electrophysiologically. Electrophysiology showed both axonal and demyelinating nerve involvement (mosaic pattern). All the three features are present in leprous neuropathy. In corollary, if a patient has these electrophysiological features, he should be thoroughly investigated for leprosy.

Conclusion  Triple findings, such as subclinical neuropathy with electroclinical dissociation, mononeuritis multiplex, and mosaic pattern of demyelination and axonopathy, suggest leprous neuropathy

Peripheral neuropathy in severe COVID-19 resolved with therapeutic plasma exchange

Peripheral neuropathies including Guillain-Barré syndrome may be linked to life-threatening COVID-19. Plasma exchange is a safe rescue therapy in severe COVID-19 with associated neurological manifestations and thromboinflammation.

Peripheral neuropathies in rheumatic diseases: More diverse and frequent than expected. A cross-sectional study

BACKGROUND/OBJECTIVE

Peripheral neuropathies (PN) are heterogeneous nerve disorders; frequently rheumatic patients have neuropathic symptoms. In some rheumatic diseases (RD) PN are secondary to nerve compression while others are related to metabolic abnormalities, inflammation or vasculitis. Our aim was to explore the frequency of neuropathic symptoms with three neuropathy questionnaires (NQ) and nerve conduction studies (NCS) in RD.

METHODS

This is a cross-sectional study in patients with any RD attending for the first time to a rheumatology outpatient clinic. We included all patients who accepted to participate and who answered three NQ and received a physical evaluation. Twenty patients were randomly selected to perform NCS and 10 healthy subjects were included as controls. The topographic diagnoses were: mononeuropathy, multiplex mononeuropathy, and/or polyneuropathy.

STATISTICAL ANALYSIS

descriptive statistics (mean, median, standard deviation, interquartile range and frequency, odds ratios and Pearson correlation test).

RESULTS

One hundred patients and 10 healthy subjects were included. Sixty-nine were female, mean age 40.6 ± 15.7 years. Rheumatic diagnoses were: systemic lupus erythematosus (26%), rheumatoid arthritis (16%), gout (14%), and osteoarthritis (11%). Fifty-two patients had neuropathic signs during physical examination and 67% had positive questionnaires with variable scores among several RD. Abnormal NCS was reported in 14 patients (70%): 6 (42.8%) median nerve mononeuropathies, 4 (28.5%) multiplex mononeuropathies and 4 (28.5%) polyneuropathies. None of the healthy subjects had neuropathy (NQ, physical evaluation, or NCS). Risk of being NCS positive is higher when the patients were NQ positive.

CONCLUSION

PN has variable distribution and high frequency in patients with RD; NQ+ increases the risk of presenting NCS+ for PN.

Electrophysiological findings in immune checkpoint inhibitor-related peripheral neuropathy

OBJECTIVE

To report the electrodiagnostic features of immune checkpoint inhibitor (ICI)-related neuropathy.

METHODS

We retrospectively reviewed clinical presentations and electrodiagnostic features of 23 patients studied after receiving immune checkpoint inhibitors (ICIs). The presentations for electrodiagnostic evaluation included an acute neuropathy or neuromuscular junction disorder. We applied established electrodiagnostic criteria for polyneuropathy and acute demyelinating neuropathy.

RESULTS

We identified acute demyelinating neuropathy (13 cases), axonal sensory motor neuropathy (5), pure sensory neuropathy (4) and mononeuropathy (1). 13 patients had acute demyelinating neuropathy confirmed by demonstrating demyelination in 2 or more nerves; 3 additional patients had demyelination in only one nerve. Analysis of motor nerve conduction parameters revealed demyelination involving median and ulnar nerve distal motor latencies as well as median, ulnar and peroneal nerve conduction velocities. Conduction block was found in median, ulnar and peroneal nerves. The remaining one-third patients without demyelination had acute painful axonal neuropathy. Coexisting myopathic changes (6) and neuromuscular junction dysfunction (4) were also identified.

CONCLUSIONS

Our findings suggest that, while immune-mediated motor nerve demyelination is the primary underlying mechanism of ICI-related neuropathy, axonal painful neuropathy can also be an important presentation. Early recognition and effective intervention may reduce morbidity and permanent disability.

SIGNIFICANCE

Electrophysiological studies might be useful in the evaluation of ICI-related neuropathy.

Polyneuropathy associated with chronic hemodialysis: Clinical and electrophysiological study

AIM

To estimate the frequency and pattern of peripheral polyneuropathy (PNP) that may affect patients maintained on hemodialysis.

PATIENTS AND METHODS

The study was carried out on 60 middle-aged male patients attending the Internal Medicine Department for maintenance hemodialysis. All were subjected to a complete neurological examination. Motor and sensory nerve conduction studies of both lower limbs (the tibial, peroneal and sural nerves) and both upper limbs (median and ulnar nerves), as well as F-wave measurements of both tibial and median nerves, were done. The patients were subdivided clinically into two groups, clinically apparent neuropathy and inapparent groups. Then they were divided according to the types of peripheral neuropathy detected by electrophysiological studies into axonal, demyelinated and mixed polyneuropathy. In addition, they were divided into motor, sensory and sensorimotor groups.

RESULTS

Polyneuropathy was found clinically presented in 33 (55%) cases, while evident by electrophysiological examination in 100% of the clinically apparent group (33 patients) and evident in 92.5% of the clinically inapparent group (27 patients). The frequency of pathologic electrophysiological parameters was significantly higher in patients with longer duration of hemodialysis. Axonal polyneuropathy is the most prevalent type in those patients.

CONCLUSION

Peripheral polyneuropathy is a common presentation in patients maintained on hemodialysis. The longer the duration of hemodialysis, the more liability to develop PNP that can be detected earlier by electrodiagnostic studies in the subclinical cases.

Steering Peripheral Neuropathy Workup

Learning to recognize the various clinical and electrodiagnostic patterns of peripheral neuropathy enables a targeted approach to etiologic investigation, and subsequently guides patient discussions of self-management, disease course, and prognosis. Moreover, as advancements in neuropathology and pharmacotherapy inform the many etiologies of polyneuropathy, it is imperative for clinicians to identify the underlying etiology to appropriately guide treatment options and prevent complications.

Diagnostic utility of distal nerve conduction studies and sural near-nerve needle recording in polyneuropathy

OBJECTIVE

The electrodiagnosis of polyneuropathy (PNP) may benefit from examination using near-nerve needle technique (NNT) and from inclusion of distal nerves. This study compared the diagnostic utility of distal nerve conduction studies (NCS) and NNT recording.

METHODS

Bilateral NNT and surface recording of the sural nerve and surface recording of the dorsal sural and medial plantar nerves were prospectively done in 91 patients with clinically suspected PNP. Distal NCS were additionally done in 37 healthy controls. Diagnostic reference standard was the final clinical diagnosis retrieved from the patients medical records after 1-4years.

RESULTS

The clinical follow-up diagnosis confirmed PNP in 68 patients. Equally high sensitivities of the dorsal sural (72%), medial plantar (75%), and sural nerve with NNT recording (77%) were seen, while the sensitivity of conventional surface recording of the sural nerve was lower (60%). Sural NCS with both NNT and surface recording and dorsal sural NCS showed high specificities (85-95%) and positive predictive values (94-98%), while a lower specificity was seen for the medial plantar nerve (68%).

CONCLUSION

NCS of distal nerves, especially the dorsal sural nerve, have high diagnostic power equalling sural NNT recording.

SIGNIFICANCE

The electrodiagnostic evaluation of patients with suspected PNP benefits from NCS of distal nerves.

Sural sensory nerve action potential: A study in healthy Indian subjects

BACKGROUND

The sural sensory nerve action potential (SNAP) is an important electrodiagnostic study for suspected peripheral neuropathies. Incorrect technique and unavailability of reference data can lead to erroneous conclusions.

OBJECTIVES

To establish reference data for sural SNAP in age-stratified healthy subjects at three sites of stimulation.

MATERIALS AND METHODS

A prospective study was conducted in 146 nerves from healthy subjects aged between 18 years and 90 years, stratified into six age groups (a = 18-30 years, b = 31-40 years, c = 41-50 years, d = 51-60 years, e = 61-70 years, and f >71 years). Sural SNAP was recorded antidromically, stimulating at three sites at distances of 14 cm, 12 cm, and 10 cm from the recording electrode. Mean - 2 standard deviation (SD) of the transformed data was used to generate reference values for amplitudes. Analysis of variance (ANOVA) test was used for inter-group and between three sites comparisons of amplitudes.

RESULTS

The lower limits of amplitude at 14 cm were 12.4 μV, 10.4 μV, 6.5 μV, 5.3 μV, 2.9 μV, and 1.9 μV; at 12 cm were 13.5 μV, 13.6 μV, 8.5 μV, 7.8 μV, 3.5 μV, and 2.8 μV; and at 10 cm were 16.3 μV, 16.3 μV, 11.1 μV, 10.0 μV, 4.8 μV, and 3.7 μV for groups a, b, c, d, e, and f, respectively. A statistically significant difference in amplitudes was noted from the three different sites of stimulation (P < 0.001). The amplitude differed significantly above the age of 60 years (P < 0.01) but not between groups e and f (P > 0.05).

CONCLUSION

This study provides reference data for sural SNAP in Indian population at three different sites of stimulation along the calf in six age groups. It also shows significant variation in amplitude from the three different sites of stimulation.

Correlation of Michigan neuropathy screening instrument, United Kingdom screening test and electrodiagnosis for early detection of diabetic peripheral neuropathy

Background

Almost half of Diabetic Peripheral Neuropathies (DPNs) are symptom-free. Methods including questionnaires and electrodiagnosis (EDx) can be fruitful for easy reach to early diagnosis, correct treatments of diabetic neuropathy, and so decline of complications for instance diabetic foot ulcer and prevention of high costs. The goal of our study was to compare effectiveness of the Michigan neuropathy screening instrument (MNSI), United Kingdom screening test (UKST) and electrophysiological evaluation in confirming diabetic peripheral neuropathy.

Methods

One hundred twenty five known diabetes mellitus male and female subjects older than 18 with or without symptoms of neuropathy comprised in this research. All of them were interviewed in terms of demographic data, lipid profile, HbA1C, duration of disease, and history of retinopathy, so examined by Michigan neuropathy screening instrument (MNSI), United Kingdom screening test (UKST), and nerve conduction studies (NCS). The collected data were analyzed by SPSS software 18.

Results

One hundred twenty five diabetic patients (70 female, 55 male) were recruited in this study with a mean age of 58.7 ± 10.2, and mean duration of diabetes was 10.17 ± 6.9 years. The mean neuropathy score of MNSI and UKST were 2.3 (1.7) and 4.16 (2.9), respectively. Each instrument detected the peripheral neuropathy in 78 (69 %) and 91 (73 %) of patients, respectively. There was a significant relationship between number of neuropathies and mean of diabetes duration and development of retinopathy in both questionnaire evaluations and NCS. By nerve conduction study, neuropathy was detected in 121 (97 %) diabetic patients were reported in order 15 (12 %) mononeuropathy (as 33 % sensory and 67 % motor neuropathy) and 106 (85 %) polyneuropathy (as 31 % motor and 69 % sensorimotor neuropathy).

Conclusions

As regards NCS is an objective, simple, and non-invasive tool and also can determine level of damage and regeneration in peripheral nerves, this study suggests electrodiagnosis as a convenient option for screening, confirming, and follow up of diabetic peripheral neuropathy.

Novel Method for Neuronal Nanosurgical Connection

Neuronal injury may cause an irreversible damage to cellular, organ and organism function. While preventing neural injury is ideal, it is not always possible. There are multiple etiologies for neuronal injury including trauma, infection, inflammation, immune mediated disorders, toxins and hereditary conditions. We describe a novel laser application, utilizing femtosecond laser pulses, in order to connect neuronal axon to neuronal soma. We were able to maintain cellular viability, and demonstrate that this technique is universal as it is applicable to multiple cell types and media.

Peripheral Neuropathy After Fecal Microbiota Transplantation for Clostridium difficile Infection: A Case Report

We present a case of a 71-year-old man with Clostridium difficile infection who underwent fecal transplantation. The patient was found to have a predominantly demyelinating sensorimotor peripheral polyneuropathy upon electrodiagnostic testing. To our knowledge, only one case of peripheral neuropathy after fecal transplantation has previously been reported. Although the exact cause of this patient's neuropathy cannot be confirmed, it has been speculated that the pathophysiology is an immune-mediated process. Given the increasing incidence of C difficile infections and the emergence of fecal transplantation as treatment, it is important to note that peripheral neuropathy is a potential adverse complication.

Reduced evoked motor and sensory potential amplitudes in obstructive sleep apnea patients

It is unknown to what extent chronic intermittent hypoxaemia in obstructive sleep apnea causes damage to the motor and sensory peripheral nerves. It was hypothesized that patients with obstructive sleep apnea would have bilaterally significantly impaired amplitudes of both motor and sensory peripheral nerve-evoked potentials of both lower and upper limbs. An observational study was conducted on 43 patients with obstructive sleep apnea confirmed by the whole-night polysomnography, and 40 controls to assess the relationship between obstructive sleep apnea and peripheral neuropathy. All obstructive sleep apnea subjects underwent standardized electroneurographic testing, with full assessment of amplitudes of evoked compound muscle action potentials, sensory neural action potentials, motor and sensory nerve conduction velocities, and distal motor and sensory latencies of the median, ulnar, peroneal and sural nerves, bilaterally. All nerve measurements were compared with reference values, as well as between the untreated patients with obstructive sleep apnea and control subjects. Averaged compound muscle action potential and sensory nerve action potential amplitudes were significantly reduced in the nerves of both upper and lower limbs in patients with obstructive sleep apnea compared with controls (P < 0.001). These results confirmed that patients with obstructive sleep apnea had significantly lower amplitudes of evoked action potentials of both motor and sensory peripheral nerves. Clinical/subclinical axonal damage exists in patients with obstructive sleep apnea to a greater extent than previously thought.

Clinical description of toxic neuropathies

Toxic neuropathy, although rare, is an important consideration in the setting of a known or suspected toxic exposure in the workplace or other environment. This chapter discusses the clinical and electrodiagnostic evaluation of peripheral neuropathies, highlighting findings that direct further workup and may point to specific toxins as etiology. The difficulty of establishing causality of a toxin in relation to peripheral neuropathy is discussed; guidelines for establishing causality are presented. Examples of common industrial toxins are listed, including their typical industrial uses and their mechanisms of action in producing neuropathy. Characteristic clinical presentations of specific toxic neuropathies are highlighted with selected case studies.

Electrodiagnostics and clinical correlates in acquired polyneuropathies

Peripheral neuropathies result from a variety of inherited and acquired pathologies. They display an assortment of clinical signs and symptoms and present with a broad range of severity. Electrodiagnosis can play a key role in the evaluation of a suspected peripheral neuropathy. A peripheral nerve disorder is first suspected on the basis of history and physical examination findings. Electrodiagnosis is then used to confirm the diagnosis and to characterize the peripheral neuropathy, providing information about its distribution, pathophysiologic process (demyelinating vs axonal), and chronicity.

Evaluation of miglustat as maintenance therapy after enzyme therapy in adults with stable type 1 Gaucher disease: a prospective, open-label non-inferiority study

Background

Previous studies have provided equivocal data on the use of miglustat as maintenance therapy in Gaucher disease type 1. We report findings from a clinical trial evaluating the effects of miglustat treatment in patients with stable type 1 Gaucher disease after enzyme therapy.

Methods

Adult type 1 Gaucher disease patients stabilized during at least 3 years of previous enzyme therapy were included in this 2-year, prospective, open-label non-inferiority study. The primary endpoint was percent change from baseline in liver volume. Secondary endpoints included changes in spleen volume, hemoglobin concentration and platelet count.

Results

Forty-two patients were enrolled (mean±SD age, 45.1±12.7 years; previous enzyme therapy duration 9.5±4.0 years). Median (range) exposure to miglustat 100 mg t.i.d. was 658 (3–765) days. Twenty-one patients discontinued treatment prematurely; 13 due to adverse events, principally gastrointestinal. The upper 95% confidence limit of mean percent change in liver volume from baseline to end of treatment was below the non-inferiority margin of 10% (–1.1%; 95%CI −6.0, 3.9%). Mean (95%CI) changes in spleen volume, hemoglobin concentration and platelet count were 102 (24,180) mL, –0.95 (−1.38, –0.53) g/dL and −44.1 (–57.6, –30.7) ×10⁹/L, respectively.

Conclusions

The primary efficacy endpoint was met; overall there was no change in liver volume during 24 months of miglustat therapy. Several patients showed a gradual deterioration in some disease manifestations, suggesting that miglustat could maintain clinical stability, but not in all patients. Miglustat demonstrated a predictable profile of safety and tolerability that was consistent with that reported in previous clinical trials and experience in clinical practice.

Trial registration

Clinicaltrials.gov identifier NCT00319046

Neuromuscular medicine competency in physical medicine and rehabilitation residents: a method of development and assessment

This project endeavored to create an educational module including methodology to instruct physical medicine and rehabilitation residents in the evaluation and appropriate treatment of patients with neuromuscular disorders. It further sought to verify acquired competencies in neuromuscular rehabilitation through objective evaluation methodology. An American Association of Neuromuscular and Electrodiagnostic Medicine board-certified physician with 10 yrs of clinical experience in neuromuscular and general rehabilitation trained 19 residents using a standardized competency-based module. The residents were trained through clinical training, lectures, and review of self-assessment examination concepts from the American Academy of Physical Medicine & Rehabilitation syllabus provided in the Archives of Physical Medicine and Rehabilitation. After delivery of the educational module, knowledge acquisition and skill proficiency were measured in (1) completion of neuromuscular history and physical examination satisfactorily, (2) diagnosis and ability to design a patient care management plan via chart stimulated recall examinations, (3) physician-patient interaction via patient surveys, (4) physician-staff interaction via 360-degree global ratings, and (5) ability to write a comprehensive patient care report and to document a patient care management plan in accordance with Medicare guidelines via written patient reports. Assessment tools developed for this program address the basic competencies outlined by the Accreditation Council for Graduate Medical Education. To test the success of the standardized educational module, data were collected on an ongoing basis. The objective measures compared resident self-assessment examination scores in neuromuscular rehabilitation before and after the institution of the comprehensive neuromuscular competency module in the residency program. Nineteen (100%) of 19 residents successfully demonstrated proficiency in every segment of the evaluation module by the end of the postgraduate year 2 inpatient neuromuscular rehabilitation rotation. Furthermore, the residents' proficiency, as demonstrated by the evaluation after the implementation of the standardized educational module, positively correlated with an increase in the residents' self-assessment examination scores in neuromuscular rehabilitation compared with the residents' scores before the educational module implementation throughout all 3 yrs of training. Resident proficiency in the skills and knowledge pertaining to neuromuscular rehabilitation were objectively verified after completion of the standardized educational module. Validation of the assessment tool is evidenced by the collected data correlating with significantly improved self-assessment examination scores, as outlined in the "RESULTS" section. In addition, the clinical development tool was validated by the residents being individually observed performing history and physical examinations and being deemed competent by the American Association of Neuromuscular and Electrodiagnostic Medicine board-certified physical medicine and rehabilitation physician. The standardized educational module and evaluation methodology provide a potential framework for the definition of baseline competency in the clinical training area of neuromuscular rehabilitation.

An electrodiagnostic approach to the evaluation of peripheral neuropathies

Electrodiagnosis, which includes nerve conduction and needle electromyographic studies, is an essential element in the evaluation of peripheral neuropathies. A systematic approach to the electrodiagnostic evaluation aids in clarifying the distribution and extent of involvement, type of nerve damage, and time course. When these data are combined with clinical information, a full characterization of the neuropathy is possible leading to a sound differential diagnosis and selection of rational tests to order. This article will discuss the relevant anatomy and physiology of peripheral nerves and the principles of nerve conduction and needle electromyographic studies, including how they help distinguish between prototypic examples of primary axonal and demyelinating neuropathies, how to plan electrodiagnostic studies, and how to interpret data from outside studies.

A rational diagnostic approach to peripheral neuropathy

Peripheral neuropathies are among the most common disorders encountered by neuromuscular specialists and their evaluation can be challenging. The first part of this review outlined an algorithm based on anatomy, pathology, electrodiagnosis, and clinical localization that leads to a full characterization of the peripheral neuropathy. In the second part, we apply this approach, emphasizing recognition of atypical features and formulation of a focused differential diagnosis, thus reducing the number of uninformative tests. We review evidence supporting the routine use of commonly ordered laboratory tests and recommend a panel of tests that should be performed in patients with symmetric, distal, sensory-predominant peripheral neuropathy. Using this diagnostic approach, a diagnosis could be made in two thirds of patients.

Electrodiagnosis of peripheral neuropathy

Electrodiagnostic studies are an important component of the evaluation of patients with suspected peripheral nerve disorders. The pattern of findings and the features that are seen on the motor and sensory nerve conduction studies and needle electromyography can help to identify the type of neuropathy, define the underlying pathophysiology (axonal or demyelinating), and ultimately help to narrow the list of possible causes. This article reviews the electrodiagnostic approach to and interpretation of findings in patients with peripheral neuropathies.

Acupuncture for chemotherapy-induced peripheral neuropathy (CIPN): a pilot study using neurography

OBJECTIVES

Chemotherapy-induced peripheral neuropathy (CIPN) can produce severe neurological deficits and neuropathic pain and is a potential reason for terminating or suspending chemotherapy treatments. Specific and effective curative treatments are lacking.

METHODS

A pilot study was conducted to evaluate the therapeutic effect of acupuncture on CIPN as measured by changes in nerve conduction studies (NCS) in six patients treated with acupuncture for 10 weeks in addition to best medical care and five control patients who received the best medical care but no specific treatment for CIPN.

RESULTS

In five of the six patients treated with acupuncture, NCS improved after treatment. In the control group, three of five patients did not show any difference in NCS, one patient improved and one showed impaired NCS.

CONCLUSION

The data suggest that acupuncture has a positive effect on CIPN. The encouraging results of this pilot study justify a randomised controlled trial of acupuncture in CIPN on the basis of NCS.

Electrophysiologic changes in patients with untreated primary hypothyroidism

Thyroid diseases may cause signs and symptoms of neuromuscular dysfunction. Hypothyroidism has been associated with the clinical features of proximal muscle weakness, mononeuropathy, and sensorimotor polyneuropathy. This study aimed at evaluating the electrophysiologic findings in patients with untreated spontaneous hypothyroidism and comparing them with a healthy control group. In a case-control cross-sectional study, 40 patients with definite diagnosis of clinical hypothyroidism and 40 healthy control subjects were evaluated by electromyography and nerve conduction studies in the specialized clinic of the Tabriz University of Medical Sciences during an 18-month period. Seven male and 33 female patients with a mean age of 39.5 ± 11.8 years were enrolled. In this group, there were 12 cases (30%) with clinical muscle weakness, with severity of approximately 4/5, 18 cases (45%) with decreased or absent deep tendon reflexes, 6 cases (15%) with neuropathy, including 4 sensory and 2 sensorimotor, of which 5 cases were mild and 1 case was moderate, 3 cases (7.5%) with myopathy, and 13 cases (32.5%) with carpal tunnel syndrome, which was mild in 7, moderate in 10, and severe in 2 hands. Patients with neuropathy were significantly older than those without neuropathy (P = 0.001). There was no significant relation between gender, duration of the disease, serum TSH level, and the presence of clinical muscle weakness with the occurrence of neuropathy or myopathy. Female gender, increasing age, duration of the disease, and the frequency of clinical weakness were, however, significantly related to the presence of carpal tunnel syndrome (P < 0.05). In conclusion, in patients with untreated primary hypothyroidism, majority had the carpal tunnel syndrome. Mild neuropathy mainly of sensory type and myopathy were uncommon and rare findings, respectively. Early treatment would hinder the progression of mentioned abnormalities and minimize their occurrence.

Peripheral neuropathy in adult type 1 Gaucher disease: a 2-year prospective observational study

Type 1 Gaucher disease is currently categorized as non-neuronopathic, although recent studies suggest peripheral neurological manifestations. We report prevalence and incidence data for peripheral neuropathy and associated conditions from a multinational, prospective, longitudinal, observational cohort study in patients with type 1 Gaucher disease, either untreated or receiving enzyme replacement therapy. The primary outcome parameters were the prevalence and incidence of polyneuropathy, evaluated by standardized assessments of neurological symptoms and signs, and electrophysiological studies. All diagnoses of polyneuropathy were adjudicated centrally. Secondary outcome parameters included the prevalence and incidence of mononeuropathy, other neurological or electrophysiological abnormalities not fulfilling the criteria for a mono- or polyneuropathy and general type 1 Gaucher disease symptoms. Furthermore, a literature search was performed to identify all studies reporting on prevalence and incidence of polyneuropathy in the general population. One hundred and three patients were enrolled [median (range) age: 42 (18-75) years; disease duration: 15 (0-56) years; 52% female]; 14 (13.6%) were untreated and 89 (86.4%) were on enzyme replacement therapy. At baseline, 11 patients [10.7%; 95% confidence interval (CI): 5.9-18.3] were diagnosed with sensory motor axonal polyneuropathy. Two (1.9%; 95% CI: 0.1-7.2) had a mononeuropathy of the ulnar nerve. The 2-year follow-up period revealed another six cases of polyneuropathy (2.9 per 100 person-years; 95% CI: 1.2-6.3). Patients with polyneuropathy were older than those without (P<0.001). Conditions possibly associated with polyneuropathy were identified in four patients only, being monoclonal gammopathy, vitamin B(1) deficiency, folic acid deficiency, type 2 diabetes mellitus, renal insufficiency, alcohol abuse and exposure to toxins related to profession. The 11 cases of polyneuropathy found at baseline were confirmed during follow-up. According to the literature, the prevalence of polyneuropathy in the general population was estimated between 0.09 and 1.3% and the incidence was estimated between 0.0046 and 0.015 per 100 person-years. Thus, we conclude that the prevalence and incidence of polyneuropathy in patients with type 1 Gaucher disease is increased compared with the general population.

Necrotizing lymphocytic vasculitis limited to the peripheral nerves: report of six cases and review

Background. The systemic vasculitides are syndromes characterized by inflammation and injury (necrosis or thrombosis) of blood vessels, resulting in clinical manifestations according to the affected vascular bed, but not classically in stocking-glove neuropathy. Objective. To describe a form of primary vasculitis affecting strictly peripheral nerves manifesting as stocking-glove neuropathy. Methods. Case series of 110 patients seen in three centers in Bogotá who presented with symptoms and signs of polyneuropathy and/or were identified with vasculitis affecting only the peripheral nerves, and who underwent sural nerve biopsy. Results. Six patients had a vasculitis affecting only the peripheral nerves diagnosed on sural nerve biopsy which demonstrated a mixed infiltrate of monocytes/macrophages and lymphocytes especially in the small epineurial blood vessels. Over time, all had worsening of symptoms, with grip weakness and motor deficits in the hand and feet. Serologies and acute phase reactants were normal in all patients. Treatment response to immunosuppression was satisfactory in 5 patients; 1 patient had progressive neurologic damage. Conclusions. There is a distinct form of primary vasculitis of the peripheral nervous system characterized by distal sensory polyneuropathy with stocking-glove distribution with good prognosis, few and minor relapses and good response to treatment even after delayed diagnosis.

Clinical features and electrodiagnosis of diabetic peripheral neuropathy in the dysvascular patient

Diabetic peripheral neuropathy (DPN) is a common disorder that can lead to limb loss and death. Up to 50% of DPN patients can be asymptomatic. This fact contributes to making DPN the leading cause of lower limb amputation. The degree of heterogeneity in the clinical manifestations of DPN makes diagnosing this condition difficult. This article reviews the characteristics, diagnosis, electrodiagnosis, classification, pathogenesis, and treatment of DPN.

The Sensitivity of Clinical Diagnostic Methods in the Diagnosis of Diabetic Neuropathy

This study assessed the sensitivity of various methods for the clinical diagnosis of diabetic peripheral neuropathy. A total of 147 randomly selected patients with diabetes mellitus and 65 age- and sex-matched healthy controls were evaluated by various clinical (the neuropathy symptom score [NSS], the neuropathy disability score [NDS], vibration perception thresholds [VPTs], Tinel's sign and Phalen's sign), laboratory (fasting plasma glucose and glycosylated haemoglobin levels) and electrophysiological (nerve conduction studies, H-reflex and F-wave measurements) methods. In the patient group, 8.2% had an abnormal NSS, 28.5% had a positive Phalen's sign, 32.6% had a positive Tinel's sign, 42.8% had an abnormal VPT and 57.1% had an abnormal NDS. Significant correlations were found between electrophysiologically confirmed neuropathy and the two provocation tests and abnormal VPTs. In conclusion, assessment with a complete neurological examination and standard electrophysiological tests is very important for the diagnosis of diabetic peripheral neuropathy and the prevention of morbidity in patients with or without symptoms.

Membrane property abnormalities in simulated cases of mild systematic and severe focal demyelinating neuropathies

The investigation of multiple nerve membrane properties by mathematical models has become a new tool to study peripheral neuropathies. In demyelinating neuropathies, the membrane properties such as potentials (intracellular, extracellular, electrotonic) and indices of axonal excitability (strength-duration time constants, rheobases and recovery cycles) can now be measured at the peripheral nerves. This study provides numerical simulations of the membrane properties of human motor nerve fibre in cases of internodal, paranodal and simultaneously of paranodal internodal demyelinations, each of them mild systematic or severe focal. The computations use our previous multi-layered model of the fibre. The results show that the abnormally greater increase of the hyperpolarizing electrotonus, shorter strength-duration time constants and greater axonal superexcitability in the recovery cycles are the characteristic features of the mildly systematically demyelinated cases. The small decrease of the polarizing electrotonic responses in the demyelinated zone in turn leads to a compensatory small increase of these responses outside the demyelinated zone of all severely focally demyelinated cases. The paper summarizes the insights gained from these modeling studies on the membrane property abnormalities underlying the variation in clinical symptoms of demyelination in Charcot-Marie-Tooth disease type 1A, chronic inflammatory demyelinating polyneuropathy, Guillain-Barré syndrome and multifocal motor neuropathy. The model used provides an objective study of the mechanisms of these diseases which up till now have not been sufficiently well understood, because quite different assumptions have been given in the literature for the interpretation of the membrane property abnormalities obtained in hereditary, chronic and acquired demyelinating neuropathies.

Acupuncture treatment improves nerve conduction in peripheral neuropathy

The etiology of peripheral neuropathy (PN) often remains elusive resulting in a lack of objective therapeutic strategies. We conducted a pilot study to evaluate the therapeutic effect of acupuncture on PN as measured by changes in nerve conduction and assessment of subjective symptoms. One hundred and ninety-two consecutive patients with PN as diagnosed by nerve conduction studies (NCS) were evaluated over a period of 1 year. Of 47 patients who met the criteria for PN of undefined etiology, 21 patients received acupuncture therapy according to classical Chinese Medicine as defined by the Heidelberg Model, while 26 patients received the best medical care but no specific treatment for PN. Sixteen patients (76%) in the acupuncture group improved symptomatically and objectively as measured by NCS, while only four patients in the control group (15%) did so. Three patients in the acupuncture group (14%) showed no change and two patients an aggravation (10%), whereas in the control group seven showed no change (27%) and 15 an aggravation (58%). Importantly, subjective improvement was fully correlated with improvement in NCS in both groups. The data suggest that there is a positive effect of acupuncture on PN of undefined etiology as measured by objective parameters.

The Electrodiagnosis of Neuropathy: Basic Principles and Common Pitfalls

Electrodiagnostic studies are a critical tool for the identification and study of peripheral neuropathy, enabling definition of the pathophysiologic type of nerve injury, its distribution, severity, and the degree of motor or sensory nerve involvement. These data help to differentiate the varieties of neuropathy from other neuromuscular diseases. Nerve conduction studies and electromyography, although widely performed, are complex techniques and are subject to a wide range of artifacts, which can result in missed or erroneous diagnoses. Without proper education, training, and experience in neuromuscular disease and the techniques of electrodiagnosis and careful attention to potential sources of error, the critical information needed to properly diagnose and treat patients with neuropathy is unreliable and may lead to wasted resources and patient injury.

Polyneuropathy in hemodialysis patients: The most sensitive electrophysiological parameters and dialysis adequacy

BACKGROUND

Polyneuropathy (PNP) is a common complication in hemodialysis (HD) patients. Electrophysiological parameters are quantitative indices of its severity. The aim of our study was to find the prevalence of pathologic electrophysiological parameters, to assess their prevalence in relation to duration of HD treatment and age, to establish which parameters are the most sensitive in demonstrating PNP and to find an association between them and HD adequacy.

PATIENTS AND METHODS

We included 84 (50 men, 34 women) HD patients (average age 47.32 years; average dialysis duration 62.56 months) and divided them into three groups according to the duration of HD treatment. Each group was further divided into two subgroups according to age. We included electrophysiological parameters for evaluation of motor and sensory nerve functions (Medelec Sapphire Premiere device). HD adequacy was measured with urea kinetic modeling (Kt/V).

RESULTS

PNP was found in 77 (91.6%) HD patients and was more common in men (P < 0.016). The association between the number of pathologic electrophysiological parameters and age (P < 0.0001), duration of HD treatment (P < 0.009) and HD adequacy (P < 0.0001) was statistically significant. The most sensitive electrophysiological parameter was the latency of the F wave (pathologic values of F wave latency in the lower limbs in 86% patients and in the upper limbs in 49%). Sensory conduction velocities and the amplitudes of the orthodromic sensory action potentials and the M wave were also sensitive parameters. The F wave latency of different nerves was associated with dialysis adequacy.

CONCLUSIONS

PNP is frequent in HD patients and is associated with age and duration of dialysis treatment. The most sensitive electrophysiological parameter of PNP is F wave latency, which may also be used as a parameter of dialysis adequacy.

Pathophysiology inferred from electrodiagnostic nerve tests and classification of polyneuropathies. Suggested guidelines

OBJECTIVE

To present criteria for pathophysiological interpretation of motor and sensory nerve conduction studies and for pathophysiological classification of polyneuropathies suggested by a group of European neurophysiologists.

METHODS

Since 1992 seven neurophysiologists from six European countries have collected random samples of their electrodiagnostic examinations for peer review medical audit in the ESTEEM (European Standardized Telematic tool to Evaluate Electrodiagnostic Methods) project. Based on existing criteria in the literature, the experience with a patient material of 572 peer reviewed electrodiagnostic examinations, and productive discussions between the physicians at workshops, the collaboration has produced a set of criteria now routinely used at the centres involved in the project.

RESULTS

The first part of the paper considers pathophysiology of individual nerve segments. For interpretation of motor and sensory nerve conduction studies, figures showing change in amplitude versus change in conduction velocity/distal latency and change in F-wave frequency versus change in F-wave latency are presented. The suggested boundaries delimit areas corresponding to normal, axonal, demyelinated, or neuropathic nerve segments. Criteria for motor conduction block in upper and lower extremities are schematically depicted using the parameters CMAP amplitude and CMAP duration. The second part of the paper suggests criteria for classification of polyneuropathies into axonal, demyelinating, or mixed using the above-mentioned criteria.

CONCLUSIONS

The suggested criteria are developed during many years of collaboration of different centres and may be useful for standardization in clinical neurophysiology.

SIGNIFICANCE

Consistent interpretation of nerve conduction studies is an important step in optimising diagnosis and treatment of nerve disorders.

Differences in potentials and excitability properties in simulated cases of demyelinating neuropathies. Part II. Paranodal demyelination

OBJECTIVE

The purpose of the present investigation is to study the potentials and axonal excitability properties in progressively greater degrees of uniform paranodal demyelination of human motor nerve fibres.

METHODS

Using our previous double cable model of human motor nerve fibre, 3 paranodally systematically demyelinated cases (termed as PSD1, PSD2 and PSD3) are simulated by an uniform paranodal resistance reduction (20, 50 and 77%) along the fibre length.

RESULTS

Considerably reduced amplitudes, prolonged durations and slowed conduction velocities are obtained for the intracellular potentials of the PSD2 and PSD3 cases. In contrast, the electrotonic potentials show abnormally greater increase in the early part of the hyperpolarizing responses. The extracellular potentials indicate increased polyphasia in the PSD3 case. The strength-duration time constants are shorter and the rheobases higher in the demyelinated cases. In the recovery cycles, the demyelinated cases have less refractoriness, greater supernormality and less late subnormality than the normal case.

CONCLUSIONS

The reduction of the paranodal seal resistance has significant effects on the potentials and axonal excitability properties of the simulated demyelinated human motor fibres. The obtained abnormalities in the potentials and excitability properties can be observed in vivo in patients with chronic inflammatory demyelinating polyneuropathy.

SIGNIFICANCE

The study provides important information about the pathology of human demyelinating neuropathies.