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Tiwana HK, Lawson VH. Green shoots but deep roots: New antibodies in small fiber neuropathy. Muscle Nerve 2020; 61:433-435. [DOI: 10.1002/mus.26818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 01/24/2020] [Accepted: 01/26/2020] [Indexed: 11/07/2022]
Affiliation(s)
- Harmanpreet K. Tiwana
- Department of Neurology, Dartmouth Hitchcock Medical CenterGeisel School of Medicine at Dartmouth Lebanon, New Hamshire
| | - Victoria H. Lawson
- Department of Neurology, Dartmouth Hitchcock Medical CenterGeisel School of Medicine at Dartmouth Lebanon, New Hamshire
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Lawson VH, Baets J. Tempering our metrics. Neurology 2020; 94:373-374. [DOI: 10.1212/wnl.0000000000009028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Robbins NM, Mozaffar T, Mammen AL, Liewluck T, Guidon A, Lawson VH. Reader response: Pearls & Oy-sters: Pembrolizumab-induced myasthenia gravis. Neurology 2019; 93:183-184. [PMID: 31332091 DOI: 10.1212/wnl.0000000000007845] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Prior DE, Stommel E, Lawson VH, Kandel J, Robbins NM. Distribution of serum creatine kinase levels in amyotrophic lateral sclerosis. Muscle Nerve 2019; 61:E16-E18. [PMID: 31811651 DOI: 10.1002/mus.26776] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 12/01/2019] [Accepted: 12/03/2019] [Indexed: 12/12/2022]
Affiliation(s)
- Devin E Prior
- Dartmouth-Hitchcock Medical Center, Department of Neurology, Lebanon, New Hampshire
| | - Elijah Stommel
- Dartmouth-Hitchcock Medical Center, Department of Neurology, Lebanon, New Hampshire
| | - Victoria H Lawson
- Dartmouth-Hitchcock Medical Center, Department of Neurology, Lebanon, New Hampshire
| | - Jason Kandel
- Dartmouth-Hitchcock Medical Center, Department of Neurology, Lebanon, New Hampshire
| | - Nathaniel M Robbins
- Dartmouth-Hitchcock Medical Center, Department of Neurology, Lebanon, New Hampshire
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Caress JB, Lewis JA, Pinyan CW, Lawson VH. A charcot-marie-tooth type 1B kindred associated with hemifacial spasm and trigeminal neuralgia. Muscle Nerve 2019; 60:62-66. [PMID: 30920665 DOI: 10.1002/mus.26478] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/24/2019] [Indexed: 01/30/2023]
Abstract
INTRODUCTION Charcot-Marie-Tooth (CMT) phenotypes can be distinguished by electrophysiology and genetic analysis but few can be identified by their clinical characteristics. Distinctive phenotypes are useful in identifying affected individuals and providing additional clues about the mechanism of the neuropathy. Cranial neuropathies are uncommon features of CMT, and few reports of familial hemifacial spasm (HFS) and trigeminal neuralgia (TN) have been published. METHODS Sixty-three members of a large CMT 1B kindred were assessed for signs of peripheral neuropathy and cranial neuropathies then tested for the G163R mutation in the myelin protein zero (MPZ) gene. RESULTS Of 27 individuals with the G163R mutation in MPZ, 10 had HFS or TN. Co-existing HFS and TN were found in 3 of these and 4 had bilateral HFS or TN. CONCLUSIONS This kindred exhibits a distinct CMT phenotype characterized by the development of HFS or TN decades after clinical signs of hereditary neuropathy are manifest. Muscle Nerve, 2019.
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Affiliation(s)
- James B Caress
- Department of Neurology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina 27157, USA
| | | | - Clark W Pinyan
- Wake Forest School of Medicine, Winston-Salem, North Carolina, USA
| | - Victoria H Lawson
- Dartmouth Hitchcock Medical Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA
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Lawson VH, Grewal J, Hackshaw KV, Mongiovi PC, Stino AM. Fibromyalgia syndrome and small fiber, early or mild sensory polyneuropathy. Muscle Nerve 2018; 58:625-630. [PMID: 29572887 PMCID: PMC6283273 DOI: 10.1002/mus.26131] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/17/2018] [Indexed: 01/30/2023]
Abstract
INTRODUCTION Pain mechanisms in fibromyalgia syndrome (FMS) are not clearly understood. Growing evidence appears to suggest a role for small fiber polyneuropathy (SFPN) in some FMS patients, as measured by epidermal nerve fiber density (ENFD). We aimed to better characterize and distinguish the subset of patients with both fibromyalgia and small fiber, early or mild sensory polyneuropathy (FM-SFSPN). METHODS 155 FMS patients with neuropathic symptoms completed a Short Form McGill Questionnaire and visual analog scale in addition to having skin biopsies, nerve conduction studies (NCS), and serologic testing. RESULTS Sural and medial plantar (MP) response amplitudes correlated with ENFD, with markers of metabolic syndrome being more prevalent in this subset of patients. Pain intensity and quality did not distinguish patients. DISCUSSION The FM-SFSPN subset of patients may be identified through sural and MP sensory NCS and/or skin biopsy but cannot be identified by pain features and intensity. Muscle Nerve 58: 625-630, 2018.
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Affiliation(s)
- Victoria H Lawson
- Dartmouth-Hitchcock Medical Center Department of Neurology, One Medical Center Drive, Lebanon, New Hampshire, 03766, USA
| | - Jessie Grewal
- Ohio State University Medical Center Department of Neurology, Columbus, Ohio, USA
| | - Kevin V Hackshaw
- Ohio State University Medical Center Department of Internal Medicine, Division of Rheumatology, Columbus, Ohio, USA
| | - Phillip C Mongiovi
- University of Rochester Department of Neurology, Rochester, New York, USA
| | - Amro M Stino
- Ohio State University Medical Center Department of Neurology, Columbus, Ohio, USA
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Hopkin RJ, Jefferies JL, Laney DA, Lawson VH, Mauer M, Taylor MR, Wilcox WR. The management and treatment of children with Fabry disease: A United States-based perspective. Mol Genet Metab 2016; 117:104-13. [PMID: 26546059 DOI: 10.1016/j.ymgme.2015.10.007] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 10/21/2015] [Accepted: 10/21/2015] [Indexed: 01/08/2023]
Abstract
Fabry disease is an inherited X-linked disorder that presents during childhood in male and female patients. Young patients may initially experience pain, hypohidrosis, and gastrointestinal symptoms. Other manifestations of Fabry disease, such as renal and cardiac disease, manifest later in adolescence or adulthood. In the pediatric population, renal damage is typically subclinical and identifiable only through biopsy. Specialists from the United States with expertise in Fabry disease convened during 2013-2014 in order to develop these consensus guidelines about the management and treatment of children with Fabry disease. The presence of symptoms in boys and girls of any age is an indication to begin therapy. Early treatment before the onset of potentially irreversible vital organ pathology is ideal. Asymptomatic children with Fabry mutations should be followed closely for the development of renal, cardiac, neurological, or gastrointestinal signs, symptoms, or laboratory changes, which would warrant treatment initiation. A comprehensive care plan should be implemented by the treating physicians to guide the management of children with Fabry disease.
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Affiliation(s)
- Robert J Hopkin
- Cincinnati Children's Hospital Medical Center Division of Human Genetics, University of Cincinnati College of Medicine, Department of Pediatrics, 3333 Burnet Avenue, Cincinnati, OH 45229-3026, USA.
| | - John L Jefferies
- Cincinnati Children's Hospital Medical Center Division of Human Genetics, University of Cincinnati College of Medicine, Department of Pediatrics, 3333 Burnet Avenue, Cincinnati, OH 45229-3026, USA.
| | - Dawn A Laney
- Division of Medical Genetics, Department of Human Genetics, Emory University School of Medicine, 2165 North Decatur Road, Decatur, GA 30033, USA.
| | - Victoria H Lawson
- Ohio State University, 395 W. 12th Ave, Columbus, OH 43210, USA; Dartmouth College, Dartmouth Hitchcock Medical Center, Lebanon, Geisel School of Medicine at Dartmouth, One Medical Center Drive, Lebanon, NH 03756-0001, USA.
| | - Michael Mauer
- University of Minnesota, 100 Church St. S.E., Minneapolis, MN 55455, USA.
| | - Matthew R Taylor
- University of Colorado, 13001 E 17th Pl., Aurora, CO 80045, USA.
| | - William R Wilcox
- Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Whitehead 305H, Atlanta, GA 30322, USA.
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Abstract
INTRODUCTION Small-amplitude, short-duration motor unit action potentials are non-specific findings seen in myopathies and neuromuscular junction (NMJ) disorders. NMJ studies (repetitive nerve stimulation and single-fiber electromyography) can determine if such findings are related to NMJ abnormalities but are not considered routinely in atypical cases. METHODS Medical records of 338 patients with confirmed NMJ disorders were reviewed to identify cases with a clinical or electrodiagnostic impression of myopathy during initial evaluation. A history of muscle biopsy with findings that did not support a myopathic process was required for inclusion. RESULTS Four patients met the inclusion criteria. NMJ studies were abnormal in all cases. One patient had elevated acetylcholine receptor antibodies. Three patients were antibody negative: 2 demonstrated immunotherapy responsiveness, and 1 had a Rapsyn mutation. CONCLUSIONS NMJ disorders may mimic myopathies, and NMJ studies should be performed to clarify so-called "myopathic" electromyographic findings to avoid unnecessary testing and delayed diagnosis.
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Abstract
Multifocal motor neuropathy (MMN) is an uncommon, purely motor neuropathy associated with asymmetric deficits with predilection for upper limb involvement. Even in the early descriptions of MMN, the associations of anti-GM1 antibodies and robust response to immunomodulatory treatment were recognized. These features highlight the likelihood of an underlying autoimmune etiology of MMN. The clinical presentation of MMN can closely mimic several neurological conditions including those with more malignant prognoses such as motor neuron disease. Therefore early and rapid recognition of MMN is critical. Serological evidence of anti GM-1 antibodies and electrodiagnostic findings of conduction block are helpful diagnostic clues for MMN. Importantly, these diagnostic features are not universally present, and patients lacking these characteristic findings can demonstrate similar robust response to immunodulatory treatment. In the current review, recent research in the areas of diagnosis, pathogenesis, and treatment of MMN and needs for the future are discussed. The characteristic findings of MMN and treatment implications are reviewed and contrasted with other mimicking disorders.
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Affiliation(s)
- Victoria H Lawson
- Division of Neuromuscular Disorders, Department of Neurology, Wexner Medical Center at The Ohio State University, Columbus, Ohio, USA
| | - W David Arnold
- Division of Neuromuscular Disorders, Department of Neurology, Wexner Medical Center at The Ohio State University, Columbus, Ohio, USA ; Department of Physical Medicine and Rehabilitation, Wexner Medical Center at The Ohio State University, Columbus, Ohio, USA
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Fonkem E, Skordilis MA, Binkley EM, Raymer DS, Epstein A, Arnold WD, Kissel JT, Lawson VH. Ethambutol toxicity exacerbating the phenotype of CMT2A2. Muscle Nerve 2013; 48:140-4. [PMID: 23733358 DOI: 10.1002/mus.23766] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/20/2012] [Indexed: 11/07/2022]
Abstract
INTRODUCTION CMT2A2 is associated with mutations in the mitofusin 2 gene, which encodes a protein involved in mitochondrial fusion. Ethambutol is an antimycobacterial agent associated with toxic optic neuropathies. Ethambutol-induced optic neuropathy occurs in patients with mutations in a related fusion gene, OPA1, which is responsible for autosomal dominant optic atrophy. METHODS We describe a patient with CMT2A2 (MFN2 mutation: T669G, F223L) who developed accelerated weakness, vocal cord paralysis, and optic atrophy after receiving ethambutol. RESULTS Deterioration began within months of initiating ethambutol therapy. After discontinuation of ethambutol, neurologic deterioration stabilized with subsequent improvement in visual fields. CONCLUSIONS CMT2A2 is part of a group of genetic disorders which share an association with the process of mitochondrial fusion. This case shows that patients with CMT2A2, and possibly other mitochondrial fusion defects, may be uniquely susceptible to ethambutol-induced neurotoxicity. This has implications regarding the underlying pathophysiology of mitochondrial fusion defects.
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Affiliation(s)
- Ekokobe Fonkem
- Harvard Medical School, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA
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Kolb SJ, Snyder PJ, Poi EJ, Renard EA, Bartlett A, Gu S, Sutton S, Arnold WD, Freimer ML, Lawson VH, Kissel JT, Prior TW. Mutant small heat shock protein B3 causes motor neuropathy: utility of a candidate gene approach. Neurology 2010; 74:502-6. [PMID: 20142617 DOI: 10.1212/wnl.0b013e3181cef84a] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVE Idiopathic peripheral neuropathy is common and likely due to genetic factors that are not detectable using standard linkage analysis. We initiated a candidate gene approach to study the genetic influence of the small heat shock protein (sHSP) gene family on an axonal motor and motor/sensory neuropathy patient population. METHODS The promoter region and all exonic and intronic sequences of the 10 sHSP genes (HSPB1-HSPB10) were screened in a cohort of presumed nonacquired, axonal motor and motor/sensory neuropathy patients seen at the Ohio State University Neuromuscular Clinic. RESULTS A missense mutation in the gene encoding small heat shock protein B3 (HSPB3, also called HSP27, protein 3) was discovered in 2 siblings with an asymmetric axonal motor neuropathy. Electrophysiologic studies revealed an axonal, predominantly motor, length-dependent neuropathy. The mutation, HSPB3(R7S), is located in the N-terminal domain and involves the loss of a conserved arginine. CONCLUSIONS The discovery of an HSPB3 mutation associated with an axonal motor neuropathy using a candidate gene approach supports the notion that the small heat shock protein gene family coordinately plays an important role in motor neuron viability.
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Affiliation(s)
- S J Kolb
- Department of Neurology, The Ohio State University Medical Center, Hamilton Hall, Room 337B, 1645 Neil Ave., Columbus, OH 43210-1228, USA.
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Abstract
Ultrasound is emerging as a useful tool for evaluation of neuromuscular conditions, because it can provide high-resolution anatomic information to complement electrodiagnostic data. There have been few studies in which ultrasound was used to assess the peripheral nerves of individuals with Charcot-Marie-Tooth (CMT) disease and none involving CMT type 1B. In this study we compared nerve cross-sectional area in individuals from a single large family with CMT 1B with normal, healthy controls. We also assessed for cranial nerve enlargement in those with CMT 1B with cranial neuropathies compared to those with CMT 1B without cranial neuropathies. Individuals with CMT 1B have significantly larger median and vagus nerves than healthy controls, but no difference was seen in cranial nerve size between those with versus those without cranial neuropathies. This is the first study to characterize the ultrasonographic findings in the peripheral nerves of individuals with CMT 1B.
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Affiliation(s)
- Michael S Cartwright
- Department of Neurology, Wake Forest University School of Medicine, Medical Center Boulevard, Meads Hall, Winston-Salem, North Carolina 27157, USA.
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Bennett CL, Lawson VH, Brickell KL, Isaacs K, Seltzer W, Lipe HP, Weiss MD, Carter GT, Flanigan KM, Chance PF, Bird TD. Late-onset hereditary axonal neuropathies. Neurology 2008; 71:14-20. [PMID: 18495953 DOI: 10.1212/01.wnl.0000304048.94023.73] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Hereditary motor-sensory neuropathy or the Charcot-Marie-Tooth syndrome is known to represent considerable genetic heterogeneity. Onset is usually in childhood, adolescence, or young adulthood. The objective of this study was to define late-onset forms of the disorder. METHODS A clinical and genetic study of families with uniformly late onset of peripheral neuropathy was performed in a university neurogenetics setting. RESULTS Six families were identified with consistently late onset of a primarily axonal neuropathy. Median age at symptom onset was 57 years (range 35-85 years) of a mixed motor and sensory neuropathy with electrophysiologic characteristics of an axonal rather than demyelinating condition. There was a possible association with deafness. Two families showed autosomal dominant inheritance whereas four families had only one affected generation with an excess of males. An extensive mutation screen of nine genes known to cause Charcot-Marie-Tooth was negative. CONCLUSIONS There are late-onset forms of hereditary axonal neuropathies. The genetic causes remain unknown and genetic heterogeneity within this entity is likely.
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Affiliation(s)
- C L Bennett
- Department of Pediatrics, University of Washington Medical School, Children's Hospital and Regional Medical Center, Seattle, WA, USA
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Amiott EA, Lott P, Soto J, Kang PB, McCaffery JM, DiMauro S, Abel ED, Flanigan KM, Lawson VH, Shaw JM. Mitochondrial fusion and function in Charcot-Marie-Tooth type 2A patient fibroblasts with mitofusin 2 mutations. Exp Neurol 2008; 211:115-27. [PMID: 18316077 PMCID: PMC2409111 DOI: 10.1016/j.expneurol.2008.01.010] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2007] [Revised: 01/06/2008] [Accepted: 01/11/2008] [Indexed: 01/10/2023]
Abstract
Charcot-Marie-Tooth Type 2A is a dominantly inherited peripheral neuropathy characterized by axonal degeneration of sensory and motor nerves. The disease is caused by mutations in the mitochondrial fusion gene MFN2. Mfn2 is an integral outer mitochondrial membrane protein composed of a large GTPase domain and two heptad repeat (HR) domains that face the cytoplasm. Mitochondrial membrane fusion and division are balanced processes that are necessary to maintain tubular mitochondrial morphology, respiratory function, and uniform distribution of the organelle throughout the cell. We have utilized primary fibroblasts from CMT2A patients to survey mitochondrial phenotypes associated with heterozygous MFN2 alleles expressed at physiological levels. Our results indicate that, in fibroblasts, mitofusin expression, mitochondrial morphology, ultrastructure, mtDNA content, and respiratory capacity are not affected by the presence of mutant Mfn2 protein. Consistent with a lack of mitochondrial dysfunction, we also show that mitochondrial fusion occurs efficiently in CMT2A patient-derived fibroblasts. Our observations are in agreement with the neuronal specificity of the disease and are consistent with a recent finding that mitochondrial fusion can be maintained in cells that express mutant Mfn2 protein due to complementation by a second mitofusin, Mfn1. We discuss our results and those of others in terms of a comprehensive model for the mechanism(s) by which mutations in MFN2 may lead to CMT2A disease.
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Affiliation(s)
- Elizabeth A Amiott
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112
| | - Paul Lott
- Departments of Neurology, Human Genetics, Pathology, and Pediatrics, University of Utah School of Medicine, Salt Lake City, UT 84112
| | - Jamie Soto
- Division of Endocrinology Metabolism and Diabetes and Program in Human Molecular Biology and Genetics, University of Utah, School of Medicine, Salt Lake City, UT 84112
| | - Peter B Kang
- Department of Neurology, Children’s Hospital Boston and Harvard Medical School, Boston, MA 02115
| | - J Michael McCaffery
- Integrated Imaging Center, Department of Biology, Johns Hopkins University, Baltimore, MD 21218
| | - Salvatore DiMauro
- Department of Neurology, Columbia University Medical Center, New York, NY 10032
| | - E Dale Abel
- Division of Endocrinology Metabolism and Diabetes and Program in Human Molecular Biology and Genetics, University of Utah, School of Medicine, Salt Lake City, UT 84112
| | - Kevin M Flanigan
- Departments of Neurology, Human Genetics, Pathology, and Pediatrics, University of Utah School of Medicine, Salt Lake City, UT 84112
| | - Victoria H Lawson
- Departments of Neurology, Human Genetics, Pathology, and Pediatrics, University of Utah School of Medicine, Salt Lake City, UT 84112
| | - Janet M Shaw
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112
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Abstract
BACKGROUND Axonal neuropathy linked to the CMT2A locus was originally associated with a mutation in the KIF1B gene. However, mutations in this gene have not been described associated with any other CMT2A families. Recently, mutations in the MFN2 gene, encoding the mitochondrial GTPase mitofusin 2 (Mfn2), have been identified as causative of CMT2A in seven families. The authors report three additional CMT2A families associated with novel mutations in highly conserved regions of the Mfn2 GTPase domain. METHODS The authors performed a standardized neuromuscular and nerve conduction examination, genotyped known CMT loci, and analyzed the MFN2 gene by direct sequencing in three pedigrees and 10 additional probands affected by axonal CMT. RESULTS Sequencing of the MFN2 gene revealed a novel mutation in each family (c.818T>G, c.638T>C, and c.314C>T). The largest family demonstrated an age-independent variable expression such that approximately one quarter of individuals with the mutation presented with features mild enough as to remain occult even with electrophysiologic evaluation. CONCLUSION These results confirm that the majority of cases of CMT linked to the CMT2A locus are due to MFN2 mutations. The phenotype is largely indistinguishable from KIF1B-related CMT and from CMT2E and CMT2F. At least in some families, as many as 25% of individuals with MFN2 mutations may be asymptomatic and have a normal electrophysiologic examination, although a detailed neuromuscular examination may suggest the trait. Given the frequency of MFN2 mutations among CMT2 probands (3/13, or 23%), genetic testing of CMT2 patients should begin with a screen of the MFN2 gene.
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Affiliation(s)
- Victoria H Lawson
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84132-2305, USA
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Lawson VH, Bromberg MB, Stashuk D. Comparison of conventional and decomposition-enhanced spike triggered averaging techniques. Clin Neurophysiol 2004; 115:564-8. [PMID: 15036051 DOI: 10.1016/j.clinph.2003.11.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/01/2003] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Spike triggered averaging (STA) is a technique to extract an estimate of a recurring motor unit potential from a complex electromyographic (EMG) signal. In conventional STA (C-STA), potentials related to the discharges of single intramuscular motor units are isolated and used to trigger an averager to obtain an individual surface-detected motor unit potential (S-MUP) from an EMG signal. In decomposition-enhanced STA (DE-STA), EMG signal decomposition algorithms determine discharges of a number of different motor units (4 to 10) that can be used to trigger an averager to obtain their corresponding S-MUPs. We tested the accuracy of extracting and averaging S-MUPs using DE-STA compared to C-STA for the same EMG signals. METHODS We compared the intramuscular potentials used for triggering and the resultant averaged S-MUPs that were common in both techniques. RESULTS We found no statistically significant differences in the metrics used to describe the triggering potentials and S-MUPs. CONCLUSIONS We conclude that DE-STA is an accurate and efficient method to obtain a large number of intramuscular motor unit potentials and their corresponding S-MUP in proximal and distal muscles.
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Affiliation(s)
- Victoria H Lawson
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA
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Lawson VH, Gordon Smith A, Bromberg MB. Assessment of axonal loss in Charcot–Marie–Tooth neuropathies. Exp Neurol 2003; 184:753-7. [PMID: 14769367 DOI: 10.1016/s0014-4886(03)00293-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2003] [Revised: 05/23/2003] [Accepted: 05/28/2003] [Indexed: 11/28/2022]
Abstract
Sensory loss and weakness in Charcot-Marie-Tooth (CMT) neuropathy is due to axonal loss. However, the pattern and degree of axonal loss cannot be accurately determined from routine electrodiagnostic or strength testing due to collateral reinnervation. We sought to quantify axonal loss in two upper extremity muscles in CMT1A and CMT2 subjects using the electrophysiologic endpoint measure of motor unit number estimation (MUNE). Hypothenar and biceps-brachialis muscle groups were studied in 9 CMT1A, 9 CMT2, and 10 control subjects. The spike-triggered averaging (STA) technique was used to collect surface motor unit potentials for MUNE calculations, and a needle electrode was used to collect corresponding intramuscular data. Maximal voluntary hypothenar and handgrip strength was measured quantitatively, while biceps-brachialis strength was measured qualitatively. Compared to normal subjects, CMT1A and CMT2 subjects had significantly lower MUNE values in hypothenar muscles. Biceps-brachialis MUNE values were reduced in CMT2 but not in CMT1A subjects. In support of proximal axonal loss in CMT2 subjects, surface motor unit and intramuscular potential amplitudes were higher in biceps-brachialis muscles compared to controls. Correlations between quantitative strength and MUNE were significant for hypothenar but not for grip muscle groups. Axonal loss is demonstrated in distal muscles in CMT1A and CMT2 supporting a length-dependent axonopathy. Despite clinical findings of normal or near-normal strength and small reductions in compound muscle action potential (CMAP) amplitude, MUNE values were significantly lower in CMT2 subjects in proximal muscles, consistent with more diffuse denervation. These data indicate that subclinical axonal loss is present that cannot be appreciated using clinical examination or routine electrodiagnostic techniques.
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Affiliation(s)
- Victoria H Lawson
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
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Abstract
The degree of motor unit loss can not be accurately quantified in chronic motor neuropathies with routine electrodiagnostic testing or with pathologic examination. We used motor unit number estimation (MUNE), which is a unique electrophysiologic method that can estimate the number of surviving motor units innervating a muscle, to study axonal loss in spinal muscular atrophy (SMA) and Charcot-Marie-Tooth (CMT) neuropathies. MUNE is based on the ratio of the maximal compound muscle action potential (CMAP) to the average surface-recorded motor unit potential (S-MUP). The hypothenar muscle group was studied in infant and older subjects with SMA, and the hypothenar and biceps-brachialis muscle groups were studied in adult CMT1A and CMT2 subjects. The multiple point stimulation MUNE technique was used in SMA subjects and the spike triggered averaging MUNE technique was used in CMT subjects. In SMA, motor unit loss was profound in types 1 and 2 subjects and more moderate in type 3 subjects. In CMT, motor unit loss was prominent in distal muscles in both CMT1A and 2 subjects, and present in proximal muscles in CMT2 subjects. MUNE is efficient in assessing the degree of motor unit loss in chronic motor neuropathies. SMA is considered to be a proximal muscle disorder, but loss was marked in distal muscles in all SMA types. In CMT1A, the demyelinating form, motor unit loss was marked in distal muscles, consistent with the idea that axonal loss and not slow conduction velocity is the important pathologic condition. The pattern of proximal motor unit loss differed between CMT1A and 2, suggesting differences in underlying axonal pathology.
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Affiliation(s)
- Mark B Bromberg
- Department of Neurology, University of Utah, Salt Lake City, UT 84132, USA.
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Lawson VH, Bland BH. The role of the septohippocampal pathway in the regulation of hippocampal field activity and behavior: analysis by the intraseptal microinfusion of carbachol, atropine, and procaine. Exp Neurol 1993; 120:132-44. [PMID: 8477826 DOI: 10.1006/exnr.1993.1047] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The role of the septohippocampal pathway in the regulation of hippocampal field activity and behavior was assessed using the technique of intraseptal microinfusion of carbachol, atropine, and procaine. The effects of these manipulations were assessed by comparing them with the effects of intraseptal saline control infusions on spontaneously occurring motor behaviors and their correlated hippocampal field activities. In control conditions hippocampal theta field activity, with up to 40% of the total power concentrated in a 1-Hz band around the peak frequency, was recorded only during type 1 voluntary motor behaviors. Hippocampal large-amplitude irregular activity was recorded during type 2 automatic motor behaviors and during immobility. Microinfusion of carbachol into the MS/vDBB (medial septum/vertical limb of the diagonal band of Broca) resulted in continuous theta field activity regardless of what type of motor behavior the animal performed or whether it was immobile. However, under these conditions the performance of a voluntary movement consistently resulted in an upward shift of theta frequency, demonstrating that the frequency of carbachol-elicited type 2 theta can be modulated by the behavioral activation of type 1 theta. The subsequent infusion of atropine abolished the carbachol-elicited theta, while that occurring during type 1 voluntary movement was preserved. In contrast to the selective blockade of carbachol-elicited theta by atropine, procaine suppression of the MS/vDBB abolished both spontaneous movement-related (type 1) theta and carbachol-elicited (type 2) theta. During the postprocaine period theta frequency recovered rapidly in contrast to theta amplitude (power). This result applied to the recovery of both the coactivated type 1 and type 2 theta occurring during spontaneous movement and the carbachol-elicited type 2 theta alone. The behavioral results were discussed within the context of Bland's (Prog. Neurobiol. 26, 1-54, 1986) sensorimotor model which posits that hippocampal theta activity recorded during voluntary movement represents the coactivation of a cholinergically mediated sensory processing component and a feedback (possibly serotonergic) motor component.
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Affiliation(s)
- V H Lawson
- Department of Psychology, University of Calgary, Alberta, Canada
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Smythe JW, Cristie BR, Colom LV, Lawson VH, Bland BH. Hippocampal theta field activity and theta-on/theta-off cell discharges are controlled by an ascending hypothalamo-septal pathway. J Neurosci 1991; 11:2241-8. [PMID: 2066781 PMCID: PMC6575487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The nature of the control of hippocampal formation field activity [theta (theta) and large-amplitude irregular activity (LIA)] and theta-on/theta-off cell discharges by an ascending hypothalamo-septal pathway was investigated in urethane-anesthetized rats. Electrical stimulation of the dorsomedial-posterior hypothalamus in the range of 0.1-1.0 mA in 0.1-mA steps produced theta in the hippocampal formation, with a linear positive relation between stimulus intensity, theta frequency, and theta amplitude. Reversible blockade of the medial septal (MS)/vertical limb of the diagonal band of Broca (vDBB) region by microinjection of procaine hydrochloride abolished spontaneous and hypothalamically elicited theta, resulting in a field activity at 1-min post-procaine that had a lower power than pre-procaine LIA levels. The efficacy and recovery of the MS/vDBB suppression was tested at 1, 10, 20, 30, 40, 50, and 60 min post-procaine using 0.5, 0.8, and 1.0 mA of hypothalamic stimulation. All three of the dependent measures of hippocampal field activity (frequency, amplitude, and power) showed a progressive recovery during the 60-min post-procaine period. Frequency exhibited a rapid recovery with a shallow slope between 20 and 60 min post-procaine. In contrast, the amplitude and power of theta exhibited a gradual recovery with a steeper slope between 20 and 60 min post-procaine. During the time of maximal MS/vDBB suppression, theta-on cell discharges were reduced to 0 in most cases. The initial recovery of theta-on cells in the post-procaine condition was correlated with the first appearance of theta and was characterized by low discharge rates.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- J W Smythe
- Department of Psychology, University of Calgary, Alberta, Canada
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