Chapter 14 Peripheral nerve hyperexcitability and the neuromuscular junction

Virtually all primary neuromuscular diseases result in changes in the electric activity recorded from muscle fibers. These changes can best be depicted using fine needle electrodes inserted into the muscle to record spontaneous and voluntary EMG. Thus, EMG can be used to distinguish among lower motor neuron, peripheral nerve, neuromuscular junction, and muscle disease with great sensitivity and some specificity. The sensitivity is usually greater than clinical measures; specificity in identifying the cause of the disease often requires muscle biopsy or other clinical measures. Although EMG is somewhat uncomfortable for patients because needles need to be inserted into the muscles, it generally is well tolerated by patients and provides a rapid, efficient means of testing the motor unit.

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A Patient with Double-Negative VGKC, Peripheral Nerve Hyperexcitability, and Central Nervous System Symptoms: A Postinfectious Autoimmune Disease

Case Reports in Neurological Medicine ◽

10.1155/2020/3579419 ◽

2020 ◽

Vol 2020 ◽

pp. 1-7

Author(s):

Birte Eikeland

Keyword(s):

Central Nervous System ◽

Nervous System ◽

Autoimmune Disease ◽

Peripheral Nerve ◽

Skin Lesions ◽

Double Negative ◽

Pathogenic Potential ◽

Peripheral Nerve Hyperexcitability ◽

Systemic Symptoms ◽

Kinetics Of

Research in the last few years has indicated that most voltage-gated potassium channel- (VGKC-) complex antibodies without leucine-rich glioma-inactivated protein 1 or contactin-associated protein-like 2 antibody specificity lack pathogenic potential and are not clear markers for autoimmune inflammation. Here we report on a patient with double-negative VGKC who developed severe peripheral nerve hyperexcitability, central nervous system symptoms with agitation and insomnia, dysautonomia, and systemic symptoms with weight loss, itch, and skin lesions. The disease started acutely one month after an episode of enteroviral pericarditis and responded well to immunotherapy. The patient is presumed to have developed a postinfectious immunotherapy-responsive autoimmune disease. In the setting of anti-VGKC positivity, it seems likely that anti-VGKC contributed to the pathogenesis of the patient’s symptoms of nerve hyperexcitability and that the disease was caused by an acquired autoimmune effect on the neuronal kinetics of VGKC. It is still unknown whether or not there are unidentified extracellular molecular targets within the VGKC-complex, i.e., a novel surface antigen and a pathogenic antibody that can cause affected individuals to develop a peripheral nerve hyperexcitability syndrome. This case highlights the fact that less well-characterized autoimmune central and peripheral nervous system syndromes may have infectious triggers.

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Therapeutic Implications of Peripheral Nerve Hyperexcitability in Muscle Cramping

Journal of Clinical Neurophysiology ◽

10.1097/wnp.0000000000000291 ◽

2016 ◽

Vol 33 (6) ◽

pp. 560-563 ◽

Cited By ~ 3

Author(s):

Rebecca L. Hurst ◽

Lisa D. Hobson-Webb

Keyword(s):

Peripheral Nerve ◽

Therapeutic Implications ◽

Peripheral Nerve Hyperexcitability

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Peripheral nerve conduction studies and neuromuscular junction testing

Handbook of Clinical Neurophysiology - Clinical Neurophysiology of Motor Neuron Diseases ◽

10.1016/s1567-4231(04)04012-2 ◽

2004 ◽

pp. 241-270 ◽

Cited By ~ 1

Author(s):

Jun Kimura

Keyword(s):

Neuromuscular Junction ◽

Peripheral Nerve ◽

Nerve Conduction ◽

Nerve Conduction Studies

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Electrodiagnostic Findings in Neuromuscular Disorders

10.1093/med/9780190603434.003.0004 ◽

2018 ◽

Author(s):

Bashar Katirji

Keyword(s):

Neuromuscular Junction ◽

Peripheral Nerve ◽

Myasthenia Gravis ◽

Nerve Conduction ◽

Neuromuscular Disorders ◽

Nerve Conduction Studies ◽

Anterior Horn Cell ◽

Peripheral Neuropathies ◽

Peripheral Nerve Lesions ◽

Myasthenic Syndrome

Neuromuscular disorders are often classified into four major categories: anterior horn cell disorders, peripheral neuropathies, neuromuscular junction disorders and myopathies. This chapter discusses the electrodiagnostic and clinical EMG findings in these various neuromuscular disorders. Peripheral neuropathies are subdivided into focal mononeuropathies, radiculopathies, plexopathies and generalized peripheral polyneuropathies. Focal peripheral nerve lesions and generalized peripheral polyneuropathies may be axonal or demyelinating, and manifest quite distinctly on nerve conduction studies. Neuromuscular junction disorders may be presynaptic, as seen with the Lambert-Eaton myasthenic syndrome, or postsynaptic, as seen with myasthenia gravis.

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Insomnia and Dysautonomia with Contactin-Associated Protein 2 and Leucine-Rich Glioma Inactivated Protein 1 Antibodies: A “Forme Fruste” of Morvan Syndrome?

Case Reports in Neurology ◽

10.1159/000497817 ◽

2019 ◽

Vol 11 (1) ◽

pp. 80-86

Author(s):

Ezgi Bakırcıoğlu-Duman ◽

Zeynep Acar ◽

Gülçin Benbir ◽

Hande Yüceer ◽

Hürtan Acar ◽

...

Keyword(s):

Peripheral Nerve ◽

Neuropsychological Assessment ◽

Executive Dysfunction ◽

Cognitive Symptoms ◽

Neurologic Examination ◽

Cognitive Domains ◽

Needle Electromyography ◽

Muscle Twitching ◽

Peripheral Nerve Hyperexcitability ◽

History Of

Morvan syndrome (MoS) is typically characterized by neuromyotonia, sleep dysfunction, dysautonomia, and cognitive dysfunction. However, MoS patients with mild peripheral nerve hyperexcitability (PNH) or encephalopathy features have been described. A 46-year-old woman presented with a 2-month history of constipation, hyperhidrosis, and insomnia. Neurologic examination revealed muscle twitching and needle electromyography showed myokymic discharges in all limbs. No clinical or electrophysiological features of neuromyotonia were present. Although the patient denied any cognitive symptoms, neuropsychological assessment revealed executive dysfunction, while other cognitive domains were preserved. Cranial and spinal MRIs were unrevealing and tumor investigation proved negative. Polysomnography examination revealed total insomnia, which was partially reversed upon immune-modulatory therapy. Investigation of a broad panel of antibodies revealed serum leucine-rich glioma inactivated protein 1 and contactin-associated protein 2 antibodies. The features of this case indicate that the presentation of PNH syndromes may show significant variability and that MoS patients may not necessarily exhibit full-scale PNH and encephalopathy symptoms.

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