Generator sites for spontaneous activity in neuromyotonia. An EMG study

A 16-year-old female patient with symptoms and signs compatible with neuromyotonia was studied with various neurophysiological tests and with muscle biopsy. Nerve conduction studies revealed signs of axonal motor neuropathy. EMG showed denervation in distal muscles, and moderate neurogenic changes i...

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Bibliographic Details
Published in:Electroencephalography and clinical neurophysiology 1996-04, Vol.101 (2), p.69-78
Main Authors: Torbergsen, Torberg, Stålberg, Erik, Brautaset, Nils J.
Format: Article
Language:English
Subjects:
Adolescent
Anesthetics - pharmacology
Biological and medical sciences
Biopsy
Diseases of striated muscles. Neuromuscular diseases
Electric Stimulation
Electromyography
EMGG
Female
Humans
Hydantoins - pharmacology
Medical sciences
Muscle Cramp - drug therapy
Muscle Cramp - physiopathology
Muscle cramps
Muscle Fibers, Skeletal - physiology
Muscle, Skeletal - innervation
Muscle, Skeletal - physiopathology
Myotonia - drug therapy
Myotonia - physiopathology
Nervous System Diseases - drug therapy
Nervous System Diseases - physiopathology
Neural Conduction - physiology
Neurology
Neuromyotonia
Polysomnography
Repetitive discharges
Spontaneous activity
Ulnar Nerve - drug effects
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Summary:A 16-year-old female patient with symptoms and signs compatible with neuromyotonia was studied with various neurophysiological tests and with muscle biopsy. Nerve conduction studies revealed signs of axonal motor neuropathy. EMG showed denervation in distal muscles, and moderate neurogenic changes in other muscles. Abundant spontaneous motor unit activity was recorded in all muscles. This activity did not disappear upon proximal nerve blockade with local anaesthetics. Based on the shape of spontaneous discharges and their behaviour on nerve stimulation and during voluntary effort, the site of generation was suggested. This varied for different discharges, from proximally in the nerve, to various sites along the intramuscular nerve tree. In some axons there were signs of conduction block proximal to the generation site for the spontaneous discharges. Different axons showed various degrees of abnormality; local hyperexcitability triggering new impulses only after the passage of a preceding impulse, increased hyperexcitability generating spontaneous activity, total impulse blocking, and finally axonal degeneration. Treatment with dihydantoin reduced the spontaneous activity with concomitant clinical improvement.
ISSN:0924-980X
0013-4694
1872-7093
1872-6380
DOI:10.1016/0924-980X(95)00235-D