Myokymia, muscle hypertrophy and percussion "myotonia" in chronic recurrent polyneuropathy

Neurology (Impact Factor: 8.29). 12/1978; 28(11):1130-4. DOI: 10.1212/WNL.28.11.1130
Source: PubMed


Three unusual features were observed in a patient with chronic relapsing polyneuropathy: myokymia, muscle hypertrophy, and prolonged contraction in response to muscle percussion. Low nerve conduction velocity and conduction block were demonstrated in all motor nerves tested, indicating a demyelinating peripheral neuropathy. Myokymia was caused by spontaneous motor unit activity which was shown to originate in peripheral nerves, since it persisted after nerve block and was abolished by regional curarization. Muscle hypertrophy was attributed to increased peripheral nerve activity, and the prolonged contraction of muscle in response to direct percussion was attributed to irritability of intramuscular nerve terminals.

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    • "The patient's subsequent neuromyotonia should be considered severe, as rhabdomyolysis has not previously been described in this condition , to our knowledge. Acquired neuromyotonia has been described in combination with a variety of autoimmune diseases[1]and peripheral neuropathies, including chronic inflammatory demyelinating polyradiculopathy (CIDP)[11]and other demyelinating neuropathies[12,13], however we know of no case reports detailing VGKC antibody-positive Isaacs' syndrome in a patient with a known history of GBS. These two autoimmune neurologic conditions are associated with different antibodies: Isaacs' syndrome appears to be mediated by anti-VGKC antibodies[14]while GBS is most often associated with anti-glycosphingolipid antibodies[15]. "
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    ABSTRACT: Acquired neuromyotonia, or Isaacs' syndrome, has been described in combination with a variety of other autoimmune disorders; however there has never been a report of seropositive Isaacs' syndrome in a patient with a history of Guillain-Barré syndrome (GBS). Both conditions involve antibody-mediated autoimmune effects on the peripheral nervous system, although the clinical manifestations are quite different. We present a man who experienced an episode of GBS at the age of 21 and subsequently developed Isaacs' syndrome at the age of 24 which was positive for anti-voltage-gated potassium channel (VGKC) antibodies. When treated with intravenous immunoglobulins (IVIg) he developed an eczematous rash that differed markedly in pattern and duration from the usual presentation for this IVIg reaction.
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    ABSTRACT: Delayed relaxation of muscle following voluntary contraction was an unusual feature of a mild chronic sesorimotor peripheral neuropathy in an adult. This abnormality resulted from rapid repetitive discharges in motor nerves occurring only in response to passing impulses; there was no spontaneous nerve discharge. Voluntary contraction of affected muscles generated involuntary high-frequency discharges of motor unit potentials, which persisted briefly after attempted relaxation. Nerve blocks localized independent zones of hyperexcitability in distal and proximal sections of nerve from which such repetitive discharges could be triggered. Intravenous administration of phenytoin diminished the discharge. Examination of intramuscular nerve bundles revealed loss of myelinated nerve fibers with numberous sprouting and remyelinating axons. These findings, along with muscle biopsy changes of neurogenic atrophy and type grouping, strongly favor an axonal neuropathy. An explanation for the repetitive nerve discharge is slow waning of heightened excitability of a motor nerve after passage of an impulse.
    No preview · Article · Mar 1980 · Annals of Neurology
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