Muscle cramp in Machado-Joseph disease - Altered motor axonal excitability properties and mexiletine treatment

Kazuaki Kanai, Satoshi Kuwabara, Kimihito Arai, Jia Ying Sung, Kazue Ogawara, Takamichi Hattori

Research output: Contribution to journalArticlepeer-review

105 Citations (Scopus)


Machado-Joseph disease is one of the most common hereditary spinocerebellar degenerative disorders with a wide range of clinical manifestations. Pathology studies have shown mild to moderate loss of anterior horn cells and, in terms of spinal pathology, Machado-Joseph disease is regarded as a type of lower motoneuron disease. Muscle cramps are often associated with lower motoneuron disorders, but features of cramps in Machado-Joseph disease patients have never been studied. We investigated the incidence and nature of muscle cramps in Machado-Joseph disease patients, the excitability properties of motor axons [strength-duration time constant (τSD), threshold electrotonus, refractoriness and supernormality] using threshold tracking and the effects of mexiletine hydrochloride on those cramps. Of 20 consecutive patients, 16 (80%) had frequent, severe muscle cramps in the legs, trunk or arms that disturbed their daily activities. The frequency of pathological muscle cramps was similar to that for patients with amyotrophic lateral sclerosis (68%) and higher than those for patients with spinal muscular atrophy (33%) or peripheral axonal neurophathy (24%). Threshold-tracking studies showed that τSD, which in part reflects Na+ conductance at the resting membrane potential, was significantly greater in the Machado-Joseph disease patients than in normal subjects; severe muscle cramps were associated with a longer τSD. Threshold electrotonus, refractoriness and supernormality were not significantly different between Machado-Joseph disease patients and normal subjects. Eight Machado-Joseph disease patients with severe cramps, who received mexiletine treatment, experienced nearly complete relief with a partial normalization of τSD (P = 0.08). Muscle cramps are a very frequent and disabling factor in Machado-Joseph disease. Pathological muscle cramps responded well to mexiletine treatment, and this is consistent with the hypothesis that they are caused by an increase in persistent Na+ conductance, possibly associated with axonal regeneration or collateral sprouting.

Original languageEnglish
Pages (from-to)965-973
Number of pages9
Issue number4
Publication statusPublished - Apr 1 2003
Externally publishedYes


  • Axonal excitability
  • Machado-Joseph disease
  • Muscle cramps
  • Na conductance
  • Strength-duration time constant

ASJC Scopus subject areas

  • Clinical Neurology


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