Neuromyotonia
- neuromyotonia (Isaacs syndrome) is a disorder of peripheral nerve hyperexcitability characterized by myokymia, muscle cramps and stiffness, delayed muscle relaxation after contraction (pseudomyotonia), and hyperhidrosis, associated with well described spontaneous electromyographic features
- usually neuromyotonia is an acquired disorder associated with autoantibodies against neuronal voltage-gated potassium channels
- familial neuromyotonia occurs very rarely
- mutations of KCNA1, encoding the K+ channel subunit hKv1.1, have been reported in rare families with neuromyotonia
- clinical features are diverse and include cramps, generalized muscle twitching, stiffness, and pseudomyotonia
- some patients experience paresthesias or hyperhidrosis that may be secondary to muscle overactivity
- underlying electrophysiologic basis of Isaacs’ syndrome is the spontaneous repetitive burst of single motor-unit potentials, with high intraburst frequency
- most common electromyographic abnormalities are myokymic and neuromyotonic discharges
- both terms are used to describe this spontaneous electrical activity, and both forms of discharge are sometimes seen in the same patient
- main difference between them arises from the higher frequencies (150-300 Hz) and waning features of neuromyotonic discharges
- both terms are used to describe this spontaneous electrical activity, and both forms of discharge are sometimes seen in the same patient
- most common electromyographic abnormalities are myokymic and neuromyotonic discharges
- distinction between neuromyotonia and other entities, such as cramp-fasciculation syndrome and stiff-man syndrome, lies in the electromyographic and clinical findings
- rippling-muscle disease is a rare autosomal-dominant disorder (characterized by mechanically induced, involuntary muscle contractions) which should always be included in the differential diagnosis of Isaacs’ syndrome
- in addition to conventional pharmacotherapy with anticonvulsants such as phenytoin or carbamazepine, immunomodulatory treatments using high doses of intravenous immunoglobulin and plasmapheresis have also been employed (3)
Reference:
Related pages
Create an account to add page annotations
Annotations allow you to add information to this page that would be handy to have on hand during a consultation. E.g. a website or number. This information will always show when you visit this page.