[Myoclonic spasms: their clinical and neurophysiological characteristics, aetiology and treatment]

Myoclonus refers to the brief, sudden, involuntary movements like jerks or twitches which produce a sudden muscular contraction.

To review the clinical and neurophysiological features of myoclonus, or myoclonic spasms, and to carry out an updated examination of their causation and treatment.

Myoclonic spasms can be classified on the basis of different criteria. According to the underlying physiological mechanism, myoclonic spasms can be classified as cortical, subcortical, spinal or peripheral. Myoclonic spasms appear in a wide range of neurological diseases. So-called symptomatic myoclonus is the type that occurs secondary to an identifiable disorder; it is usually accompanied by other neurological signs and is the most frequent kind. Epileptic myoclonus is that which forms part of an epileptic syndrome with a genetic or idiopathic cause, or that is due to static encephalopathy. Essential myoclonus is the least frequent type and includes palatal myoclonus and dystonia-myoclonus syndrome. The main therapeutic objective consists in treating the underlying cause of the myoclonus if possible and in using symptomatic treatment when this is not the case. Antiepileptic drugs that enhance the effect of gamma-aminobutyric acid are still the most effective medication. Among the non-antiepileptic drugs, piracetam and 5-hydroxytryptophan stand out above the rest. Botulinum toxin has proved to be effective in palatal myoclonus. In dystonia-myoclonus syndrome, research has been conducted on the effectiveness of deep brain stimulation on the internal globus pallidus. In the most severe forms of myoclonus, monotherapy is not usually effective.

Progress has been made in furthering our knowledge of the neurophysiology of myoclonus, although no very effective forms of treatment have been reported for this motor disorder, which can be extremely disabling.