[Paroxysmal movement disorders]

Paroxysmal movement disorders are of sudden onset, paroxystic or intermittent, with normality or at least absence of abnormal movements between episodes. They are uncommon conditions with high familial incidence. The commonest form is paroxystic dystony. Paroxystic ataxia and paroxystic tremor are much rarer.

Paroxystic dystony is seen clinically as paroxystic episodes of variable duration, consisting of dystonic movements and postures which present spontaneously or are triggered by certain stimuli or situations. There are different types: kinesgenic paroxystic choreoathetosis, dystonic paroxystic choreoathetosis, intermediate paroxystic choreoathetosis and nocturnal paroxystic choreoathetosis. The paroxystic ataxias are characterized by recurrent episodes of ataxia in the absence of any known metabolic defect. In type 1 episodic ataxia there are also episodes of ataxia and myochemical changes. The gene responsible for this condition has been found on the short arm of chromosome 12. Type 2 episodic ataxia is characterized by its excellent response to acetazolamide. The gene responsible is found on the short arm of chromosome 19.

Very few cases of paroxystic tremor have been described.