Alternating hemiplegia of childhood (AHC) is a typical example of a disease that combines movement disorders and epileptic manifestations in addition to other neurological features, especially hemiplegic episodes. The latter were first recognized (Verret & Steele, 1971) and the condition named after them. Progressively, other symptoms were reported, including abnormalities of ocular motor function (Dittrich et al., 1979), dystonia and choreoathetosis either paroxysmal or permanent (Dittrich et al., 1979; Krägeloh & Aicardi, 1980; Dalla Bernardina et al., 1987), quadriplegic episodes and autonomic dysfunction (Bourgeois et al., 1993). These features proved to be an integral part of the clinical picture of AHC and served to separate the condition from other forms of episodic hemiplegia, especially hemiplegic migraine to which AHC was initially thought to belong.
AHC is a rare disorder; less than 150 cases have been reported up to now (Bourgeois et al., 1993; Sakuragawa, 1992; Campistol Plana et al., 1990; Silver & Andermann, 1993). Recently, Mikati et al. (2000) systematically collected 71 cases so far detected in the United States and were able to perform a detailed study of 44 of these patients. The clinical picture is generally stereotyped. All patients have repeated attacks of hemiplegia or hemiparesis involving either side of the body alternatively. However, hemiplegias are never the sole clinical manifestation of the disorder and are always associated with and often preceded by, other manifestations, especially dystonic or choreoathetotic attacks, abnormal ocular movements, autonomic abnormalities and episodes of quadriplegia, that are described below. No cause for the disorder has been recognized. The disease has its onset in infancy and is usually sporadic.