Introduction

Paroxysmal epileptic motor phenomena occurring in the first year of life in symptomatic encephalopathies (hypoxic–ischemic, metabolic or malformative) are frequently constituted by spasms. Apart from the West syndrome, epileptic spasms are characteristic of some specific infantile epileptic syndromes such as Ohtahara syndrome (Ohtahara, 1978), early myoclonic epileptic encephalopathy (Aicardi & Goutires, 1978), tuberous sclerosis complex and Aicardi disease. They may also occur in neurofibromatosis and in other symptomatic encephalopathies of different origin (Commission on Pediatric Epilepsy of the ILAE, 1992; Roger & Dulac, 1994). In these syndromes epileptic spasms tend to recur in clusters. Recently it has been established that epileptic spasms may be present beyond infancy (Gobbi et al., 1987; Commission on Paediatric Epilepsy of the ILAE, 1992; Roger & Dulac, 1994; Talwar et al., 1995). Among these ‘non-age-related’ epileptic spasms, a particular type named periodic spasms has been described and their electroclinical characteristics have been detailed (Gobbi et al., 1987; Bednarek et al., 1998). The term ‘periodic spasms’ has been chosen to emphasize one of the most striking characteristics of these spasms: their repetition into the cluster in an almost periodic sequence at rather regular intervals. The most important aspect of periodic spasms is that the whole cluster of spasms has to be considered as a single, complicated partial seizure, with a particular type of secondary generalization, and not simply as the result of a long-lasting series of seizures (the spasms), which repeat in a periodic sequence (Gobbi et al., 1987). Finally, periodic spasms may be very polymorphous and their clinical expression may be very subtle or suggestive of a movement disorder. As a consequence they may be missed or misdiagnosed.