Immediate transition from a petit mal absence into a grand mal seizure. Case report.

Petit mal absences in childhood are often followed by grand mal seizures in adolescence and a coexistence of both types of seizures is not uncommon at all. It is noteworthy, however, that such a coexistence does not imply immediate transition from one type of seizure into the other one. Hence, a grand mal attack may be prepared by all sorts of focal seizures, psychomotor automatisms or bilateral-synchronous myoclonus but immediately preceding petit mal (with generalized spike-wave discharges) is probably extremely rare. The presented case is characterized by unusually late onset of petit mal and grand mal seizures at age 32 and, following a mild head injury, a few episodes of petit mal status (ictal stupor) at age 52. At that time, a series of petit mal absences and eventually a smooth transition from petit mal to grand mal could be recorded. Uncommon frequency characteristics (especially some interspersed spiking at a rate of 9-15/sec) were found at the onset of the ictal spike-wave activity during the petit mal absences. This is regarded as the expression of failing inhibitory mechanisms which generally prevent the immediate development of a grand mal out of a petit mal absence.