Subjective signs in premotor epilepsy: confirmation by stereo-electroencephalography

Subjective manifestations inaugurating frontal seizures are less well known than those observed in temporal seizures. We report eleven consecutive patients who underwent surgery for premotor epilepsy. Six of them had focal cortical dysplasia. Ictal symptomatology was analysed to establish electroclinical correlations. The localisation of the epileptogenic zone was assessed by stereoelectroencephalographic studies. Subjective manifestations were described in all cases, more frequently in a sensory rather than an emotional or psychological fashion. Focal seizures limited to subjective features were recorded in two patients. In one, psychological illusions and visual hallucinations were related to the superior frontal sulcus. Another presented isolated paraesthesia in the left arm with the implication of the supplementary motor area. Electrical stimulation of an electrode located in the premotor area evoked isolated subjective manifestations in three other patients. One patient reported sensory manifestations and another, ideational manifestations. Cephalic sensations and emotional manifestations were associated in one case. Subjective manifestations were observed in all patients, and were proved to be related to a discharge restricted to the premotor area in five. These were non-specific signs, but were always the same in a given patient. Spontaneous, isolated sensations and stimulation data tended to be contradictory. This illustrates the complexity of analyzing subjective signs, as well as the complexity of the neuronal networks participating in the propagation of discharges arising in the premotor frontal area.