Carlo A. Tassinari, Franco Valzania, Roberto Michelucci, Guido Rubboli, Francesca Pastorelli, Anna Zaniboni
Department of Neurology, University of Bologna, Bellaria Hospital - Bologna, Italy
December 9, 8:00 a.m. - 12:00 Noon, Exhibit Hall B

Rationale:
To elucidate the mechanisms of motor involvement during clinical and subclinical epileptic discharges. Methods: Motor system assessment during paroxysmal discharges was performed by means of single pulse transcranial magnetic stimulation (TMS) with recording of motor evoked potentials (MEPs), H reflex, and stretch reflex induced by computerized posturography. 1 patient with epilepsia partialis continua, 2 patients with absence seizures (n=20) and subclinical photic-induced generalized spike-wave discharges (n=45), 6 patients with tonic seizures during sleep (n=55) were investigated.

Results:
In the patient with epilepsia partialis continua, the only MEP abnormality was a significantly lower threshold intensity of cortical stimulation in the affected hemisphere. In the 2 cases with subclinical photic-induced paroxysmal discharges, MEPs showed similar amplitude and latency to those recorded during interictal periods. MEPs elicited during sleep-linked fast recruiting rhythms (with or without concomitant EMG tonic activation), in patients with tonic seizures, were either increased or decreased in amplitude as compared to interictal periods. In this latter group, H reflex was constantly increased during the discharges, the maximal amplitude being obtained in concomitance with seizure-related tonic EMG activity. Evaluation of stretch reflex provided similar findings.

Conclusions:
Our data suggest that even infraclinical epileptic discharges may induce variations of motor excitability, both at a cortical or spinal level.