Habituation of orienting reaction in therapy-resistant generalized epilepsy

A polygraphic study on resistance to habituation of the somatic, autonomic and EEG components of the orienting reaction elicited by a repetitive auditory stimulus was performed in 39 epileptics with therapy-resistant generalized seizures (TRGS) and in 119 matched subjects in two control groups. The study showed a significantly higher resistance to habituation of the orienting reaction in epileptics with TRGS vs. the normal subjects of control group I. A significantly higher resistance to habituation was also noted in epileptics with therapy-controlled generalized seizures of control group II. The correlational analysis of data showed that the severity of these habituation disturbances in epileptics with TRGS depended on the patients' age, type of electroclinical seizures, pretrial seizure frequency, type of resting EEG, administered treatment (no. of administered antiepileptic drugs/patient), daily dose, as well as on the serum level of these drugs. The multivariate regression analysis showed that the most significant predictive variables for the habituation disturbances were the pretrial seizure frequency, type of electroclinical seizures, daily dose of administered antiepileptic drugs and their serum level. The data also evidenced that the antiepileptic treatment improves the interictal habituation disturbances, the effect being the more marked as the treatment was more sustained. The above-mentioned habituation changes in epileptics with TRGS should be ascribed to some disturbances in nervous excitability.