Biting behavior, aggression, and seizures

Purpose: to describe the semiological features of aggressive behaviours observed in human epileptic seizures with particular reference to the act of biting a conspecific. Methods: we analysed the biting behaviour (BB) and other aggressive gestures occurring in a group of eleven patients retrospectively selected out of more 1000 patients subjected to video-EEG/SEEG monitoring for pre-surgical evaluation of drug-resistant seizures. Results: patients displaying BB showed: (i) a male sex predominance; (ii) heterogeneous aetiologies and lesion locations; (iii) seizures involving the fronto-temporal regions of both hemispheres. The act of biting was a rapid motor action, lasting about 600 ms, occurring in the context of strong emotional arousal, fear, anger with various bodily gestures with aggressive connotation. BB was mainly a ‘reflexive’ behaviour in that biting acts were evoked (both during and after seizures) by actions of people in close contact with the patient. The sole intrusion of the examiner’s hand in the space near the patient’s face was effective in triggering BB. Rarely self-directed or object-directed biting acts were not triggered by external stimuli. Intracranial data (SEEG) obtained in one subject showed that the amygdala/hippocampal region plus the orbital-medial prefrontal cortex had to be involved by ictal activity in order to observe BB.Conclusions: anatomical and electrophysiological data in our patients suggest that a model of dual – temporal and frontal – dysfunction could account for the occurrence of ictal/postictal BB. Behavioural data suggest also that BB and related aggressive gestures can be considered as the emergence of instinctive behaviours with an adaptative significance of defence of the peripersonal space.