Affective aggression in patients with temporal lobe epilepsy: A quantitative MRI study of the amygdala

Recurrent episodes with interictal affective aggression are a rare but well-recognized problem in patients with temporal lobe epilepsy. They are referred to as episodic dyscontrol or, more precisely, as intermittent explosive disorder (IED). The amygdala play a crucial role in the affective evaluation of multimodal sensory input and the neurobiological mediation of aggressive behaviour. With hippocampal sclerosis, in the context of mesial temporal lobe sclerosis, being the most common cause of temporal lobe epilepsy, we hypothesized that the amygdala might be affected by the same pathogenic process in aggressive patients. We investigated 50 patients with temporal lobe epilepsy: 25 with and 25 without a history of IED. Data from clinical, electrophysiological, neuropsychological and psychometric investigations were obtained, as well as MRI scans for the quantitative assessment of possible amygdala pathology. We found no evidence of a higher prevalence of amygdala sclerosis in the aggressive patients. Hippocampal sclerosis was significantly less common in patients with temporal lobe epilepsy and IED. However, a significant subgroup of patients (20%) with temporal lobe epilepsy and aggressive behaviour had severe amygdala atrophy in the context of a history of encephalitis. Another subgroup of aggressive patients (28%) had different left temporal lesions affecting either the amygdala or periamygdaloid structures. IED was associated with left-sided or bilateral EEG and MRI abnormalities, low IQ and high scores in depression and anxiety.