Case series: the paradox of epilepsy surgery and psychiatric disorder.

De novo psychiatric disorder following epilepsy surgery is an infrequent but very interesting phenomenon. The authors described 4 distinct cases with medically intractable epilepsy who had epilepsy surgery and developed postsurgical psychiatric disorder. The onset of psychiatric disorder was during dramatic improvement of their epilepsy after surgery. There was no history of psychiatric disorder in their familial members or in the patients prior to the surgery. Since three patients also had mental retardation, presurgical cognitive impairment may be one of the risk factors for developing postsurgical psychiatric disorder. Potential mechanisms include volume reduction of gray matter in frontal, temporal and parietal cortexes secondary to epilepsy surgery as well as forced normalization. Several other mechanisms may also play important role for this phenomenon and further studies will be required which may reveal the connection between these two aspects.