As many as 50% of patients with epilepsy have psychiatric syndromes, with mood, anxiety, and psychotic disturbances being the most common. Recognition and treatment of neuropsychiatric disturbances in individuals with epilepsy is influenced by the complexity of the epilepsies, which are a heterogeneous group of chronic conditions. Epileptic syndromes are classified according to seizure type and differ in their respective diagnostic criteria, epidemiology, etiologies, medical and surgical treatments, and associated psychiatric conditions. This chapter focuses on interictal psychiatric disturbances. Periictal and ictal psychiatric phenomena are addressed in the discussions of the differential diagnosis for the various interictal phenomena and in other reviews (Trimble, 1991; Schwartz and Marsh, 2000; Marsh and Rao, 2002). The prevalence of epilepsy ranges from 0.4% to 1%, with variation attributed to actual differences in the frequency of epilepsy among population subgroups as well as varying definitions of seizures and of epilepsy (Hauser and Rocca, 1996). The idiopathic generalized epilepsies comprise nearly one-third of all epilepsies and are primarily genetic in origin ( Jallon and Latour, 2005). Partial seizures are the most common seizure type and localization-related or focal epilepsy, especially of temporal lobe origin, is the most common epilepsy syndrome (Keranen, Sillanpaa, and Riekkinen, 1988). The incidence of epilepsy in industrialized countries is highest in the first year of life; it then remains stable until it peaks again after the age of 60 years, when epilepsy is associated with vascular and neurodegenerative conditions. In older adults, however, seizure presentations can be subtle and the diagnosis of epilepsy is frequently missed. Epilepsy is more common in men than women. Multiple factors contribute to higher rates of psychiatric illness in patients with epilepsy. Whether epilepsy itself increases the risk of psychiatric disturbance is unclear; it is important to understand the type and severity of the patient’s epilepsy syndrome, the ictal and peri-ictal features of the seizure, and the relationship of these to the occurrence of the psychiatric phenomena. It is also important to identify whether the patient has any of the special vulnerabilities that influence the risk of psychiatric dysfunction such as the presence of brain injury (eg, from head injury, a congenital neurodevelopmental disorder); use of medications to treat seizures or other conditions that have the potential for adverse psychoactive effects (eg, phenobarbital, benzodiazepines); untoward environmental and psychosocial circumstances; global versus selective cognitive impairments; and temperamental (ie, personality) traits that limit adaptability (Reynolds, 1981).
Cortical Dysplasia-Focal Epilepsy Syndrome