Psychiatric disorders in epilepsy
STERGIOU B., KARLOVASITOU A.

Epilepsy is closely related to several psychiatric disorders, such as mood disorders (major depresssion, dysthymic disorder, "interictal dysphoric disorder", bipolar disorder), anxiety disorders (panic disorder with or without agoraphobia, generalized anxiety disorder, social anxiety disorder), psychosis, conversion disorder ("pseudoseizures"), dissociative states, aggresion, suicide, sexual disorders (hyposexuality, paraphilias) and personality disorders. They are mainly characterised by episodic, pleomorphic, atypical features and sometimes it is difficult to be classified according to the international psychiatric classification scales (DSM-IV-TR, ICD-10). They frequently remain under-recognized and untreated. They can be classified according to how they relate in time to seizure occurence, i.e. ictal, peri-ictal and inter-ictal. They are more common among patients with complex partial seizures with temporal lobe foci. The presence of psychiatric disorders may lead to poorer quality of life and to a more severe functional impairment and disability than the seizures themselves..

According to Kanner, psychotic disorders in epilepsy can be categorized in: a) psychotic disorders with temporal relation to seizures (pre-ictal, ictal, post-ictal), b) those linked to seizure remission and "forced normalisation" ("alternative psychosis"), c) interictal psychotic disorder due to epilepsy, which is the most common and d) iatrogenic psychotic symptoms related to anti-epileptic drugs.

The prevelance of interictal psychosis is reported to be 2-9%. Its onset is variable and slow and it usually occurs after 8-14 years of epilepsy. It is more common in patients with partial complex seizures, ecpecially with left-sided temporal lobe foci. Other risk factors for developing psychosis in epilepsy include: a) early onset of the disease, b) the presence of drug-resistant seizures, c) the presence of "alien tissue", d) mesial temporal sclerosis, e) a family history of epilepsy and psychosis, f) psychosocial factors such as a disturbed family backround, the absence of interpersonal relationships and the lack of a professional occupation. Some authors include left-handedness and female sex as predisposing factors.

Persistent interictal psychoses or "the schizophrenia-like psychoses of epilepsy" are generally chronic disorders and may clinically resemble paranoid scizophrenia. However, they can be distinguished from schizophrenia by the following clinical features: a) absence of negative and catatonic symptoms or cognitive decline, b) lack of flattening of affect and preserved affective warmth, c) higher premorbid level of functioning, d) less social withdrawal, e) lack of bizarre delusions, f) absence of personality deterioration, g) high level of comorbidity with depressive symptoms, h) adequate response to lower doses of neuroleptics and i) a more benign course. These clinical differences between the two disorders (i.e. psychotic disorder due to epilepsy and schizophrenia) can probably be attributed to different pathophysiological causes. The underlying structural abnormalities in interictal psychotic disorder include the mesial temporal gyrus and the limbic system (hippocampi, amygdala, cingulate). On the other hand, patients with scizophrenia may have additional functional dysregulation in various other brain structures, such as the prefrontal cortex and the basal ganglia. This is probably the main reason that severe, disabling symptoms such as looseness of associations, poverty of thought, impaired attention, cognitive deficits and catatonia are relatively rare in interictal psychotic disorder. It is also important to note that sometimes a personality disorder, which is associated with temporal lobe epilepsy (Geschwind syndrome) and is characterized by viscocity, circumstantiality, suspisiousness, lack of humor, hypergraphia and hyperreligiosity or behavioural disorders due to epilepsy, such as aggresion and impulsivity may be falsely diagnosed as interictal psychotic disorder.

Postictal psychosis remits spontaneously even without treatment, but antipsychotic agents may shorten its duration. It is important to bear in mind that patients with a long history of postictal psychotic episodes may have a higher risk of developing interictal psychosis. Interictal psychotic disorder is treated with antipsychotics. The treatment is usually long term. Neuroleptics that lower seizure threshold, such as chloropromazine and clozapine should be avoided. Atypical antipsychotics, such as risperidone and quetiapine are more often used. Small doses are usually efficient. Benzodiazepines and antidepressants may also be helpfull. Encephalos 2010, 47(1):5-9.

Key words: Interictal psychosis, complex partial seizures, temporal lobe foci.