An epileptic seizure has been defined as ‘a clinical manifestation presumed to result from an abnormal and excessive discharge of a set of neurones in the brain’.⁽¹⁾ A diagnosis of epilepsy applies with the recurrence of two or more discrete and unprovoked seizures (febrile and neonatal seizures are excluded from this definition).

Epilepsy is one of the more common neurological disorders. It carries with it a greater psychiatric morbidity than is to be found in other neurological disorders of comparable severity. Many of its manifestations resemble and may be confused with psychiatric phenomenology. It is often associated with learning difficulties; it may be a manifestation of acquired brain damage or disease; seizures may occur in the course of substance abuse or be caused by psychiatric treatment. For these and for many other reasons psychiatrists should be familiar with epilepsy, its manifold aetiologies, presentations, and treatment.

A comprehensive taxonomy should embrace classifications of both seizure semiology (i.e. the manifestations of abnormal discharge activity) and of epilepsy syndromes. The position of each seizure type in a seizure classification system is determined by its clinical manifestations, by electroencephalographic changes during the seizure, and by the interictal electroencephalographic abnormalities. A classification of epilepsy syndromes takes into account seizure subtype, and also anatomical substrate, aetiology, age of onset, and other characteristics. Seizure classification is dependent upon entities that are immediately ascertainable; epilepsy syndrome classification depends upon entities (e.g. neuroanatomical substrate) that are more speculative. The International League Against Epilepsy
(ILAE) has chosen to give the former priority, while recognizing the importance of the latter.

A familiarity with terminology, with the more common seizure subtypes, and the more commonly encountered epileptic syndromes, will assist in an understanding of the psychiatric disorders that occur in patients with epilepsy. The aura is a simple partial seizure, i.e. a seizure of focal onset in which consciousness is retained. It may progress to a complex partial seizure in which consciousness is disturbed, or into a generalized tonic, clonic, or tonic-clonic seizure. It may subside without further development. It rarely lasts for more than a few seconds, although patients often find time estimation difficult. It is to be distinguished from the epileptic prodrome, a period characterized by dysphoria, impaired memory and concentration, and minor motor manifestations, which precede the seizure and may last for hours or even days. An automatism may be defined as ‘a state of clouding of consciousness which occurs during or after a seizure, and during which the individual retains the control of posture and muscle tone and performs simple or complex movements without being aware of what is happening’.⁽²⁾ The initial phase, consisting of staring or simple chewing movements, may progress to more complex, stereotyped, and repetitive movements such as fumbling or picking. Automatisms rarely last more than a few minutes and are often very brief. They usually arise from temporal lobe discharges, but may be associated with orbital and mesial frontal lesions. The ictus refers to the period of manifest seizure activity. If this persists for 30 min or more it is described as status epilepticus and constitutes a medical emergency (Table 5.3.3.1).

The ILAE, in order to embrace a wider range of clinical features than is possible in a classification based on seizure types, introduced a classification of seizures and epilepsy syndromes. In this classification the broad division lies between the localizationrelated or partial epilepsies, the great majority of which, in adults, is made up of symptomatic epilepsies (i.e. epilepsy arising from a known or suspected cause) and the generalized epilepsies. The characteristics of the partial epilepsies are determined by the function of the cortical site from which the seizure emanates. The more common generalized epilepsies are age-related. Though admirable in concept, the classification has proved unwieldly and
the terminology clumsy: as such it seems unlikely to displace the seizure-type classification.

The cumulative incidence (i.e. lifetime risk) is 3.4 per cent for males, 2.8 per cent for females, but the prevalence is only 7 per 1000. This is because prevalence represents the balance between newly diagnosed cases and permanent remission or death, and epilepsy has a good prognosis with 76 per cent of newly diagnosed cases entering long-term remission.⁽³⁾ Approximately half can be classified as partial seizures and 40 per cent as generalized. Prognosis varies according to the epilepsy subtype, with partial epilepsy having a poorer outcome. Consequently, people who attend a hospital clinic are unrepresentative, in that they are more likely to have treatment-refractory partial seizures along with the other adverse prognostic factors such as mental handicap, neurological dysfunction, or psychiatric disorders.

Aetiology varies according to the age of onset. In childhood- and adolescence-inherited disorders of metabolism, ante- and perinatal complications, infection, migrational errors, and the consequences of febrile convulsions predominate, in middle life trauma and tumour are most common, and in advanced years cerebrovascular disease and degenerative disorders are predominant.

Only one-quarter to one-third of cases of epilepsy are due to known causes. Many others fall into recognizable syndromes about which much is understood. The partial epilepsies are, by definition, due to focal areas of damage and dysfunction usually involving the cortex. However, although the site may be suggested by the seizure semiology, comprehensive investigation may fail to identify any abnormality. Even when it does so, the radiological appearance may lack aetiological specificity. Some generalized seizures may be identified as primary generalized epilepsy syndromes; for example, juvenile myoclonic epilepsy. These are of uncertain aetiology, though genetic factors are considered important; onset is in childhood or adolescence and the prognosis favourable.

In psychiatric practice seizures may arise iatrogenically; they are usually due to pharmacotherapy, less commonly to electroconvulsive therapy. They may result from the overhasty withdrawal of benzodiazepines or to the use of antidepressant or antipsychotic drugs, most of which are epileptogenic. Such seizures are thought to be provoked and do not form grounds for a diagnosis of epilepsy. Adjustment of drug dosage is usually all that is required. Provoked seizures may also occur during alcohol intoxication (‘rum fits’) or withdrawal; a genetic predisposition may play a part.

The diagnosis of epilepsy depends first and foremost on historical information; the patient’s own account of the seizure and the observations of a reliable informant are of tantamount importance. A family history of epilepsy should be sought; age of onset should be determined when possible. A history of birth complications, febrile fits, early head injury, or cerebral infection is of particular importance in seizures starting in childhood, adolescence, or early adult life. In middle life symptoms suggestive of developing intracranial pathology and in later life cerebrovascular and degenerative disorders should be sought. The clinician should be aware of specific circumstances and situations that may provoke seizures: alcohol or substance abuse, prescribed drugs that have epileptogenic properties, and intermittent photic stimulation. Physical examination will detect not only gross congenital abnormalities such as tuberosclerosis, but also more subtle features, for example facial or skull asymmetries. The differential diagnosis varies according to age group, but will include vasovagal attacks and pseudoseizures, particularly in the young, vertigo and transient ischaemic attacks in the elderly, and cardiogenic syncope, hypoglycaemic episodes, and migraine at any age.