[Differential diagnosis in epilepsy. Anamnesis is still the most important guide]

Epilepsy is defined by the WHO as "a chronic brain disorder of various aetiologies characterised by recurrent seizures due to excessive discharge of cerebral neurones." There are many other episodic conditions including systemic, neurological and psychiatric disorders, which may be confused with epileptic seizures but are not the result of epileptic neuronal discharge. The principal differential diagnoses in cases of episodic seizures in adults and children are outlined in this review, and the importance of adequate history taking is stressed. Correct interpretation of the history is dependent upon the physician's recognition of the clinical features typical of epileptic seizures. Both the importance and the limitations of electroencephalography (EEG) are discussed. The contribution of EEG in cases where a diagnosis of therapy-resistant epilepsy has been questioned is exemplified in case studies of 42 patients, of whom 43 per cent were found to have psychiatric disease only, 26 per cent to have epilepsy only, 12 per cent to have both epileptic seizures and episodic symptoms of psychiatric origin, and the remaining 19 per cent to have episodic disorders of non-epileptic and non-psychiatric origin. The importance of adequate history taking before making a diagnosis of epilepsy is emphasised, as is the conclusion that an incorrect diagnosis of epilepsy often causes more harm than postponing the diagnosis until it becomes more clear.