Epilepsy

What it is

A seizure is a clinical event in which there is a sudden disturbance of neurological function caused by an abnormal or excessive neuronal discharge, and seizures may be epileptic or non-epileptic. Epilepsy is 2 unprovoked seizures, 24 h apart: a chronic neurological disorder characterised by recurrent unprovoked seizures, consisting of transient signs and/or symptoms associated with abnormal, excessive or synchronous neuronal activity in the brain. It is classified as generalised, where the discharge arises from both hemispheres and the seizure may be absence, myoclonic, tonic, tonic-clonic or atonic, and focal, where seizures arise from one or part of one hemisphere.

Causes and risk

In epilepsy, 70-80% is idiopathic, with the cause unknown but presumed genetic. The secondary causes are cerebral dysgenesis or malformation, cerebral vascular occlusion, cerebral damage such as congenital infection, hypoxic-ischaemic encephalopathy and intraventricular haemorrhage or ischaemia, cerebral tumour, neurodegenerative disorders and neurocutaneous syndromes. The non-epileptic causes of seizures are febrile seizures; metabolic causes, which are hypoglycaemia, hypocalcaemia or hypomagnesaemia, and hypo- or hypernatraemia; head trauma; meningitis or encephalitis; and poisons or toxins.