Management of a first unprovoked seizure

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. A single first unprovoked seizure is not yet epilepsy. Epilepsy is defined as 2 unprovoked seizures 24 h apart, a chronic neurological disorder characterised by recurrent unprovoked seizures, consisting of transient signs and symptoms associated with abnormal, excessive or synchronous neuronal activity in the brain. Seizures are classified as generalised, where the discharge arises from both hemispheres and the seizure may be absence, myoclonic, tonic, tonic-clonic or atonic, or focal, where the seizure arises from one or part of one hemisphere. The question after a first event is therefore whether it was provoked, and whether the risk of a second one is high enough to start a drug now.

Causes and risk

The causes divide into epilepsy and non-epileptic causes.

• Epilepsy is idiopathic in 70-80%, where the cause is unknown but presumed genetic. Secondary epilepsy follows cerebral dysgenesis or malformation, cerebral vascular occlusion, cerebral damage such as congenital infection, hypoxic-ischaemic encephalopathy or intraventricular haemorrhage and ischaemia, cerebral tumour, neurodegenerative disorders and neurocutaneous syndromes.
• Non-epileptic causes are febrile seizures, metabolic causes (hypoglycaemia, hypocalcaemia and hypomagnesaemia, hypo/hypernatraemia), head trauma, meningitis and encephalitis, and poisons or toxins.

After a first seizure the risk of recurrence is raised by a prior brain lesion, an epileptiform EEG abnormality, a significant brain imaging abnormality, and a nocturnal seizure.