Page 139 - ILAE_Lectures_2015

Chapter 12

Adult onset epilepsies

FERGUS J. RUGG-GUNN

Department of Clinical and Experimental Epilepsy, National Hospital for Neurology and
Neurosurgery, Queen Square, London

Not all seizures occurring during adult life are due to epilepsy. Many are acute symptomatic
seizures which must be recognised to avoid inappropriate antiepileptic drug (AED) treatment.
Acute symptomatic seizures can complicate any acute encephalopathy caused by drugs
(particularly alcohol, cocaine, antidepressant overdosage) or metabolic disturbance (uraemia,
hepatic encephalopathy, etc). They are almost exclusively generalised tonic-clonic seizures
that may sometimes be preceded by myoclonus. As seizures of this type rarely present for the
first time over the age of 30 years as part of an epilepsy syndrome, one should always have a
high index of suspicion about such seizures. Also, acute symptomatic seizures can occur in
association with acute cerebral insults such as head injury, stroke, and encephalitis; while
their occurrence increases the risk of post-traumatic epilepsy the two are not inevitably linked
(see below).

Seizure types in adult epilepsies

Epilepsy may develop in adults for a number of reasons. In the early part of adult life it is
common to see a number of patients presenting with idiopathic generalised epilepsies,
particularly juvenile myoclonic epilepsy and epilepsy with wakening tonic-clonic seizures.
Such epilepsies will be characterised by a high probability of generalised spike and wave in
the EEG, and patients will be neurologically normal and not require further investigation.

Most other patients presenting with epilepsy in adult life will have a form of partial epilepsy.
This may be overtly declared by the presence of an aura to seizures that clearly identifies the
localised onset. However, patients will be seen in whom the focal onset does not result in
significant symptoms that can be recalled subsequently by the patient, or witnessed by
observers. This is particularly the case for seizures that occur during sleep. All seizures
occurring during sleep which commence during adult life must be regarded as being of focal
onset unless proven otherwise.

While the onset of a partial epilepsy during adult life is more commonly associated with the
identification of an underlying neurological disorder than is the case with epilepsies
developing in childhood, it must be recognised that over 50% of patients with adult onset
epilepsy have no aetiology that can be determined by the investigative means currently
available, although this proportion is decreasing as advances in magnetic resonance imaging
occur. A number of aetiological groups of adult onset epilepsies will be considered here in
more detail.

Causes of adult-onset epilepsy

Post-traumatic epilepsy
The incidence of post-traumatic epilepsy varies depending on the population studied. The
best available information on the risk of epilepsy following head injury comes from the
community-based survey summarised in Table 1. This would indicate that mild injuries (e.g.