Page 147 - ILAE_Lectures_2015

Chapter 13

Temporal lobe epilepsy

BEATE DIEHL and JOHN S. DUNCAN

UCL Institute of Neurology, National Hospital for Neurology and Neurosurgery, Queen
Square, London, and Epilepsy Society, Chalfont St Peter, Buckinghamshire

In community studies, the cumulative incidence of non-febrile seizures is about 20 per 1000.
The prevalence of active epilepsy is 5 per 1000 and about 50% of these patients have seizures
(16 patients with active focal epilepsy in a population of 6000). About 6070% of focal
seizures originate in the temporal lobe. It has been attempted to link seizure semiology to
activation of different anatomical regions of the temporal lobe. One attempt was to divide
temporal lobe seizures into opercular, temporal polar, and basal or limbic types1; whether
such detailed classification schemes are valid or useful is debatable. The distinction into
mesio-basal and lateral neocortical types however is widely accepted, and even though
symptomatology overlaps and spread from lateral to mesial cortex (and vice versa) is
common, this remains a useful distinction2.

Epilepsy arising in the medial temporal lobe (MTLE) (Table 1)

The commonest pathology underlying this type of epilepsy is hippocampal sclerosis3,4, and
the entity of mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE with HS) is
recognised as a distinctive constellation among the focal epilepsies5. This pathology is
associated with febrile convulsions in young children (particularly complex prolonged febrile
convulsions), possibly due to a factor predisposing the child to febrile seizures or maybe as
the result of a complex febrile convulsion. Other pathologies include dysembryoplastic
neuroepithelioma and other benign tumours, cavernous angiomas, glioma, malformations of
cortical development, or gliosis as a result of encephalitis or meningitis.

The symptoms during epileptic seizures may be subjective only (epileptic auras, with clear
consciousness) or may progress to seizure signs that can be observed and analysed when
recorded during video EEG recordings, often associated with impairment of awareness6.
Seizures arising from the temporal lobe typically have a relatively gradual evolution
(compared to extra-temporal seizures), develop over 12 minutes, have an indistinct onset
with partial awareness at the onset, and last longer than most extra-temporal seizures (210
minutes). Often, three components can be seen:

Aura. An aura is defined as a subjective feeling typically involving sensory or psychic
phenomena only. It may comprise visceral, cephalic, gustatory, olfactory, déjà vu or affective
symptoms and fear. The rising epigastric sensation is the commonest aura, others include
perceptual or autonomic auras. Ictal events arising in the amygdala commonly have several
different types of auras. Autonomic symptoms include changes in skin colour, blood pressure,
heart rate, pupil size, and piloerection. Speech usually ceases or is severely reduced, but
occasionally repetitive vocalisation may occur. Simple auditory phenomena such as
humming, buzzing, hissing, and roaring may occur if the discharges arise in the superior
temporal (Heschl’s) gyrus; and olfactory sensations, which are usually unpleasant and
difficult to define, can signal the start of seizures in the sylvian region or ento-rhinal cortex.