Temporal Lobe Epilepsy: a Clinical View Point

January 2009 Version 9 TEMPORAL LOBE EPILEPSY: A CLINICAL VIEW POINT Background: Temporal lobe epilepsy (TLE) was defined in 1985 by the International League Against Epilepsy (ILAE) as a condition characterized by recurrent unprovoked seizures originating from the medial or lateral temporal lobe. The seizures associated with TLE consist of simple partial seizures without loss of awareness (with or without aura) and complex partial seizures (ie, with loss of awareness). The individual loses awareness during a complex partial seizure because the seizure spreads to involve both temporal lobes, which causes impairment of memory. TLE was first recognized in 1881 by John Hughlings Jackson, who described "uncinate fits" and the “dreamy state." In the 1940s, Gibbs et al introduced the term "psychomotor epilepsy." The international classification of epileptic seizures (1981) replaced the term psychomotor seizures with complex partial seizures. The ILAE classification of the epilepsies uses the term temporal lobe epilepsy and divides the etiologies into cryptogenic (presumed unidentified etiology), idiopathic (genetic), and symptomatic (cause known, eg, tumor). Pathophysiology: Hippocampal sclerosis is the most common pathologic finding in TLE. Hippocampal sclerosis involves hippocampal cell loss in the CA1 and CA3 regions and the dentate hilus. The CA2 region is relatively spared. For more information, see Pathophysiology in the article Seizures and Epilepsy: Classification and management. Frequency: In the US: Approximately 50% of patients with epilepsy have partial epilepsy. Partial epilepsy is often of temporal lobe origin. However, the true prevalence of TLE is not known, since not all cases of presumed TLE are confirmed by video-EEG and most cases are classified by clinical history and interictal EEG findings alone. The temporal lobe is the most epileptogenic region of the brain. In fact, 90% of patients with temporal interictal epileptiform abnormalities on their EEG have a history of seizures.