Temporal lobe epilepsy (TLE) is a term that refers to a condition where seizures are generated in the portion of the brain called the temporal lobe. Either the right or the left temporal lobe can be involved, and in rare cases both temporal lobes can be involved in a particular individual.
Under the broad category of TLE, there are a number of specific types. In mesial TLE (MTLE), there are characteristic abnormalities in the mesial aspect of the temporal lobe. This variably involves sclerosis (scarring), loss of nerve cells in the hippocampus and mossy cell fiber sprouting. Of course, there are other different pathologies that can be seen in the temporal lobe including tumors, stroke, multiple sclerosis plaques, and tubers (as seen in tuberous sclerosis). Another type of TLE is lateral TLE. This is where the seizures originate in the lateral portion of the particular temporal lobe. Again, various pathologies can be found such as cortical malformations and stroke. However, imaging studies, such as magnetic resonance imaging (MRI), often may not show any obvious lesions or abnormalities. As more information is gathered regarding the genetics that may be involved in some cases, the classification of TLE will likely change.
TLE, as a whole, constitutes a common type of epilepsy. The exact incidence is not clear but it is suspected to make up a significant proportion of medication-resistant epilepsy. Approximately 30% (of the 2.7 million cases of epilepsy in the United States) do not adequately respond to medications. Up to a half of these may be due to TLE. One of the risk factors that may predispose children to, in particular, mesial TLE is complicated or prolonged febrile convulsions before the age of five years. Mesial TLE can also run in some families.
Roy Sucholeiki MD, The Gale Group Inc., Gale, Detroit,