Mesial temporal lobe epilepsy with hippocampal sclerosis

John M Stern MD (

Dr. Stern, Director of the Epilepsy Clinical Program at the University of California in Los Angeles, received honorariums from Eisai, Greenwich, SK Life Sciences, and UCB Pharma as an advisor and from Eisai, Greenwich, LivaNova, Neurelis, and UCB Pharma as a lecturer.

Jerome Engel Jr MD PhD, editor. (

Dr. Engel of the David Geffen School of Medicine at the University of California, Los Angeles, received honorariums from Cerebel for advisory committee membership.

Originally released July 26, 1994; last updated January 18, 2021; expires January 18, 2024


Mesial temporal lobe epilepsy is the most prevalent form of epilepsy and among the most resistant to medical treatment. Hippocampal sclerosis is a frequent pathological substrate, but other lesions in mesial temporal structures give rise to the same electroclinical syndrome. Although the etiology of hippocampal sclerosis and the natural history of mesial temporal lobe epilepsy are inadequately understood, referral to a comprehensive epilepsy center is important when seizures persist after a trial of first-line medications and interfere with daily living. Patients with mesial temporal lobe epilepsy often are excellent candidates for surgical treatment, with 70% to 90% becoming free of disabling seizures after treatment. Best results with respect to quality of life are obtained when surgical therapy is soon after failure of medications.

Key points


• Mesial temporal lobe epilepsy with hippocampal sclerosis (TLE-HS) is a common form of epilepsy.


• Mesial temporal lobe epilepsy with hippocampal sclerosis often is progressive with worsening seizures, cognitive function, and depression.


• When medications fail to fully control seizures, resective surgery can be highly effective.

Historical note and terminology

Hippocampal sclerosis was first identified during postmortem examination of the brains of patients with chronic epilepsy in 1825 by Bouchet and Cazauvieilh, but it was thought to be an effect rather than a cause of epileptic seizures (Bouchet and Cazauvieilh 1825). By the late 19th century, John Hughlings Jackson associated clinical ictal manifestations that we now characterize as focal seizures with impaired awareness (complex partial seizures) as related to structural lesions in the mesial temporal lobe, and suggested a causal relationship (Jackson 1880; Jackson and Colman 1898). After the introduction of the EEG, these ictal behaviors were demonstrated to be correlated with electrographic abnormality in the mesial temporal lobe (Jasper 1941; Jasper and Kershman 1941). Evidence for a causal role of hippocampal sclerosis and for the existence of a syndrome came initially from the work of Murray Falconer, who performed en bloc anterior temporal lobe resections for medication resistant temporal lobe seizures (Falconer 1953). As a result of careful pathological evaluation of the resected specimens, mesial temporal sclerosis was shown to be the most common substrate of this condition, and its removal resulted in a good surgical outcome (Falconer 1971). A workshop was convened by the International League Against Epilepsy to determine if mesial temporal lobe epilepsy with hippocampal sclerosis is a syndrome or a disease, and it was concluded that it was neither and probably represents a number of different syndromes (Wieser 2004).

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