Phenotypic characteristics of temporal lobe epilepsy: the impact of hippocampal sclerosis

Whether mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is a condition with a unique biological background that can be delineated from other TLE, is unresolved. Here we performed a comparative analysis of two TLE patient cohorts - one cohort with HS and one without HS - in order to identify phenotypic characteristics specifically associated with MTLE-HS.

Epidemiological data and clinical and diagnostic features were compared between patients with MTLE-HS and TLE patients without HS. When appropriate, data were compared with healthy controls.

Fifty-six (26%) patients were diagnosed with MTLE-HS and 162 (74%) with other TLE. Age at epilepsy onset was lower in patients with MTLE-HS (P = 0.003) than in TLE patients without HS. Incidence of simple partial seizures was higher in the MTLE-HS group (P = 0.006), as were complex partial seizures (P = 0.001), ictal psychiatric symptoms (P = 0.015), and autonomic symptoms (P < 0.001). Interictal psychiatric symptoms, including depression, were less frequent in MTLE-HS (P = 0.043). MTLE-HS patients had a higher incidence of childhood febrile seizures (FS; P = 0.043) than TLE patients without HS. In contrast, the former group had the lower frequency of first-grade family members with childhood FS (P = 0.019).

We identified phenotypic characteristics that distinguish MTLE-HS from other types of TLE. These characteristics will be important in diagnostics, treatment, and determination of prognosis, and provide a basis for future phenotype-genotype studies.