Familial mesial temporal lobe epilepsy and the borderland of déjà vu

Objective: The cause of mesial temporal lobe epilepsy (MTLE) is often unknown. We ascertained to what extent newly-diagnosed non-lesional MTLE actually represents familial MTLE (FMTLE). Methods: We identified all consecutive patients presenting to the Austin Heath First Seizure Clinic with MTLE and a normal MRI or MRI-evidence of hippocampal sclerosis over a 10-year period. Patients' first-degree relatives and pairwise age- and sex-matched controls underwent a comprehensive epilepsy interview. Each interview transcript was reviewed independently by two epileptologists, blinded to relative or control status. Reviewers classified each subject as follows: epilepsy, specifying if MTLE; manifestations suspicious of epilepsy; or unaffected. Physiological deja vu was noted. Results: Forty-four patients were included. At the Clinic, MTLE had been recognized to be familial in 2 patients only. Among 242 subjects interviewed, MTLE was diagnosed in 9/121 relatives vs 0/121 controls (p=0.008). All affected relatives had seizures with intense deja vu and accompanying features; 6 relatives had not been previously diagnosed. Deja vu experiences which were suspicious, but not diagnostic, of MTLE occurred in 6 additional relatives vs none of the controls (p=0.04). Physiological deja vu was common, and did not differ significantly between relatives and controls. After completing the relatives' interviews, FMTLE was diagnosed in 8 of 44 patients (18.2%). Interpretation: FMTLE accounts for almost one-fifth of newly diagnosed non-lesional MTLE, and it is largely unrecognized without direct questioning of relatives. Relatives of patients with MTLE may experience deja vu phenomena which clinically lie in the ‘borderland' between epileptic seizures and physiological deja vu. This article is protected by copyright. All rights reserved.