Purpose Following temporal lobectomy, a phenomenon of exclusively nocturnal seizures has been recognised but not widely studied. Here we analyse such a patient group to try and understand factors that determine this unusual outcome pattern.

Methods Among 476 patients who underwent temporal lobectomy between 1978 and 2007, 18 patients were identified with exclusively nocturnal seizures occurring for at least 5 years post surgery. They were compared with 20 controls matched for histology (majority hippocampal sclerosis) and seizure frequency.

Results The age at seizure onset was significantly older in the cases (mean 15.6 years) compared with the controls (mean 5.6 years, p=0.001). Presence of febrile seizures, presence of generalised seizures pre–op and concordance of supporting investigations (MRI/EEG/Ictal SPECT/Ictal PET) did not differ significantly between the groups.

78% of cases and 65% of matched controls experienced seizures within the first post operative year. All the cases experienced a reduction in seizure frequency postoperatively; seizure frequency plateaued by the second year post surgery in 13 of the 18 (72%) cases. The majority experienced infrequent (<1/month) seizures, though seizures were bilaterally convulsive in at least half of patients. The mean duration of follow up was 16.8 years, demonstrating long–term stability of the nocturnal seizures only pattern.

Conclusions Patients who experience exclusively nocturnal seizures following temporal lobectomy appear to be older at seizure onset compared with controls of similar pathology and (daytime) seizure frequency. Seizures are infrequent and although not formally assessed here, nocturnal only seizures appear to associated with improved quality of life, including the ability to drive.