Clinical characteristics of MRI-negative temporal lobe epilepsy.

Purpose: To investigate the characteristics of patients with MRI-negative temporal lobe epilepsy (TLE) (1.5 T brain MRI) in comparison with: (i) patients with hippocampal sclerosis (HS)-TLE; (ii) persons with non-HS structural TLE; and (iii) patients with dual pathology.

Methods: This was a retrospective study. All patients with an electro-clinical diagnosis of TLE were studied at the outpatient epilepsy clinic at Shiraz University of Medical Sciences, Shiraz, Iran, from 2008 until 2020.

Results: Six hundred and forty-one patients were studied [273 (42.6%) HS, 154 (24.0%) non-HS structural TLE, 174 (27.1%) MRI-negative TLE, and 40 (6.2%) dual pathology]. The groups differed significantly. Important dissimilarities included: (i) compared with HS-TLE group, patients with MRI-negative TLE more often had a family history of epilepsy and less often had a history of febrile convulsion; (ii) compared with non-HS structural TLE group, patients with MRI-negative TLE more often had focal to bilateral tonic-clonic seizures, less often had focal seizures with impaired awareness, and more often had a family history of epilepsy; (iii) compared with the dual pathology group, patients with MRI-negative TLE less often were male and less often had a history of febrile convulsion.

Conclusion: Patients with MRI-negative TLE are not a homogenous group of people and it is not necessarily a distinct entity from other forms of TLE either. With the emergence of advanced imaging technologies, the underlying pathologies of MRI-negative TLE may be revealed.