Clinical Characteristics Of MRI-negative Temporal Lobe Epilepsy

Objective:The clinical characteristics of MRI-negative temporal lobe epilepsy(TLE-NL)are not well known.Based on a cohort of TLE-NL which were strictly selected,the clinical characteristics,neuroimaging features and cognitive function were analyzed.These clinical parameters were compared with those in temporal lobe epilepsy with hippocampal sclerosis(TLE-HS).Our study could provide an insight for classification of temporal lobe epilepsy(TLE).Methods:Patients with TLE-NL who met the inclusion criteria were included from the Second Affiliated Hospital of Zhejiang University from September 1st 2012 to August 31st 2017.We systematically analyzed the clinical data including sex,age,age of seizure onset,duration of epilepsy,family history of epilepsy,history of febrile convulsion,epileptogenic zone,seizure semiology,aura,seizure frequency,pharmacoresistance to antiepileptic drugs,memory quotient(MQ),hippocampal volume and hippocampal surface shape.The clinical characteristics of these patients were compared with 53 patients with unilateral TLE-HS.Results:Totally,71 cases of TLE had no abnormalities on common MRI.After high-resolution MRI with a dedicated epilepsy protocol,27 cases with subtle MRI lesions were excluded.A total of 44 cases of TLE-NL were included.Compared with TLE-HS,the patients with TLE-NL had later seizure onset age(24.30±12.55 vs 15.75±10.29y,p=0.000),shorter duration of epilepsy(6.60±6.60 vs 15.64±9.89y,p=0.000),lower prevalence of febrile convulsions(5%vs 62%,p=0.000),lower incidence of pharmacoresistant epilepsy(47.7%vs 84.9%,p=0.000),less impairment of memory function(MQ,105.23 ± 17.41 vs 84.49±20.25,p=0.000),and less prevalence of abdominal aura(11.4%vs 34.0%,p=0.009).However,there were no significant differences between TLE-NL and TLE-HS in sex ratio,family history of epilepsy,lateralization of the epileptogenic zone,presence of aura,seizure types and seizure frequency(p>0.05).In both groups of TLE,the emotional aura were more frequently seen in the right temporal lobe(26.3%vs 73.7%,p=0.024),percentage of female patients was higher(59%and 64%,respectively),CPS was the major semiological type,and the seizure usually occurred monthly(1-4 seizures/month).There was no significant difference in total hippocampal volume,the ipsilateral or contralateral hippocampal volume between TLE-NL and normal controls(p>0.05).Hippocampal surface shape analysis showed no significant surface shape change in the bilateral hippocampus surface in TLE-NL compared with normal control.On the contrary,patients with TLE-HS had contralateral as well as ipsilateral hippocampal atrophy.Conclusion:TLE-NL is a subgroup of TLE.Its clinical characteristics are different from those of TLE-HS.Although it shares similar seizure semiology with TLE-HS,patients with TLE-NL had later seizure onset age,shorter duration of epilepsy,lower prevalence of febrile convulsions and pharmacoresistant epilepsy,less impairment of memory function and lower prevalence of abdominal aura.Neither quantitative analysis of hippocampal volume nor hippocampal surface shape analysis revealed an obvious morphological change in TLE-NL.Our data are helpful in classification of temporal lobe epilepsy.