Clinical characteristics of nonlesional temporal lobe epilepsy

Abstract

Objective To investigate the clinical characteristics, memory and neuroimaging features of nonlesional temporal lobe epilepsy (TLE-NL). Methods Forty-four patients with TLE-NL and 53 patients with unilateral temporal lobe epilepsy with hippocampal sclerosis (TLE-HS) were recruited from the Second Affiliated Hospital of Zhejiang University from September 1st 2012 to August 31st 2017. The clinical characteristics were systematically analyzed and compared between TLE-NL and TLE-HS. Twenty healthy volunteers were also recruited. Memory assessment and high resolution magnetic resonance imaging (MRI) scanning were completed in the patients and healthy volunteers. Volume and shape of the hippocampus were compared between patients and healthy volunteers. Results Compared with the TLE-HS, TLE-NL patients showed later seizure onset ((24.3±12.6) vs (15.8±10.3) years; t=3.684, P<0.01), shorter duration of epilepsy ((4.00 (2.00, 8.75)) vs (14.00 (7.50, 22.00)) years; Z=-4.675, P<0.01), less history of febrile convulsions (4.5% (2/44) vs 62.3% (33/53); χ2=32.270, P<0.01) and lower incidence of pharmacoresistant epilepsy (47.7% (21/44) vs 84.9% (45/53); χ2=15.282, P<0.01). However, there were no statistically 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. TLE-NL patients had normal memory quotient compared to normal controls (105.2±17.4 vs 103.8±16.2; P=1.000), while TLE-HS patients had significant memory impairment compared to normal controls (84.5±20.3 vs 103.8±16.2; P<0.01). Compared to normal controls, TLE-NL patients did not have significant alteration in hippocampal volume and shape, while TLE-HS patients had significant atrophy in the ipsilateral hippocampus ((2 953±481) mm3vs (4 431±505) mm3; P<0.01), and shape analysis showed significant atrophy in the head and body of the hippocampus. Conclusion TLE-NL has different characteristics compared with TLE-HS, including later seizure onset, shorter duration of epilepsy, less history of febrile convulsions, better response to antiepileptic drugs, and no significant memory impairment and hippocampal atrophy. Key words: Temporal lobe epilepsy; Magnetic resonance imaging; Hippocampus; Memory