MRI-negative PET-positive temporal lobe epilepsy: a distinct surgically remediable syndrome.
Most patients with non-lesional temporal lobe epilepsy (NLTLE) will have the findings of hippocampal sclerosis (HS) on a high resolution MRI. However, a significant minority of patients with NLTLE and electroclinically well-lateralized temporal lobe seizures have no evidence of HS on MRI. Many of these patients have concordant hypometabolism on fluorodeoxyglucose-PET ([18F]FDG-PET). The pathophysiological basis of this latter group remains uncertain. We aimed to determine whether NLTLE without HS on MRI represents a variant of or a different clinicopathological syndrome from that of NLTLE with HS on MRI. The clinical, EEG, [18F]FDG-PET, histopathological and surgical outcomes of 30 consecutive NLTLE patients with well-lateralized EEG but without HS on MRI (HS-ve TLE) were compared with 30 consecutive age- and sex-matched NLTLE patients with well-lateralized EEG with HS on MRI (HS+ve TLE). Both the HS+ve TLE group and the HS-ve TLE patients had a high degree of [18F]FDG-PET concordant lateralization (26 out of 30 HS-ve TLE versus 27 out of 27 HS+ve TLE). HS-ve TLE patients had more widespread hypometabolism on [18F]FDG-PET by blinded visual analysis [odds ratio (OR = + infinity (2.51, -), P = 0.001]. The HS-ve TLE group less frequently had a history of febrile convulsions [OR = 0.077 (0.002-0.512), P = 0.002], more commonly had a delta rhythm at ictal onset [OR = 3.67 (0.97-20.47), P = 0.057], and less frequently had histopathological evidence of HS [OR = 0 (0-0.85), P = 0.031]. There was no significant difference in surgical outcome despite half of those without HS having a hippocampal-sparing procedure. Based on the findings outlined, HS-ve PET-positive TLE may be a surgically remediable syndrome distinct from HS+ve TLE, with a pathophysiological basis that primarily involves lateral temporal neocortical rather than mesial temporal structures.
Victorian Epilepsy Centre, St Vincent's Hospital, Victoria, Australia. carnero@svhm.org.au
R P
RP
Carne
T J
TJ
O'Brien
C J
CJ
Kilpatrick
L R
LR
MacGregor
R J
RJ
Hicks
M A
MA
Murphy
S C
SC
Bowden
A H
AH
Kaye
M J
MJ
Cook
D000328:Adult; D004569:Electroencephalography / Q000379:methods; D004833:Epilepsy, Temporal Lobe / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D005192:Family Health; D005260:Female; D006624:Hippocampus / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D012189:Retrospective Studies; D012598:Sclerosis; D012640:Seizures / Q000473:pathology / Q000503:physiopathology; D014055:Tomography, Emission-Computed / Q000379:methods*; D016896:Treatment Outcome