Long term outcome of temporal lobe epilepsy surgery: analyses of 140 consecutive patients
Jutila L, Immonen A, Mervaala E, Partanen J, Partanen K, Puranen M, Kälviäinen R, et al.;
Commented by , 16 Dec 2002
Background
Temporal lobe epilepsy (TLE) is known to be resistant to treatment with antiepileptic drugs (AED). Recently it has been shown in a randomized controlled study that surgical treatment is superior to AED in drug refractory individuals (Wiebe et al., New England Journal of Medicine, 2001; 345; 311-318).
Preoperative measurements have evolved in order to characterize and select relevant patients for surgery. MRI has been the most important technique in this context, revealing a large number of patients with hippocampal changes eligible for surgery. Although the postoperative outcome is well characterized in TLE, there is still a need to explore preoperative prognostic factors for good long-term outcome.
Aim
To evaluate the long-term results of temporal lobe surgery and preoperative factors predicting a good postoperative outcome.
Methods
The study was a longitudinal follow up of 140 consecutive patients operated for drug resistant TLE at a national epilepsy surgery centre. The presurgical evaluation consisted of neurological examination, ictal video EEG, neuropsychological evaluation, sodium amobarbital (WADA) test, psychiatric evaluation and MRI.
Between 1988 and 1993 MRI was performed at various kinds of imagers and with different protocols. After 1993, state of the art MRI (1,5 T) equipment and a standardized protocol was used. The postoperative outcome was assessed according to a classification adapted from Engel.
Results
46% of all patients with unilateral temporal lobe epilepsy became seizure free, 10% had only postoperative auras and 15% had rare seizures on follow up for 5,4 (0,25-10,5) years. The best outcome followed the introduction of state of the art MRI procedures.
In this subgroup, 52% of unilateral TLE patients became seizure free, 7% had only postoperative auras and 17% rare seizures for 3,8 years (0,25-6,5). Most seizure relapses (86%) occurred within one year of the operation, and outcome at one year did not differ from the long-term outcome.
Logistic regression analysis showed that predictors of Engel I – II outcome were:
- unilateral hippocampal atrophy without temporal cortical atrophy
- other unitemporal structural lesions
- onset of temporal epilepsy before age of five years
- focal seizures with ictal impairment of consciousness and focal ictal EEG as a predominant seizure type and
- hippocampal volume reduction of at least 1 SD from the mean of controls on the side of the seizure onset.
Discussion
The study shows that surgical treatment has a central position in drug refractory TLE, which also has been the conclusion of other studies. It furthermore reveals a number of helpful prognostic factors for postoperative outcome. Among these are early onset of seizures and focal seizures with ictal impairment of consciousness and a focal ictal EEG, which formerly has been associated with a poor outcome.
The authors conclude that these symptoms are consistent findings in mesial temporal lobe epilepsy and should be evaluated in this regard. The study clearly demonstrates the superior prognostic value of qualitative and volumetric MRI while e.g. localization of ictal onset by video EEG was not related to outcome.
Other non invasive measurements with potential predictive value should be evaluated in TLE, and in this regard MR spectroscopy seem promising (Guye et al., Epilepsia, 2002; 43; 1197).