Abstracts

Rationale: Patients with refractory epilepsy and normal MRI findings represent a challenging sub-set of patients. Many of them would need invasive monitoring, and the outcome regarding seizures is generally worse then that obtained in patients with positive MRI findings. This paper reviewed the outcome and pathological findings in these patients with normal MRI. Methods: Twenty-nine patients with refractory temporal lobe epilepsy (TLE) and 65 patients with refractory extra-temporal epilepsy (eTLE) were studied. Age ranged from 10 to 58 years (mean= 24,3 years). Three patients with refractory TLE were operated without invasive monitoring (after surface video-EEG recording); the other 26 patients needed invasive recordings with subdural grids. All TLE patients were submitted to cortico-amygdalo-hypoocampectomy. All patients with refractory eTLE needed invasive recording with subdural grids. Among the eTLE patients there were 41 frontal, 14 posterior quadrant (parietal+occipital+posterior temporal) and 10 anterior quadrant (frontal+temporal) resections. All patients were submitted to surgery under general anesthesia and without intraoperative electrocorticography. Results: 72% of the TLE patients got seizure-free after surgery (including those 3 who did not need invasive recordings); 24% were in Engel II and 4% in Engel III. 65% of the patients with frontal, 60% with anterior quadrant and 71% posterior quadrant resections were seizure-free after surgery. Pathological evaluation showed that eight patients with TLE (including those 3 who did not undergo invasive monitoring) had mesial temporal sclerosis (6 with end-folium type); additionally, microdisgenesis was noted in 5 patients with TLE and in 16 patients there was no brain pathology. In the eTLE group, microdisgenesis was noted in 16 patients; atrophy was noted in 32 patients and in 17 patients there was no brain pathology. There was no relationship between the presence of microdisgenesis and seizure outcome. Conclusions: Approximately 25% of the patients with refractory TLE and normal MRI would have mesial temporal sclerosis, especially of the end-folium type, but the majority of them would have no definite brain pathology. In the eTLE group, no specific brain pathology was found in patients with normal MRI. Although patients with normal MRI findings do have a worse prognosis when compared to those with positive scans, the results are consistently better then those obtained with medical treatment alone in this patient population. Patients with normal MRI would very likely have no detectable brain pathology.