High-resolution MRI can detect dual pathology (an extrahippocampal lesion plus hippocampal atrophy) in about 5-20% of patients with refractory partial epilepsy referred for surgical evaluation. We report the results of 41 surgical interventions in 38 adults (mean age 31 years, range 14-63 years) with dual pathology. Three patients had two operations. The mean postoperative follow-up was 37 months (range 12-180 months). The extrahippocampal lesions were cortical dysgenesis in 15, tumour in 10, contusion/infarct in eight and vascular malformation in five patients. The surgical approach aimed to remove what was considered to be the most epileptogenic lesion, and the 41 operations were classified into lesionectomy (removal of an extrahippocampal lesion); mesial temporal resection (removal of an atrophic hippocampus); and lesionectomy plus mesial temporal resection (removal of both the lesion and the atrophic hippocampus). Lesionectomy plus mesial temporal resection resulted in complete freedom from seizures in 11/15 (73%) patients, while only 2/10 (20%) patients who had mesial temporal resection alone and 2/16 (12.5%) who had a lesionectomy alone were seizure-free (P< 0.001). When classes I and II were considered together results improved to 86, 30 and 31%, respectively. Our findings indicate that in patients with dual pathology removal of both the lesion and the atrophic hippocampus is the best surgical approach and should be considered whenever possible.

Cortical developmental malformations are best diagnosed by MRI and are often the cause of refractory epilepsy. Little is known about the metabolic cell function on MR spectroscopy of these types of brain anomaly. We studied 23 patients with cortical developmental malformations and refractory epilepsy using proton MR spectroscopic imaging. Mean age was 28 years (range, 9 to 47 years). The lesions examined were focal cortical dysplasia (n = 5), heterotopia (four band, six periventricular, two subcortical), polymicrogyria (n = 3), tuberous sclerosis (n = 2), and polymicrogyria and periventricular nodular heterotopia (n = 1). We measured the relative signal intensity of N-acetylaspartate/creatine (NAA/Cr) in the lesion, in the perilesional region, and in the region remote from the visible lesion. The values were compared with those from similar brain regions of 25 normal control subjects. The mean NAA/Cr z score values for the 23 patients were as follows: lesion, -2.20 +/- 0.32 (mean +/- SE), n = 21; perilesional region, -1.01 +/- 0.38, n = 15; and distant region, -0.03 +/- 0.34, n = 18 (p < 0.0002). Despite the presence of a large number of neurons, heterotopia showed a relative decrease of NAA in some patients, suggesting that the neurons present were dysfunctional. The maximal NAA/Cr decrease, indicating metabolic dysfunction, colocalized to the structural malformation as defined by MRI and extended to normal-appearing regions adjacent to the visible lesion.

Modern neuroimaging can disclose epileptogenic lesions in many patients with partial epilepsy and, at times, display the coexistence of hippocampal atrophy in addition to an extrahippocampal lesion (dual pathology). We studied the postoperative seizure outcome of 64 patients with lesional epilepsy (median follow-up, 30 months) and considered separately the surgical results in the 51 patients with a single lesion and in the 13 who had dual pathology. In patients with a single lesion, 85% were seizure free or significantly improved (Engel's class I-II) when the lesion was totally removed compared with only 40% when there was incomplete resection (p < 0.007). All three patients with dual pathology who had both the lesion and the atrophic hippocampus removed became seizure free. In contrast, only 2 of the 10 patients with dual pathology undergoing surgery aimed at the lesion or at the hippocampus alone became seizure free (p < 0.05), although 4 of them showed significant improvement (Engel's class II). We conclude that the outcome in patients with single epileptogenic lesions is usually dependent upon the completeness of lesion resection. In patients with dual pathology, surgery should, if possible, include resection of both the lesion and the atrophic hippocampus.