Abstracts

Rationale: Magnetic resonance imaging (MRI) is pivotal in defining the presence of an epileptogenic lesion that may coexist with the site of seizure onset. Refractory temporal lobe epilepsy (TLE) may be associated with several benign mesial temporal lesions like hippocampal sclerosis (HS), low grade gliomas, cortical dysphasia and cavernous malformations. More recently adult onset autoimmune limbic encephalitis has been recognized as a cause of refractory TLE After prolonged febrile and non-febrile seizures the hippocampus (HC) may become enlarged and hyperintense and later atrophy to HS. Temporal lobe surgery for lesional epilepsy carries a more favorable prognosis than nonlesional epilepsy. Therefore identifying a lesion is crucial for prognosis. We describe a cohort of TLE patients with isolated enlargement of amygdala (AG) or amygdala and HC combined with benign epilepsy prognosis. Methods: Thirty one (17 female) randomly selected patients with symptomatic mesial lesional TLE had AG or AG and HC enlargement on visual analysis of MRI (T1, T2, FLAIR, Gadolinium contrast, and MR Spectroscopy). Three were excluded (1 had no digital MRI and 2 had other obvious MRI lesions). We assessed interictal and ictal EEG features histopathology in operated cases and outcomes with regard to seizures and MRI changes. Results: Average age was 47 years (range 20-80), epilepsy duration was 14 years (range <1-43). Twenty patients had isolated AG enlargement and eight had AG HC enlargement, involving right and left temporal lobes equally. In eight patients who had epilepsy surgery histopathology showed HS in two, AG gliosis in one, cortical dysplasia in one and normal structures in four. On repeat MRI at an average of 11 years (range 1 to 30 years), the enlargement resolved in 6 (4 to normal and 2 to HS), and persisted in 14. Majority of MRI reports included low grade glioma in the differential diagnosis. No patient developed further enlargement or malignant features. Of six patients who had AG MR Spectroscopy five showed increased myoinositol levels. Epileptiform discharges were present in 19/28, all but one ipsilateral to the lesion. The seizure types were complex partial in 19, simple partial in 17 and generalized tonic clonic in 17 subjects. AED treatment continues in 20/28 patients, 17 on monotherapy. Nineteen patients (68%) remain seizure free on average 4 years (range 1-9 years) of follow-up.