Hippocampal sclerosis in children with intractable temporal lobe epilepsy: detection with MR imaging

Abstract

Objective: Hippocampal sclerosis is the most common lesion associated with temporal lobe epilepsy. Temporal lobectomy is effective for the control of medically refractory seizures in these patients. Before the advent of MR imaging, hippocampal sclerosis was rarely diagnosed preoperatively. The purpose of this study was to determine the frequency of hippocampal sclerosis in children with intractable temporal lobe epilepsy and the accuracy and reliability with which hippocampal sclerosis can be diagnosed on the basis of MR findings in children.

Materials and methods: We reviewed the MR images of 53 children (mean age, 10 years) with medically refractory temporal lobe epilepsy. The MR images were reviewed blindly and independently by two radiologists on two occasions, and were classified as showing hippocampal sclerosis, other lesions, or no abnormality. Hippocampal sclerosis was diagnosed when evidence of hippocampal atrophy was present or hippocampal signal intensity was abnormal without evidence of a mass lesion.

Results: MR images showed hippocampal sclerosis in 30 children (57%), other lesions in 10 (19%) (tumors in eight, cavernous angioma in one, and ectopic gray matter in one), and no abnormality in 13 (24%) (intraobserver agreement: kappa = 0.77 and 0.84, interobserver agreement: kappa = 0.76). MR lateralization was concordant with ictal EEG in 36 (92%) of 39 children. Hippocampal sclerosis was bilateral in one child and associated with extrahippocampal lesions in nine. Hippocampal sclerosis was detected on MR images of 11 (85%) of 13 children with pathologic confirmation of hippocampal sclerosis. Beneficial results were seen in 26 (90%) of 29 children who had temporal lobectomy.

Conclusion: Hippocampal sclerosis is the most common lesion in children with intractable temporal lobe epilepsy, and it can be detected reliably and accurately on MR images. We suspect that hippocampal sclerosis is underdiagnosed in children, possibly leading to postponement of surgery in children with refractory seizures.