Temporal pole MRI abnormalities in temporal lobe epilepsy

Abstract

ABSTRACT Magnetic resonance imaging (MRI) demonstrates an abnormal aspect of the temporo‐polar region in 1/3 to 2/3 of patients suffering from cryptogenic temporal lobe epilepsy. This abnormal aspect is described as a white matter increased T2 signal, resulting in a loss of gray‐white matter demarcation, often associated with atrophy, as recently confirmed by quantitative volumetric measurements. These temporo‐polar MRI findings appear to correctly lateralize the epileptogenic temporal lobe with a very high specificity, and have never been reported in extra‐temporal lobe epilepsy nor in control subjects. They are usually associated with MRI signs of hippocampal sclerosis, but the two conditions seem to be partly distinct from a pathophysiological point of view. Pathological correlates of temporo‐polar white matter increased T2 signal are controversial, but the role of an abnormal myelin seems more likely than that of ectopic neurons. A myelin dysfunction would also be consistent with the correlation observed between lateral temporal hypometabolism and temporo‐polar MRI abnormalities. Whether or not these MRI findings are associated with a better seizure outcome following temporal lobectomy remains a debated issue.