MRI Assessment of Hippocampal Sclerosis

Abstract

Hippocampal Sclerosis (HS) is the most common cause of refractory temporal lobe epilepsy in adults. The aim of our study was to evaluate the diagnostic accuracy of conventional MRI sequences in HS and devise a cost-effective protocol of choice. Forty-eight patients, 26 men and 22 women, aged 16–55 years (mean age 29 years) with seizures refractory to medical treatment were evaluated by MR imaging. Hippocampal formation was assessed by transverse spin-echo (SE) T1-weighted (WI) and fast spin-echo (FSE) T2-WI sequences and by coronal Fluid Attenuated Inversion Recovery (FLAIR) and Inversion Recovery (IR) images. Increased signal intensity in FLAIR (93.2%), hippocampal atrophy (84.8%) and decreased signal intensity in IR images (72.7%) were the most common pathological findings of HS, while loss of the ipsilateral temporal lobe gray/white matter demarcation (66,7%) and amygdala sclerosis (15.1%) were encountered less frequently. FLAIR sequence was found to be more sensitive than FSE T2-WI in detecting HS. Thin coronal images were particularly helpful in assessing hippocampal formation, while IR images were additionally useful for the detection of possible co-existent cortical abnormalities. A brief review of the imaging findings of HS in more recent MR sequences is also made, though emphasizing that conventional SE T1-WI, FSE T2-WI, FLAIR and IR sequences, with a total examination duration of less than eight minutes, provide high sensitivity and specificity in the assessment of HS.