Hippocampal sclerosis: Correlation of MR imaging findings with surgical outcome

Objective: Atrophy and a high T2 signal of the hippocampus are known to be the principal MR imaging findings of hippocampal sclerosis. The purpose of this study was to determine whether or not individual MRI findings correlat e with surgical outcome in patients with this condition. Materials and Methods: Preoperative MR imaging findings in 57 consecutive p atients with pathological ly-proven hippocampal sclerosis who underwent ant erior temporal lobectomy and were followed-up for 24 months or more were re trospectively reviewed, and the results were compared with the postsurgical outcome (Engel classification). The MR images included routine sagittal T1 -weighted and axial T2-weighted spin-echo images, and oblique coronal T1-we ighted 3D gradient-echo and T2-weighted 2D fast spin-echo images obtained o n either a 1.5 T or 1.0 T unit. The images were visually evaluated by two n euroradiologists blinded to the outcome; their focus was the presence or ab sence of atrophy and a high T2 hippocampal signal, Results: Hippocampal atrophy was seen in 96% of cases (55/57) [100% (53/53) of the good outcome group (Engel class I and II), and 50% (2/4) of the poo r outcome group (class ill and IV)]. A high T2 hippocampal signal was seen in 61% of cases (35/57) [62% (33/53) of the good outcome group and 50% (2/4 ) of the poor outcome group]. All 35 patients with a high T2 signal had hip pocampal atrophy. 'Normal' hippocampus, as revealed by MR imaging, occurred in 4% of patients (2/57), both of whom showed a poor outcome (Engel class III). The presence or absence of hippocampal atrophy correlated well with s urgical outcome (p <0.01). High T2 signal intensity did not, however, signi ficantly correlate with surgical outcome (p >0.05). Conclusion: Compared with a high T2 hippocampal signal, hippocampal atrophy is more common and correlates better with surgical outcome. For the predic tion of this, it thus appears to be the more useful indicator.