Histologically confirmed hippocampal structural features revealed by 3T MR imaging: potential to increase diagnostic specificity of mesial temporal sclerosis.

BACKGROUND AND PURPOSE

With appropriate selection, temporal lobe epilepsy is potentially curable with surgical intervention achieving seizure freedom in ~80% of individuals. MR imaging-based identification of MTS remains central to the selection process but currently relies on qualitative visual analysis. We sought to determine if new ultrastructural hippocampal details seen on 3T MR imaging had histopathologic correlates and whether these could serve as a useful tool in MTS identification.

MATERIALS AND METHODS

Patients undergoing selective anterior temporal lobectomy (n = 5) were scanned using 3T MR imaging preoperatively. En bloc resections were rescanned and subsequently prepared for histopathologic analysis of all hippocampal layers in the CA1-3 regions. Using a newly identified landmark from 3T FSTIR coronal images in 20 patients with histologically confirmed MTS, blinded studies compared ipsilateral and contralateral sides to generate threshold measurements for application in a fast quantitative analysis tool.

RESULTS

Histopathologic analysis and correlation with 3T imaging of en bloc resections identified the low-intensity signal as the stratum lacunosum. MTS was associated with extensive gliosis throughout the CA1-3 regions, with loss of tissue thickness in the stratum pyramidale most pronounced in CA1. Fast quantitative analysis by using the stratum lacunosum as a landmark provided a test that identifies MTS with a SN of 70% and SP of 85%.

CONCLUSIONS

Here we delineated ultrastructural hippocampal details seen on 3T MR imaging in both the in vivo and ex vivo setting, correlating these with histopathologic features consistent with MTS, and provided preliminary data suggesting their utility in the development of a quantitative analysis assessment tool for application in surgical-candidate selection.