Medial temporal sclerosis (MTS), also known as hippocampal sclerosis, is a feature commonly associated with temporal lobe epilepsy (TLE). MTS refers to neuronal loss and atrophy in association with fibrillary gliosis of the temporal lobe. Trauma, infection, tumor, hypoxic damage, and seizures have all been implicated in scarring of the temporal lobe specifically in the region of the hippocampus. TLE is an example of focal or partial epilepsy whereby the seizure initiation point is found within the temporal lobe with structures including the hippocampus, amygdala, and parahippocampal gyrus. TLE is the most common epileptic syndrome in adults with onset typically occurring during late childhood or adolescence. MTS is the most common pathological abnormality found in temporal lobe specimens surgically resected for medically intractable TLE.

Several studies have demonstrated that MRI is superior in identifying the characteristic lesions associated with MTS. MRI has played a vital role in the recognition of the association between MTS and TLE over the last 20 years. 3D FSPGR MRI of the temporal lobes is considered the preferred modality. Thin sections oriented perpendicular to the plane of the hippocampus have the highest sensitivity and specificity for detecting MTS. PET and SPECT scans with 18-fluorodeoxyglucose (FDG) as well as EEG may be used as adjuncts in lesion localization. The radiologic diagnosis of MTS is made based on findings of hippocampal atrophy and/or hippocampal T2 signal changes seen with optimized high resolution MRI. The gliosis seen with MTS is strongly indicated by an abnormally increased T2 signal in the hippocampus. This increased T2 signal is believed to be secondary to the presence of gliosis and the subsequent increase in free water content.

The widely accepted treatment of MTS is a temporal lobectomy with hippocampectomy, and MRI is instrumental in the pre-operative assessment of hippocampal abnormalities. Patients with MTS visible on MRI were found to have improved post-surgical outcomes. In addition, the extent of MTS depicted on MRI can be utilized in the prediction of patient outcome following surgical intervention. TLE is exacerbated by additional seizures emphasizing the significance of surgical intervention. The most promising outcome is for patients with MTS limited to one side of the brain and for those with resection of the maximum amount of sclerotic tissue.