Mesial temporal Sclerosis.

MRI detects mesial temporal sclerosis by demonstrating this size asymmetry and abnormal signal within the atrophied hippocampus.

Thin-section, high-resolution coronal MR images are best for detecting these abnormalities, which can be subtle. T1-weighted images are best for detecting size asymmetry, and T2-weighted images are most sensitive for detecting signal changes. A special T2-weighted sequence called FLAIR (fluid attenuated inversion recovery) is even more sensitive for detecting signal abnormalities.

The most common cause of complex partial seizures is mesial temporal sclerosis, occurring in 35 to 65 percent of patients who undergo temporal lobe surgery. In mesial temporal sclerosis, the hippocampus is smaller than normal. This usually occurs on one side of the brain, but can occur bilaterally in 10 to 15 percent of cases.

Magnetic resonance imaging (MRI) is very important in planning for epilepsy surgery because of its ability to detect temporal lobe lesions that can cause seizures.

 In addition to mesial temporal sclerosis, other temporal lobe lesions can cause seizures, including benign and malignant neoplasms, cortical dysplasia, vascular malformations (like cavernous angiomas) and post-traumatic brain injury.