This usually occurs on one side of the brain, but can occur bilaterally in 10 to 15 percent of cases. With subtle hippocampal atrophy, quantitative three-dimensional volume measurements of each hippocampus can be useful. These volume measurements can be especially helpful when there is bilateral hippocampal atrophy. In addition to mesial temporal sclerosis, other temporal lobe lesions can cause seizures, including benign and malignant neoplasms, cortical dysplasia, vascular malformations and post-traumatic brain injury. The most common types of neoplasms are low-grade astrocytomas and oligodendrogliomas in adults, and gangliogliomas and pilocytic astrocytomas in children.
Cortical dysplasia is a focal area of abnormal brain development.
Although the abnormal area is present before birth, seizures usually do not occur until childhood or adulthood. It is much less common than tumors. Its MRI appearance is similar to tumors, with mass effect and abnormal signal. Contrast enhancement, however, does not occur with cortical dysplasia. The most common vascular malformation associated with temporal lobe seizures is the cavernous angioma.