Radiology Resident Case of the Week
Clinical Sx:
The most common epileptic syndromes that are refractory to medical management are those associated with complex partial seizures. Complex partial seizures arise most commonly form the temporal lobe with the most frequent histologic substrate (found in approximately 65% of temporal lobectomy specimens) being mesial temporal sclerosis (MTS).
Etiology/Pathophysiology
It has been postulated that mesial temporal sclerosis may be related to a complicated delivery, febrile convulsions during childhood, and status epilepticus. These circumstances are believed to cause metabolic disturbances in neurons in the hippocampus, which may disappear and be subsequently replaced by gliosis.
Pathology:
MTS consists of neuron loss and gliosis in certain areas of the hippocampus.
Miscellaneous
Imaging
The MR criteria include: increased signal in the hippocampus (which is the most consistent finding), a decreased size of the hippocampus (which is the second most common finding), atrophy of collateral white matter adjacent to the hippocampus, enlargement of the temporal horn, diminished gray-white matter demarcation in the temporal lobe, and reduction in size of the temporal lobe.
DDX
The difficulty may be in seeing what can sometimes be a subtle diagnosis. Coronol T2 weighted images allow for the best visualization of the abnormality.
Unilateral dilatation of the hippocampal or choroidal fissure of the temporal horn is a common noramal variant and not necessarily indicaative of hippocampal atrophy.
Key references
1. Jack CR, Krecke KN, Luetmer PH, Cascino GD, Sharbrough FW, OÕBrien PC, Parisi JE. Diagnosis of mesial temporal sclerosis with conventional versus fast spin-echo MR imaging. Radiology 1994; 192: 123-127.
2. Meiners LC, van Gils A, Jansen GH, et. al. Temporal lobe epilepsy: the various MR appearances of histologically proven mesial temporal sclerosis. AJNR. 1994; 15: 1547-1555.
ACR Code
Keywords:
Mesial temporal sclerosis, temporal lobe epilepsy