Recurrent seizures may cause hippocampal damage in temporal lobe epilepsy

To investigate whether recurrent seizures cause hippocampal damage in temporal lobe epilepsy (TLE).

Eighteen patients with newly diagnosed cryptogenic TLE, 14 patients with chronic well-controlled cryptogenic TLE, 32 patients with chronic drug-resistant cryptogenic TLE, and 25 healthy subjects were studied.

Hippocampal MRI volumetry and T2 relaxometry were used.

Chronic drug-resistant patients with seizure focus in the left temporal lobe had an 18% smaller left hippocampus and chronic drug-resistant patients with seizure focus in the right temporal lobe had a 14% smaller right hippocampus than did the control group (p < 0.05). Chronic drug-resistant patients with seizure focus on the left side had longer T2 relaxation times in the body of the left hippocampus than did the control group (p < 0.001) and chronic drug-resistant patients with seizure focus on the right side had longer T2 relaxation times in the body of the right hippocampus than did the control subjects (p < 0.01). In all patients with a left seizure focus, the left hippocampal volume correlated inversely with the estimated total number of partial (r = -0.391, p < 0.01) or generalized (r = -0.312, p < 0.05) seizures the patient had experienced. The prolongation of the left T2 relaxation time in the body of the hippocampus correlated with the total number of both partial (r = 0.670, p < 0.001) and generalized (r = 0.481, p < 0.001) seizures and with the duration of TLE symptoms (r = 0.580, p < 0.001).

In patients with cryptogenic epilepsy, recurrent seizures may cause damage to the hippocampus throughout the lifetime of the patient.