Objective: To investigate whether recurrent seizures cause hippocampal damage in temporal lobe epilepsy (TLE).
Patients: 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.
Measurements: Hippocampal MRI volumetry and T2 relaxometry were used.
Results: 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).
Conclusions: In patients with cryptogenic epilepsy, recurrent seizures may cause damage to the hippocampus throughout the lifetime of the patient.