INTERICTAL BRAIN ~(99)Tc~m-HMPAO SPECT STUDY IN CASES OF EPILEPSY WITH SINGLE RING ENHANCING CT LESION

摘要

Contrast enhancing single ring or disc lesion (CESRL), a frequent finding in the computed tomography (CT) scans of Indian patients with seizures, has a diverse aetiology. The underlying cause in many of these cases remains conjectural. Some lesions show spontaneous resolution without any specific treatment. In a study, 17 cases of epilepsy were examined with a CT scan finding of CESRL. Detailed clinical evaluation and an interictal electroencephalogram (EEG) were performed. A CT scan and single photon emission computed tomography (SPECT) study were repeated after four weeks in six cases, and in two cases again after three months. In the second CT scan, one lesion disappeared and two were reduced in size, while three showed no change in size. A third CT scan showed complete disappearance in one case and no change in the second case. The initial SPECT study was abnormal in all 17 cases, showing areas of hypoperfusion corresponding to the anatomical location of ring lesions. In a follow-up, patients with decreased ring size in a CT scan showed a decrease in the area of perfusion deficit on the SPECT, but in cases in which the lesion disappeared in the CT scan, the SPECT perfusion abnormality continued to persist, though to a lesser extent. The persistence of perfusion defects suggests the presence of an altered underlying physiology. Hence, early withdrawal of anti-epileptic drugs after disappearance of ring lesions in CT scans may lead to a recurrence of seizures. SPECT studies repeated after three months may help to prognosticate on cases with CESRL and also help in deciding the optimum duration of anti-epileptic therapy in individual cases.