Interictal brain 99m Tc-HMPAO SPECT study in cases of epilepsy with single ring enhancing CT lesion.

BACKGROUND: Contrast enhancing single ring or disc lesion (CESRL), a frequent finding in the CT scan of Indian patients with seizures, has a diverse etiology. Underlying cause in many of these cases remains conjectural. Some of these ring lesions show spontaneous resolution without any specific treatment and in others their temporal profile remains unpredictable. MATERIAL AND METHODS: In a prospective study we studied 17 cases of epilepsy, with the CT scan finding of single contrast enhancing ring lesion. Detailed clinical evaluation and interictal EEG was performed. CT scan and SPECT study was done initially and were then repeated. RESULTS: On the second CT, one lesion disappeared and 2 reduced in size, three showed no change in size. Third CT showed complete disappearance in one case and no change in the second case. Initial SPECT study was abnormal in all 17 cases, showing areas of hypoperfusion corresponding to the anatomical location of ring lesion. On follow up, patients with decreased ring size on CT showed decrease in area of perfusion deficit on the SPECT, but cases in which the lesion disappeared on the CT, the SPECT perfusion abnormality continued to persist, though to a lesser extent. CONCLUSION: Persistence of perfusion defects suggest the presence of altered underlying physiology. Hence, early withdrawal of antiepileptic drugs after disappearance of ring lesion on CT may lead to seizure recurrence. SPECT studies repeated after 3 months may help to prognosticate cases with CESRL and also help in deciding the optimum duration of antiepileptic therapy in individual cases.

Interictal brain 99m Tc-HMPAO SPECT study in chronic epilepsy.

We performed interictal brain 99m Tc-HMPAO study in eight cases of chronic epilepsy. SPECT (single photon emission computed tomography) study showed abnormality in seven cases. As compared to computed tomography (CT) scan and electroencephalogram (EEG) which were positive in 25% and 62% cases respectively it showed abnormality in 87%. In two cases where CT scan and EEG both were normal, SPECT showed areas of hypoperfusion. In one case where EEG indicated a bilateral focus, SPECT study showed a clearly defined unilateral focal hypoperfusion defect. Areas of hyperperfusion were not seen in any of our cases. Our results indicate that HMPAO SPECT is more sensitive than CT scan and EEG, in localising an epileptogenic focus in cases of chronic epilepsy.