[Intercritical SPECT in drug-resistant partial epilepsy with normal MRI: a study of 33 cases]

We made a prospective study of the intercritical changes in cerebral perfusion using SPECT with 99mTc-HMPAO in 33 adult patients with focal epilepsy which was resistant to polypharmacy and showed normal MR, to evaluate the relationship between these changes and the clinico-electrical focus (FCE) and the clinical features of epilepsy. All SPECT studies (100%) showed one or more areas of hypoperfusion. There was good topographical relationship between the perfusion defects and FCE which coincided exactly in 15 patients (45.4%); was acceptable with FCE identification but with associated defects in 12 (36.4%) and poor, bearing no relation to each other in 6 (18.2%). There was no correlation between a good, acceptable or poor relationship of SPECT-FCE and the age of the patient, time-course of the illness, number of crises, number of drugs or type of treatment given. There were more cases showing poor relationship amongst the pure temporal lobe foci (p < 0.05), but when these were considered together with the fronto-temporal cases, no difference was seen when compared with the extra-temporal cases. There was a tendency to greater secondary generalization of the crises in the group showing a good relationship. There were more cases of a clinical history of previous CNS diffuse lesions (anoxia, trauma or meningitis) amongst those with a poor relationship (83%) but not amongst those with a good relationship (20%, p < 0.05), or an acceptable relationship (25%, p < 0.05). This would seem to suggest that the anomalies found were more a result of the cause of the epilepsy than of the repetition of crises. SPECT should be included in the diagnostic algorithms of focal epilepsy with normal.