[Single-photon, emission-computed tomography (SPECT) in the diagnosis of epilepsy]

Regional cerebral blood flow can be measured using single photon emission computed tomography (SPECT). Hexamethyl propyleneamine oxime (HMPAO) is commercially available as a 99mTc-labeled tracer and has the advantage of fixing a blood flow pattern during its first passage through the capillaries. This can be used, for example, to evaluate a short-term ictal phase. With dedicated SPECT systems a spatial resolution of 5-8 mm can be achieved. Measurement using 133Xe allows absolute quantification of blood flow values, but the spatial resolution is lower. In about 50-70% of patients suffering from temporal lobe epilepsy a decreased blood flow in the focus can be visualized in the interictal phase. Ictally, focal hyperperfusion can be observed in most cases. The sensitivity and specificity of SPECT in the ictal phase are superior compared with interictal study. During the postictal phase a hyperperfusion of the anterior and mesial parts of the affected temporal lobe with simultaneous lateral hypoperfusion can often be demonstrated. At present, receptor SPECT has not yet reached clinical significance in the diagnosis of epilepsy.