SPECT (single-photon emission computed tomography) shows the blood flow in the brain. A safe, very low-level radioactive compound is injected into your arm, and the particles it emits are measured. The more blood that flows through a certain area, the more particles are emitted. The result is displayed as a picture with different colors representing different levels of blood flow.

This test is readily available in most hospitals, but it is seldom needed routinely in epilepsy. SPECT scans obtained during or immediately after a seizure may show increased blood flow in the area where seizures arise. Scans performed between seizures can be misleading, however.

New computer techniques allow doctors to measure the differences between SPECT scans taken during and between seizures to obtain "subtraction" SPECT images. These can be superimposed onto the patient's MRI in an effort to pinpoint the seizure focus. This technique may be most helpful when seizures begin outside the temporal lobe and MRI scans do not show a structural abnormality.

Topic Editor:Ruben Kuzniecky, M.D.
Last Reviewed:4/16/04