What is a single photon emission computed tomography (SPECT) scan
What role does it have in evaluating patients?
SPECT is a functional neuroimaging modality that compares differences in regional cerebral blood flow.
It is performed in both the ictal and the interictal periods during the epilepsy surgery workup.
Focal seizures are typically found to cause local hyperperfusion on SPECT. Subtraction of the interictal scan from the ictal scan and superimposition on an MRI scan can provide an anatomic and physiologic picture of the epileptogenic zone.
This subtraction SPECT coregistered to magnetic resonance images is referred to as SISCOM .
It has been claimed that ictal SPECT correctly identifies the seizure focus in more than 90% of patients with temporal lobe epilepsy, while extratemporal epilepsy has a lower sensitivity (66%).
Common tracers used in SPECT to evaluate epilepsy patients are Tc-99m hexamethylpropyleneamine oxime and Tc-99m ethyl cysteinate dimer.