Comparison of pseudocontinuous arterial spin labeling perfusion MR images and time-of-flight MR angiography in the detection of periictal hyperperfusion

BACKGROUND: Magnetic resonance imaging (MRI), including perfusion MRI with three-dimensional pseudocontinuous arterial spin labeling (ASL) and diffusion-weighted imaging (DWI), are applied in the periictal (including ictal and postictal) detection of circulatory and metabolic consequences associated with epilepsy. Our previous report revealed that periictal hyperperfusion can firstly be detected on ASL, and cortical hyperintensity of cytotoxic edema secondarily obtained on DWI from an epileptically activated cortex. Although magnetic resonance angiography (MRA) using three-dimensional time-of-flight is widely used to evaluate arterial circulation, few MRA studies have investigated the detection of periictal hyperperfusion. METHODS: To compare the ability of ASL and MRA to detect the periictal hyperperfusion on visual inspection, we retrospectively selected 23 patients who underwent ASL and MRA examination on both periictal and interictal periods. Patients were divided into the following three groups according to periictal ASL/DWI findings: positive ASL and DWI findings (n = 13, ASL+/DWI+ group), positive ASL and negative DWI findings (n = 5, ASL+/DWI- group), and negative ASL and DWI findings (n = 5, ASL-/DWI- group). RESULTS: Periictal hyperperfusion on MRA was detected in 6 out of 13 patients (46.2%) in the ASL+/DWI+ group, but not in all patients in the ASL+/DWI- and ASL-/DWI- groups. Furthermore, in 5 out of these 6 patients, the diagnosis of periictal MRA hyperperfusion could not be made without referring to interictal MRA and/or periictal ASL findings, because the periictal MRA findings were so minute. CONCLUSION: The minimum requirement for the development of periictal MRA hyperperfusion is that its epileptic event is intense enough to induce the uncoupling between metabolism and circulation, with the induction of glutamate excitotoxity, and severe cytotoxic edema on DWI. ASL is vastly superior to MRA in the detection of periictal hyperperfusion.