Usefulness of pulsed arterial spin labeling MR imaging in mesial temporal lobe epilepsy

Abstract

Purpose: Arterial spin labeling (ASL) is a developing magnetic resonance imaging (MRI) method for noninvasive measurement of cerebral blood flow (CBF). The purpose of this study was to evaluate the usefulness of ASL for detecting interictal temporal hypoperfusion in temporal lobe epilepsy (TLE). ASL-derived CBF measurements were compared with those derived from H(2)(15)O positron emission tomography (PET).

Methods: 11 normal controls and 10 patients with medically intractable TLE were studied. Pulsed ASL (PASL) with quantitative imaging of perfusion using a single subtraction, second version (QUIPSS II) was performed in all subjects and H(2)(15)O PET was performed in patients. Regional CBF values in the mesial and lateral temporal lobes were measured utilizing quantitative analysis of perfusion images. A perfusion asymmetry index (AI) was calculated for each region.

Results: In patients, mean CBF in the mesial temporal lobe was not significantly different between PASL and H(2)(15)O PET, and ipsilateral mesial temporal CBF was lower than contralateral CBF with both techniques. PASL detected significant mesial temporal perfusion asymmetry agreeing with EEG laterality in four patients. H(2)(15)O PET found ipsilateral interictal hypoperfusion in three. Both scans found unilateral hypoperfusion in one patient with bilateral EEG discharges.

Conclusions: Pulsed ASL may be a promising approach to detecting interictal hypoperfusion in TLE. This method has potential as a clinical alternative to H(2)(15)O PET due to noninvasiveness and easy accessibility.

Figure 1

Bar graph comparing mean absolute asymmetric indices of temporal perfusion between patients and controls. Patients had greater perfusion asymmetry in the mesial temporal lobe than controls, but the difference between groups did not reach statistical significance (p = 0.26). Data are expressed as mean ± standard error of the mean. AI, asymmetric index; MTL, mesial temporal lobe; LTL, lateral temporal lobe.

Figure 2

Anatomical MR and perfusion images obtained from a patient with left temporal lobe epilepsy (patient 6). Panel A: axial spoiled gradient recalled echo (SPGR) image; Panel B: pulsed arterial spin labeling (PASL) image at the same anatomic level; Panel C: H₂¹⁵O PET CBF image at the same anatomic level. PASL CBF map (B) shows more prominent perfusion decrease in the ipsilateral mesial temporal lobe as compared to H₂¹⁵O PET CBF image (C).