Hemodynamic assessment of carotid stenosis by functional magnetic resonance imaging

Functional magnetic resonance imaging (fMRI) is a method usually used to identify cortical representations of cerebral functions. Some studies and case reports suggest that stenoses of the brain-supplying arteries influence the BOLD (blood-oxygenation-level-dependent) signal. The objective of this study was to find out whether the BOLD signal differs in the ipsilateral hemisphere of patients with hemodynamically relevant and those with irrelevant stenosis of the internal carotid artery (ICA) and if a successful treatment might have an influence on the BOLD signal.

We included 10 patients with hemodynamically relevant stenosis in group 1; another 10 patients with hemodynamically irrelevant stenosis of the ICA were included in group 2. Patients underwent recanalization by either stenting or operation of the ICA. fMRI with a hand-tapping task was performed before and after treatment. Data were analyzed with 'Statistical Parametric Mapping' 2 for both hemispheres. An asymmetry index (AI, range 0-2) was calculated for the hand motor areas.

All data are given as means +/- SD. The mean preinterventional AI in group 1 was 1.08 +/- 0.87 and 0.30 +/- 0.54 in group 2 (p = 0.029). The mean postinterventional AI was 0.32 +/- 0.29 in group 1 and 0.25 +/- 0.21 in group 2 (p = 0.599).

fMRI is not only capable of delivering spatial information, but also of distinguishing a hemodynamically relevant from an irrelevant stenosis of the ICA.