Higher Pulsatility in Cerebral Perforating Arteries in Patients With Small Vessel Disease Related Stroke, a 7T MRI Study

Abstract

Background and Purpose- Cerebral small vessel disease (SVD) is a major cause of stroke and dementia, but underlying disease mechanisms are still largely unknown, partly because of the difficulty in assessing small vessel function in vivo. We developed a method to measure blood flow velocity pulsatility in perforating arteries in the basal ganglia and semioval center. We aimed to determine whether this novel method could detect functional abnormalities at the level of the small vessels in patients with stroke attributable to SVD. Methods- We investigated 10 patients with lacunar infarction (mean age 61 years, 80% men), 11 patients with deep intracerebral hemorrhage (ICH) considered to be caused by SVD (ICH, mean age 58 years, 82% men) and 18 healthy controls that were age- and sex-matched. We performed 2-dimensional phase contrast magnetic resonance imaging at 7 T to measure time-resolved blood flow velocity in cerebral perforating arteries of the semioval center and the basal ganglia. We compared the number of detected arteries, pulsatility index and mean velocity between the patient groups and controls. Results- In the basal ganglia, the number of detected perforators was lower in lacunar infarction (26±9, P=0.01) and deep ICH patients (28±6, P=0.02) than in controls (35±7). The pulsatility index in the basal ganglia was higher in lacunar infarction (1.07±0.13, P=0.03), and deep ICH patients (1.02±0.11, P=0.11), than in controls (0.94±0.10). Observations in the semioval center were similar. Number of detected perforators was lower in lacunar infarction (32±18, P=0.06), and deep ICH patients (28±18, P=0.02), than in controls (45±16). The pulsatility index was higher in lacunar infarction (1.18±0.15, P=0.02), and deep ICH patients (1.17±0.14, P=0.045) than in controls (1.08±0.07). No velocity differences were detected. Conclusions- This exploratory study shows that SVD can be expressed in terms of functional measures, such as pulsatility index, which are derived directly from the small vessels themselves. Future studies may use this technique to further unravel the mechanisms underlying SVD.

Keywords: blood flow velocity; cerebral hemorrhage; cerebral small vessel disease; magnetic resonance imaging; perforating artery; pulsatility index; stroke, lacunar.

Figure 1.

Slice planning. The 2-dimensional phase contrast magnetic resonance imaging (2D PC) slice through the basal ganglia (BG) was planned parallel to and just below the genu and splenium of the corpus callosum. The slice through the semioval center (CSO) was planned parallel to the BG slice at 15 mm above the corpus callosum.

Figure 2.

Region of interest creation and perforator examples. These images show representative 2-dimensional (2D) phase contrast slices of a patient with a lacune (left: magnitude images, right: velocity maps). The rows show the basal ganglia (A), the semioval center (B), and perforator velocity curves (C). The left images show the average magnitude and the right images show the average velocity. The green circles mark a detected perforator in each slice, for which the velocity curves are shown in C. Because the subject moved downward in the scanner during the experiment, the automatically generated region of interest (red) in the semioval center (CSO) had to be manually adjusted (blue) to only include white matter.

Figure 3.

Basal Ganglia (BG) measurements. The horizontal axes show patients with lacunar infarction (LAC, in blue), with deep intracerebral hemorrhage (ICH, in red) and controls (CTRL, in green). The horizontal bars indicate the comparisons for which the P values are listed. A, Shows boxplots of the number of detected perforators. B, Shows boxplots of the pulsatility index (PI). The boxplots show interquartile ranges with markers for each participant. C, Shows the probability density distribution of blood flow velocity (V_mean) of all detected BG perforators of all participants in a group. The marker shows the blood flow velocity as fitted by the linear mixed effects model, with its 95% CI shown by error bars.

Figure 4.

Semioval center (CSO) measurements. The horizontal axes show patients with lacunar infarction (LAC, in blue), with deep intracerebral hemorrhage (ICH, in red) and controls (CTRL, in green). The horizontal bars indicate the comparisons for which the P values are listed. A, Shows boxplots of the number of detected perforators. B, Shows boxplots of the pulsatility index (PI). The boxplots show interquartile ranges with markers for each participant. C, Shows the probability density distribution of blood flow velocity (V_mean) of all detected CSO perforators of all participants in a group. The marker shows the blood flow velocity as fitted by the linear mixed effects model, with its 95% CI shown by error bars.