The Posterior Limb of the Internal Capsule as the Subcortical Transitional Zone of the Anterior and Posterior Circulations: Insights from Human 7T MRI.

BACKGROUND: In patients with cerebral infarction, identifying the distribution of infarction and the relevant artery is essential for ascertaining the underlying vascular pathophysiological mechanisms and preventing subsequent stroke. However, visualization of the basal perforating arteries (BPAs) has had limited success, and simultaneous viewing of background anatomical structures has only rarely been attempted in living human brains. Our study aimed at identifying the BPAs with 7T MRI and evaluating their distribution in the subcortical structures, thereby showing the clinical significance of the technique. METHODS: Twenty healthy subjects and 1 patient with cerebral infarction involving the posterior limb of the internal capsule (ICpost) and thalamus underwent 3-dimensional fast spoiled gradient-echo sequence as time-of-flight magnetic resonance angiography (MRA) at 7T with a submillimeter resolution. The MRA was modified to detect inflow signals from BPAs, while preserving the background anatomical signals. BPA stems and branches in the subcortical structures and their origins were identified on images, using partial maximum intensity projection in 3 dimensions. RESULTS: A branch of the left posterior cerebral artery (PCA) in the patient ran through both the infarcted thalamus and ICpost and was clearly the relevant artery. In 40 intact hemispheres in healthy subjects, 571 stems and 1,421 branches of BPAs were detected in the subcortical structures. No significant differences in the numbers of stems and branches were observed between the intact hemispheres. The numbers deviated even less across subjects. The distribution analysis showed that the subcortical structures of the telencephalon, such as the caudate nucleus, anterior limb of the internal capsule, and lenticular nucleus, were predominantly supplied by BPAs from the anterior circulation. In contrast, the thalamus, belonging to the diencephalon, was mostly fed by BPAs from the posterior circulation. However, compared with other subcortical structures, the ICpost, which marks the anatomical boundary between the telencephalon and the diencephalon, was supplied by BPAs with significantly more diverse origins. These BPAs originated from the internal carotid artery (23.1%), middle cerebral artery (38.5%), PCA (17.3%), and the posterior communicating artery (21.1%). CONCLUSIONS: The modified MRI method allowed the detection of the relevant BPA within the infarcted area in the stroke survivor as well as the BPAs in the subcortical structures of living human brains. Based on in vivo BPA distribution analyses, the ICpost is the transitional zone of the anterior and posterior cerebral circulations.

Effects of GV20 acupuncture on cerebral blood flow velocity of middle cerebral artery and anterior cerebral artery territories, and CO2 reactivity during hypocapnia in normal subjects.

OBJECTIVES: Acupuncture has been gaining popularity among practitioners of modern medicine as an alternative and complementary treatment. However, the mechanism of its therapeutic effect still remains uncertain. The present study chose the GV20 acupoint to evaluate acupoint effectiveness, hypothesizing that its stimulation induces cerebrovascular responses. DESIGN AND SETTING: The effects of GV20 acupuncture treatment on middle cerebral artery (MCA) and anterior cerebral artery (ACA) blood flow velocities, and CO(2) reactivity during hypocapnia were evaluated in 10 healthy male subjects (mean age 25.6 ± 0.8 years). Measurements were done at rest and during hypocapnia, and were repeated four times each at different cerebral artery territories with an interval of 1 week. MCA and ACA blood flow velocities were measured with a transcranial Doppler flowmeter. Blood flow velocity was corrected to 40 mm Hg of end-tidal CO(2) partial pressure (P(ETCO2)), and was expressed as CV40. CO(2) reactivity was measured as percent change in mean blood flow velocity/mm Hg P(ETCO2). RESULTS: Mean MCA and ACA blood flow velocities at rest, CV40, and CO(2) reactivity during hypocapnia increased significantly after GV20 acupuncture treatment, whereas mean arterial blood pressure and pulse rate at rest did not change significantly. The increases in MCA and ACA blood flow velocity were associated with improved CO(2) reactivity after GV20 acupuncture treatment. CONCLUSIONS: The data suggest that GV20 acupuncture treatment increases cerebral blood flow. The results of this small-scale study provide preliminary evidence for acupuncture effectiveness.