Cerebral Perfusion

Cerebral blood flow in Alzheimer's disease

Authors: Roher AE, Debbins JP, Malek-Ahmadi M, Chen K, Pipe JG, Maze S, Belden C, Maarouf CL, Thiyyagura P, Mo H, Hunter JM, Kokjohn TA, Walker DG, Kruchowsky JC, Belohlavek M, Sabbagh MN, Beach TG.

BACKGROUND: Alzheimer's disease (AD) dementia is a consequence of heterogeneous and complex interactions of age-related neurodegeneration and vascular-associated pathologies. Evidence has accumulated that there is increased atherosclerosis/arteriosclerosis of the intracranial arteries in AD and that this may be additive or synergistic with respect to the generation of hypoxia/ischemia and cognitive dysfunction. The effectiveness of pharmacologic therapies and lifestyle modification in reducing cardiovascular disease has prompted a reconsideration of the roles that cardiovascular disease and cerebrovascular function play in the pathogenesis of dementia.
METHODS: Using two-dimensional phase-contrast magnetic resonance imaging, we quantified cerebral blood flow within the internal carotid, basilar, and middle cerebral arteries in a group of individuals with mild to moderate AD (n = 8) and compared the results with those from a group of age-matched nondemented control (NDC) subjects (n = 9). Clinical and psychometric testing was performed on all individuals, as well as obtaining their magnetic resonance imaging-based hippocampal volumes.
RESULTS: Our experiments reveal that total cerebral blood flow was 20% lower in the AD group than in the NDC group, and that these values were directly correlated with pulse pressure and cognitive measures. The AD group had a significantly lower pulse pressure (mean AD 48, mean NDC 71; P = 0.0004). A significant group difference was also observed in their hippocampal volumes. Composite z-scores for clinical, psychometric, hippocampal volume, and hemodynamic data differed between the AD and NDC subjects, with values in the former being significantly lower (t = 12.00, df = 1, P = 0.001) than in the latter.
CONCLUSION: These results indicate an association between brain hypoperfusion and the dementia of AD. Cardiovascular disease combined with brain hypoperfusion may participate in the pathogenesis/pathophysiology of neurodegenerative diseases. Future longitudinal and larger-scale confirmatory investigations measuring multidomain parameters are warranted.

Effects of Body Position on Intracranial Pressure and Cerebral Perfusion in Patients With Large Hemispheric Stroke

Authors: Stefan Schwarz, MD; Dimitrios Georgiadis, MD; Alfred Aschoff, MD; Stefan Schwab, MD

Background and Purpose— The purpose of this study was to prospectively evaluate the effects of body position in patients with large supratentorial stroke.

Methods— We performed 43 monitoring sessions in 18 patients with acute complete or subtotal middle cerebral artery (MCA) territory stroke. Intracranial pressure (ICP) was monitored with a parenchymal probe. Mean arterial blood pressure, ICP, and MCA peak mean flow velocity (VmMCA) were continuously recorded. Patients with acute ICP crises were excluded. After baseline values at a 0° supine position were attained, the backrest was elevated in 2 steps of 5 minutes each to 15° and 30° and then returned to 0°.

Results— Baseline mean arterial pressure was 90.0±1.6 mm Hg and fell to 82.7±1.7 mm Hg at 15° and 76.1±1.6 mm Hg at 30° backrest elevation (P<0.0001). ICP decreased from 13.0±0.9 to 12.0±0.9 mm Hg at 15° and 11.4±0.9 mm Hg at 30° backrest elevation (P<0.0001). As a result, cerebral perfusion pressure decreased from a baseline value of 77.0±1.8 to 70.0±1.8 mm Hg at 15° and 64.7±1.7 mm Hg at 30° backrest elevation (P<0.0001). VmMCA was already higher on the affected side during baseline measurements. VmMCA decreased from 72.8±11.3 cm/s at 0° to 67.2±9.7 cm/s at 15° and 61.2±8.9 cm/s at 30° on the affected and from 49.9±3.7 cm/s at 0° to 47.7±3.6 cm/s at 15° and 46.2±2.2 cm/s at 30° on the contralateral side (P<0.0001).

Conclusions— In patients with large hemispheric stroke without an acute ICP crisis, cerebral perfusion pressure was maximal in the horizontal position although ICP was usually at its highest point. If adequate cerebral perfusion pressure is considered more desirable than the absolute level of ICP, the horizontal position is optimal for these patients.

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