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Computational fluid dynamic (CFD) simulations have provided detailed information about the complex flow and pressure field within the cerebrospinal fluid (CSF) system. The solutions of these simulations are sensitive to boundary conditions and thus need validation with in vivo measurements. However, validation of CFD flow results and MRI CSF flow measurements have been limited to through-plane pcMR measurements. Recent advancements in MRI flow measurement technology has enabled measurement of the 4D flow field within the spinal subarachnoid space (SSS), superior sagittal sinus and ventricles of the brain. Alterations in cerebrospinal fluid (CSF) dynamics have been associated with neurological symptoms and formation of Syringomyelia in patients with Chiari malformation and spinal stenosis. In these patients, analysis of morphology alone has proved to be insufficient in explaining the absence or presence of symptoms. In the present study, we compare quantitatively 4D flow measurements to CFD analysis within the SSS (C1-T1, cervical spinal segment) of a healthy volunteer without any lesions at the craniocervical junction or the cervical spinal canal.

Continuous Positive Airway Pressure (CPAP) is used as the gold standard treatment for sleep disordered breathing, acting as a pneumatic splint to prevent collapse of the pharyngeal airway. However, the influence that CPAP has on Cerebral Blood Flow (CBF) dynamics is not well understood. This preliminary study investigates the influence of CPAP on total CBF in 23 healthy awake subjects by measuring flow velocity and lumen diameter of the left and right proximal Internal Carotid Arteries (ICA), Vertebral Arteries (VA), and Middle Cerebral Arteries (MCA) using Duplex Color Doppler Ultrasound (US) with and without CPAP at a level of 15 cm H2O. Transcutaneous Carbon Dioxide (PtcCO2) level, heart rate, Blood Pressure (BP), and oxygen saturation (SaO2) were monitored before and after each test. The preliminary measurements indicate that CPAP results in a decrease of CBF by 17% (p-value < 0.05). The theoretically predicted decrease in CBF from PtcCO2 variation was 6%. The study should be further explored in patients with sleep apnea and various types of cerebrovascular and craniospinal disorders.Copyright © 2011 by ASME