Introduction: The cranial contents are enclosed in a rigid vault. The normal windkessel mechanism by which capillary beds are protected from the arterial pulse by dissipation of pulsatility into the surrounding soft tissues requires modification in the cranium. The modification is a system of reflection and venting, by which the arterial pulse is coupled via the CSF to the intracranial veins and is thus reflected back to the right heart. This reflection and venting is the windkessel mechanism in the cranium. Optimal venting of the arterial pulse in the cranium depends on a precise coupling of the arterial pulse to the ICP pulse.

Methods: Over the past two decades, our team and other investigators have explored the phase, pressure and flow relationships associated with intracranial pulsatility and the cerebral windkessel using laboratory animals and flow sensitive MRI studies on animals and humans.

Results: The windkessel system has the hallmarks of a pulsation absorber, which is a well-known mechanism used in engineering for vibration control. Optimal venting of pulsations appears on a graph of the arterial-ICP pulse pressure transfer function as a notch, which suggests the name ‘windkessel notch’ to describe the system. Using transfer function analysis, normal intracranial dynamics appears to be associated with a windkessel notch at the frequency of the heart rate. Abnormal intracranial dynamics, for example increased intracranial pressure, is associated with ablation of the notch and shifting of the phase relationships between the arterial pulse and the ICP pulse.

Conclusions: The pulsation absorber model of the cerebral windkessel provides insight into pulsatile intracranial dynamics and suggests potential novel approaches to treatment of disorders of intracranial dynamics.

Patient Care: Our research will help provide insight into intracranial dynamics and suggests new approaches to the management of increased intracranial pressure, brain swelling, stroke, and hydrocephalus.

Learning Objectives: By the conclusion of this session, participants should be able to describe the nature and importance of the cerebral windkessel 2) discuss, in small groups,the evidence supporting the pulsation absorber model of the cerebral windkessel 3) Identify implications for the model for our understanding of pulsatile intracranial dynamics and for novel approaches to treatment of abnormal intracranial dynamics.

References: Egnor M, Zheng L, Rosiello A, Gutman F, Davis R. A Model of Pulsations in Communicating Hydrocephalus. Pediatr Neurosurg 2002;36:281-303. Egnor M, Wagshul M, Zheng L, Rosiello A:Resonance and the synchrony of arterial and CSF pulsations. Pediatr Neurosurg 2003;38:273-276 Wagshul M, Chen J, Egnor M, McCormack E, Roche P. Amplitude and phase of cerebrospinal fluid pulsations: experimental studies and review of the literature. J Neurosurg./Volume 104/May, 2006: 810-819, 2006 M.E. Wagshul, E.J. Kelly, H.J. Yu, B. Garlick, T. Zimmerman, M.R. Egnor, “Resonant and notch behavior in intracranial pressure dynamics”, J Neurosurg Pediatr. 3(5):354-64 (2009). M.E. Wagshul, J.J. Chen, M.R. Egnor, E.J. McCormack, P.E. Roche, “Amplitude and Phase of Cerebrospinal Fluid Pulsations: Experimental Studies and Review of the Literature”, J Neurosurg 104:810-819 (2006).