Opposing CSF hydrodynamic trends found in the cerebral aqueduct and prepontine cistern following shunt treatment in patients with normal pressure hydrocephalus

Abstract

BackgroundThis study investigated cerebrospinal fluid (CSF) hydrodynamics using cine phase-contrast MRI in the cerebral aqueduct and the prepontine cistern between three distinct groups: pre-shunt normal pressure hydrocephalus (NPH) patients, post-shunt NPH patients, and controls. We hypothesized that the hyperdynamic flow of CSF through the cerebral aqueduct seen in NPH patients was due to a reduction in cisternal CSF volume buffering. Both hydrodynamic (velocity, flow, stroke volume) and peak flow latency (PFL) parameters were investigated.MethodsScans were conducted on 30 pre-treatment patients ranging in age from 58 to 88 years along with an additional 12 controls. Twelve patients also received scans following either ventriculoatrial (VA) or ventriculoperitoneal (VP) shunt treatment (9 VP, 3 VA), ranging in age from 74 to 89 years with a mean follow up time of 6 months.ResultsSignificant differences in area, velocity, flow, and stroke volume for the cerebral aqueduct were found between the pre-treatment NPH group and the healthy controls. Shunting caused a significant decrease in both caudal and cranial mean flow and stroke volume in the cerebral aqueduct. No significant changes were found in the prepontine cistern between the pre-treatment group and healthy controls. For the PFL, no significant differences were seen in the cerebral aqueduct between any of the three groups; however, the prepontine cistern PFL was significantly decreased in the pre-treatment NPH group when compared to the control group.ConclusionsAlthough several studies have quantified the changes in aqueductal flow between hydrocephalic groups and controls, few studies have investigated prepontine cistern flow. Our study was the first to investigate both regions in the same patients for NPH pre- and post- treatment. Following shunt treatment, the aqueductal CSF metrics decreased toward control values, while the prepontine cistern metrics trended up (not significantly) from the normal values established in this study. The opposing trend of the two locations suggests a redistribution of CSF pulsatility in NPH patients. Furthermore, the significantly decreased latency of the prepontine cisternal CSF flow suggests additional evidence for CSF pulsatility dysfunction.

Predicting the Aqueductal Cerebrospinal Fluid Pulse: A Statistical Approach

“…In particular, it is important to understand why The dynamics of the aCSF pulse are an issue of clinical importance. Increased amplitude of the aCSF pulse has been shown to be associated with MS [3][4][5][6][7], NPH [8][9][10][11][12][13], and early-stage WM changes [14,15]. However, the mechanism linking aCSF pulse dynamics with these pathologies is poorly understood.…”

“…Further work is also needed to better understand the intracranial fluid dynamic changes that occur in MS and NPH patients. In both these conditions the amplitude of the aCSF pulse has been shown to markedly increase [4,5,12,13] and it may be that the linear model might be able to shed new insights into the altered fluid dynamics associated with these neurological diseases.…”

“…As such, the aCSF pulse is often measured in order to evaluate structural changes that may occur in the brain parenchyma. Numerous studies have found increased pulsatility of the aCSF to be associated with multiple sclerosis (MS) [3][4][5][6][7], normal pressure hydrocephalus (NPH) [8][9][10][11][12][13], and white matter (WM) alterations [14,15], suggesting that increases in the amplitude of the aqueductal pulse may be linked to pathological changes.…”

CNS fluid and solute movement: physiology, modelling and imaging

“…2 Department of Neurosurgery, University of Michigan, Ann Arbor, MI 48105, USA. 3 Department of Biomedical Sciences, University of Minnesota Medical School Duluth, Duluth, MN 55812, USA.…”

“…These studies in normal subjects can set the baseline for improved diagnosis of abnormal CSF dynamics in disease. For example, flow velocity and displacement volume were both increased in the aqueduct of a group of NPH patients but were reduced after shunt surgery [3]. Another study [4] found that both NPH and AD patients had similar but abnormal aqueduct CSF pressure gradients.…”