Normal-pressure hydrocephalus: evaluation with cerebrospinal fluid flow measurements at MR imaging.

Abstract

CSF velocity MR imaging is useful in the selection of patients with NPH to undergo shunt formation.

Idiopathic normal pressure hydrocephalus may be a “Two Hit” disease: Benign external hydrocephalus in infancy followed by deep white matter ischemia in late adulthood

“…In eight suspected NPH patients in whom CSF velocity imaging was technically flawed due to cardiac arrhythmia or velocity aliasing, hyperdynamic CSF flow was diagnosed on the basis of a marked aqueductal CSF flow void on the proton density-weighted conventional spin-echo image (15). As noted previously (14), the CSF flow void is much less sensitive than when originally described (15), due to the ubiquitous use of flow compensation for the last two decades and fast spin echo for the last 10 years. Regardless, when the flow void is seen, it is very specific for hyperdynamic CSF flow.…”

“…The diagnosis of NPH was not confirmed by response to shunting. Although hyperdynamic CSF flow has been shown to correlate with response to shunting in symptomatic NPH patients (14,15), the surrogate measure is less convincing than shunt response per se (which was unfortunately not available). The height and weight of the patients were also not available to adjust for head size; the only mechanism to account for different body size was to compare men and women separately.…”

“…Phase-contrast CSF velocity imaging was performed to measure the "aqueductal CSF stroke volume" (SV), i.e., the volume of CSF pulsating back or forth through the aqueduct over the cardiac cycle (14). A 4-mm-thick slice was angled perpendicular to the aqueduct utilizing a 512 ϫ 512 matrix over a 16 ϫ 16 cm 2 FOV, yielding pixels 312 m on a side.…”

“…A 4-mm-thick slice was angled perpendicular to the aqueduct utilizing a 512 ϫ 512 matrix over a 16 ϫ 16 cm 2 FOV, yielding pixels 312 m on a side. Retrospective cardiac gating and an aliasing velocity of 200 mm/second were utilized (14). Only patients with hyperdynamic CSF flow were included in the study group, leaving 51 patients.…”

“…Only patients with hyperdynamic CSF flow were included in the study group, leaving 51 patients. "Hyperdynamic CSF flow" was defined as an SV greater than 60 L, which is approximately 50% higher than the normal value in the literature (14). In eight suspected NPH patients in whom CSF velocity imaging was technically flawed due to cardiac arrhythmia or velocity aliasing, hyperdynamic CSF flow was diagnosed on the basis of a marked aqueductal CSF flow void on the proton density-weighted conventional spin-echo image (15).…”