Magnetic Resonance Demonstration of Normal CSF Flow

Abstract

The magnetic resonance (MR) imaging appearance and incidence of flowing cerebrospinal fluid (CSF) in the brain were investigated. The MR scan of 46 randomly selected patients with normal examinations were retrospectively reviewed. All patients were studied using both T₂-weighted and T₁-weighted spin-echo pulse sequences. Thirty-one patients (67%) had decreased intensity in the aqueduct of Sylvius on the T₂-weighted images when compared with the intensity of CSF in the lateral ventricles. This was termed the CSF flow-void sign. The feature was present in the caudal fourth ventricle in 15 patients (32%) and in the third ventricle in two patients (4%) on T₂-weighted scans. It was seen in only 13% of patients on T₁-weighted scans. It is believed the CSF flow-void sign represents pulsatile CSF flow. Its recognition is important because it explains the inhomogeneity in the appearance of the CSF, which could be confused with pathologic processes. It is valuable in the routine evaluation of MR examinations since it reflects CSF circulatory dynamics. (AJNR 7: 3–6, 1986)