gms | German Medical Science

Objective: The objective of this study was to detect CSF flow alterations using timed-resolved 3D magnetic resonance (MR) velocity mapping in normal pressure hydrocephalus (NPH) and to evaluate CSF flow changes after treatment by ventriculoperitoneal shunt (VP-shunt) implantation.

Method: A total of 8 NPH patients (3 female, 5 male, age range 65–80 years) were included in this study. All patients underwent timed-resolved 3D MR velocity mapping additionally to routine diagnostic assessment including Kiefer Score and the number of required steps for a walking distance of 20 m before and 3–8 months after VP-shunt placement. MRI examinations were performed using a 3Tesla MR-system. Time-resolved 3D MR velocity mapping data were acquired using a standard 3D phase-contrast (PC) MR-sequence with cardiac-triggering. The maximum peak value (vpeak) and the mean value (vmean) of the magnitude of the velocity vector were determined for the lateral ventricles, the foramina of Monro, the 3^rd ventricle, the aqueduct, the 4^th ventricle and the cerebellomedullary cistern. Statistical analysis was performed using Wilcoxon rang sum test. MR velocity mapping data were also quantitatively evaluated using the GTFlow software tool (GyroTools, Zurich, Switzerland) by calculation of time-resolved 3D CSF flow patterns in the ventricular system.

Results: All NPH patients showed increased (“hypermotile”) CSF flow dynamics before VP-shunt placement in all compartments and both the mean (vmean, 0.47–1.24 cm/s) and the peak CSF flow velocity (vpeak, 1.40–3.32 cm/s) was increased in all CSF compartments when compared to healthy subjects (vmean, 0.17–0.70 cm/s; vpeak, 0.68–1.83 cm/s). After VP-shunt implantation vmean and vpeak decreased in all compartments on average by 13% and 15%, respectively. Decrease in vmean was statistically significant within the lateral ventricles, the 3^rd and 4^th ventricle; that for vpeak was within the lateral ventricles, the foramina of Monro, the 3^rd ventricle and the aqueduct. Velocity values, however, did not reach normal levels in the time period under investigation. Kiefer Score and the number of required steps for a walking distance of 20 m decreased by 46% and 27%, respectively.

Conclusions: This study demonstrates that timed-resolved 3D MR velocity mapping is a useful imaging investigation for diagnostic assessment and follow-up in NPH-patients treatment by VP-shunt. This new technique provides an insight in the physiological CSF flow changes related with NPH and its treatment.