Decreased Craniocervical CSF Flow in Patients with Normal Pressure Hydrocephalus: A Pilot Study

BACKGROUND AND PURPOSE: Normal pressure hydrocephalus is characterized by systolic peaks of raised intracranial pressure, possibly due to a reduced compliance of the spinal CSF spaces. This concept of a reduced spinal CSF buffer function may be reflected by a low cervical CSF outflow from the cranium. The aim of this study was to investigate craniospinal CSF flow rates by phase-contrast MR imaging in patients with normal pressure hydrocephalus. MATERIALS AND METHODS: A total of 42 participants were included in this prospective study, consisting of 3 study groups: 1) 10 patients with normal pressure hydrocephalus (mean age, 74 [SD, 6] years, with proved normal pressure hydrocephalus according to current scientific criteria); 2) eighteen age-matched healthy controls (mean age, 71 [SD, 5]?years); and 3) fourteen young healthy controls (mean age, 21 [SD, 2]?years, for investigation of age-related effects). Axial phase-contrast MR imaging was performed, and the maximal systolic CSF and total arterial blood flow rates were measured at the level of the upper second cervical vertebra and compared among all study groups (2-sample unpaired t test). RESULTS: The maximal systolic CSF flow rate was significantly decreased in patients with normal pressure hydrocephalus compared with age-matched and young healthy controls (53?[SD, ?40] mL/m; 329?[SD, ?175] mL/m; 472?[SD, 194] mL/m; each P?<?.01), whereas there were no significant differences with regard to maximal systolic arterial blood flow (1160?[SD, 404] mL/m; 1470?[SD, ?381] mL/m; 1400?[SD, 254] mL/m; each P?>?.05). CONCLUSIONS: The reduced maximal systolic craniospinal CSF flow rate in patients with normal pressure hydrocephalus may be reflective of a reduced compliance of the spinal CSF spaces and an ineffective spinal CSF buffer function. Systolic craniospinal CSF flow rates are an easily obtainable MR imaging?based measure that may support the diagnosis of normal pressure hydrocephalus.