J Neurosurg 120:218–227, 2014 218 J Neurosurg / Volume 120 / January 2014 ©AANS, 2014 N ormal CSF movement is important for the health of the brain, and disturbances in CSF movements can be directly linked to a variety of abnormali- ties, including hydrocephalus. Typically, assessment of the health of the CSF space involves invasive techniques such as CSF pressure monitoring with a ventricular cath- eter or through lumbar drainage, by using either metri- zamide 19 as a contrast agent or radioisotopes, 11 both of which require injection into the CSF. These conventional examination methods change the physical and physi- ological characteristics of the CSF space. Therefore, the condition of the CSF space can be better evaluated using noninvasive methods such as MRI. 8,9 For example, the PC MRI method 13 has a long history of use for observing the dynamics of the CSF. 13,16,24 However, a noninvasive method for assessing the CSF space in the cranial cav- ity is still lacking. In the feld of hydromechanics, the pressure gradient is an alternative parameter for describ- ing the CSF fow feld. The localized pressure gradient is related to the motion of the CSF and is indicative of the velocity of the CSF, compliance and elastance within the cavity, CSF viscosity, and distribution and pulsation of the CSF in the skull. Once these physiological factors of the CSF are measured, what information do they pro- vide to the neurosurgeon? Medical imaging techniques and computer analysis methods provide the neurosurgeon with information that can be easily understood and inter- preted. For example, data presented in a vector format, as a color scale, or as a movie are easy to comprehend and familiar to neurosurgeons. In this study, we observed the fow velocities of the Velocity and pressure gradients of cerebrospinal fuid assessed with magnetic resonance imaging Clinical article Mitsunori MatsuMae, M.D., D.M.sc., 1 akihiro hirayaMa, M.D., 1 hiDeki atsuMi, M.D., Ph.D., 1 satoshi y atsushiro, B.sc., 2 anD kagayaki kuroDa, Ph.D. 2 1 Department of Neurosurgery, Tokai University School of Medicine, Isehara, Kanagawa; and 2 Course of Information Science and Engineering, Tokai University Graduate School of Engineering, Kitakaname, Hiratsuka, Kanagawa, Japan Object. New approaches for understanding CSF motion in healthy individuals and patients with hydrocephalus and Chiari malformation are presented. The velocity and the pressure gradient of CSF motion were determined using phase contrast (PC) MRI. Methods. The authors examined 11 healthy control subjects and 2 patients (1 with hydrocephalus and 1 with Chiari malformation), using 4-dimensional PC (4D-PC) MRI and a newly developed computer analysis method that includes calculation of the pressure gradient from the velocity feld. Sagittal slices including the center of the skull and coronal slices of the foramen of Monro and the third ventricle were used. Results. In the ventricular system, mixing and swirling of the CSF was observed in the third ventricle. The veloc- ity images showed that the CSF was pushed up and back down to the adjacent ventricle and then returned again to the third ventricle. The CSF traveled bidirectionally in the foramen of Monro and sylvian aqueduct. Around the choroid plexus in the lateral ventricle, the CSF motion was stagnant and the CSF pressure gradient was lower than at the other locations. An elevated pressure gradient was observed in the basal cistern of the subarachnoid space. Sagittal imag- ing showed that the more prominent pressure gradients originated around the cisterna magna and were transmitted in an upward direction. The coronal image showed a pressure gradient traveling from the central to the peripheral subarachnoid spaces that diminished markedly in the convexity of the cerebrum. The 2 patients, 1 with secondary hydrocephalus and 1 with Chiari malformation, were also examined. Conclusions. The observed velocity and pressure gradient felds delineated the characteristics of the CSF mo- tion and its similarities and differences among the healthy individuals and between them and the 2 patients. Although the present results did not provide general knowledge of CSF motion, the authors’ method more comprehensively described the physiological properties of the CSF in the skull than conventional approaches that do not include mea- surements of pressure gradient felds. (http://thejns.org/doi/abs/10.3171/2013.7.JNS121859) key WorDs • cerebrospinal fuid • hydrodynamics • hydrocephalus • magnetic resonance imaging • image analysis • Chiari malformation • diagnostic and operative techniques Abbreviations used in this paper: PC = phase contrast; 4D-PC = 4-dimensional PC.