Abstract

Part 2 describes measurements of intracranial cerebrospinal fluid (CSF) pressure in 18 adult patients with CSF shunts, all pressure measurements being referred to a horizontal plane close to the foramina of Monro. All 18 patients had normal CSF pressure by lumbar puncture; however, in one patient an intracranial pressure of +280 mm was subsequently measured after pneumoencephalography. Twelve patients had pre-shunt CSF pressures measured intracranially: 11 ranged from +20 to +180 mm H₂O and one was +280 mm H₂O in the supine position. In the upright posture nine patients had values of −10 to −140 mm H₂O, while three others were +60, +70, and +280 mm H₂O. After CSF shunting in these 18 patients the pressures were −30 to +30 mm H₂O in the supine position and −210 to −370 mm in the upright position. The effect of posture on the siphoning action of these longer shunts in the erect, adult patient is a major uncontrollable variable in maintenance of intracranial pressure after shunting. Other significant variables are reviewed. In Part 3 a concept of the hydrocephalus phenomenon is described. Emphasis is placed on the pressure differential (P_d) and force differential (F_d) causing pre-shunt ventricular enlargement and post-shunt ventricular size reduction. The site of P_d, which must be very small and not to be confused with measured ventricular pressure, P, must be at the ventricular wall.