Shunted hydrocephalus: normal upright ICP by CSF gravity-flow control. A clinical study in young adults.

Hydrocephalic patients with years of ventricle shunts may be disabled by shunt overdrainage. Gravity-induced upright CSF shunt flow produces this overdrainage with abnormally low, upright ICP. Consequently, the concept of a normal level of zero ICP, which ventricle shunts must mimic, was developed. For 4.5 years, this concept has been applied in hydrocephalus patients by using a Siphon Control Device as a Zero Pressure Device in ventricle shunts. The results in 56 patients, including 42 overdrainage problems, were assessed by clinical grading, ICP record analyses, and computed tomographic (CT) ventricle size comparisons. All patients ultimately achieved satisfactory clinical results. This occurred in 80% of the patients on the first insertion. Adjustment of the vertical level of the Zero Pressure Device was necessary in 20%. The optimum clinical result correlated with an upright ICP of -66 mm of H2O. This postoperative ICP correlated within 4 mm of the Zero Pressure Device placement below vertex. Ventricle size correlated poorly with clinical grade and normal ICP. Only 73% of slit ventricles enlarged by 16.5 months. The need to mimic normal upright ICP by maintaining a normal level of zero upright ICP in shunted patients is supported by these results.