The predictive value of cerebrospinal fluid dynamic tests in patients with th idiopathic adult hydrocephalus syndrome

J. Malm, B. Kristensen, T. Karlsson, M. Fagerlund, J. Elfverson and J. Ekstedt
Department of Neurology, University Hospital of Northern Sweden, Umea.

OBJECTIVE: To evaluate the predictive value of the cerebrospinal fluid (CSF) tap test and CSF outflow conductance in the selection of patients with the idiopathic adult hydrocephalus syndrome, defined exclusively on a clinical basis, for shunt surgery. DESIGN: A prospective, consecutive case series. All patients were assessed before surgery and at 3 months after shunt placement. Preoperatively, CSF pressure, conductance, and CSF formation rate were assessed by a constant-pressure infusion method. Improvement in gait and cognitive functions after removal of CSF was noted (ie, with the CSF tap test). Postoperatively, the infusion method was used to evaluate shunt function. SETTING: Tertiary, academic referral center. PATIENTS: Thirty-five patients with idiopathic adult hydrocephalus (normal-pressure hydrocephalus) syndrome based on conservative clinical criteria. No predictive tests were used for inclusion. All patients had a typical gait disturbance and a communicating hydrocephalus. Twenty-eight patients also had dementia or incontinence, or both. INTERVENTION: The CSF diversion (Cordis, [Orbis-Sigma]) valve, six patients; Hakim's standard system (Cordis Hakim standard system), 29 patients. OUTCOMES OF SURGERY: Serial videotaping of gait, a comprehensive neuropsychologic battery, and the Bartel index of activities of daily life. RESULTS: Gait was improved in 25 (72%) of the 35 patients, whereas the Bartel index remained unchanged. The conditions of five of seven patients with gait disturbance as the sole symptom improved. The spatial function (37% improved) and the findings from the Fuld object memory tests (29% improved) were significantly improved. Shunt dysfunction could not explain the lack of effect of an operation in the remaining patients. It should be noted that these results obtained at 3 months postoperatively may not be applicable in a long-term perspective. The CSF outflow conductance or CSF tap test were not able to identify those patients who would or would not benefit from a CSF diversion procedure. However patients had a lower conductance and a higher CSF pressure than did control subjects. CONCLUSIONS: Considerable improvement in gait was seen, but cognitive function was little affected. The CSF tap test or conductance does not provide additional information that is necessary to distinguish between patients whose conditions will or will not respond to shunting, when selection for surgery is based on conservative clinical criteria.