Adult hydrocephalus. Intracranial pressure, B-wave and clinical analysis in patients with noncommunicating and communicating hydrocephalus

Abstract

Aims of present investigations. Adult patients with clinical and radiological findings consistent with normal pressure hydrocephalus (NPH) were studied. Two of the aims were to document intracranial pressure (ICP) levels and quantity of B-waves during sleep and wakefulness, and to compare the results with preoperative clinical symptoms and outcome after surgery. The third aim was to document if a pressure gradient over the mantle of the brain (transmantle pressure gradient) exists. The fourth aim was to evaluate the effectiveness of endoscopic third ventriculostomy (ETV) as a treatment of primary aqueduct stenosis. The fifth aim was to determine if adult patients with an early-onset hydrocephalus that resurfaces later in life and diagnosed with ¡°asymptomatic¡±, ¡°arrested¡±, or ¡°compensated¡± hydrocephalus really were ¡°asymptomatic¡± and evaluating if they would benefit from surgery. Material and methods. A total of 95 patients with communicating or noncommunicating hydrocephalus were investigated. Demographic and clinical data, brain and cerebrospinal fluid imaging were systematically documented and analysed before and after surgery. Surgical treatment consisted of ETV or shunt surgery, and in cases of failed ETV a shunt implantation was recommended. Follow up was three months after last surgery in all surgically treated patients. Fifty-six underwent a long term ICP registration. Computerised analysis of ICP levels and B-waves were performed (in 55) after the final postoperative results and compared to clinical and demographic data. Ten patients had a measurement of the transmantle pressure. Eighteen patients who had been treated with ETV for aqueduct stenosis were identified and examined. Those who had not improved as expected were further investigated and recommended a shunt implantation. Twenty-three patients with clinical and radiological characteristics consistent with one of the diagnoses ¡°asymptomatic¡±, ¡°compensated¡±, ¡°arrested¡± or symptomatic congenital hydrocephalus were investigated and advised to have surgery. Results and conclusions. Contrary to the general conviction, the preoperative magnitudes of the cardinal NPH symptoms and signs were strongly interrelated. There was no correlation of the number of B-waves or magnitude of ICP with demographic data, clinical findings or outcome after surgery. The mean ICP was higher in noncommunicating hydrocephalus; however, most patients in both groups had a normal mean ICP (¡Ü 15 mm Hg). The lack of correlation between the clinical picture of NPH and ICP undermines the use of pressure in classifying hydrocephalus. There is no transmantle pressure gradient in patients with communicating or noncommunicating hydrocephalus. The long term efficacy of ETV for adult patients with noncommunicating hydrocephalus was sufficient in only 50% of the cases. One-third demonstrated temporary improvement after ETV and then deteriorated to an even worse clinical condition, despite patent ventriculostomies. All patients who did not permanently improve after ETV benefited from shunt surgery. Patients with longstanding nonprogressive hydrocephalus, even for decades, can benefit from surgery.The traditional model of CSF circulation and hydrocephalus development cannot adequately explain clinical findings and investigational results in hydrocephalic patients. A new model is proposed that assumes a strong relationship between the CSF dynamics and the fluid equilibrium of the brain.