Viscosity is the resistance to flow of a fluid and it is the only property of a fluid that will affect its flow through a system of valveless tubing (surface tension will affect the opening and closing of valves that are included in the system). The effect that an elevated protein concentration has upon CSF viscosity has received little study, yet many neurosurgeons believe that CSF with an elevated protein content is too viscous to flow satisfactorily through shunts. The total protein content and viscosity of 126 specimens of CSF from hydrocephalic patients were measured and analysed with reference to the aetiology of the hydrocephalus. The results indicate that high protein concentrations do not greatly affect the viscosity of CSF, and that the aetiology is also of little consequence. These findings were highly significant on linear regression analysis (p < 0.001). The flow of the most viscous CSF that is likely to be encountered would be reduced by only 7% through a given catheter, compared with that of the least viscous CSF.
A 65-year-old man had a perimesencephalic subarachnoid haemorrhage with normal angiography initially. After a rebleed 5 days later, a repeat angiogram revealed a pea-like aneurysm a short distance behind and below the basilar bifurcation. It was not amenable to endovascular treatment and the feeding vessel was coagulated and divided at open surgery via a sub temporal approach. He developed a right hemiparesis and dysphasia, from which he slowly recovered. Basilar perforating artery aneurysms are extremely rare, with only 4 previous cases reported.
It has long been assumed that a high cerebrospinal fluid protein concentration adversely affects the performance of shunts. There is little experimental evidence to support this viewpoint, however, and the few reports that have been published can be criticized for poor experimental design or presentation of results. A flow-dependent shunt perfusion model was constructed. PS Medical Flow Control valves (PS Medical Corporation, Goleta, CA) and Cordis-Hakim valves (Cordis Corporates, Miami, FL) were perfused with saline-plasma solutions in concentrations from 0 to 9 g/L of protein. Blood suspensions in dilutions from 0.25 to 1% were also studied. The opening and closing pressures of the valves were measured with a simple manometer, and the physical properties of the solutions were studied. The results indicated that the valves performed within the ranges specified by their manufacturers, even with markedly increased protein concentrations in the perfusate. Furthermore, the valve opening and closing pressures were lower with the protein-containing solutions than with the control solutions. Thus, the protein did not impair shunt function and we conclude that shunts can be inserted into patients who have elevated cerebrospinal fluid protein contents. However, blood cells did adversely affect performance and, therefore, patients with hemorrhagic cerebrospinal fluid should not receive shunts.
Objective-To assess the quantity and nature of the proteins that adsorb to hydrocephalus shunt catheters after implantation, and to determine whether sufficient could accumulate to obstruct the catheter. Design-Elution of proteins from 102 explanted shunt catheters, with protein assay and electrophoresis of the eluate, and scanning electron microscopy (SEM) of the catheters. Results-The amount of protein elutable was extremely low, and significant protein, apart from a thin film, was not found on SEM. Qualitative analysis disclosed that most of the adsorbed protein was albumin. Conclusions-Protein deposition on hydrocephalus catheters does not occur in suYcient quantities to cause catheter obstruction. (J Neurol Neurosurg Psychiatry 1998;64:643-647)
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