Large and giant vestibular schwannomas: does cisterna magna hyperproteinorrhachia influence visual status?

Abstract

Hyperproteinorrhachia associated with vestibular schwannomas (VSs) may influence visual status independent of the effect caused by raised intracranial pressure. The role of cisterna magna CSF protein levels (CMCP) in determining visual outcome in patients with large to giant vestibular schwannomas (VSs) was prospectively investigated. The mean CMCP levels in VSs and control group; and, levels in VSs with or without visual deterioration were compared. Spearman's rank correlation coefficient tested for relationships between CMCP level with symptom duration and tumour volume (Kawamoto's method). Vision was regarded as normal when visual acuity was >6/18; and, deteriorated when it was between 6/18 and PL negative in the worse eye. Papilloedema (n = 26)/secondary optic atrophy (n = 6) and hydrocephalus (based on Evan's ratio, mild to moderate: n = 22; none: n = 18) were also recorded. The analysis of factors predicting diminished vision was done using logistic regression analysis (p < 0.05 significant). There was a significant difference (p < 0.001) in mean CMCP levels between VS (456.3 SD 213.6mg/dl) and control groups (96.3 SD 74.3mg/dl). The mean CMCP levels in the VS group were also markedly higher than the ventricular mean protein levels. The CMCP levels in patients with visual diminution (<6/18 to PL negative; n = 23) was 561.4 SD 186.9mg/dl and those without visual loss (n = 17) was 314.2 SD 160.8mg/dl (p < 0.001). Their grade of visual diminution had a positive correlation with mean CMCP levels (p < 0.001). There was a negative correlation between total duration of symptoms and CMCP levels (p < 0.015). Logistic regression analysis using five independent factors (symptom duration, papilloedema/secondary optic atrophy, tumour volume, hydrocephalus and mean CMCP level) revealed that only CMCP level had a significant association with visual diminution. Elevated cisternal CSF proteins may play an important role in determining visual outcome in large to giant VSs. Ventricular CSF analysis is often unable confirm the presence of VS-associated cisternal hyperproteinorrhachia. High CMCP levels may influence decision-making while instituting a permanent CSF diversion for postoperative hydrocephalus or recalcitrant pseudomeningocoele.