Age and sex
The group of patients who underwent shunting procedures was older but did not reach statistical significance. This correlates well with other studies. In the study by Dorai et al. (2003), the mean age for the study population was 53.2 years (range, 17–89 years). The median age for the shunt-treated population was 60 years, in comparison with 51 years for the non-shunt-treated population. The authors stated a possible explanation; older patients have wider subarachnoid spaces which can hold larger amounts of subarachnoid blood, thus increasing their risk of developing CSF circulation disturbances. Moreover, the ventricular compliance decreases with age leading to the increased liability to symptomatic hydrocephalus (Dorai et al. 2003). The study by Rincon et al. (2010) reported comparable results in which the median age for the shunt-treated group was 59. The median age for non-shunt-treated group was 53 (Rincon et al. 2010).
Gender did not correlate statistically with shunt placement. In the available literature, female sex was more liable for VP shunt placement. In the study by Dorai et al. (2003), 23.8% of the female patients underwent shunting procedures, compared with 15.9% of the male patients. In the study by Chan et al. (2009), 63.5% of the patients who required shunting after failure of external ventricular drainage (EVD) weaning were females and 34.5% were males.
The location of the aneurysm correlated clinically well with the need for shunting. Our results are comparable to the study by Pietilä et al. (1995), in which all the patients with MCA aneurysms did not require VP shunt placement. Nineteen percent of the patients with ACoA aneurysms required shunting, and those came second only to the patients with posterior circulation aneurysms (53%) (Pietilä et al. 1995). Our study did not include posterior circulation aneurysms. In literature posterior circulation, aneurysms are associated with increased incidence of VP shunt placement as in the studies by Dorai et al. (2003), Chan et al. (2009), and de Oliveira et al. (2007). Different aneurysm locations produce different amounts and patterns of bleeding. Posterior circulation and ACoA aneurysms create large amounts of blood in the basal cisterns. The subarachnoid space around them is wide and offers little resistance to extravasation, whereas the narrow sylvian cistern is tighter. Anterior communicating artery and PCoA aneurysms are more often associated with intraventricular hemorrhage (Sethi et al. 2000).
Our results are comparable to the study by Rincon et al. (2010), in which a bicaudate index higher than 0.2 was found to be associated with the need for ventriculoperitoneal shunting. In the study by Little et al. (2008), hydrocephalus was measured by the relative bicaudate index (RBCI) measured on computed tomographic scans at the time of shunting by dividing the bicaudate index by the normal upper age limit. Patients were divided into three groups by ventricle size: group 1 (RBCI less than1.0), group 2 (RBCI between 1.0 and 1.4), and group 3 (RBCI more than 1.4). VP shunt was performed in 16, 49, and 90% of the three groups respectively. Thus, higher bicaudate index correlated more with the need for VP shunt placement. The authors pointed out, however, that the borderline group in the middle ought to be managed more conservatively. These results are comparable to our study (Little et al. 2008).
Our results were inconclusive regarding the relationship between high Fisher grade and the need for shunting. Varelas et al. (2006) had comparable results to our study in which they found out that Fischer grade did not correlate with the need for shunting. However, mostly in the available literature, higher Fisher grade correlates with shunt dependency. In the study by Dorai et al. (2003), 19.2% of the patients with thick blood, i.e., Fisher grade 3 required shunting. 10.8% of the patients with thin blood, i.e., Fisher grade 1 required shunting (Dorai et al. 2003). In the study by Dehdashti et al. (2004), in which 245 patients were studied prospectively over 6 years, 33 and 53% of the patients who underwent shunting had Fisher grades 3 and 4 respectively. In the study by de Oliveira et al. (2007), 385 patients were studied retrospectively over a 6-year period and 71 patients (18.4%) required shunting. They found that 93% had Fisher grade 3 (de Oliveira et al. 2007). The study by Gruber et al. (1999) also concluded that high Fisher grade leads to shunt dependency in 26.7 and 32.8% of Fisher grade 3 and Fisher grade 4 respectively.