To date, this is the first study to determine the potential risk factors that are predictive of shunt-dependent hydrocephalus in patients with aneurysmal SAH but without hydrocephalus upon arriving at the hospital. Differences in the relative prevalence of hydrocephalus following aneurysmal SAH vary with case ascertainment and inclusion criteria, timing and methods of neuro-imaging studies, serial follow-up neuro-imaging studies, surgical procedure, and presence of complications [1
]. In the current study, hydrocephalus accounts for 61.9% (104/168) of all episodes, including 82 with initial hydrocephalus on admission and 22 with subsequent hydrocephalus. Such figures are higher than those of two recent studies [3
] and the largest study [5
The present study examined the risk factors and outcome of shunt-dependent hydrocephalus in aneurysmal SAH patients and produced two major findings. First, the presence of intra-ventricular hemorrhage, lower mean score of Glasgow Coma Scale, higher mean scores of both the modified Fisher SAH grade and the World Federation of Neurosurgical grade on admission, and complications with post-operative intra-cerebral hemorrhage are significant risk factors for shunt-dependent hydrocephalus in patients without hydrocephalus on admission. Second, shunt-dependent hydrocephalus patients have worse short- and long-term outcomes and longer duration of hospitalization.
For research on the risk factors and outcomes of shunt-dependent hydrocephalus, most large studies have focused on acute or chronic hydrocephalus together, [2
]. Very few have examined both clinical features and outcomes for acute and subsequent hydrocephalus, respectively [4
]. The pathogenesis of acute hydrocephalus is thought to result from blockage of CSF flow, producing a pressure gradient, and ultimately leading to enlarged ventricles, whereas the pathogenesis of chronic hydrocephalus involves arachnoid adhesions formed as a result of meningeal reaction to blood products, impairing CSF absorption at the basal cisterns [15
The presence of hydrocephalus does not always lead to the development of shunt dependency although it is a strong predictor of such, as noted in previous studies [17
] and in the current study. The data here demonstrates that 39% of patients with acute hydrocephalus on admission and 50% of those with subsequent hydrocephalus have undergone permanent shunting procedures. Furthermore, there is evidence in literature suggesting that aggressive external ventricular drainage significantly reduces the need for permanent shunting among these patients [19
]. Although the effect of temporary ventriculostomy placement on the development of hydrocephalus is not studied, its effects on the outcome of hydrocephalus may also be considered in future studies.
Several studies demonstrate a strong relationship between poor levels of consciousness on admission and hydrocephalus [5
]. Both acute and subsequent hydrocephalus cases also have similar results. Some studies show that the amount of blood in the sub-arachnoid space has special significance [5
] while the current study demonstrates higher mean modified Fisher SAH grade on presentation in patients who have shunt-dependent hydrocephalus. The effect of intra-ventricular hemorrhage on the development of hydrocephalus is also well established [5
]. Some authors suggest that the presence of blood clots and high CSF viscosity can lead to an obstructive form of hydrocephalus and early CSF circulation disturbances [20
]. In the current series, intra-ventricular hemorrhage is a significant risk factor for the development of shunt-dependent hydrocephalus in patients with aneurysmal SAH but without hydrocephalus on admission.
The outcomes of hydrocephalus have been extensively studied. Hydrocephalus can result in long-term cognitive decline and the development of psycho-organic disorders [22
]. This study demonstrates the worst short-term outcome and longest duration of hospitalization in patients with subsequent hydrocephalus, and the prognosis is also worst after 1.5
years of follow-up. Worse short- and long-term outcomes and longer duration of hospitalization are also noted in shunt-dependent hydrocephalus patients.
The current study has several limitations. First, it is a retrospective analysis and therefore subject to bias of unmeasured factors. Second, patients who were comatose or considered unlikely to survive for more than one week and had pre-existing neurologic deficits have been excluded. Third, hydrocephalus can occur in both the acute stage and later stages during treatment. The findings may underestimate the “true” frequency of hydrocephalus in asymptomatic patients. Thus, there is continued uncertainty in assessing the incidence of hydrocephalus after aneurysmal SAH in non-selected patients.