The existence of hydrocephalus and the development of chronic hydrocephalus is a problem, awaiting a solution in patients who didn't undergo surgical treatment for cerebellar hemorrhage. This may be affected by the location of a hematoma, the degree of IVH severity, and the grade of fourth ventricular obliteration. The importance of the location, especially the hematoma in the midline occupying the vermis, is related to the grade of fourth ventricular compression. In these cases, hematoma has ruptured into the fourth ventricle, and brought out greater degrees of fourth ventricular obstruction. Also, the hematoma in the vermis, without IVH, can result in hydorcephalus by fourth ventricle compression. Thus, midline hematomas may be associated with obstructive hydrocephalus, caused by fourth ventricle compression and IVH. In our series, the hematoma, occupying the vermis, tended to have the development of chronic hydrocephalus, and there was a significant difference in the location of cerebellar hematoma between the VP shunt group and the non-VP shunt group (p=0.015).
Many previous reports have indicated that IVH could be the most consistent predictor of the development of shunt-dependent hydrocephalus7,19)
. The lower threshold for a poor outcome at postadmission may be due to the prolonged exposure of the ventricles to the blood, which worsens IVH-mediated injuries and neurological outcome4,15)
. However, it is not clear how much IVH may affect a clinically ventricular dysfunction. Hwang et al.6)
reported that the admission IVH volume of 6.0 mL was associated with a significant increase in the likelihood of poor functional outcome and subacute worsening in IVH volume, which may not have a significant influence on the outcome in patients with cerebellar hematoma. In our study, the degree of IVH severity may have a significant influence on the ventricular dysfunction and the progress of shunt-dependent hydrocephalus, and there was the significant difference in the IVH severity between the VP shunt group and the non-VP shunt group (p
=0.028). Also, based on our data, the ROC curve analysis showed a cutoff value of 6.5 in the IVH scores, which achieved 70.0% specificity and 76.2% sensitivity. From the formula for converting IVH score to IVH volume, 6.5 in the IVH score means 3.7 mL in the IVH volume4)
. However, this cutoff value is insufficient to be used clinically because of not only its low sensitivity and specificity but also a small number of subjects. Additionally, two patients who underwent VP shunt received all 4 (<6.5) of IVH score in an initial CT scan; all of them had complete obliteration (Grade II) of only the fourth ventricle. This suggests that IVH score does not reflect the severity of IVH well and tends to overlook the important influence of fourth ventricular hemorrhage on obstructive hydrocephalus to be a necessity of a VP shunt. This is the reason why the fourth ventricle score was set at only 0 or 1 in the formula for calculating the IVH score. It means that not only IVH severity, but also fourth ventricular obstruction, should be estimated for a VP shunt operation.
EVD in patients having acute hydrocephalus with cerebellar hematoma can present an upward transtentorial herniation, causing neurologic deterioration11,17)
. Based on our data, 16 patients with acute hydrocephalus were treated by EVD. They all did not show an upward transtentorial herniation after EVD, this suggest that they have small amounts of cerebellar hematoma, which was not included in the aforesaid surgical criteria.
This study has some limitations. This study is retrospective; thus, selection bias and protocol deviations were inevitably present. That is, some patients who suffered cerebellar hematoma may not have been found, especially in the clinically severe cases. In addition, due to this study having a relatively small number of subjects, it lacks sufficient power to clarify clinical factors of shunt placement in patients with cerebellar hematoma and/or IVH. Finally, the location of hematoma, the degree of fourth ventricle obstruction, and hydrocephalus might be evaluated more by a magnetic resonance imaging (MRI) than CT. Therefore, a prospective, large sample sized trial, using an MRI, will be required.