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TO THE EDITOR: We are thankful to Ascanio et al.1 for their work on nontraumatic subarachnoid hemorrhage (SAH) (Ascanio LC, Gupta R, Adeeb N, et al: Relationship between external ventricular drain clamp trials and ventriculoperitoneal shunt insertion following nontraumatic subarachnoid hemorrhage: a single-center study. J Neurosurg [epub ahead of print March 16, 2018. DOI: 10.3171/2017.10.JNS171644]). They conducted a retrospective review of all consecutive patients with nontraumatic SAH complicated by acute hydrocephalus who were admitted over a period of 10 years to a single major academic institution in the United States. After considering the exclusion criteria, 114 patients who underwent external ventricular drain (EVD) insertions during the first 24 hours after admission and who underwent at least 1 clamp trial prior to removal were included in the final analysis. Through this paper the authors delivered a crucial message that failure of initial EVD clamp trials in such patients “does not necessarily indicate that the patient should receive a shunt,” which is commendable. However, some points are worth mentioning with respect to the methodology and findings in this study. First, the inclusion of patients with EVD infections in the final sample size is debatable. In the setting of an EVD infection, there would be a change in the entire line of management with respect to CSF diversion. The process of clamping will have to be discontinued because the patient cannot receive a shunt irrespective of the result of the clamp trial. Also, an increase in length of ICU stay is likely in this subset of patients. Hence, the presence of EVD infection anytime during the hospital stay could have been an exclusion criterion. Second, there is evidence in the literature to suggest that surgical clipping of ruptured intracranial aneurysms may be associated with a lower risk of shunt-dependent hydrocephalus.2,3 Varelas et al.,6 in their retrospective study involving 188 patients, found that permanent shunting was associated with coiling. They postulated that during clipping, blood or clots may have been evacuated from the subarachnoid space, which is not possible in an endovascular approach. However, in the paper by Ascanio et al., the authors remain silent with respect to the method used for securing ruptured aneurysms. An inhomogeneity in the patient population with regard to this characteristic may have confounded the results of the study. Last, in patients who underwent surgical clipping, the question of whether lamina terminalis fenestration was performed is a factor that deserves a mention. Fenestration of the lamina terminalis can reduce the rates of shuntdependent hydrocephalus, although there is still conflicting evidence in this regard.4,7 A prospective randomized controlled trial such as the ongoing FISH trial5 could help settle this debate.

Letter to the Editor. EVD clamp trials and ventriculoperitoneal shunt insertions in patients with nontraumatic SAH