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Letter to the Editor: Whole-brain CT perfusion and subarachnoid hemorrhage.

TO THE EDITOR: We read with keen interest the article by Malinova et al.3 (Malinova V, Dolatowski K, Schramm P, et al: Early whole-brain CT perfusion for detection of patients at risk for delayed cerebral ischemia after subarachnoid hemorrhage. J Neurosurg 125:128–136, July 2016). The authors have described the utility of wholebrain CT perfusion (CTP) in predicting the occurrence of delayed ischemic neurological deficits and delayed cerebral infarction in patients with acute subarachnoid hemorrhage (aSAH). We commend the authors for their study, which sheds light on the enigma of delayed ischemic neurological deficits and delayed cerebral infarction following aSAH. In days to come, CTP may become part of routine study in patients with aSAH. Global cerebral edema (GCE) occurs after aSAH and is associated with functional and cognitive dysfunction. It usually occurs during the early phase (0–3 days) after aSAH. GCE is identified on CT scan by the following characteristics: 1) effacement of hemispheric sulci and basal cisterns, and 2) bilateral and extensive disruption of the cerebral gray-white matter junction at the level of the centrum semiovale.1,2 Patients with GCE have global perfusion deficits when compared to patients without GCE.1 This may affect early CT perfusion studies, and it probably was not considered by the authors. The number of such patients and the CTP findings in such patients should be addressed. Acute hydrocephalus after aSAH is known to be associated with reduced cerebral blood flow in the deep gray matter and periventricular white matter.4 This could also have affected the results, and interpretation of this study and the number of patients with hydrocephalus have not been mentioned. The authors’ study has very few patients with Fisher Grade 2 SAH and no patient with Fisher Grade 1 SAH, and it may be very difficult to generalize the result of this study to patients in these two groups. Thus, a study with a larger patient population and one composed of these two groups needs to be done, considering the radiation and the use of contrast agents for CTP studies. We once again commend the authors for this study and concur with them that a larger study group is required to compare various subgroups and to analyze the effects of CTP on outcome of patients with aSAH.