Reply to the Commentary on the Article of C. Woertgen, O. W. Ullrich, R. D. Rothoerl, A. Brawanski: ”Comparison of the Claassen and Fisher CT Classification Scale
to Predict Ischemia after Aneurysmatic SAH”
by J. Claassen, K. T. Kreiter, S. A. Mayer

Thank you very much for your interest in our study comparing the Claassen CT scale and the Fisher scale. Concerning the point that our series is highly selected; we excluded 185 patients of 477 patients in order to have a homogenous group of patients with aneurysmatic SAH. We think that patients without angiographic evidence of an aneurysm, for example with a mostly perimesencephalic SAH, are patients with a different pathology, which is not directly comparable with patients who suffer from aneurysmatic SAH. Patients with SAH of unknown etiology are at lower risk to develop vasospasm and therefore DCI [1]. Regarding the patients operated on in deep hypothermia, these patients suffered from complex giant aneurysms, which were operated on in circulatory arrest for vessel reconstruction. We think that these patients are not comparable with patients suffering from aneurysmatic SAH. To study DCI in patients with aneurysmatic SAH, we tried to exclude all other influence factors like operative ischemia. There is no patient showing cerebral infarction due to herniation in this group. Due to the prospective character of the data collection, we are convinced that the DCI in this series is due to vasospasm. The CT scans were not reviewed by blinded physicians. Regarding grade 3 and 4 of the Fisher scale, we have to remember the original paper, this item is discussed in the paper. The number of patients in the original study is probably too low to predict DCI in patients with grade 4.

To our opinion the series is selected, but is homogenous concerning the pathology. The Claassen CT scale is predictive for DCI, but the scale does not seem to give additional information in this setting.

Reference

• 1 Schwartz T H, Solomon R A. Perimesencephalic nonaneurysmal subarachnoid hemorrhage: Review of the literature.  Neurosurgery. 1996;  39 433-440