Imaging Cerebral microdialysis and positron emission tomography after surgery for aneurysmal subarachnoid hemorrhage in grade I patients D.P. Noske, MD, PhD a , S.M. Peerdeman, MD, PhD a , E.F.I. Comans, MD, PhD b , C.M.F. Dirven, MD, PhD a , D.L. Knol, MD, PhD c , A.R.J. Girbes, MD, PhD d , W.P. Vandertop, MD, PhD a, * Departments of a Neurosurgery, b Nuclear Medicine, c Clinical Epidemiology and Biostatistics, and d Intensive Care, VU University Medical Center, 1007 MB Amsterdam, The Netherlands Received 4 March 2004; accepted 20 September 2004 Abstract Background: Using cerebral microdialysis, baseline values for energy-related chemical markers have been reported in awake patients. Radionuclide studies have demonstrated a locally decreased metabolism, thought to be the result of brain retraction. These baseline values, however, may not be applicable to patients after surgical aneurysm repair following a subarachnoid hemorrhage (SAH). We assessed metabolic chemical marker levels in World Federation of Neurological Surgeons Committee (WFNS) grade I SAH patients after aneurysm surgery and compared them with previously reported baseline values. Methods: In 5 WFNS grade I SAH patients, energy-related chemical marker levels were obtained using microdialysis in the area of brain retraction after aneurysm surgery. In addition, an [ 18 F]2- deoxy-d-glucose positron emission tomography (FDG-PET) was performed. Results: The FDG-PET showed a decrease of glucose metabolism in the frontotemporal area. Comparing the mean values for chemical markers of this study with reported baseline values, the most striking difference was a mild decrease of pyruvate and an increase of the lactate/pyruvate ratio. In individual patients, some markers indicated possible ischemia. A consistent pattern or ischemic profile for all markers, however, was not found. Conclusion: FDG-PET scanning confirmed postoperative metabolic changes found in previous studies. Mean interstitial chemical marker levels ranged from normal to mildly deviant compared with reference chemical marker levels for awake patients and are likely to be applicable in SAH patients after aneurysm repair. D 2005 Elsevier Inc. All rights reserved. Keywords: Intracranial aneurysm; Subarachnoid hemorrhage; Microdialysis; Radionuclide imaging 1. Introduction Cerebral microdialysis is a new modality for bedside monitoring of cerebral metabolism [17]. Microdialysis is based on the principle of diffusion of water-soluble substances through a semipermeable membrane in a catheter, which is inserted approximately 15 mm into brain parenchyma, through which so-called perfusion fluid flows. While passing the membrane, substances from the extracel- lular fluid diffuse into the perfusion fluid (ie, bdialysateQ), which is collected and can be bedside analyzed at certain time intervals (eg, every hour). Extracellular metabolite concentrations thus serve as chemical markers that reflect metabolism at a cellular level. In patients with subarachnoid hemorrhage (SAH), it is well known that vasospasm can affect energy metabolism and can lead to neurological deterioration. Bedside moni- toring with conventional methods such as transcranial Doppler scan provide information related to vasospasm, 0090-3019/$ – see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.surneu.2004.09.036 * Corresponding author. Tel.: +31 20 444 3724; fax: +31 20 444 3784. E-mail address: wp.vandertop@vumc.nl (W.P. Vandertop). Surgical Neurology 64 (2005) 109 – 115 www.surgicalneurology-online.com