1. ¹Division of Anaesthesia, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK
2. ²Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK
3. ³Benito Menni, CASM and CIBERSAM, Dr. Antoni Pujadas, Barcelona, Spain
4. ⁴Department of Neurosurgery, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK

Correspondence: Dr DK Menon, Department of Anaesthesia, University of Cambridge, Box 63, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK. E-mail: dkm13@wbic.cam.ac.uk

Received 7 November 2008; Revised 4 February 2009; Accepted 22 February 2009; Published online 18 March 2009.

Abstract

We defined lesion and structurally normal regions using magnetic resonance imaging at follow-up in patients recovering from head injury. Early metabolic characteristics in these regions of interest (ROIs) were compared with physiology in healthy volunteers. Fourteen patients with severe head injury had positron emission tomography within 72 h, and magnetic resonance imaging at 3 to 18 months after injury. Cerebral blood flow (CBF), oxygen utilization (CMRO₂), and oxygen extraction fraction (OEF) were all lower in lesion ROIs, compared with nonlesion and control ROIs (P<0.001); however, there was substantial overlap in physiology. Control ROIs showed close coupling among CBF, blood volume (CBV), and CMRO₂, whereas relationships within lesion and nonlesion ROIs were abnormal. The relationship between CBF and CMRO₂ generally remained coupled but the slope was reduced; that for CBF and OEF was variable; whereas that between CBF and CBV was highly variable. There was considerable heterogeneity between and within patients. Although irreversibly damaged tissue is characterized by marked derangements in physiology, a more detailed analysis shows acute changes in physiology and physiologic relationships within regions of the brain that appear structurally normal at follow-up. Such pathophysiological derangements may result in selective neuronal loss and impact on functional outcome.