Clinical Study Bedside saccadometry as an objective and quantitative measure of hemisphere-specific neurological function in patients undergoing cranial surgery Y. Saleh a , H.J. Marcus a,b,⇑ , R. Iorga a , R. Nouraei a , R.H. Carpenter c , D. Nandi a a Department of Neurosurgery, Imperial College Healthcare NHS Trust, Charing Cross Hospital, London, UK b The Hamlyn Centre, Institute of Global Health Innovation, Imperial College London, Paterson Building (Level 3), Praed Street, London W2 1NY, UK c Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge, UK article info Article history: Received 29 January 2014 Accepted 24 May 2014 Keywords: Bedside Cranial surgery Saccadometry abstract Cranial surgery continues to carry a significant risk of neurological complications. New bedside tools that can objectively and quantitatively evaluate cerebral function may allow for earlier detection of such com- plications, more rapid initiation of therapy, and improved patient outcomes. We assessed the potential of saccadic eye movements as a measure of cerebral function in patients undergoing cranial surgery peri- operatively. Visually evoked saccades were measured in 20 patients before (À12 hours) and after (+2 and +5 days) undergoing cranial surgery. Hemisphere specific saccadic latencies were measured using a simple step-task and saccadic latency distributions were compared using the Kolmogorov–Smirnov test. Saccadic latency values were incorporated into an empirically validated mathematical model (Linear Approach to Threshold with Ergodic Rate [LATER] model) for further analysis (using Wilcoxon signed rank test). Thirteen males and seven females took part in our study (mean age 55 ± 4.9 years). Following cranial surgery, saccades initiated by the cerebral hemisphere on the operated side demonstrated signif- icant deteriorations in function after 2 days (p < 0.01) that normalised after 5 days. Analysis using the LATER model confirmed these findings, highlighting decreased cerebral information processing as a potential mechanism for noted changes (p < 0.05). No patients suffered clinical complications after sur- gery. To conclude, bedside saccadometry can demonstrate hemisphere-specific changes after surgery in the absence of clinical symptoms. The LATER model confirms these findings and offers a mechanistic explanation for this change. Further work will be necessary to assess the practical validity of these changes in relation to clinical complications after surgery. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Although the outcome of patients undergoing cranial surgery has improved over the past few decades, these operations continue to carry a significant risk of morbidity and mortality [1,2]. Early detection of the onset of complications is critical in avoiding per- manent residual neurological damage as it encourages early inter- vention [3]. The Glasgow Coma Scale (GCS), conceived by Teasdale and Jennet in 1974, is the cornerstone bedside test for assessing conscious state in neurosurgical patients [4,5]. Since its inception, the GCS has been invaluable in communicating levels of conscious- ness in peri-operative patients; however it was not designed with the intent to detect early complications in the neurosurgical patient. Furthermore, the GCS is an ordinal scale. Thus although the GCS is a useful tool in expressing impaired neurological states on a numerical scale, in no way does the GCS actually quantify gen- eral cerebral function [5]. In terms of patient care this means that the detection of early neurological deterioration before obvious clinical manifestations is not achievable. We feel that there is a role for an adjunctive assessing tool that can objectively and quantita- tively evaluate cerebral function in neurosurgical patients through a simple, reliable, and rapidly performed bedside test that allows comparison between brain hemispheres. Neuropsychological tests have been utilised in an attempt to improve assessments of cognitive function peri-operatively, how- ever, they are also limited for several reasons [6,7]. They may require specialist training and can be time consuming, lasting as long as 100 minutes [6]. Extended assessment periods may not be tolerated by the elderly population, and can delay surgical http://dx.doi.org/10.1016/j.jocn.2014.05.049 0967-5868/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +44 20 3312 5139; fax: +44 20 7594 8260. E-mail address: hani.marcus10@imperial.ac.uk (H.J. Marcus). Journal of Clinical Neuroscience 22 (2015) 280–285 Contents lists available at ScienceDirect Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn