Magnetoencephalographic virtual recording: a novel diagnostic tool for concussion
Neurosurg Focus 33 (6):E9, 2012 1 T here is no agreed-upon neuroimaging strategy to diagnose concussion. The diagnosis of concussion, which is also called MTBI, is based on patient symptom self-report and neuropsychological testing as the basis for medical decisions and the treatment paradigms. A significant percentage of patients with concussion have no abnormal findings on CT or MRI studies of the brain. 1 The absence of a formal, objective neuroimaging tool to diagnose concussion reliably is
... cussion reliably is a major impediment in the field. Magnetoencephalography shows promise for the assessment of neurophysiological derangements in neurological disorders, including TBI. This promise arises from the noninvasiveness and harmlessness of the method, its high temporal resolution, and the interpretation of results as measures of localized neurophysiological function. These properties have given hope for the development of reliable functional neuroimaging measures with which to demonstrate the mechanisms underlying the neuropsychological consequences of concussion. 3 Resting MEG measures have previously enabled identification of approximately 60% of patients with concussions. 7,9,10 A recent study 6 demonstrated 85% classification accuracy. We have developed a novel MEG-based neuroim-Object. Heightened recognition of the prevalence and significance of head injury in sports and in combat veterans has brought increased attention to the physiological and behavioral consequences of concussion. Current clinical practice is in part dependent on patient self-report as the basis for medical decisions and treatment. Magnetoencephalography (MEG) shows promise in the assessment of the pathophysiological derangements in concussion. The authors have developed a novel MEG-based neuroimaging strategy to provide objective, noninvasive, diagnostic information in neurological disorders. In the current study the authors demonstrate a novel task protocol and then assess MEG virtual recordings obtained during task performance as a diagnostic tool for concussion. Methods. Ten individuals (5 control volunteers and 5 patients with a history of concussion) were enrolled in this pilot study. All participants underwent an MEG evaluation during performance of a language/spatial task. Each individual produced 960 responses to 320 sentence stimuli; 0.3 sec of MEG data from each word presentation and each response were analyzed: the data from each participant were classified using a rule constructed from the data obtained from the other 9 participants. Results. Analysis of response times showed significant differences (p < 10 -4 ) between concussed and normal groups, demonstrating the sensitivity of the task. The MEG measures enabled the correct classification of 8 of 10 individuals as concussed versus nonconcussed (p = 0.055). Analysis of single-trial data classified 70% of trials correctly (p < 10 -10 ). Concussed patients showed increased activation in the occipitoparietal and temporal regions during evaluation. Conclusions. These pilot findings are the first evidence of the utility of MEG virtual recording in diagnosing concussion. With further refinements, MEG virtual recordings may represent a noninvasive test to diagnose concussion and monitor its resolution. Key worDS • concussion • mild traumatic brain injury • magnetoencephalography 1 Abbreviations used in this paper: EP = evoked potential; ERP = event-related potential; MEG = magnetoencephalography; MTBI = mild traumatic brain injury.