Research Reports - Resting state magnetoencephalography functional connectivity in traumatic brain injury

J Neurosurg. 2013 Apr 19

Tarapore PE, Findlay AM, Lahue SC, Lee H, Honma SM, Mizuiri D, Luks TL, Manley GT, Nagarajan SS, Mukherjee P

Object Traumatic brain injury (TBI) is one of the leading causes of morbidity
worldwide. One mechanism by which blunt head trauma may disrupt normal cognition
and behavior is through alteration of functional connectivity between brain
regions. In this pilot study, the authors applied a rapid automated resting state
magnetoencephalography (MEG) imaging technique suitable for routine clinical use
to test the hypothesis that there is decreased functional connectivity in
patients with TBI compared with matched controls, even in cases of mild TBI.
Furthermore, they posit that these abnormal reductions in MEG functional
connectivity can be detected even in TBI patients without specific evidence of
traumatic lesions on 3-T MR images. Finally, they hypothesize that the reductions
of functional connectivity can improve over time across serial MEG scans during
recovery from TBI. Methods Magnetoencephalography maps of functional connectivity
in the alpha (8- to 12-Hz) band from 21 patients who sustained a TBI were
compared with those from 18 age- and sex-matched controls. Regions of altered
functional connectivity in each patient were detected in automated fashion
through atlas-based registration to the control database. The extent of reduced
functional connectivity in the patient group was tested for correlations with
clinical characteristics of the injury as well as with findings on 3-T MRI.
Finally, the authors compared initial connectivity maps with 2-year follow-up
functional connectivity in a subgroup of 5 patients with TBI. Results Fourteen
male and 7 female patients (17-53 years old, median 29 years) were enrolled. By
Glasgow Coma Scale (GCS) criteria, 11 patients had mild, 1 had moderate, and 3
had severe TBI, and 6 had no GCS score recorded. On 3-T MRI, 16 patients had
abnormal findings attributable to the trauma and 5 had findings in the normal
range. As a group, the patients with TBI had significantly lower functional
connectivity than controls (p < 0.01). Three of the 5 patients with normal
findings on 3-T MRI showed regions of abnormally reduced MEG functional
connectivity. No significant correlations were seen between extent of functional
disconnection and injury severity or posttraumatic symptoms (p > 0.05). In the
subgroup undergoing 2-year follow-up, the second MEG scan demonstrated a
significantly lower percentage of voxels with decreased connectivity (p < 0.05)
than the initial MEG scan. Conclusions A rapid automated resting-state MEG
imaging technique demonstrates abnormally decreased functional connectivity that
may persist for years after TBI, including cases classified as "mild" by GCS
criteria. Disrupted MEG connectivity can be detected even in some patients with
normal findings on 3-T MRI. Analysis of follow-up MEG scans in a subgroup of
patients shows that, over time, the abnormally reduced connectivity can improve,
suggesting neuroplasticity during the recovery from TBI. Resting state MEG
deserves further investigation as a prognostic and predictive biomarker for TBI.

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