Vestibulo-ocular monitoring in severe traumatic brain injury: early prediction of outcome

Introduction: Oculomotor response (OMR) to galvanic labyrinth polarization (GaLa) recorded soon after TBI should indicate the outcome of patients when considering the extent of brainstem damage after severe traumatic brain injury (TBI) as critical for the evaluation. This importance of brainstem for outcome has been demonstrated by previous studies employing imaging techniques to visualize structural or functional brainstem lesions.

Methods: Vestibulo-ocular monitoring (VOM) is based on video-oculographic recording of eye movements during GaLa stimulation of both labyrinths. The OMR is elicited via the vestibulo-ocular reflex (VOR), i.e. via the afferents from the peripheral neurons to the vestibular nuclei and subsequently to the oculomotor neurons. These pathways are situated in the brainstem and therefore reflect alterations caused by a functional lesion. The aim of the study is to examine whether, and to what extent, early VOM correlates with outcome after six months (Glasgow Outcome Score) in severe TBI and a comparison from the predictive value of VOM with the predictive value of pupillary size is presented.

Results: On twenty-seven patients VOM was performed within three days after severe TBI. Three-dimensional eye movements were obtained from the VOM recordings and frequency analysed. GOS was determined by evaluation of a standardised outpatient interview. In 16 patients an OMR, synchronous with the GaLa stimulus was found. In the remaining 11 patients no such OMR could be observed.

One patient was excluded from the study. Outcome scores yielded GOS1 (n=11), GOS2 (n=3), GOS3 (n=9), GOS4 (n=3) and GOS5 (n=1). The GOS1–2 patients determined six-months after trauma were characterised by no OMR in early VOM, whereas GOS3–5 patients showed an OMR in early VOM. This significance of VOM is described by the exact two-sided Fisher-Test (p<10–3)). At the early time after tbi only two patients presented a dilated pupil. Both had an unfavourable outcome (GOS1–2) but the sensitivity of pupil diameter as an predictor of outcome was low.

Conclusion: It was possible to predict patients outcome by distinguishing two groups using VOM in the acute phase. As an indicator of brainstem function VOM provides a useful, complementary approach to the identification of brainstem lesions by imaging techniques.