Video Head Impulse Test in Children – A Systematic Review of Literature

Background: and objectives: The video head impulse test (vHIT) is a landmark in vestibular diagnostic methods to assess high frequency semicircular canal system. This test is well established in the adult population seeing immense research since its discovery. The usefulness and feasibility of the test in children is not very well defined as research has been limited. This systematic review investigated and analysed the existing evidence regarding the test. The objectives were to derive meaningful inferences in terms of feasibility, implementation and normative vestibulo-ocular reflex (VOR gain) in normal children and in children with vestibular hypofunction. Methods: Research repositories were searched with key words and set inclusion and exclusion criteria to select publications that investigated the vHIT in both a normative population of children as well in pathological cohorts. Average normal VOR gain was then calculated in all semicircular canals for both the normal and the vestibular hypofunction group. For case-controlled studies, a metanalysis was performed to assess heterogeneity and pooled effect sizes. Results: The review analyed 26 articles in all that included 6 case-controlled studies fulfilling the study selection criteria out of more than 6000 articles that have been published on the vHIT. The technique described suggested 10-15 head impulses at 100-200 deg/sec head velocity fixating on a wall target 1 m away. The average VOR gain in the lateral semicircular canals combining all studies was 0.96+/- 0.07; that in anterior semicircular canals was 0.89 +/- 0.13 and for posterior semicircular canals it was 0.9 +/- 0.12. The pooled effect size in the control group was 1 and heterogeneity was high. It was also observed that implementing the test is different from that in adults and requires considerable practice with children factoring in the issue of peripheral and central vestibular maturation. Special considerations were suggested in terms of pupillary calibration, goggle fitting and slippage and play techniques. Conclusions: The vHIT as a diagnostic test is eminently doable in children with important caveats, practice and knowledge regarding a developing vestibular system. It yields significantly meaningful inferences about high frequency semicircular canal function in children. Adult norms should not be extrapolated in children as VOR gain is different in children.