Visual verticality perception after stroke: A systematic review of methodological approaches and suggestions for standardization.

OBJECTIVE

Visual vertical (VV) measurements are being increasingly used for routine clinical assessment of spatial cognition, to investigate otolithic vestibular function and identify altered verticality perception as a possible cause of postural disorders after stroke. The objective of this paper was to synthesize knowledge of assessment methods for testing VV after stroke.

METHODS

This systematic review, following the PRISMA statement, involved a search for articles in MEDLINE via PubMED published up to November 2015 by using the search terms "visual vertical," "verticality perception" and "stroke". We included only case or group studies on VV perception after hemispheric, brainstem or cerebellar strokes. Two authors independently assessed data on patients' and VV assessment characteristics, outcome measures, ranges of normality and psychometric properties.

RESULTS

We assessed reports for 61 studies (1982 patients) of VV for hemispheric (n=43), brainstem (n=18) or cerebellar (n=8) stroke. VV assessment procedures varied widely in paradigm, type of stimulus, patient posture, number of trials and outcome measures. However, on the basis of recent studies it is recommended assessing VV in absolute darkness, with an even number of trials, from 6 to 10, with the body maintained upright. Under these conditions, normal VV orientation (mean of VV estimates) can be considered from -2.5° to 2.5° and is highly reliable for use in clinical practice and research. A difference ≥ 2° between repeated measures for a given patient can be interpreted as a real change in VV perception. Myriad of protocols have been proposed, for which psychometric properties must be better analyzed.

CONCLUSIONS

This first review of VV assessment methods after stroke shows a great heterogeneity of procedures, settings and parameters, among which only some are eligible for standardization to limit measurement errors and better interpret the results.