Michelle Christina Johansen, MD
Visual Vertical (VV) testing may be a concept unfamiliar to many neurologists but does this simple assessment hold promise for directing physical therapy regimens after stroke?
Falls are associated with increased morbidity in the elderly and especially are of great concern in a post stroke patient placed on anticoagulation. Prior review of the literature on verticality perception after stroke by Piscicelli, first author on this publication, demonstrates that patients with a hemispheric stroke align their posture tilted to the side opposite the lesion and those with brainstem strokes demonstrate ipsilateral lateropulsion. How should this guide rehabilitation? In order to develop effective therapies, a quantitative technique that characterizes the deficit is first needed.
In order to establish the veracity of the VV, Piscicelli et al. evaluated the inter and intra-rater reliability in 20 subacute stroke patients in neuro-rehabilitation who had suffered a first and unique hemispheric stroke. The patient population enrolled was mainly male (12), middle aged (64±15years) with an ischemic (13) right sided lesion (12). Brainstem and cerebellar strokes were excluded due to the thought that VV orientation in these patients is different. Notable exclusions also include those with aphasia or dementia.
In testing VV perception, the patients were asked while sitting upright in a dark room to verbally adjust a bright line to the vertical (light bar test) without a time limit or feedback from the examiner. Mean VV orientation and uncertainty was calculated over 10 trials with a 5 minute break between trials. VV was assessed three times: once by a novice to the technique, once by an expert and then again the next day at the same time by the same expert. Reliability was assessed using the intraclass correlation coefficient (ICC), Bland-Altman plots (also called difference plots) and minimal detectable change (MDC).
The investigators found that inter- and intra-rater reliability for VV orientation (direction perceived as vertical) was excellent with ICC way above 0.75 (0.979, 0.982). The Bland-Altman plots and the MDC revealed a difference <2 degrees between the two tests meaning that a change ≥2 degrees can be interpreted with 95% confidence as a real change. There was excellent concordance between the two examiners for diagnosis of abnormal VV orientation.
In contrast, the intra-rater reliability was satisfactory and inter-rater reliability poor when testing for VV uncertainty (robustness of the internal model of verticality).
The conclusion of the authors is that VV orientation is highly reliable and should be used as a tool at the bedside as well as for research. They acknowledge some of the more concerning limitations of the study to include the patient population (subacute hemispheric strokes who are not aphasic) but state that a code could be established for aphasic patients. The study also contains a small sample size (20) and occurred at a single European neuro-rehabilitation center limiting generalizability. In consideration of the results, does the duration of rehabilitation the patient had received prior to testing influence the results? Those with brainstem and cerebellar strokes were excluded but clinically, this patient population suffers the most devastating symptoms concerning vertical perception and thus VV orientation could be most useful in this cohort.
Visual Vertical testing certainly warrants additional investigation and could represent an inexpensive, easily performed method by which to quantify verticality disorders post stroke.