Limitations
vestibular migraine, peripheral hypofunction, nystagmus, dizziness, central disorders, HMD, visual vertigo, disability
VIRUS, RECRUITMENT, NYSTAGMUS, DISORDERS, REGRESSION
The study was designed as a small pilot RCT and then became even smaller due to the challenges posed to in-person research in an outpatient setting by the covid-19 pandemic. The high dropout rate (both due to the study closure in March and later associated with challenges in transportation and quarantines), while similar between groups, may have influenced the outcome. While both groups showed significant improvements, it is possible that we were under-powered to detect differences between groups. It is possible for example, that the C.S.I intervention could lead to greater gains in visual vertigo (87.5% of the C.S.I group reported improvement vs. 50% of the traditional) and the traditional intervention in overall disability due to dizziness (62.5% reported some improvement in the C.S.I group vs. 90% of the traditional) but this needs to be investigated in future, larger studies. Functionally, however, the groups showed no trend for differences between them. This was also seen in our companion analysis of head sway data pre and post intervention where the vestibular participants were significantly higher than controls on all outcomes pre rehabilitation. Post rehabilitation they were only significantly higher on sway in mid-frequencies (0.25 to 0.5 Hz) with no indication of any difference between the intervention groups [We did not officially track adherence to the home program and no long-term follow up was conducted. In order to continue the study under covid restrictions including limited personnel, quarantines, difficulty of patients to travel etc., we had to conduct several protocol changes that may influence the internal and external validity of the study. We originally planned to recruit only patients with chronic unilateral peripheral hypofunction. To maximize recruitment post covid we included patients with central disorders as well (2 post-concussion, 2 vestibular migraine) as well as 2 patients (1 in each group) who were considered subacute. While this shows that the C.S.I. intervention is feasible in patients with central disorders, the sample is too small for generalizability. The program was originally planned for 10 weeks: baseline, 8 sessions, post sessions. Due to quarantines and difficulty with travel, some patients took longer to complete, and we often opted to run the assessment on the last day of rehabilitation to mitigate the risk that a patient may not come back due to exposure to the virus. We had originally planned on having a blinded assessor to complete the FGA pre and post but following covid this was no longer feasible, and the treating therapist had to conduct the FGA which may create bias. Note that these modifications influenced both groups in a similar way. While theoretically, all outcomes could be influenced by an assessor, the FGA requires greater clinical judgment than stopwatch-based measures or self-reported outcomes that patients complete on their own. The lack of a blinded outcomes assessor may have influenced the result. There was one variable that significantly differed between groups at baseline: more patients in the C.S.I. group presented with gaze evoked nystagmus which is typically indicative of a more acute lesion. However, these patients were on average equally chronic as the traditional group and so the likelihood of this one different finding influencing the study outcome is low. Lastly, HMD technology continues to develop rapidly, and untethered, high-end headsets are already commercially available at low cost. While this technology carries huge potential for patient-specific sensory integration training in the clinic and possibly at the home, it is important to consider that the hardware was not originally developed for vestibular patients and so development of vestibular-specific applications and rigorous research regarding safety, benefits, progression and regression rules etc. is required to support this potential clinical translation and make sure that only the most effective and safe interventions are disseminated on a large scale.