Kristal M. Riska

Vestibular consequences of mild traumatic brain injury and blast exposure: a review

ABSTRACT The purpose of this article is to review relevant literature on the effect of mild traumatic brain injury (mTBI) and blast injury on the vestibular system. Dizziness and imbalance are common sequelae associated with mTBI, and in some individuals, these symptoms may last for six months or longer. In war-related injuries, mTBI is often associated with blast exposure. The causes of dizziness or imbalance following mTBI and blast injuries have been linked to white matter abnormalities, diffuse axonal injury in the brain, and central and peripheral vestibular system damage. There is some evidence that the otolith organs may be more vulnerable to damage from blast exposure or mTBI than the horizontal semicircular canals. In addition, benign paroxysmal positional vertigo (BPPV) is a common vestibular disorder following head injury that is treated effectively with canalith repositioning therapy. Treatment for (non-BPPV) mTBI-related vestibular dysfunction has focused on the use of vestibular rehabilitation (VR) augmented with additional rehabilitation methods and medication. New treatment approaches may be necessary for effective otolith organ pathway recovery in addition to traditional VR for horizontal semicircular canal (vestibulo-ocular reflex) recovery.

Reliability and Normative Data for the Dynamic Visual Acuity Test for Vestibular Screening

Hypothesis: The purpose of this study was to determine reliability of computerized dynamic visual acuity (DVA) testing and to determine reference values for younger and older adults. Background: A primary function of the vestibular system is to maintain gaze stability during head motion. The DVA test quantifies gaze stabilization with the head moving versus stationary. Commercially available computerized systems allow clinicians to incorporate DVA into their assessment; however, information regarding reliability and normative values of these systems is sparse. Methods: Forty-six healthy adults, grouped by age, with normal vestibular function were recruited. Each participant completed computerized DVA testing including static visual acuity, minimum perception time, and DVA using the NeuroCom inVision System. Testing was performed by two examiners in the same session and then repeated at a follow-up session 3 to 14 days later. Intraclass correlation coefficients (ICCs) were used to determine inter-rater and test–retest reliability. Results: ICCs for inter-rater reliability ranged from 0.323 to 0.937 and from 0.434 to 0.909 for horizontal and vertical head movements, respectively. ICCs for test–retest reliability ranged from 0.154 to 0.856 and from 0.377 to 0.9062 for horizontal and vertical head movements, respectively. Overall, raw scores (left/right DVA and up/down DVA) were more reliable than DVA loss scores. Conclusion: Reliability of a commercially available DVA system has poor-to-fair reliability for DVA loss scores. The use of a convergence paradigm and not incorporating the forced choice paradigm may contribute to poor reliability.

A Benign Paroxysmal Positional Vertigo Triage Clinic

Purpose The purpose of this study was to evaluate the effectiveness of triaging patients with motion-provoked dizziness into a benign paroxysmal positional vertigo (BPPV) clinic. Method A retrospective chart review was performed of veterans who were tested and treated for BPPV in a triaged BPPV clinic and veterans who were tested and treated for BPPV in a traditional vestibular clinic. Results The BPPV triage clinic had a hit rate of 39%. On average, the triaged BPPV clinic reduced patient wait times by 23 days relative to the wait times for the traditional vestibular clinic while also reducing patient costs. Conclusion Triaging patients with BPPV is one method to improve access to evaluation and treatment and a mechanism for the effective use of clinic time and resources.

Characteristics and Treatment Outcomes of Benign Paroxysmal Positional Vertigo in a Cohort of Veterans

Background The Mountain Home Veterans Affairs (VA) Medical Center has been diagnosing and treating veterans with benign paroxysmal positional vertigo (BPPV) for almost 2 decades. The clinic protocol includes a 2-week follow-up visit to determine the treatment outcome of the canalith repositioning treatment (CRT). To date, the characteristics of BPPV and treatment efficacy have not been reported in a cohort of veterans with BPPV. Purpose To determine the prevalence and characteristics of veterans diagnosed with BPPV in a Veterans Affairs Medical Center Audiology Clinic and to examine treatment outcomes. Research Design Retrospective chart review. Study Sample A total of 102 veterans who tested positive for BPPV in the Vestibular Clinic at the Mountain Home VA Medical Center from March 2010 to August 2011. Results In 102 veterans who were diagnosed with BPPV, the posterior semicircular canal was most often involved (75%), motion-provoked vertigo was the most common symptom (84%), and the majority (43%) were diagnosed with BPPV in their sixth decade. The prevalence of BPPV in the Audiology Vestibular Clinic was 15.6%. Forty-one percent of veterans reported a symptom onset within 12 months of treatment for BPPV; however, 36% reported their symptoms began > 36 months prior to treatment. CRT was effective (negative Dix-Hallpike/roll test) in most veterans (86%) following 1 treatment appointment (M = 1.6), but more than half reported incomplete symptom resolution (residual dizziness) at the follow-up appointment. Eighteen percent of veterans experienced a recurrence (M = 1.8 years; SD = 1.7 years). Conclusions The characteristics and treatment outcomes of BPPV in our veteran cohort was similar to what has been reported in the general population. Future work should focus on improving the timeliness of evaluation and treatment of BPPV and examining the time course and management of residual dizziness.

Video Head Impulse Testing (vHIT) and the Assessment of Horizontal Semicircular Canal Function.

BACKGROUND Vestibular function (specifically, horizontal semicircular canal function) can be assessed across a broad frequency range using several different techniques. The head impulse test is a qualitative test of horizontal semicircular canal function that can be completed at bedside. Recently, a new instrument (video head impulse test [vHIT]) has been developed to provide an objective assessment to the clinical test. Questions persist regarding how this test may be used in the overall vestibular test battery. PURPOSE The purpose of this case report is to describe vestibular test results (vHIT, rotational testing, vestibular evoked myogenic potentials, and balance and gait performance) in an individual with a 100% unilateral caloric weakness who was asymptomatic for dizziness, vertigo or imbalance. DATA COLLECTION AND/OR ANALYSIS Comprehensive assessment was completed to evaluate vestibular function. Caloric irrigations, rotary chair testing, vHIT, and vestibular evoked myogenic potentials were completed. RESULTS A 100% left-sided unilateral caloric weakness was observed in an asymptomatic individual. vHIT produced normal gain with covert saccades. CONCLUSIONS This case demonstrates the clinical usefulness of vHIT as a diagnostic tool and indicator of vestibular compensation and functional status.

The Video Head Impulse Test

Video head impulse testing, an instrumented expansion of the bedside head impulse test using video eye tracking and quantification of eye and head movement, is a relatively new objective measure of dynamic semicircular canal function. This article provides an overview of both the bedside and video head impulse tests. The anatomical and physiological bases of the test are briefly reviewed, along with test administration and response characteristics in healthy individuals and patients with vestibular loss. Literature examining the use of the video head impulse test in several common vestibular disorders, in children, and in patients with acute vestibular syndrome is summarized.