Determining the prevalence of vestibular screening failures in pediatric cancer patients whose therapies include radiation to the head/neck and platin-based therapies: A pilot study.

BACKGROUND: Sensorineural hearing loss due to ototoxic cancer therapy is well established; effects on the vestibular system are unknown. We examined the feasibility of implementing vestibular screens for pediatric cancer survivors exposed to ototoxic agents. The prevalence of screening failures is reported. METHODS: Cancer survivors who were 6-17 years, at least 1-month posttreatment, and received ototoxic therapy (radiation to the head/neck, cisplatin, carboplatin) were eligible. Screening measures included (1) Pediatric Vestibular Symptom Questionnaire, (2) Modified Clinical Test of Sensory Interaction on Balance, and (3) Dynamic Visual Acuity. RESULTS: Vestibular screening failures were observed in 30 participants (60%). Patients with a brain tumor diagnosis were at increased risk for failures compared to nonbrain tumor patients (74.2% vs. 36.8%, P = 0.009). Patients who underwent brain surgery were at increased risk for failures compared to patients without brain surgery (71% vs. 42%, P = 0.043). Patients with a longer duration between end of treatment and vestibular screening had a reduced risk of failures, with an almost 20% decrease for each year between the time points (odds ratio = 0.812; 95% confidence interval: 0.683-0.964, P = 0.018). Receiving carboplatin correlated with a decreased risk of failure (P = 0.016), due to a negative correlation with other clinical risk factors (diagnosis of a brain tumor, major brain surgery) that are associated with vestibular screening failure. CONCLUSION: Vestibular screening failures are highly prevalent in childhood cancer survivors who received ototoxic therapy. Broad screening of this population and further characterization of these patients are warranted.

Detection of VOR dysfunction during the gaze stabilization test: Does target size matter?

BACKGROUND: The Gaze Stabilization Test (GST) identifies vestibulo-ocular reflex (VOR) dysfunction using a decline in target recognition with increasing head velocity, but there is no consensus on target (optotype) size above static visual acuity. OBJECTIVE: To determine the optimal optotype size above static visual acuity to be used during the GST in subjects with unilateral vestibular dysfunction and healthy individuals. METHODS: Eight subjects with unilateral vestibular dysfunction (UVD) and 19 age-matched, healthy control subjects were studied with the standard GST protocol using two optotype sizes, 0.2 and 0.3 logMAR above static visual acuity (ΔlogMAR). Maximal head velocity achieved while maintaining fixation on both optotypes was measured. Sensitivity, specificity and receiver-operator characteristic area under the curve (ROC AUC) analyses were performed to determine the optimal head velocity cut off point for each optotype, based on ability to identify the lesioned side of the UVD group from the control group. RESULTS: There was a significant difference in maximal head velocity between the UVD group and control group using 0.2 ΔlogMAR (p = 0.032) but not 0.3 ΔlogMAR (p = 0.061). While both targets produced similar specificities (90%) for distinguishing normal from subjects with UVD, 0.2 ΔlogMAR targets yielded higher sensitivity (75%) than 0.3 logMAR (63%) and accuracy (86% vs 80%, respectively) in detecting the lesioned side in subjects with UVD versus controls with maximal head velocities≤105 deg/s (p = 0.017). Furthermore, positive likelihood ratios were nearly twice as high when using 0.2 ΔlogMAR targets (+ LR 10) compared to 0.3 ΔlogMAR (+ LR 6.3). CONCLUSION: The 0.2 ΔlogMAR optotype demonstrated significantly superior identification of subjects with UVD, better sensitivity and positive likelihood ratios than 0.3 ΔlogMAR for detection of VOR dysfunction. Using a target size 0.2logMAR above static visual acuity (ΔlogMAR) during GST may yield better detection of VOR dysfunction to serve as a baseline for gaze stabilization rehabilitation therapy.

Comparison of the gaze stabilization test and the dynamic visual acuity test in unilateral vestibular loss patients and controls.

OBJECTIVE: Compare the dynamic visual acuity test (DVAT) and gaze stabilization test (GST) in patients with unilateral vestibular loss (UVL) and healthy control subjects using a novel computerized testing system prototype. STUDY DESIGN: Cross-sectional study. SETTING: Tertiary academic referral laboratory. PATIENTS: Seventeen UVL patients (median age 62 yr) with bithermal caloric asymmetry (≥49%) or ablative surgery and 17 control subjects (median age 57 yr). INTERVENTION(S): Diagnostic. MAIN OUTCOME MEASURE(S): Comparison of DVAT and GST results during self-generated sinusoidal head movements using transient unpredictable target presentations less than 95 milliseconds in duration. RESULTS: UVL patients had significantly higher DVAT scores toward the lesioned side compared with controls (p = 0.001) and the non-lesioned side (p = 0.003), but the non-lesioned side was not significantly different from controls (p = 0.157). When comparing GST scores, UVL patients required a slower head velocity to maintain visual acuity with movement toward the lesioned side compared with controls (p < 0.001) and the non-lesioned side (p = 0.004). In addition, UVL patients had significantly lower scores toward the non-lesioned side (p = 0.002) compared to controls. ROC curve analysis identified optimal thresholds for abnormal test results to discriminate the lesioned side from controls. A DVAT score greater than or equal to 0.3 ΔlogMAR provided 65% sensitivity and 88% specificity while a GST score less than or equal to 95 degrees/s provided 71% sensitivity and 100% specificity. When GST results were normal, adding DVAT increased overall sensitivity to 88% with 88% specificity. CONCLUSIONS: Both GST and DVAT demonstrated reduced gaze stabilization toward the lesioned side in the patient group compared with normal controls. Performing GST first and utilizing DVAT when GST was normal provides optimal identification of patients with vestibular dysfunction.

Utility of an Abbreviated Dizziness Questionnaire to Differentiate Between Causes of Vertigo and Guide Appropriate Referral: A Multicenter Prospective Blinded Study.

OBJECTIVE: Test performance of a focused dizziness questionnaire's ability to discriminate between peripheral and nonperipheral causes of vertigo. STUDY DESIGN: Prospective multicenter. SETTING: Four academic centers with experienced balance specialists. PATIENTS: New dizzy patients. INTERVENTIONS: A 32-question survey was given to participants. Balance specialists were blinded and a diagnosis was established for all participating patients within 6 months. MAIN OUTCOMES: Multinomial logistic regression was used to evaluate questionnaire performance in predicting final diagnosis and differentiating between peripheral and nonperipheral vertigo. Univariate and multivariable stepwise logistic regression were used to identify questions as significant predictors of the ultimate diagnosis. C-index was used to evaluate performance and discriminative power of the multivariable models. RESULTS: In total, 437 patients participated in the study. Eight participants without confirmed diagnoses were excluded and 429 were included in the analysis. Multinomial regression revealed that the model had good overall predictive accuracy of 78.5% for the final diagnosis and 75.5% for differentiating between peripheral and nonperipheral vertigo. Univariate logistic regression identified significant predictors of three main categories of vertigo: peripheral, central, and other. Predictors were entered into forward stepwise multivariable logistic regression. The discriminative power of the final models for peripheral, central, and other causes was considered good as measured by c-indices of 0.75, 0.7, and 0.78, respectively. CONCLUSION: This multicenter study demonstrates a focused dizziness questionnaire can accurately predict diagnosis for patients with chronic/relapsing dizziness referred to outpatient clinics. Additionally, this survey has significant capability to differentiate peripheral from nonperipheral causes of vertigo and may, in the future, serve as a screening tool for specialty referral. Clinical utility of this questionnaire to guide specialty referral is discussed.

Vestibular tests for rehabilitation: applications and interpretation.

Vestibular function testing plays a critical role in understanding balance disorders. These tests augment a well-performed history and physical exam in providing quantitative information regarding vestibular reflexes, central oculomotor function and postural control strategies. Video-oculography (VOG) and caloric stimulation play a major role in evaluation of both peripheral vestibular and central oculomotor disorders. Rotational chair testing and, more recently the Dynamic Visual Acuity Test (DVAT) and Gaze Stabilization Test (GST) provide information regarding higher frequency vestibulo-ocular reflex (VOR) function. Computerized Dynamic Posturography (CDP) explores the interaction of the vestibular, visual and proprioceptive systems for posture control. Finally, the cervical Vestibular Evoked Myogenic Potential (cVEMP) test and the Dynamic Subjective Visual Vertical (DSVV) test provide information regarding saccular and utricular function, respectively. New techniques and applications continue to provide knowledge both of disease processes and potential medical, surgical and rehabilitative interventions.

Caloric test versus rotational sinusoidal harmonic acceleration and step-velocity tests in patients with and without suspected peripheral vestibulopathy.

OBJECTIVE: To identify the predictive capabilities of caloric and rotational testing to distinguish peripheral from nonperipheral vestibular causes of vertigo. STUDY DESIGN: Retrospective case review. SETTING: Academic tertiary care vestibular function test center. PATIENTS: Two hundred dizzy patients (132 with and 68 without suspected peripheral vestibular dizziness) evaluated with bithermal binaural caloric and sinusoidal and step-velocity rotary chair (RC) tests. INTERVENTION: Caloric and RC tests. MAIN OUTCOME MEASURES: 1) Receiver operating characteristic (ROC) analysis of individual caloric and rotary parameters for area under the curve (AUC) as indication of predictive value, and 2) logistic regression analysis of parameter combinations for identification of optimal test battery for predicting peripheral vestibular dysfunction RESULTS: Analysis of the individual receiver operating characteristic (ROC) curves for each caloric and RC test parameter for prediction of peripheral vestibulopathy revealed that the best overall predictive parameter was percentage of caloric weakness (CW; AUC-ROC, 0.73; 95% confidence interval, 0.66-0.80). Using 29.5% as the optimal cutoff point for CW, a specificity of 84% and sensitivity of 55% were obtained. Because of the reduced AUC for the RC parameters, no optimal cutoff points were chosen. Using a logistic regression model in predicting patients with peripheral vestibulopathy demonstrated that either comprehensive caloric and RC testing or the combination of caloric and 0.025 Hz, 0.5 Hz, and time-constant rotational testing yielded the highest predictive value (AUC-ROC, 0.79) CONCLUSION: Calculation of CW was the most promising single marker for identifying peripheral from nonperipheral vestibulopathic patients. Individual RC parameters showed limited predictive value to differentiate peripheral from nonperipheral vestibular dysfunction. However, the combination of subtests yielded an AUC-ROC only slightly less than caloric testing. The combination of caloric and RC testing revealed the strongest predictive capabilities for identifying peripheral vestibular injury. Furthermore, the combination of an abbreviated form of RC testing with caloric testing yielded nearly identical results as full caloric and rotational testing.

Effectiveness of head-mounted vibrotactile stimulation in subjects with bilateral vestibular loss: a phase 1 clinical trial.

OBJECTIVE: Evaluate the effectiveness of a head-mounted vibrotactile prosthesis for balance improvement in subjects with severe bilateral vestibular loss (BVL). STUDY DESIGN: Crossover study. SETTING: Academic tertiary care vestibular function test center. PATIENTS: Five subjects with severe BVL as defined by video-oculography, rotational chair, and computerized dynamic posturography criteria. INTERVENTION: Vibrotactile head tilt feedback MAIN OUTCOME MEASURES: Change in Sensory Organization Test (SOT) Conditions 5 and 6 performance (fall-no fall, time to fall, strategy analysis) and dynamic subjective visual vertical (DSVV) response. RESULTS: 1) Significant improvement in binary fall-no fall ratio on SOT 5 and SOT 6 combined (chi2 = 9.603, df = 1, p = 0.001); 2) Significant increase in time to fall measurements on SOT 5 (p < 0.001) and SOT 6 (p < 0.01; 1-tailed t test); 3) Nonsignificant improvement in strategy scores on SOT 5 (p = 0.156) and SOT 6 (p = 0.259; 1-tailed t test); and 4) No significant effect during eccentric DSVV testing (analysis of variance). CONCLUSION: Head-mounted vibrotactile stimulation produced significant improvement in postural stability in subjects with BVL undergoing SOT 5 and 6 testing with no effect on subjective visual vertical during DSVV testing.