Clinical and Physiologic Predictors and Postoperative Outcomes of Near Dehiscence Syndrome.

OBJECTIVE: To identify predictors of near dehiscence (ND) or thin rather than dehiscent bone overlying the superior semicircular canal in patients with signs and symptoms suggestive of superior semicircular canal dehiscence syndrome (SCDS), as well as postoperative outcomes. STUDY DESIGN: Retrospective case-control study. SETTING: Tertiary referral center. PATIENTS: All 288 patients who underwent middle cranial fossa approach for repair of SCDS (1998-2018) were reviewed for cases of ND. Demographics, symptoms, and clinical signs including nystagmus, ocular vestibular-evoked myogenic potential (oVEMP) amplitude, cervical vestibular-evoked myogenic potential (cVEMP) thresholds, and low-frequency air-bone gap were compared before and after surgery. MAIN OUTCOME MEASURE: Presence of preoperative ND and postoperative symptoms and physiologic measures. RESULTS: Seventeen cases of ND (16 patients, 17 ears) and 34 cases (34 ears) of frank SCDS were identified. ND cases differed from frank dehiscence cases in that they were less likely to have nystagmus in response to ear canal pressure or loud sounds, OR = 0.05 (95% CI 0.01-0.25) and Valsalva, OR = 0.08 (0.01-0.67), smaller peak-to-peak oVEMP amplitudes, OR = 0.84 (0.75-0.95), and higher cVEMP thresholds, OR = 1.21 (1.07-1.37). Patients with ND had similar symptoms to those with frank SCDS before surgery, and after surgery had outcomes similar to patients with frank SCDS. CONCLUSIONS: In patients with symptoms consistent with SCDS, predictors of ND include absence of nystagmus in response to pressure/loud sounds, greater cVEMP thresholds, and smaller oVEMP amplitudes. We propose ND is on a spectrum of dehiscence that partially accounts for the diversity of clinical presentations of patients with SCDS.

Forward and backward locomotion in individuals with dizziness.

The vestibular system plays an important role in locomotion. Individuals with vestibular pathology present with gait abnormalities, which may increase their fall frequency. Backward walking (BW) has been suggested as a predictor of falls in other patient populations; however it has not been studied in individuals with dizziness. Our aims were: (1) to investigate the differences in forward walking (FW) and BW both between and within 3 groups: Healthy controls, individuals with dizziness and vestibular pathology, and individuals with dizziness without vestibular pathology, (2) describe differences in FW and BW between individuals that have fallen and those that have not. We studied 28 healthy controls (mean 53.8 ± 17 years), 21 individuals with pathophysiology of the vestibular system (mean 68.5 ± 13 years), and 18 individuals without a vestibular cause for their dizziness (mean 67.4 ± 17 years). Subjects performed 2 FW and 2 BW trials over the GAITRite walkway. Data on history of falls in the preceding year were collected. We found BW was different to FW within each group. When comparing between groups and correcting for age and gender, only BW velocity (beta=-11.390, p=0.019), cadence (beta=-8.471, p=0.021), step time (beta=0.067, p=0.007) and stride time (beta=0.137, p=0.005) were significantly affected by having dizziness, with no differences in FW characteristics. There were no differences between FW and BW between fallers and non-fallers. BW appears to be a better biomarker than FW for identifying individuals with symptoms of dizziness; though it does not appear to characterize those who fall.

Head impulse test abnormalities and influence on gait speed and falls in older individuals.

OBJECTIVE: To assess the prevalence of vestibular dysfunction in older adults using the head impulse test (HIT) and to assess the independent influence of HIT abnormalities on gait speed and fall risk in older individuals. STUDY DESIGN: Cross-sectional study. SETTING: Tertiary care academic medical center. PATIENTS: Fifty community-dwelling individuals age 70 and older. INTERVENTIONS: HIT (abnormal HIT defined as right or left HIT abnormality), visual acuity, monofilament testing, and grip strength. MAIN OUTCOME MEASURES: Gait speed on a 4-meter walk and a history of falls (including number of falls) in the last 1 and 5 years. RESULTS: The participants' mean age was 77 years (range, 70-95 yr); 52% were female subjects. Fifty percent of participants had an abnormal HIT. An abnormal HIT was significantly associated with a 0.23 m/s reduction in gait speed (p = 0.042), 0.44 more falls in the last 1 year (p = 0.047), and a 5-fold increase in the odds of falling in the last 5 years (p = 0.024) in multivariate analyses adjusted for age, sex, and other balance and fall risk factors. CONCLUSION: We observed that half of the community-dwelling older individuals in our study had evidence of vestibular dysfunction, which was significantly associated with gait speed and fall risk in adjusted analyses. Screening for vestibular impairment using the simple HIT and directing targeted vestibular therapy may be important to reduce gait impairment and fall risk in older individuals.

Association between hearing loss and saccular dysfunction in older individuals.

OBJECTIVE: 1) Describe the association between hearing loss and dysfunction of each of the 5 vestibular end-organs--the horizontal, superior, and posterior semicircular canals; saccule; and utricle--in older individuals. 2) Evaluate whether hearing loss and vestibular end-organ deficits share any risk factors. STUDY DESIGN: Cross-sectional study. SETTING: Academic medical center. PATIENTS: Fifty-one individuals age 70 years or older. INTERVENTIONS: Audiometry, head-thrust dynamic visual acuity (htDVA), sound-evoked cervical vestibular-evoked myogenic potential (cVEMP), and tap-evoked ocular VEMP (oVEMP). MAIN OUTCOME MEASURES: Audiometric pure-tone averages (PTA), htDVA LogMAR scores as a measure of semicircular canal function in each canal plane, and cVEMP and oVEMP amplitudes as a measure of saccular and utricular function, respectively. RESULTS: We observed a significant correlation between hearing loss at high frequencies and reduced cVEMP amplitudes (or reduced saccular function; r = -0.37, p < 0.0001) in subjects age 70 years or older. In contrast, hearing loss was not associated with oVEMP amplitudes (or utricular function), or htDVA LogMAR scores (or semicircular canal function) in any of the canal planes. Age and noise exposure were significantly associated with measures of both cochlear and saccular dysfunction. CONCLUSION: The concomitant decline in the cochlear and saccular function associated with aging may reflect their common embryologic origin in the pars inferior of the labyrinth. Noise exposure seems to be related to both saccular and cochlear dysfunction. These findings suggest a potential benefit of screening individuals with presbycusis-particularly those with significant noise exposure history-for saccular dysfunction, which may contribute to fall risk in the elderly.

Decline in semicircular canal and otolith function with age.

OBJECTIVE: To characterize the physiologic nature of the vestibular dysfunction that occurs with the normative aging process. STUDY DESIGN: Cross-sectional study. SETTING: Tertiary care academic medical center. PATIENTS: Fifty individuals age 70 years and above. INTERVENTIONS: Head thrust dynamic visual acuity testing and cervical and ocular vestibular-evoked myogenic potential (VEMP) testing. MAIN OUTCOME MEASURES: Semicircular canal function measured by head thrust dynamic visual acuity testing in each of the 3 semicircular canal planes, and saccular and utricular function measured by cervical VEMP and ocular VEMP testing, respectively. RESULTS: We observed significant declines in semicircular canal function in each of the canal planes as well as otolith function associated with aging. We found that individuals with impaired horizontal and superior semicircular canal function also were likely to have concomitant deficits in utricular but not saccular function. Overall, we noted that the prevalence of semicircular canal dysfunction was highest followed by saccular then utricular impairment, although we did observe individuals with isolated otolith deficits. CONCLUSION: These data suggest an overall decline in semicircular canal as well as otolith function associated with aging, although the magnitude of impairment was greater for the semicircular canals than the otoliths in this elderly population. A better understanding of the specific vestibular deficits that occur with aging can inform the development of rational screening, vestibular rehabilitation, and fall risk reduction strategies in older individuals.