Kristen L. Janky

Ocular versus cervical VEMPs in the diagnosis of superior semicircular canal dehiscence syndrome

Objectives To determine whether cervical vestibular evoked myogenic potential (cVEMP) thresholds or ocular VEMP (oVEMP) amplitudes are more sensitive and specific in the diagnosis of superior semicircular canal dehiscence syndrome (SCDS). Study Design Prospective case-control study. Setting Tertiary referral center. Subjects and Methods Twenty-nine patients with SCDS (mean age 48 yr; range, 31–66 yr) and 25 age-matched controls (mean age 48 yr; range, 30–66 yr). Intervention(s) cVEMP and oVEMP in response to air-conducted sound. All patients underwent surgery for repair of SCDS. Main Outcome Measure(s) cVEMP thresholds; oVEMP n10 and peak-to-peak amplitudes. Results cVEMP threshold results showed sensitivity and specificity ranging from 80% to 100% for the diagnosis of SCDS. In contrast, oVEMP amplitudes demonstrated sensitivity and specificity greater than 90%. Conclusion oVEMP amplitudes are superior to cVEMP thresholds in the diagnosis of SCDS.

Air-conducted oVEMPs provide the best separation between intact and superior canal dehiscent labyrinths.

Objective First, to define the best single-step suprathreshold screening test for superior canal dehiscence syndrome (SCDS); second, to obtain further insight into the relative sensitivity of vestibular afferents to sound vibration in the presence of a superior canal dehiscence. Study Design Prospective study. Setting Tertiary referral center. Patients Eleven patients with surgically confirmed SCDS (mean, 50 yr; range, 32–66 yr) and 11 age-matched, healthy subjects (right ear only) with no hearing or vestibular deficits (mean, 50 yr; range, 33–66 yr). Intervention All subjects completed ocular and cervical vestibular evoked myogenic potential (o- and cVEMP) testing in response to air conduction (click and 500 Hz tone burst) and midline bone conduction (reflex hammer and Mini-shaker) stimulation. Main Outcome Measures OVEMP n10 amplitude and cVEMP corrected peak-to-peak amplitude. Results OVEMP n10 amplitudes were significantly higher in SCDS when compared with healthy controls in response to all stimuli with the exception of reflex hammer. Likewise, cVEMP-corrected peak-to-peak amplitudes were significantly higher in SCDS when compared with healthy controls for air conduction stimulation (click and 500 Hz toneburst). However, there were no significant differences between groups for midline taps (reflex hammer or mini-shaker). Receiver operating characteristic curves demonstrated that oVEMPs in response to air conduction stimulation provided the best separation between SCDS and healthy controls. Conclusion OVEMPs in response to air conduction stimulation (click and 500 Hz toneburst) provide the best separation between SCDS and healthy controls and are therefore the best single-step screening test for SCDS.

Can Vestibular-Evoked Myogenic Potentials Help Differentiate Ménière Disease from Vestibular Migraine?

Objectives. To characterize both cervical and ocular vestibular-evoked myogenic potential (cVEMP, oVEMP) responses to air-conducted sound (ACS) and midline taps in Ménière disease (MD), vestibular migraine (VM), and controls, as well as to determine if cVEMP or oVEMP responses can differentiate MD from VM. Study Design. Prospective cohort study. Setting. Tertiary referral center. Subjects and Methods. Unilateral definite MD patients (n = 20), VM patients (n = 21) by modified Neuhauser criteria, and age-matched controls (n = 28). cVEMP testing used ACS (clicks), and oVEMP testing used ACS (clicks and 500-Hz tone bursts) and midline tap stimuli (reflex hammer and Mini-Shaker). Outcome parameters were cVEMP peak-to-peak amplitudes and oVEMP n10 amplitudes. Results. Relative to controls, MD and VM groups both showed reduced click-evoked cVEMP (P < .001) and oVEMP (P < .001) amplitudes. Only the MD group showed reduction in tone-evoked amplitudes for oVEMP. Tone-evoked oVEMPs differentiated MD from controls (P = .001) and from VM (P = .007). The oVEMPs in response to the reflex hammer and Mini-Shaker midline taps showed no differences between groups (P > .210). Conclusions. Using these techniques, VM and MD behaved similarly on most of the VEMP test battery. A link in their pathophysiology may be responsible for these responses. The data suggest a difference in 500-Hz tone burst–evoked oVEMP responses between MD and MV as a group. However, no VEMP test that was investigated segregated individuals with MD from those with VM.

Superior Canal Dehiscence Size: Multivariate Assessment of Clinical Impact

Objective To examine the association between dehiscence length in patients with superior semicircular canal dehiscence syndrome and their clinical findings, including objective audiometric and vestibular testing results. Study Design Retrospective study. Setting Tertiary referral center. Patients Patients included in this study were diagnosed with superior semicircular canal dehiscence syndrome and underwent surgical repair of the dehiscence through middle fossa craniotomy. The dehiscence length was measured intraoperatively in all cases. Main Outcome Measures Correlation between dehiscence length with pure-tone average (PTA), average bone-conduction threshold, maximal air-bone gap, cervical vestibular evoked myogenic potential thresholds, and presenting signs and symptoms. Results The correlation between dehiscence length and maximal air-bone gap was statistically significant on both univariate and multivariate regression analyses. The correlations between dehiscence length and PTA, average bone-conduction threshold, cervical vestibular evoked myogenic potential threshold, and presenting signs and symptoms were not statistically significant. Conclusion The dehiscence length correlated positively with the maximal air-bone gap in patients with superior semicircular canal dehiscence. The correlation was statistically significant. The dehiscence length did not correlate with the other variables examined in this study.

Balance Dysfunction and Recovery after Surgery for Superior Canal Dehiscence Syndrome

OBJECTIVE To characterize (1) the impairment and recovery of functional balance and (2) the extent of vestibular dysfunction and physiological compensation following superior canal dehiscence syndrome (SCDS) surgical repair. DESIGN Prospective study. SETTING Tertiary referral center. PARTICIPANTS Thirty patients diagnosed as having SCDS. INTERVENTIONS Surgical plugging and resurfacing of SCDS. MAIN OUTCOME MEASURES Balance measures were assessed in 3 separate groups, each with 10 different patients: presurgery, postoperative short-term (<1 week), and postoperative long-term (≥6 weeks). Vestibular compensation and function, including qualitative head impulse tests (HITs) in all canal planes and audiometric measures, were assessed in a subgroup of 10 patients in both the postoperative short-term and long-term phases. RESULTS Balance measures were significantly impaired immediately but not 6 weeks after SCDS repair. All patients demonstrated deficient vestibulo-ocular reflexes for HITs in the plane of the superior canal following surgical repair. Unexpectedly, spontaneous or post-head-shaking nystagmus beat ipsilesionally in most patients, whereas contrabeating nystagmus was noted only in patients with complete canal paresis (ie, positive HITs in all canal planes). There were no significant deviations in subjective visual vertical following surgical repair (P = .37). The degree of audiometric air-bone gap normalized 6 weeks after surgery. CONCLUSIONS All patients undergoing SCDS repair should undergo a postoperative fall risk assessment. Nystagmus direction (spontaneous and post-head-shaking) seems to be a good indicator of the degree of peripheral vestibular system involvement and central compensation. These measures correlate well with the HIT.

Second-side surgery in superior canal dehiscence syndrome

Objective Bilateral superior canal (SC) dehiscence syndrome poses a challenge because bilateral SC dehiscence (SCD) plugging might be expected to result in oscillopsia and disability. Our aims were as follows: 1) to evaluate which symptoms prompted patients with bilateral SCD syndrome (SCDS) to seek second-side surgery, and 2) to determine the prevalence of disabling imbalance and oscillopsia after bilateral SC plugging. Study Design Prospective observational study. Setting Tertiary referral center. Patients Five patients with bilateral SCDS based on history, audiometric and physiologic testing, and computed tomographic findings. This includes all of our patients who have had second-side plugging surgery to date. Intervention(s) Bilateral sequential middle fossa craniotomy and plugging of SCs. Main Outcome Measure(s) Cochleovestibular symptoms, cervical and ocular vestibular-evoked myogenic potential testing, dizziness handicap inventory, short-form 36 Health Survey, dynamic visual acuity testing. Results The most common symptoms prompting second-side surgery were sound- and pressure-induced vertigo and autophony. Three of the 5 patients reported that symptoms shifted to the contralateral ear immediately after plugging the first side, whereas in 2 patients, contralateral symptoms developed several years after the first SC plugging. Two of 4 patients experienced ongoing oscillopsia after bilateral SCDS surgery; however, all patients reported relief from their SCD symptoms and were glad that they had pursued bilateral surgery. Conclusion In patients with bilateral SCDS, sound- and pressure-induced vertigo most commonly prompted second-side surgery. Despite some degree of oscillopsia after bilateral SCDS surgery, patients were very satisfied with second-side surgery, given their relief from other SCDS symptoms.

Optimizing ocular vestibular evoked myogenic potential testing for superior semicircular canal dehiscence syndrome: Electrode placement

Objective: To compare the sensitivity and specificity of ocular vestibular evoked myogenic potentials (oVEMPs) using 2 electrode montages for the diagnosis of superior canal dehiscence syndrome (SCDS). Subjects: 16 SCDS patients (17 affected-SCDS ears, 15 contralateral-SCDS ears) and 12 controls (24 ears). Methods: oVEMPs were recorded in response to 500-Hz tone bursts using 2 electrode montages. For both montages the active electrode was placed approximately 5 mm below each eye and a ground electrode on the sternum. For montage 1 (standard), the reference electrode was centered 2 cm below each active electrode. For montage 2, the reference electrode was placed on the chin. Results: For either montage, the separation between oVEMP amplitudes in affected-SCDS ears and controls was significant (p < 0.001), with excellent sensitivity and specificity (>90%). Conclusion: oVEMP recordings with the standard montage remain a reliable method for evaluation of SCDS.

The effect of increased intracranial pressure on vestibular evoked myogenic potentials in superior canal dehiscence syndrome

OBJECTIVE To determine if vestibular evoked myogenic potential (VEMP) responses change during inversion in patients with superior canal dehiscence syndrome (SCDS) compared to controls. METHODS Sixteen subjects with SCDS (mean: 43, range 30-57 years) and 15 age-matched, healthy subjects (mean: 41, range 22-57 years) completed cervical VEMP (cVEMP) in response to air conduction click stimuli and ocular VEMP (oVEMP) in response to air conduction 500 Hz tone burst stimuli and midline tap stimulation. All VEMP testing was completed in semi-recumbent and inverted conditions. RESULTS SCDS ears demonstrated significantly larger oVEMP peak-to-peak amplitudes in comparison to normal ears in semi-recumbency. While corrected cVEMP peak-to-peak amplitudes were larger in SCDS ears; this did not reach significance in our sample. Overall, there was not a differential change in o- or cVEMP amplitude with inversion between SCDS and normal subjects. CONCLUSIONS Postural-induced changes in o- and cVEMP responses were measured in the steady state regardless of whether the labyrinth was intact or dehiscent. SIGNIFICANCE VEMP responses are blunted during inversion. Although steady-state measurements of VEMPs during inversion do not increase diagnostic accuracy for SCDS, the findings suggest that inversion may provide more general insights into the equilibration of pressures between intracranial and intralabyrinthine fluids.

Can the Video Head Impulse Test Define Severity of Bilateral Vestibular Hypofunction

OBJECTIVE The objective of the study was to compare rotary chair and video head impulse test (vHIT) findings in patients with bilateral vestibular hypofunction (BVH) to determine whether vHIT can: 1) define severity of BVH and 2) accurately predict rotary chair findings in patients with BVH. STUDY DESIGN Retrospective chart review. SETTING Research hospital. PATIENTS Twenty subjects with bilateral vestibular hypofunction as assessed by rotary chair. INTERVENTION Rotary chair and vHIT. MAIN OUTCOME MEASURES The main outcome measures were rotary chair phase, gain, and symmetry and vHIT vestibulo-ocular reflex (VOR) gain. Rotary chair and vHIT results were assessed and subjects were stratified into groups according to the severity of their vestibular hypofunction. For rotary chair, subjects were classified as mild, moderate, or severe BVH. For vHIT, subjects were classified as normal, unilateral, or bilateral. RESULTS Average lateral canal vHIT VOR gain: 1) significantly increased as severity of BVH decreased, and 2) demonstrated a significant and positive, linear relationship with rotary chair gains. vHIT was in disagreement with rotary chair in the classification of five subjects, which could be due to right-left asymmetry of BVH. CONCLUSION vHIT can serve as an initial tool for identifying patients with BVH. Lower vHIT gains are consistent with having severe BVH. There was disagreement between vHIT and rotary chair, though not for any patients with severe BVH. Compared with rotary chair, the clinical gold standard for identifying BVH, vHIT possesses 100% sensitivity for excluding severe BVH when average vHIT gains are greater than 0.46.

Unilateral centrifugation: utricular assessment and protocol comparison.

Objective: The purpose of this study was to examine how 2 different methods of lateral translation affect subjective visual vertical (SVV), ocular torsion position, and symptoms of nausea in a healthy population. Study Design: Prospective study. Setting: Tertiary referral center. Patients: Eleven healthy control subjects ranging between 26 and 48 years of age with normal hearing sensitivity and no history of balance disorders, dizziness, or neurologic involvement. Intervention(s): Subjects underwent 2 types of lateral translation: 1) lateral translation followed by rotation, and 2) lateral translation during rotation. The order of lateral translation type and order of translation were randomized to avoid an order effect. Main Outcome Measure(s): Ocular torsion and SVV deviation were measured during each lateral translation trial. A visual analog scale was used to assess each participants level of nausea before and directly after each lateral translation trial. Results: There was no significant difference in ocular torsion, SVV deviation, or level of nausea between the 2 methods. Both ocular torsion and SVV deviation were symmetrical to the right and left within both methods, and both demonstrated a linear relationship with the gravito-inertial acceleration vector. Conclusion: Both ocular torsion and SVV have been shown to offset systematically in response to unilateral utricular stimulation regardless of the lateral translation method used, with no significant difference in subjective sensations of nausea.