Vestibular assessment in sudden sensorineural hearing loss: Role in the prediction of hearing outcome and in the early detection of vascular and hydropic pathomechanisms.

Introduction: Predicting hearing outcome in sudden sensorineural hearing loss (SSNHL) is challenging, as well as detecting the underlying pathomechanisms. SSNHL could be associated with vestibular damage since cochleo-vestibular structures share the same vascularization, along with being in close anatomical proximity. Whereas viral inflammations and autoimmune/vascular disorders most likely represent the involved aetiologies, early-stage Menière's disease (MD) can also present with SSNHL. Since an early treatment could beneficially influence hearing outcome, understanding the possible etiology plays a pivotal role in orienting the most appropriate treatment. We aimed to evaluate the extent of vestibular damage in patients presenting with SSNHL with or without vertigo, investigate the prognostic role of vestibular dysfunctions on hearing recovery and detect specific lesion patterns related to the underlying pathomechanisms. Methods: We prospectively evaluated 86 patients with SSNHL. Audio-vestibular investigation included pure-tone/speech/impedance audiometry, cervical/ocular-VEMPs, vHIT and video-Frenzel examination. White matter lesions (WML) were evaluated on brain-MRI. Patients were followed-up and divided into "SSNHL-no-vertigo," "SSNHL+vertigo" and "MD" subgroups. Results: Hearing was more impaired in "SSNHL+vertigo" patients who exhibited either down-sloping or flat-type audiograms, and was less impaired in "MD" where low frequencies were mostly impaired (p < 0.001). Otolith receptors were more frequently involved than semicircular canals (SCs). Although the "SSNHL-no-vertigo" subgroup exhibited the lowest vestibular impairment (p < 0.001), 52% of patients developed otolith dysfunctions and 72% developed nystagmus. Only "MD" subjects showed anterior SC impairment and upbeating spontaneous/positional nystagmus. They more frequently exhibited cervical-VEMPs frequency tuning (p = 0.036) and ipsilesional spontaneous nystagmus (p < 0.001). "SSNHL+vertigo" subjects presented with more frequently impaired cervical-VEMPs and posterior SC and with higher number of impaired receptors (p < 0.001). They mainly exhibited contralesional spontaneous and vibration-induced nystagmus (p < 0.05) and only they showed the highest WML score and "vascular" lesion patterns (p < 0.001). Concerning the outcomes, hearing was better in "MD" and worse in "SSNHL+vertigo" (p < 0.001). Hearing recovery was mostly affected by cervical-VEMPs impairment and the number of involved receptors (p < 0.05). Patients with "vascular" lesion patterns presented with the highest HL degree and WML score (p ≤ 0.001), while none of them exhibited a complete hearing recovery (p = 0.026). Conclusions: Our data suggest that vestibular evaluation in SSNHL can provide useful information on hearing recovery and underlying aetiologies.

Spontaneous Upbeat Nystagmus and Selective Anterior Semicircular Canal Hypofunction on Video Head Impulse Test: A New Variant of Canalith Jam?

We describe a rare case of spontaneous upbeat nystagmus (UBN) attributable to a canalith jam involving the anterior semicircular canal (ASC) in a patient in whom comprehensive vestibular assessment was useful to identify the underlying pathomechanism. A 56-year-old woman with unsteadiness following repositioning procedures for left-sided benign paroxysmal positional vertigo (BPPV) presented with spontaneous UBN that showed slight right torsional components. A vestibular test battery detected isolated left ASC hypofunction on a video-head impulse test (Video-HIT). We postulated a persistent utriculopetal deflection of the left ASC cupula, which was attributable to entrapment of debris in a narrow canal tract, with consequent sustained inhibition of the ampullary afferents. Although spontaneous UBN receded after impulsive physical therapy, unsteadiness deteriorated into positional vertigo secondary to canalolithiasis involving the ipsilateral posterior canal. In our view, physical therapy possibly fragmented the canalith jam and released free-floating otoconia that eventually settled into the ipsilateral posterior canal. Video HIT revealed normalization of ASC hypofunction, and leftsided posterior canal canalolithiasis was successfully treated using appropriate repositioning procedures. We propose that a canalith jam involving the ASC should be considered in the differential diagnosis of spontaneous UBN, particularly in patients with a history of BPPV and isolated ASC hypofunction detected on video HIT.

Fluctuating Posterior Canal Function in Benign Paroxysmal Positional Vertigo Depending on How and Where Otoconia Are Disposed.

OBJECTIVE: Though fluctuations in vestibular function represent a common finding in Menière's disease, we describe how benign paroxysmal positional vertigo (BPPV) may result in fluctuations of vestibulo-ocular reflex for the involved canal depending on the disposition of otoliths. PATIENT: A 54-year-old woman suffering from refractory posterior canal (PC)-BPPV resulting in fluctuating PC function. INTERVENTIONS: Diagnostic evaluation and rehabilitative treatment for BPPV involving the affected PC. MAIN OUTCOME MEASURES: Video-Frenzel and video-head impulse test (vHIT) findings before and after canalith repositioning procedures for PC-BPPV. RESULTS: BPPV involving the nonampullary arm of right PC was diagnosed based on presenting positional downbeat nystagmus and selective right PC hypofunction at the vHIT. During physical treatment, nystagmus first became positional paroxysmal upbeat likely due to a shift of debris into the ampullary arm of the canal, then turned to spontaneous downbeat nystagmus consistently with a plug effect exerted by particles entrapped within the nonampullary arm of PC and finally receded proving an otoliths fall within the utriculus. Simultaneously, vHIT documented fluctuations for right PC vestibulo-ocular reflex gain as it first increased to normal values, then severely declined and finally normalized, respectively. High-resolution computed tomography scan detected ipsilateral superior canal dehiscence. CONCLUSIONS: In accordance with recently reported vHIT findings in different types of BPPV, fluctuation of PC function could be likely explained by the effect of particles on cupular dynamic responses depending on the portion of the canal gradually involved. Superior canal dehiscence may have played a role facilitating otoliths mobilization by reducing labyrinthine impedance.

Enhanced Otolith Function Despite Severe Labyrinthine Damage in a Case of Pneumolabyrinth and Pneumocephalus Due to Otogenic Meningitis Associated With Superior Canal Dehiscence.

OBJECTIVE: To describe a rare case of pneumolabyrinth (PNL) and pneumocephalus (PNC) due to otogenic meningitis in a patient with superior canal dehiscence (SCD) resulting in profound sensorineural hearing loss (SNHL), semicircular canals impairment but preservation of SCD-related enhanced otolith function. PATIENT: A 65-year-old woman with otogenic meningitis. INTERVENTION: Temporal bone high-resolution computed tomography (CT) scans, brain-magnetic resonance imaging, audiometry, bedside examination, video-head impulse test, and vestibular-evoked myogenic potentials (VEMPs). MAIN OUTCOME MEASURES: Enhanced otolith function despite canal and cochlear loss. RESULTS: The patient developed right profound SNHL and acute labyrinthitis. Imaging showed middle ear inflammatory tissue, right PNL and PNC despite lack of bony fractures. Bilateral SCD and tegmen dehiscence were detected. The patient underwent mastoidectomy, drainage of effusion, and surgical repair of tegmen dehiscence. Exploratory tympanotomy was uneventful. She was treated with intravenous antibiotics and dexamethasone for 3 weeks with improvement of general condition. At 3-weeks follow-up, right profound SNHL persisted with global hypofunction for ipsilateral semicircular canals and selective impairment for left superior canal activity at video-head impulse test. Surprisingly, both cervical and ocular-VEMPs exhibited bilaterally abnormal amplitudes and reduced thresholds, consistently with preserved SCD-related macular hypersensitivity to sounds even on the affected side. CONCLUSIONS: This case report exhibits a unique clinical scenario as it offers interesting insights concerning PNL aetiology despite lack of either bony fractures or barotrauma and PNC likely conveyed intracranially by SCD. Moreover, it provides an unusual pattern of functional dissociation among inner-ear receptors showing enhanced otolith function despite severe labyrinthine damage.

Feasibility of Using the Video-Head Impulse Test to Detect the Involved Canal in Benign Paroxysmal Positional Vertigo Presenting With Positional Downbeat Nystagmus.

Positional downbeat nystagmus (pDBN) represents a relatively frequent finding. Its possible peripheral origin has been widely ascertained. Nevertheless, distinguishing features of peripheral positional nystagmus, including latency, paroxysm and torsional components, may be missing, resulting in challenging differential diagnosis with central pDBN. Moreover, in case of benign paroxysmal positional vertigo (BPPV), detection of the affected canal may be challenging as involvement of the non-ampullary arm of posterior semicircular canal (PSC) results in the same oculomotor responses generated by contralateral anterior canal (ASC)-canalolithiasis. Recent acquisitions suggest that patients with persistent pDBN due to vertical canal-BPPV may exhibit impaired vestibulo-ocular reflex (VOR) for the involved canal on video-head impulse test (vHIT). Since canal hypofunction normalizes following proper canalith repositioning procedures (CRP), an incomplete canalith jam acting as a "low-pass filter" for the affected ampullary receptor has been hypothesized. This study aims to determine the sensitivity of vHIT in detecting canal involvement in patients presenting with pDBN due to vertical canal-BPPV. We retrospectively reviewed the clinical records of 59 consecutive subjects presenting with peripheral pDBN. All patients were tested with video-Frenzel examination and vHIT at presentation and after resolution of symptoms or transformation in typical BPPV-variant. BPPV involving non-ampullary tract of PSC was diagnosed in 78%, ASC-BPPV in 11.9% whereas in 6 cases the involved canal remained unidentified. Presenting VOR-gain values for the affected canal were greatly impaired in cases with persistent pDBN compared to subjects with paroxysmal/transitory nystagmus (p < 0.001). Each patient received CRP for BPPV involving the hypoactive canal or, in case of normal VOR-gain, the assumed affected canal. Each subject exhibiting VOR-gain reduction for the involved canal developed normalization of vHIT data after proper repositioning (p < 0.001), proving a close relationship with otoliths altering high-frequency cupular responses. According to our results, overall vHIT sensitivity in detecting the affected SC was 72.9%, increasing up to 88.6% when considering only cases with persistent pDBN where an incomplete canal plug is more likely to occur. vHIT should be routinely used in patients with pDBN as it may enable to localize otoconia within the labyrinth, providing further insights to the pathophysiology of peripheral pDBN.

Case Report: Filling Defect in Posterior Semicircular Canal on MRI With Balanced Steady-State Gradient-Echo Sequences After Labyrinthine Ischemia in the Common Cochlear Artery Territory as an Early Sign of Fibrosis.

We describe a rare case of posterior semicircular canal (PSC) fibrosis following acute labyrinthine ischemia in the territory supplied by the common cochlear artery (CCA) and review the relevant literature. A 71-year-old man with multiple vascular risk factors presented 12 days after the onset of acute vertigo and profound left-sided hearing loss. Right-beating spontaneous nystagmus with downbeat components elicited by mastoid vibrations and headshaking was detected. The video head impulse test (vHIT) revealed an isolated hypofunction of the left PSC, whereas vestibular evoked myogenic potentials (VEMPs) showed ipsilateral saccular loss. The clinical presentation and instrumental picture were consistent with acute ischemia in the territory supplied by left CCA. Compared to previous imaging, a new MRI of the brain with 3D-FIESTA sequences highlighted a filling defect in the left PSC, consistent with fibrosis. Hearing function exhibited mild improvement after steroid therapy and hyperbaric oxygen sessions, whereas vHIT abnormalities persisted over time. To the best of our knowledge, this is the only case in the literature reporting a filling defect on MRI, consistent with semicircular canal fibrosis following acute labyrinthine ischemia. Moreover, PSC fibrosis was related with poor functional outcome. We therefore suggest using balanced steady-state gradient-echo sequences a few weeks following an acute lesion of inner ear sensors to detect signal loss within membranous labyrinth consistent with post-ischemic fibrosis. Besides addressing the underlying etiology, signal loss might also offer clues on the functional behavior of the involved sensor over time. In cases of acute loss of inner ear function, a careful bedside examination supplemented by instrumental assessments, including vHIT and VEMPs, of vestibular receptors and afferents may be completed by MRI with balanced steady-state gradient-echo sequences at a later time to confirm the diagnosis and address both etiology and functional outcome.

A Possible Role of Video-Head Impulse Test in Detecting Canal Involvement in Benign Paroxysmal Positional Vertigo Presenting With Positional Downbeat Nystagmus.

OBJECTIVE: To describe the possible diagnostic role of video-head impulse test (vHIT) in patients presenting with positional downbeat nystagmus (PDN) due to benign paroxysmal positional vertigo (BPPV) involving the anterior canal (AC) or the non-ampullary arm of the posterior canal (PC). PATIENTS: Three patients presenting with positional vertigo, PDN, symmetrical cervical and ocular vestibular-evoked myogenic potentials, and selective deficit of the vestibulo-ocular reflex (VOR) gain for a single vertical canal on vHIT. INTERVENTIONS: Diagnostic evaluation and rehabilitative treatment for BPPV involving the deficient canals. MAIN OUTCOME MEASURES: Video-oculographic and vHIT findings before and after canalith repositioning procedures (CRP) for AC-BPPV and apogeotropic PC-BPPV. RESULTS: Each patient was treated with CRP for BPPV involving the hypoactive canal. In one case, symptoms receded with physical therapy, whereas two patients developed a paroxysmal positional upbeat nystagmus consistent with BPPV involving the ampullary arm of the ipsilateral PC and were treated with Epley CRP. Posttreatment evaluation showed resolution of symptoms and signs and restitution of canal function in all cases. CONCLUSIONS: PDN can be due to both peripheral and central vestibular pathologies. In case of BPPV, involvement of the non-ampullary arm of the PC is hardly distinguishable from contralateral AC canalolithiasis. In these situations, vHIT may play a key role in the differential diagnosis. Considering these findings, we propose to include vHIT in the test battery of patient with PDN, as it may provide clues to the differential diagnosis with central pathologies enabling the identification of the canal involved by BPPV.