By Marcello Cherchi, MD PhD
For patients
Labyrinthitis, sometimes also called “sudden sensorineural hearing loss with vertigo,” is thought to be due to inner ear damage from a bout of inflammation, though the cause of the inflammation is unknown despite considerable research. Suspicion for labyrinthitis is based on the clinical history and can be supported by findings on physical examination and various otovestibular tests. The standard of care for the symptom of disequilibrium from labyrinthitis is appropriately targeted vestibular rehabilitation therapy, though even
For clinicians
Overview
Labyrinthitis is thought to be labyrinthine damage secondary to an inflammatory process whose etiology is unknown. It presents acutely with disequilibrium and unilateral aural symptoms (hearing loss and sometimes tinnitus). Audiometry and otoacoustic emissions show hearing loss on the affected side. Otovestibular testing shows vestibular weakness ipsilateral to the aural symptoms. For the disequilibrium, treatment in the first 1 – 3 days consists of anti-vertiginous medications and vestibular suppressants; subsequent management consists of appropriately targeted vestibular rehabilitation therapy. For the hearing loss, treatment includes amplification; some practitioners use steroids (extrapolating from the literature on sudden onset sensorineural hearing loss). Labyrinthitis does not usually recur; when it recurs, other diagnoses (such as Ménière’s disease) enter the differential diagnosis.
§1: Introduction
§1.1: What is labyrinthitis?
Labyrinthitis, sometimes also called “sudden sensorineural hearing loss with vertigo” in the otolaryngology literature (Seltzer and Mark 1991, Mark, Seltzer et al. 1992, Park, Jung et al. 2001, Iwasaki, Takai et al. 2005, Pogson, Taylor et al. 2016, Kim, Choi et al. 2018, Yu and Li 2018, Jiang, Zhang et al. 2021), is suspected to be due to an inflammatory-mediated insult (damage) to both the “hearing component” (the cochlea) and the “balance component” (the semicircular canals and otolith organs) of the inner ear (labyrinth) itself.
Although labyrinthitis is usually regarded as a process affecting the labyrinth (inner ear) itself, damage to the vestibulocochlear nerve (which transmits hearing and balance signals from the inner ear to the brain) would manifest in a similar fashion clinically; this would be termed “vestibulocochlear neuritis.” Thus, distinguishing “labyrinthitis” (inflammation of the entire inner ear) from “vestibulocochlear neuritis” (inflammation of the entire vestibulocochlear nerve) would be difficult.
§1.2: What is the cause of labyrinthitis?
The short answer is that the underlying cause of labyrinthitis is unknown. Viral and vascular causes have been proposed, but reviews of this literature reveal the supporting evidence to be circumstantial at best (Nadol 1995, Strupp and Brandt 2009). Placebo-controlled trials attempting to treat for a presumed viral cause (herpes simplex 1 infection) showed no difference in outcomes (Strupp, Zingler et al. 2004).
§2: How does labyrinthitis present?
Labyrinthitis usually manifests with severe dizziness (similar to vestibular neuritis) accompanied by ear symptoms on one side (typically hearing loss and tinnitus). These symptoms remain chronic for days to months. In many patients the symptoms improve; in some the symptoms completely resolve, while other patients experience some degree of residual symptoms indefinitely. It is less clear whether labyrinthitis recurs, because frequent recurrence is usually clinically more suggestive of Ménière’s disease.
§3: Diagnosis
§3.1: How is labyrinthitis diagnosed?
Labyrinthitis can be suspected based on a compatible clinical history. Suspicion for labyrinthitis increases when audiologic testing shows hearing loss on the same side as the vestibular deficits, and there is no evidence for a better explanation of the symptoms.
§3.2: What tests help diagnose labyrinthitis?
In order to detect the vestibular (balance-related) labyrinthitis, several tests may be needed. The reason is that there are multiple components of the inner ear that detect movement, each of which sends signals through a different bundle of fibers in the vestibular nerve; there does not currently exist a test to assess these components “all at once,” rather, there are individual tests for each component.
Briefly, each labyrinth includes five “organelles” that detect motion – specifically, three semicircular canals (the anterior/superior canal, the lateral/horizontal canal, and the posterior/inferior canal) that detect angular acceleration, and two otolith organs (the saccule and utricle) that detect linear acceleration.
Signals from each of these organelles travel along discrete fibers within the vestibular nerve to reach several vestibular nuclei in the brainstem. The microstructural anatomy of the vestibular nerve is difficult to analyze due to a variety of factors – including neuronal anastomoses with adjacent structures (Ozdogmus, Sezen et al. 2004), the gradual rotation in the disposition of the fibers along the course of the nerve (Silverstein, Norrell et al. 1986), the variable orientation between individuals (Rasmussen 1940), variability between genders (Moriyama, Itoh et al. 2007) and the attrition of nerve fibers with age (Bergström 1973, Nagai, Goto et al. 1999) – but a number of painstaking studies on human specimens have been conducted, such as Lee and Suarez’ study of 3 temporal bones (Lee, Suarez et al. 1990), and Lopez et al’s study of 13 temporal bones (Lopez, Ishiyama et al. 2005), and Bergstrom’s study of 40 human temporal bones (Bergström 1973).
For the auditory part of labyrinthitis (hearing loss, tinnitus), hearing tests are used, including standard audiometry, and otoacoustic emissions. Almost any pattern of sensorineural hearing loss can be seen in labyrinthitis, but the most common pattern seen is one of predominantly high frequency sensorineural hearing loss.
We do not usually assess auditory evoked brainstem responses in these patients, as the degree of hearing loss may make the results uninterpretable.
Given this variability, and given that all tests are fallible (meaning that any test can have false positives and false negatives), we generally try not to base the diagnosis on a single test result in isolation; confidence in the diagnosis increases when multiple independent data points (from separate tests) support the same diagnosis. Tests commonly used in diagnosing labyrinthitis include an audiogram, otoacoustic emissions, cervical vestibular evoked myogenic potentials (cVEMPs), ocular vestibular evoked myogenic potentials (oVEMPs), videonystagmography (VNG) and video head impulse testing (vHIT); this battery is a reasonable selection that assesses many of the inner ear’s “balance functions,” but it still does not provide a complete picture thereof. Ongoing research is exploring other methods of assessing vestibular neuritis (Cherchi 2019).
Occasionally, MRI of the brain and internal auditory canals without and with contrast shows enhancement of the labyrinth (Seltzer and Mark 1991), though the diagnosis does not require this.
§4: Treatment, prognosis and recurrence
§4.1: How do you treat the dizziness/imbalance symptoms resulting from labyrinthitis?
During the first few days of labyrinthitis, management of the symptom of disequilibrium is supportive, sometimes including anti-emetics (such as ondansetron, metoclopramide or promethazine) and vestibular suppressants (such as meclizine or clonazepam), but these medications play no role beyond the first few days.
After the acute phase, physical therapy is the mainstay of treatment. Physical therapy is thought to accelerate recovery by promoting sensory substitution and central compensation for the vestibular deficit (Strupp and Brandt 2009). Physical therapy usually is usually initiated with gaze stabilization exercises (Meldrum and Jahn 2019), but evolves depending on an individual’s progress.
Note that even with appropriately-targeted vestibular rehabilitation therapy, recovery may be experienced as “uneven,” in the sense that from day to day there may be fluctuation in the intensity of baseline symptoms, though when observing symptoms over a longer time frame (typically weeks) the overall trajectory is one of improvement.
The auditory symptoms (hearing loss and tinnitus) may necessitate other treatment. Some practitioners, based on extrapolation from treatment trials for sudden sensorineural hearing loss, attempt a course of oral steroids, even though the data supporting that approach are weak (Cinamon, Bendet et al. 2001, Nosrati-Zarenoe and Hultcrantz 2012). If that fails, referral to otolaryngology to be evaluated for a transtympanic injection of steroids (Garavello, Galluzzi et al. 2012) is sometimes considered, even though the evidence supporting that approach are also weak (Crane, Camilon et al. 2015, El Sabbagh, Sewitch et al. 2017).
§4.2: What is the prognosis of labyrinthitis?
The prognosis of the vestibular (dizziness/imbalance) component of labyrinthitis is similarly unpredictable as vestibular neuritis (discussed elsewhere).
The hearing loss from labyrinthitis may improve spontaneously to some degree over about 4 – 6 months. A common clinical practice is to perform a hearing test as close as possible to the beginning of the disease, and then repeat a hearing test at 4 – 6 months after symptom onset. If the hearing loss appears to have “plateaued,” then consultation with audiology is appropriate in order to discuss amplification options (such as a hearing aid) and perhaps masking strategies (if tinnitus is present).
§4.3: Can labyrinthitis recur?
We have seen patients who appear to have suffered more than one bout of labyrinthitis, though it would be challenging to distinguish recurrent bouts of labyrinthitis from Ménière’s disease. In theory labyrinthitis should cause predominantly high frequency hearing loss whereas Manière’s disease should cause predominantly low frequency hearing loss, though in reality either disease can cause any pattern of hearing loss.
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