Labyrinthitis

Labyrinthitis is inflammation of the membranous labyrinth, involving both the cochlea and vestibular system. It causes vertigo and hearing loss together. In contrast, vestibular neuritis involves the vestibular nerve only, without hearing loss.

Causes:

• Viral (the most common): herpes simplex virus, varicella zoster virus, cytomegalovirus, influenza, measles, mumps, rubella, adenovirus, coxsackievirus, and enterovirus
• Bacterial: serous labyrinthitis as a complication of acute otitis media, mastoiditis and cholesteatoma through the round window; suppurative labyrinthitis after meningitis, or extension through the oval window or fistula, which destroys cochlear and vestibular function; syphilis and Lyme disease
• Autoimmune
• Toxic (aminoglycosides)

Meningogenic labyrinthitis in children is a major cause of acquired deafness (pneumococcal meningitis, 5 to 30 percent develop hearing loss). Labyrinthitis ossificans, new bone formation in the cochlea in 2 weeks to months after infection, impedes cochlear implantation.

Complications: permanent sensorineural hearing loss, chronic imbalance, and in bacterial disease, meningitis and brain abscess.

• Acute onset of severe rotatory vertigo lasting days (typically 2 to 3 days of intense vertigo, then gradually improving over weeks), with nausea, vomiting and unsteadiness.
• Sensorineural hearing loss (unilateral, sudden), tinnitus, and aural fullness, differentiating it from vestibular neuritis.
• Spontaneous horizontal torsional nystagmus beating away from the affected side (a "paralytic" pattern in viral and suppurative disease), which increases with gaze in the direction of the fast phase (Alexander law) and is suppressed by visual fixation; positive head impulse test on the affected side, and unsteadiness with falls toward the affected side.
• A preceding upper respiratory tract infection; features of otitis media, mastoiditis or cholesteatoma (otorrhoea, fever, pain) in bacterial disease; features of meningitis (headache, neck stiffness, fever) in meningogenic types; Ramsay Hunt vesicles in zoster.
• Absence of other central neurological signs (no diplopia, dysarthria, limb ataxia), to distinguish from stroke.

• Clinical diagnosis from the history and neuro otological examination: HINTS examination (head impulse test abnormal, nystagmus direction fixed horizontal and unidirectional, and test of skew absent) distinguishes peripheral from central causes (stroke); a normal head impulse test, direction changing nystagmus or skew suggests central cause.
• Pure tone audiometry: sensorineural hearing loss (varying) on the affected side; electronystagmography and video nystagmography, caloric testing (reduced or absent response), and video head impulse test confirm vestibular hypofunction.
• MRI brain and internal auditory canals with gadolinium: enhancement of the labyrinth (cochlea and vestibule) and exclusion of stroke, vestibular schwannoma, multiple sclerosis; high resolution T2 sequences show cochlear fibrosis or ossification in chronic cases; CT temporal bone for chronic otitis, mastoiditis, cholesteatoma and ossification.
• Blood tests: full blood count, inflammatory markers, glucose, syphilis serology, Lyme serology where relevant, and autoimmune screen (antinuclear antibody, antineutrophil cytoplasmic antibody) in recurrent or bilateral cases.
• Lumbar puncture if meningitis is suspected; cultures of ear discharge.

• Symptomatic therapy for acute vertigo, for 2 to 3 days only because prolonged use delays central compensation: prochlorperazine 5 to 10 mg three times daily or 12.5 mg intramuscularly, cinnarizine 15 to 30 mg three times daily, betahistine 16 mg three times daily (modest evidence), or promethazine 25 mg. For severe vertigo use diazepam 2 to 5 mg or lorazepam 0.5 to 1 mg. Antiemetics: ondansetron 4 to 8 mg. Give intravenous fluids if dehydrated.
• Corticosteroids for viral labyrinthitis with sudden hearing loss (start within 2 weeks): prednisolone 1 mg/kg daily (60 to 80 mg) for 5 to 7 days, then tapered over 10 to 14 days. Intratympanic dexamethasone (4 mg/mL, 0.5 to 1 mL, three injections over 1 to 2 weeks) is salvage therapy. Benefit is greatest in vestibular neuritis for vestibular recovery.
• Antivirals in suspected herpes zoster oticus (Ramsay Hunt syndrome): valaciclovir 1 g three times daily for 7 days (or aciclovir 800 mg five times daily), combined with prednisolone 60 mg daily for 5 to 7 days then taper. Benefit in other viral labyrinthitis is unproven.
• Bacterial labyrinthitis: urgent intravenous antibiotics (ceftriaxone 2 g every 12 hours with metronidazole 500 mg every 8 hours for suspected anaerobic involvement, or according to culture), with myringotomy or tympanostomy tube.
• Suppurative labyrinthitis with failed medical therapy: mastoidectomy or labyrinthectomy, to prevent intracranial extension. Cholesteatoma needs surgery. Manage meningitis with ceftriaxone, vancomycin and dexamethasone.
• Syphilis: benzathine benzylpenicillin 2.4 million units intramuscularly weekly for 3 weeks. In neurosyphilis, aqueous penicillin G 18 to 24 million units daily intravenously for 10 to 14 days, with prednisolone.
• Lyme disease: ceftriaxone 2 g daily for 14 to 28 days.
• Vestibular rehabilitation: early return to normal activity and customised vestibular exercises (gaze stabilisation, habituation, balance training), beginning after the acute phase (2 to 3 days). This improves central compensation, with improvement in most patients within 6 weeks.
• Hearing rehabilitation: hearing aids, contralateral routing of signal aid for unilateral deafness, and cochlear implantation for bilateral profound loss after meningitis. Implant promptly because of ossification risk (within weeks to 3 months after meningitis, as soon as the child is medically stable).
• Prevention: pneumococcal and Haemophilus influenzae type b vaccination, measles-mumps-rubella vaccination, and prompt treatment of otitis media.
• Follow up: audiogram at 2 to 4 weeks and 3 months, and assessment of balance. Most patients recover vestibular function, but hearing recovery varies (viral, 50 to 60 percent). Recurrent episodes and chronic imbalance are possible.