Labyrinthitis

Labyrinthitis is inflammation and dysfunction of the labyrinth of the inner ear. It is one of many causes of vertigo. Typically it produces disturbances of balance and hearing to varying degrees and may affect one or both ears.

• The labyrinth incorporates the peripheral sensory organs for balance and hearing in a delicate membranous network (incorporating the utricle, saccule, semicircular canals, and cochlea).
• Symptoms of labyrinthitis occur when there is inflammation of the membranous labyrinth and damage to the vestibular and auditory end organs.
• It is possible for a variety of organisms and inflammatory mediators through both local and systemic disease to produce labyrinthitis.
  Bacteria or viruses can cause labyrinthitis but are sufficiently distinct to be considered as separate disease processes:
  • Bacteria may gain access to the membranous labyrinth through anatomical connections:
    • Between the central nervous system and subarachnoid space via the internal auditory canal and cochlear aqueduct.
    • Or through congenital or acquired defects of the bony labyrinth.
  • Viruses typically spread to labyrinthine structures haematogenously or via the anatomical connections above.
• Many cases of labyrinthitis appear to be viral in origin or associated with systemic disease. A large study of 240 cases of benign positional vertigo found the aetiology was idiopathic in nearly half, with a fairly even distribution amongst the rest of post traumatic cases, viral neurolabyrinthitis and miscellaneous causes.¹ The last group included vertebrobasilar ischaemia, Ménière's disease, post surgical ototoxicity, chronic otomastoiditis and (now rare) late syphilis. Tumours may also present as labyrinthitis.

An upper respiratory tract infection precedes the onset of symptoms in about half of cases of viral labyrinthitis.Viral labyrinthitis is often confused with vestibular neuritis. It is generally accepted that vestibular neuritis is a disorder of the vestibular nerve and is not associated with hearing loss. The cochlea is affected in labyrinthine inflammation and therefore hearing loss is always present in people with viral labyrinthitis.
Herpes zoster oticus, or Ramsay-Hunt syndrome is a unique variety of viral labyrinthitis. It is caused by reactivation of varicella-zoster virus infection years after the primary infection.
It is worth noting that viral infections cause both congenital and acquired hearing loss (rubella and cytomegalovirus are viral causes of prenatal hearing loss). Postnatally viral induced hearing loss is usually due to mumps or measles. Viral infections are also implicated in idiopathic sudden sensorineural hearing loss (SNHL).

• The epidemiology of diseases causing vertigo has been described as underdeveloped.²
• Viral labyrinthitis is the most common form of labyrinthitis.
• Viral labyrinthitis is usually observed in adults aged 30-60 years and is rarely observed in children. It is most common in the 4th decade with women outnumbering men by about 2:1.
• Bacterial labyrinthitis is rare in the post-antibiotic era. Meningogenic suppurative labyrinthitis is most often seen in young children (under 2 years), when children are at most risk of meningitis. Otogenic suppurative labyrinthitis can be observed in all ages (with cholesteatoma and in untreated acute otitis media).

History

This should be thorough and include particularly details of symptoms, past medical history and current medication.

• Viral labyrinthitis is characterised by:
  • Sudden unilateral loss of vestibular function and hearing (can be with tinnitus).
  • Sudden, severe and often incapacitating, vertigo.
  • Often associated with nausea and vomiting.
  • Hearing loss may be the primary presenting symptom in many patients. Some degree of hearing loss is always present with viral labyrinthitis.³
  • The patient is often confined to bed while the symptoms abate. This takes several days to weeks in the case of vertigo but unsteadiness and positional vertigo may last months.
  • Usually it is a self-limiting condition but some cases can be chronic or recurrent.

It is very important to ask about hearing loss as it does not occur with benign paroxysmal vertigo or vestibular neuronitis but it does occur with infectious labyrinthitis and Ménière's disease. It is also frequently found in ototoxicity and autoimmune labyrinthitis. Autoimmune disease seems to cause sensori-neural hearing loss rather than labyrinthitis.⁴

Examination⁵

• Perform a coarse examination of hearing using a 256Hz (middle C) tuning fork or 512 Hz (top C). Hearing tests do not have to be prolonged or intricate for this purpose.
• Inspect the ear and tympanic membrane using an auriscope.
• Note any marked loss of hearing or asymmetry. The Weber test involves placing a vibrating tuning fork on the forehead and asking if it is heard louder in either ear. There should be no difference but in nerve deafness it is quieter in the affected ear whilst in conductive deafness the sound transmitted through the skull is louder in the affected ear.
• Perform a neurological examination with particular reference to the cranial nerves. If any cranial nerves except the VIII are abnormal this is of great significance.
• If it was not possible to demonstrate the vertigo the Hallpike manoeuvre may be employed.

• Routine blood tests are not helpful, nor are viral antibody tests. However if a systemic infection is suspected, a FBC count and blood cultures are indicated.
• Examine cerebrospinal fluid if meningitis is suggested.
• Perform culture and sensitivity testing of middle ear effusions if present (and select appropriate antibiotic therapy).
• Most patients do not require imaging. However:
  • Consider a CT scan prior to lumbar puncture in cases of possible meningitis.³
  • A CT scan can help rule out mastoiditis.
  • A temporal bone CT scan may help in patients with cholesteatoma and labyrinthitis.
  • If a sinister cause is suspected MRI scan can be helpful. It provides much better pictures of the posterior fossa and VIII nerve course than CT.
  • MRI can be used to help rule out acoustic neuroma, stroke, brain abscess, or epidural hematoma as potential causes of vertigo and hearing loss.³
• Obtain an audiogram in all patients who may have labyrinthitis.³ This is important with hearing loss or asymmetric hearing loss.
• Vestibular testing:
  • Caloric testing and an electronystagmogram by may help in diagnosing difficult cases and in determining the prognosis for recovery.
  • Patients with viral labyrinthitis have nystagmus and unilateral caloric vestibular paresis/hypofunction.
  • Vestibular dysfunction represents overactivity in benign vestibular nystagmus and underactivity in labyrinthitis. New tests have been developed to assess the condition but are not generally available.⁶

• Ramsay-Hunt syndrome is a particular variety of viral labyrinthitis:
  • Initial symptoms are deep, burning, auricular pain.
  • The eruption of a vesicular rash in the external auditory canal and concha follows after a few days.
  • Vertigo, hearing loss, and facial weakness may follow (together or independently).
  • Symptoms typically improve over a few weeks (some patients can suffer permanent hearing loss and persistent reduction of caloric responses).
• Suppurative labyrinthitis (following otitis is uncommon):
  • It is almost always associated with cholesteatoma.
  • Profound hearing loss, severe vertigo, ataxia, and nausea and vomiting are common symptoms.
• Serous labyrinthitis:
  • Is associated with acute or chronic middle ear disease and a common complication of otitis media.
  • An audiogram reveals mixed hearing loss when a middle ear effusion is present.
  • Vestibular symptoms may occur but are less common.
  • The hearing loss is usually transient but may persist if the otitis is left untreated.
  • Treatment is aimed at the underlying infection and clearing the middle ear effusion.
  • The hearing loss is usually transient but may persist if the otitis is left untreated.
• Vestibular neuronitis or neuritis:
  • Typically presents in a previously healthy person as sudden acute vertigo without hearing loss.
  • It is more common in the fourth and fifth decades of life. It affects men and women equally.
  • An upper respiratory tract infection often precedes the condition, and the disorder is more common in the spring and early summer.
  • The treatment of vestibular neuritis and viral labyrinthitis is similar.
• Benign positional vertigo(BPV)⁷:
  • The characteristic nystagmus and vertigo are associated with changes of position.
  • Onset is sudden and severity very variable.
  • People who have BPV do not usually feel dizzy all the time. Severe attacks of dizziness are triggered by head movements.
  • At rest between episodes, patients usually have few or no symptoms.

Other diagnoses to consider are:

• Ménière's disease
• Stroke, especially posterior inferior cerebellar artery syndrome (PICA)
• Transient ischaemic attack
• Multiple sclerosis
• Subarachnoid haemorrhage
• Tumours of the brain or acoustic neuroma
• Cervical spondylosis
• Vertigo associated with migraine
• Vertebrobasilar insufficiency
• Cerebellar infarct
• Disequilibrium of aging
• Drug-induced vertigo, hearing loss, or both

• Patients can usually be managed at home. During an acute attack the patient should lie still with eyes closed.
• Patients should be advised to seek further medical care for worsening symptoms. Especially neurological symptoms (such as diplopia, slurred speech, gait disturbances, localised weakness or numbness).³
• Vertigo, nausea and vomiting may be helped by meclizine, prochlorperazine, promethazine and domperidone. In an acute attack, gastric emptying will be slowed or even reversed and so a buccal version of prochlorperazine may be preferable.
• Diazepam or other benzodiazepines are occasionally helpful as a vestibular suppressant.³
• A short course of oral corticosteroids may be helpful.³
• Currently, the role of antiviral therapy is not established.
• Always advise patients not to drive or operate machinery when suffering symptoms or taking medication, as appropriate.

Although the labyrinthitis is usually considered benign and self limiting chronic or recurrent cases merit referral to exclude sinister aetiology. Also the morbidity of labyrinthitis, especially bacterial labyrinthitis, is more significant than is often appreciated. In the pediatric population the risk of hearing loss is significant.

• The acute symptoms of vertigo and nausea and vomiting resolve after several days to weeks in all the different types of labyrinthitis.
• Recovery of hearing loss is more variable:
  • Suppurative labyrinthitis usually leaves permanent and profound hearing loss.
  • Hearing loss associated with viral labyrinthitis may recover. Disequilibrium and or positional vertigo also may be present long-term following resolution of the acute infection.
  • Permanent hearing loss occurs in 10-20% of children with meningitis.
  • Permanent hearing loss also occurs in approximately 6% of patients with herpes zoster oticus.

It is important:

• Not to miss a potentially life-threatening condition, such as meningitis, cerebrovascular ischemia, or brainstem tumor. Chronic or recurrent cases should be referred.
• To counsel patients not to drive or operate machinery when suffering from vertigo or taking medication for symptoms.