Labyrinthitis - Causes, Risk Factors, Pathophysiology, Types, Clinical manifestations, Diagnostic Evaluations and Management

Labyrinthitis is an inflammation and infection of the inner ear. It derives its name from the labyrinths that house the vestibular system. Clinically, this condition produces disturbances of balance and hearing to varying degrees and may affect one or both ears. The hallmark is vertigo (vertigo is a type of dizziness).

Causes and Risk Factors

Labyrinthitis usually follows an infection in another part of the body, such as acute otitis media or meningitis. Labyrinthitis is almost always caused by viral infection, but can rarely be caused by bacterial infection, head injury, neoplasm of the middle ear or cranial nerve VIII, after middle ear or mastoid surgery extreme stress, an allergy, drinking large amount of alcohol or as a reaction to a particular medication especially aspirin.

Labyrinthitis often follows an upper respiratory tract infection. Infection may also reach the inner ear via the bloodstream from elsewhere in the body. Both bacterial and viral labyrinthitis can cause permanent hearing loss, although this is rare.

Pathophysiology

The anatomic relationships of the labyrinth, middle ear, mastoid, and subarachnoid space are essential to understanding the pathophysiology of labyrinthitis. The labyrinth is composed of an outer osseous framework surrounding a delicate membranous network that contains the peripheral sensory organs for balance and hearing.

These sensory organs include the utricle, saccule, semicircular canals, and cochlea. Symptoms of labyrinthitis occur when infectious microorganisms or inflammatory mediators invade the membranous labyrinth and damage the vestibular and auditory end organs.

The labyrinth lies within the petrous portion of the temporal bone adjacent to the mastoid cavity and connects with the middle ear at the oval and round windows. The labyrinth maintains connections with the central nervous system and subarachnoid space by way of the internal auditory canal and cochlear aqueduct. Bacterial may gain access to the membranous labyrinth by these pathways or through congenital or acquired or acquired defects of the bony labyrinth. Viruses may spread to labyrinthine structures hematogenously or by way of the aforementioned preformed pathways.

TYPES OF LABYRINTHITIS

Diffuse Serous Labyrinthitis: It is a type of acute labyrinthitis that sometimes follows drug intoxication or overindulgence in alcohol. It can also be caused by allergy

Diffuse Suppurative Labyrinthitis: If the inflammatory process continues the exudate becomes purulent, then the condition is known as diffuse suppurative or purulent labyrinthitis. Destruction of soft tissue structures from the infection can cause permanent hearing loss

Circumscribed Labyrinthitis: In this type the bony capsule is eroded and membranous labyrinth is exposed (fistula formation). Labyrinthitis is localized to the area of the fistula only

 

Clinical Manifestations

• Extreme Vertigo and Dizziness (loss of balance and a sensation that either you or the room is spinning)
• Sensorineural hearing loss
  
• Aural fullness
  
• Tinnitus (Ringing in the ears)
  
• Difficulty focusing the eyes because of involuntary eye movements
  
• Otorrhea
  
• Otalgia
  
• Nausea or vomiting
  
• Fever
  
• Facial weakness or asymmetry
  
• Neck pain/stiffness
  
• Upper respiratory tract infection symptoms (preceding or concurrent)
  
• Cognitive symptoms such as memory/thinking problems
  
• Depression and anxiety
  

 

DIAGNOSTIC EVALUATIONS

A thorough medical history, including symptoms, past medical history, and medications, is essential to diagnosing labyrinthitis as the cause of the patient’s vertigo or hearing loss.

Laboratory Studies: No specific laboratory studies are available for labyrinthitis. Examine cerebrospinal fluid if meningitis is suggested. If a systemic infection is considered, blood cultures are indicated. Perform culture and sensitivitiy testing of middle ear effusions if present and select appropriate antibiotic therapy accordingly.

Otologic Examination: Perform an external inspection for signs of mastoiditis, cellutitis or prior ear surgery. Inspect the ear canal for otitis externa, otorrhea, or vesicles. Inspect the tympanic membrane and middle ear for the presence of perforation, acute otitis media.

Ocular Examination: Inspect the ocular range of motion and pupillary response. Perform a funduscopic examination to assess for papilledema. Observe for nystagmus (spontaneous, gaze-evoked, and positional). Warming and cooling the inner ear with water (caloric stimulation) to test eye reflexes.

Neurologic Examination: Perform a complete cranial nerve examination. Assess for balance using the Romberg test and tandem gait. Assess cerebellar function by performing finger-to-nose and heel-to-shin tests.

Imaging Studies: A CT scan is also useful to help rule out mastoiditis as a potential cause. MRI can be used to help rule out acoustic neuroma, stroke, brain abscess, or epidural hematoma as potential causes of vertigo and hearing loss.

Audiography: Persons with viral labyrinthitis have mild-to-moderate high-frequency SNHL in the affected ear, although any frequency spectrum may be affected.

Vestibular Testing: Persons with viral labyrinthitis have nystagmus with unilateral caloric vestibular paresis/hypofunction.

 

MANAGEMENT

• Vertigo can be treated with medications such a meclizine or scopolamine. Medications are only used short-term for balance trouble. They allow the brain to learn to adjust to the inner ear injury. Special exercises can often help speed and improve the brain’s ability to adjust.
• The initial treatment of viral labyrinthitis consists of bed rest and hydration. The antiviral drugs acyclovir, famciclovir, and valacyclovir shorten the duration of viral shedding and may prevent some auditory and vestibular damage.
  
• For bacterial labyrinthitis, broad-spectrum antibiotic antibiotic treatment is selected based on culture and sensitivity results.
  
• Patients with severe nausea and vomiting may benefit from intravenous fluid and antiemetic medications. Benzodiazepines (Diazepam or Lorazepam) are helpful as a vestibular suppressant.
  
• Corticosteroids reduce labyrinthine inflammation and prevent the sequelae of labyrinthitis due to infectious or inflammatory causes. Intratympanic steroids may be more effective than systemic steroids in the treatment of sudden hearing loss, either alone or in combination with systemic steroids
  
• Vestibular Rehabilitation Therapy: VRT is a highly effective way to substantially reduce or eliminate residual dizziness from labyrinthitis. Rehabilitation exercises can speed up. 
  

Labyrinthitis - Causes, Risk Factors, Pathophysiology, Types, Clinical manifestations, Diagnostic Evaluations and Management