Labyrinthitis is inflammation of the membranous labyrinth.
Labyrinthitis can be divided according to aetiology.
Labyrinthitis is a potential complication of acute otomastoiditis with spread of infection or of toxins from the middle ear to the inner ear via either the round window or oval window. It is therefore typically unilateral. Typically patients will have sensory neural hearing loss (SNHL) and vertigo. When SNHL is fluctuating, a perilymphatic fistula should be suspected - typically seen in the setting of coexistant cholesteatoma or previous ossicular surgery (e.g. prosthetic stapedectomy)
When toxins only, then the term "acute toxic labyrinthitis" or ""acute serous labyrinthitis" is used. MRI may be negative.
When bacteria actually enter the labyrinth, then "acute suppurative labyrinthitis" applies, and MRI is positive.
Meningitis, most frequently bacterial, typically causes bilateral labyrinthitis, and is seen most frequently in children. It is the most common cause of acquired deafness. Spread is thought to occur through the lateral aspect of the internal acoustic meatus, into the cochlea. In HIV immunocompromised patients cytomegalovirus (CMV) has also been described.
Viral labyrinthitis is common, with respiratory tract infections being most frequent. Whether these spread haematogenously or via the middle ear is debatable. Measles and mumps are said to be haematogenously spread to the labyrinth (although the two references cited disagree). It is a much less frequent cause of labyrinthitis. Syphilis involvement of the labyrinth, known as otosyphilis is also re-emerging as a result of increased numbers of immunocompromised patients.
Infrequent cause, associated with Takayasu arteritis.
Prior to MRI no imaging findings were described, however, now enhancement of the labyrinth on post contrast T1WI enable the diagnosis to be made with confidence.
Inner ear pathology
inner ear anatomy
- enlarged vestibular aqueduct
- semicircular canal dysplasia
- classification of cochlear anomalies
- infection and inflammation
- trauma and miscellaneous
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