Labyrinthitis ossificans associated with sensorineural deafness.

A 14-year-old boy presented with right-sided sensory deafness and recurrent otitis media. Computed tomography (CT) of the right ear revealed that the cochlea was obliterated and the vestibule was partially obliterated (figure 1, A). CT of the left ear showed that it was normal (figure 1, B). Magnetic resonance imaging (MRI) of the right ear demonstrated a complete obliteration of the membranous labyrinth (figure 2). These findings indicated a diagnosis of right-sided labyrinthitis ossificans.

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Subsequent treatment of the labyrinthitis ossificans was conservative. A cochlear implantation was not performed, and the deafness did not improve.

Labyrinthitis ossificans involves the formation of novel bone that fills the normally patent cochlear and vestibular lumina. Labyrinthitis ossificans is an end-stage sequela to purulent labyrinthitis. This condition is associated with profound deafness and a loss of vestibular function.

The most common cause of labyrinthitis ossificans is suppurative labyrinthitis secondary to bacterial infection of the inner ear. The infection can reach the inner ear via a tympanogenic (most common), meningogenic, or hematogenic route. (2) In bacterial meningitis, the infection spreads to the inner ear via the subarachnoid spaces (e.g., the cochlear aqueduct and the internal auditory canal). Chronic otitis media can cause labyrinthitis via either the oval or round window.

The cells and mechanisms responsible for the ossification remain unclear. Paparella and Sugiura (1) identified three characteristic stages of the evolution of labyrinthitis ossificans--acute, fibrous, and ossifying:

* The acute stage is characterized by purulence that fills the perilymphatic spaces and spares the endolymphatic space. Discharge of serofibrinous exudate ensues.

* The fibrous stage is marked by fibroblastic proliferation within the perilymphatic spaces. This proliferation begins approximately 2 weeks following the onset of infection. Angiogenesis is also present.

* The ossifying stage is characterized by bone formation, which can develop in the basal turn of the cochlea as early as 2 months after the onset of infection.

Cephalosporins are considered to be the first-line antibiotic agents for the treatment and prevention of both meningogenic labyrinthitis and labyrinthitis associated with acute or chronic otitis media. (3) In addition, dexamethasone has been described as beneficial as a means of preventing deafness in infants and children with bacterial meningitis. (4)

Radiographic documentation of labyrinthitis ossificans is possible on both CT and MRI. CT detects ossification within the cochlea during the later stage of the process; it may not detect early ossification. (5) High-resolution, fast spin-echo T2-weighted MRI of the temporal bone is helpful in identifying cochlear soft-tissue abnormalities and residual cochlear patency. (6)

The clinical significance of identifying labyrinthitis ossificans as well as its stage increased dramatically after the cochlear implant was introduced. Because the site of entry of the electrode array is the scala tympani of the basal turn of the cochlea, local ossification can interfere with the full insertion and optimal performance of the implant. In fact, labyrinthitis ossificans was once considered to be a relative contraindication for cochlear implantation of a multichannel device. However, the development of new surgical techniques has allowed surgeons to remove connective tissue and bone at the basal turn of the cochlea; as a result, complete electrode insertion can now be accomplished. Moreover, in a patient with a totally obliterated cochlea, the number of intracochlear electrodes can be increased by implanting a double-array device. (7-9)

References

(1.) Paparella MM, Sugiura S. The pathology of suppurative labyrinthitis. Ann Otol Rhinol Laryngol 1967;76:554-86.

(2.) Bhatt S, Halpin C, Hsu W, et al. Hearing loss and pneumococcal meningitis: An animal model. Laryngoscope 1991;101(12 Pt 1): 1285-92.

(3.) Sun AH, Parnes LS, Freeman DJ. Comparative perilymph permeability of cephalosporins and its significance in the treatment and prevention of suppurative labyrinthitis. Ann Otol Rhinol Laryngol 1996;105:54-7.

(4.) Lebel MH, Freij BJ, Syrogiannopoulos GA, et al. Dexamethasone therapy for bacterial meningitis. Results of two double-blind, placebo-controlled trials. N Engl J Med 1988;319:964-71.

(5.) Seicshnaydre MA, Johnson MH, Hasenstab MS, Williams GH. Cochlear implants in children: Reliability of computed tomography. Otolaryngol Head Neck Surg 1992;107:410-17.

(6.) Arriaga MA, Carrier D. MRI and clinical decisions in cochlear implantation. Am J Otol 1996;17:547-53.

(7.) Cohen NL, Hoffman R, Waltzman S. Electrode insertion in the totally obstructed cochlea. Presented at the Third International Cochlear Implant Conference; April 1993; Innsbruck, Austria.

(8.) Eisenman DJ, Ashbaugh C, Zwolan TA, et al. Implantation of the malformed cochlea. Otol Neurotol 2001;22:834-41.

(9.) Lenarz T, Lesinski-Schiedat A, Weber BP, et al. The nucleus double array cochlear implant: A new concept for the obliterated cochlea. Otol Neurotol 2001;22:24-32.