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CASE REPORT: Primary Sectetory Otitis Media in a Cavalier King Charles Spaniel

History

A three-year-old, female (n) Cavalier King Charles Spaniel presented for investigation of sudden onset hearing loss of five months duration.  No other signs of middle ear disease had been noted by the owners or the referring veterinarians. Radiographs of the bulla, prior to referral were inconclusive and there had been no response to antibiotics, ear flushing and topical medication.

Clinical Findings

On presentation she was very bright. General physical examination was unremarkable except for deafness and some pain on deep palpation of the ears. Otoscopic examination of the ears revealed a small amount of wax in front of the tympanic membrane in the right ear.  The left was slightly opaque but not obviously bulging.

fig. 1a - transverse T2W MRI scan of bullae - high signal indicative of fluid accumulation seen in both bullae

MRI scans of the ears (fig. 1a – normals fig. 1b for comparison) showed fluid accumulation in both bulla, visible on both T1W and T2W scans. There was also an incidental finding of Chiari malformation present in the skull but no syrinx was evident in the area of spinal cord examined.

Treatment

fig.2 - aspirates from each bulla

Bilateral myringotomy was performed and the bullae were flushed with sterile saline; large amounts of yellow tinged mucus (fig. 2) were removed from both bulla and sent for cytology and bacteriology.

The dog was treated post operatively with meloxicam and amoxiclav pending culture results. The owners were contacted one week after surgery and reported an improvement in the dog’s hearing.

Microscopy showed a moderate amount of amorphous material together with low numbers of RBCs without an increase in WBCs. There was also a small number of columnar/spindloid cells present consistent with lining origin. No malignant cells or organisms were identified. Aerobic and anaerobic culture showed no growth after 48 hours.  These findings were consistent with primary secretory otitis media (PSOM).

Discussion

fig.1b - transverse T2W MRI scan of normal dog showing low signal intensity with air-filled bullae

PSOM can cause deafness, neck pain and vestibular disease.  It occurs predominantly in Cavalier King Charles Spaniels, and should be considered as a differential diagnosis along with syringomyelia, cervical disc disease and progressive hereditary deafness.

The aetiology is thought to be obstruction of the osseous part of the Eustachian tube secondary to congenital shortening of the skull.  As the function of the Eustachian tube is to equalise pressure between the pharynx and the middle ear, its blockage will result in negative pressure developing inside the bulla.  This in turn, draws out sterile transudate from the glandular tissues of the middle ear which build up to result in a loss of hearing acuity and other signs of middle ear disease.

Diagnosis of PSOM can be challenging. In one report1 an operating microscope was used to examine the tympanic membrane as it can be difficult to accurately assess opacity of the tympanic membrane or changes in pressure with an auroscope.  In this case, MRI clearly revealed bilateral fluid accumulation in the bullae.  When presenting signs include head and neck pain, this imaging modality is invaluable in differentiating PSOM from syringomyelia secondary to Chiari malformation.

Treatment of PSOM is surgical; myringotomy with subsequent flushing of the bulla is the standard recommendation.   In addition, steroids have reportedly been used in conjunction with lavage of the bullae.  In some cases, repeated surgeries may be required as the underlying abnormality leads to a potential recurrence of signs.

1.  Stern-Bertholtz W., Sjostrom L. & Wallin Hakanson N. (2003) Primary secretory otitis media in the Cavalier King Charles spaniel: a review of 61 cases.  Journal of Small Animal Practice 44 253-256