Primary Secretory Otitis Media (PSOM)

in the Cavalier King Charles Spaniel

Primary Secretory Otitis Media (PSOM or P.S.O.M.), also known as "glue ear", has become more frequently diagnosed in Cavalier King Charles Spaniels recently. It consists of a highly viscous mucus plug which fills the dog's middle ear and may cause the tympanic membrane to bulge.

In a ten year study conducted in Sweden and reported in 2003, 61 cases of primary secretory otitis media were diagnosed in 43 Cavaliers.  Because the pain and other sensations in the head and neck areas, resulting from PSOM, are similar to some symptoms caused by syringomyelia (SM), some examining veterinarians have mis-diagnosed SM in Cavaliers which actually have PSOM and not SM.

What it is

The eustachian tube connects the middle ear to the back of the nose.  The tube serves to maintain equal air pressure both inside and outside of the middle ear, to allow the eardrums to vibrate properly.  The tube also allows fluid from mucous membranes in the middle ear to drain through the nose.  If the eustachian tube is not working properly, the air in the middle ear is absorbed, but it cannot be replaced, causing air pressure inside the middle ear to be lower than the air pressure outside, in the ear canal, creating a partial vacuum.  This difference in air pressure causes the mucous fluid to collect inside the middle ear.  The fluid then begins to become thicker and build up, becoming an ever-enlarging mucus plug.

In the 2003 Swedish study, conducted by Wiwian Stern-Bertholtz, MScVetMed, Lennart Sjöström, DVM DECVS, and Nils Wallin-Håkanson, DVM DACVO DECVO, they explain the condition technically as follows:

"The eustachian tube is kept closed by the surface tension caused by contact between air and mucus. A particular agent, identified as a combination of different phospholipids, decreases the surface tension in the eustachian tube of dogs, thus reducing the pressure needed to open the tube. When the tube is closed, the pressure in the middle ear is reported to become negative in relation to the pressure in the tube, which is equivalent to atmospheric pressure. This negative pressure, caused by lack of aeration, draws out the sterile transudate from the glandular tissues in the middle ear to the surface of the mucous membrane. The negative pressure remains and the process of accumulation of mucus carries on as long as the tympanic membrane is intact and the eustachian tube is closed. Failure to open the eustachian tube and thereby release the secretory products is believed to be the cause of secretory otitis media. An obstruction of the osseous part of the eustachian tube is reported to be the most common cause. In PSOM, the overfilling of the middle ear with mucus and the subsequent bulging of the tympanic membrane, and the pain and neurological signs that are common, indicate that the pressure within the middle ear is high rather than low, at least in the final part of the disease process."


The principal symptoms are moderate to severe pain in the head or neck, holding the neck in a guarded position, and tilting the head.  Other signs may include scratching at the ears, yawning excessively, crying out in pain, ataxia, facial paralysis, some loss of hearing, seizures, and fatigue.  These symptoms, in many cases, are very similar to those of syringomyelia and, to some extent, to those of progressive hereditary deafness. Therefore, the examining veterinarian should take care to consider these other possible causes of the dog's symptomatic behaviors.

Studies have concluded that brachycephalic dogs may be predisposed to this condition.


PSOM may be detected by veterinary neurology or dermatology specialists from either magnetic resonance imaging (MRI) or a computed tomography (CT) scan. Both require that the dog be under general anesthesia.  It also may be observed using an operating microscope with good lighting and at a suitable magnification.  If the case is severe enough that the dog's tympanic membrane is bulging, the condition may be visible on x-rays and diagnosed with an otoscope.  In extreme cases, the tympanic membrane may have ruptured and the mucus plug clearly seen.  Veterinary dermatologists in the United States may be located on the American College of Veterinary Dermatology website.


Treatment consists of performing a myringotomy, making a small cut in the eardrum to remove the mucus plug from the middle ear, followed by flushing the middle ear.  Topical and/or systemic corticosteroids and antibiotics then are administered.  The procedure may have to be repeated, in some cases several times, depending upon how the dog responds.

Current Research

Drs. Andrew Hillier and Lynette Cole of the Dermatology Service at the Ohio State University's veterinary teaching hospital are conducting research into the prevalence of PSOM in the Cavalier King Charles Spaniel breed in the United States, as well as the mode of inheritance, data about the clinical signs of the disorder, alternative methods of diagnosing it, and methods of treatment.  The doctors are seeking Cavaliers to participate in this study.  They may be reached by telephone at 614-292-3551 and email Dr. Hillier at and Dr. Cole at and website  The American Cavalier King Charles Spaniel Club's charitable trust has contributed a grant to help underwrite this project.  Donate to the ACKCSC's Charitable Trust!

Veterinary Resources:

Insertion of a transtympanic ventilation tube for the teatment of otitis media with effusion. Cox C,J., Slack R.W.T., Cox G.J. J Small Animal Practice,1989, 30, 517-519

Primary secretory otitis media in the Cavalier King Charles spaniel: a review of 61 cases. Stern-Bertholtz W.; Sjöström L.; Wallin Håkanson N.  J Small Animal Practice,30 June 2003, 44(6): 253-256(4).

Material in the middle ear of dogs having magnetic resonance imaging for investigation of neurologic signs. Owen MC, Lamb CR, Targett MP. Vet. Radiology & Ultrasound, Mar 2004, 45(2):149-155.

Primary secretory otitis media in Cavalier King Charles spaniels. Clare Rusbridge. J Small Anim Pract. 2004 Apr; 45:222

Primary Secretory Otitis Media (Glue Ear). Hillier A., Cole L. CKCSC,USA Bulletin, Fall/Winter 2005:16.

Diagnosis and management of otitis media. Thomas, Randall C. Proceedings, No. Am. Vet. Conf., Vol. 20, Jan. 2006: 979.