Primary Secretory Otitis Media (PSOM)
in the Cavalier King Charles Spaniel
Primary Secretory Otitis Media (PSOM), also known as "glue ear" or Middle Ear Effusion*, 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.
* Other scientific names for PSOM include Otitis Media with Effusion (OME).
PSOM has been reported almost exclusively in cavaliers, and it may affect over half of them. 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 (tympanic membranes) 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 a ten year study conducted in Sweden and reported in 2003, 61 cases of primary secretory otitis media were diagnosed in 43 cavaliers. In that 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."
In a 2010 study, UK veterinary researchers examined MRI scans of the skulls of 34 cavalier King Charles spaniels, each of which had been scanned twice over periods from one month to 46 months. They concluded in their report that PSOM is a progressive condition in the CKCS and can progress from none to unilateral or bilateral; or from unilateral to bilateral on sequential scans, and that PSOM is an acquired condition in the CKCS and will not resolve spontaneously once it has developed. However, a few breeders report that second MRI scans of their PSOM-affected cavaliers show that the PSOM has disappeared without treatment.
Symptoms
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,
drooping ear or lip, inability to blink an eye, rapid eyeball movement, 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.
In a 2009 UK study of 23 cavaliers with PSOM, the researchers (who choose to refer to the disorder as middle ear effusion) tested the dogs' hearing with the Brainstem Auditory Evoked Reponses (BAER) test and found that, even though the dogs' owners considered their dogs' hearing capabilities to be normal, the BAER tests demonstrated a conductive hearing loss in ears affected by middle ear effusion (PSOM). See same study in 2011 Veterinary Journal.
Studies have concluded that brachycephalic dogs may be predisposed to this condition.
Diagnosis
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.
Possible alternative instruments for diagnosis of PSOM include impedance audiometry, pneumotoscopy, tympanic bulla ultrasonography, and the brain-stem auditory evoked response test (BAER). Veterinary dermatologists in the United States may be located on the American College of Veterinary Dermatology website.
Treatment
Treatment traditionally has consisted of performing a myringotomy, making a
small cut in the eardrum (tympanic membrane), followed
by flushing the middle ear to force out the mucus plug. The photograph at right
is of a myringotomy in progress. The ring in the middle of the photo is
the eardrum. The tube tip at the top is the device used to flush the inner ear
and force out the mucus. You
may watch a close up video of a myringotomy actually being performed on a
cavalier named Baylee on
YouTube here.
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. In a
March 2008 study conducted by Australian
researchers, they inserted tympanostomy tubes within the myringotomy incision in
order to provide continual tympanic cavity ventilation and drainage. They found
that in the cases of the three CKCSs which they operated on, all three dogs were
asymptomatic at the time of follow-up, 8, 6 and 4 months later, and they
concluded that the use of tympanostomy tubes may be an acceptable alternative to
repeated myringotomy.
An alternative procedure is a ventral bulla osteotomy, which involves making an incision on the under side of the neck behind the jaw bone. The middle ear -- the bulla -- then is exposed and is opened.
Some specialist veterinarians have been prescribing N-Acetyl-L-Cysteine (NAC), a mucolytic -- mucus thinning agent or expectorant -- for cavaliers with PSOM, following surgeries.
Current Research
4May 2012: OSU’s Dr. Cole needs normal hearing CKCSs for BAER tests, CT scans, and MRI scans. Dr. Lynette Cole of Ohio State University’s Veterinary Dermatology and Otology Service needs cavaliers between the ages of 1 to 2 years old with no history of hearing loss for a two-day evaluation by BAER hearing tests, computed tomography (CT) scans, and MRI scans. The study pays for all testing. She writes:
“In the dog breed Cavalier King Charles Spaniel (CKCS), hearing disorders may be due to conductive hearing loss, which may occur with primary secretory otitis media (PSOM), or due to sensorineural hearing loss, which may occur when there is damage or an abnormality of the sensory cells in the cochlea or the auditory nerve.”
If you are interested in possibly enrolling your cavalier in the study, contact Dr. Cole at telephone number 614-292-3551 or email cole.143@osu.edu A pedigree is required for entry into the study, but will be kept confidential, as will all test results. Details of the study will be given individually on the phone or via email.
4February
2012: Bluestone is still monkeying with the CKCS.
Dr. Charles D. Bluestone, renowned
self-styled chimpanzee descendant, is still monkeying with the Eustachian tubes
of our cavaliers. (See December 2010 entry
and November 2011 entry.) In
a brief resume released by the University of Pittsburgh Medical Center, he
states:
“Another ongoing research project involves a potential animal model, Cavalier King Charles Spaniel, which has a greater than 50% incidence of chronic otitis media effusion. Research being conducted with his colleagues in this animal involves histopathology of the middle-ear cleft in cadavers, and Eustachian tube function tests in live animals, conducted at the Ohio State University School of Veterinary Medicine in Columbus Ohio. ”
So now he tells us that the prevalence of PSOM in the CKCS is "greater than 50%". Each time he makes a public statement, the ante goes up, without ever providing any statistical data to support his assertions. This is much like the non-existent data supporting his claim to be descended from chimpanzees.*
* Man's alleged descent from chimpanzees has long been rejected by evolutionists and creationists, combined.
4November 2011:
Bluestone keeps mucking up research of PSOM in the cavalier. In a video released in
November 2011 by the University of Pittsburgh Medical Center,
Dr. Charles D. Bluestone, noted
self-styled chimpanzee descendant, insists he
still is researching PSOM in the cavalier King Charles spaniel. He
claims to be basing his research on what in fact is the patently false premise that the cavalier
"has been bred over 300 years to have a short snout." He goes on:
"So how did the Cavalier King Charles develop chronic persistent [sic] secretory otitis media? Their short snout changed the palatal anatomy. So the question is does the middle ear effusion with this very thick mucus in that Cavalier, it causes trouble by the way with hearing loss, have a consequence? There are two muscles that are related to this issue, the muscles that come from the palate, the tensor veli palatini, TVP, and the LVP muscles are altered causing the eustachian tube dysfunction, that’s our hypothesis. It’s a current research project which we are undergoing now."
As noted above, Dr. Bluestone also mis-names the disorder he claims to be researching. PSOM stands for "primary secretory otitis media". He oddly and repeatedly calls it "persistent" secretory otitis media. So he does not even know the name of the disorder, and he is under the abject mistaken belief that the cavalier "has been bred over 300 years to have a short snout" when, in fact, the breed was created less than 85 years ago and has been bred to have a longer snout. He also has upped his stated prevalence of PSOM in the breed from "up to 40%" to a flat "50%", all without providing any statistical data to support either assertion. Once again, we can only hope that this misguided gentleman's federal funding runs out as quickly as possible.
4December 2010: Pitt Medical Center's self-styled chimpanzee descendants muck up PSOM study of cavaliers on taxpayers' dime. Drs. Charles D. Bluestone (left), a human ear, nose, and throat specialist, and J. Douglas Swarts
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The authors were compelled to discuss PSOM in the cavalier because the main hypothesis of their article is, as they contradictorily put it:
"We posit that the high prevalence* of middle-ear disease is most likely restricted to humans, in contrast to other wild species, because the associated hearing loss would have reduced the fitness of affected individuals as a result of predation."
* They state elsewhere in the report that the prevalence of PSOM in the CKCS is "up to 40%". They do not provide any statistical data to support that assertion.
We suppose that if one must "publish or perish" (and with a taxpayer-funded grant, to boot), these two had to come up with something no one else would dare think to write about. But how do they get around PSOM in the CKCS? They do not. The very existence of PSOM in the cavalier belies their "posit" above, unless one concludes that, from its gentle nature, the cavalier should not be considered a "wild species" while the human apparently is. Anyway, these two also cannot overcome the fact that PSOM is essentially unique to the cavalier, but many other canine breeds are brachycephalic, and some even more so. There is a little value in their article, however, because Dr. Lynette Cole provided them with some quite accurate (albeit not new) information about PSOM in the cavalier, which is summarized below. Dr. Cole's input makes that part of the article worth reading.
But the scariest part of the article is their statement (threat?) near the end that:
"The underlying pathogenesis of the Cavalier's ME disease is currently under investigation in our laboratory."
We sure hope not. Leave that to Dr. Cole, please.
4September 2010: UK researchers find PSOM (OME) to be progressive. A team of UK veterinary researchers (S.J. McGuinness, E.J. Friend, C. Rusbridge, P. Knowler and N. D. Jeffery) examined MRI scans of the skulls of 34 cavalier King Charles spaniels, each of which had been scanned twice over periods from one month to 46 months. They concluded in their report that PSOM (OME) is a progressive condition in the CKCS and can progress from none to unilateral or bilateral; or from unilateral to bilateral on sequential scans, and that OME is an acquired condition in the CKCS and will not resolve spontaneously once it has developed.
4July 2010: UK researchers find association between PSOM and brachycephalic conformation in cavaliers. In their report, they find, "in CKCS, greater thickness of the soft palate and reduced nasopharyngeal aperture are significantly associated with OME [otitis media with effusion, meaning PSOM]."
4March
2010: Ohio State Vet School needs cavalier cadavers for
Eustachian tube study. Dr. Lynette Cole (right) of the Dermatology
Service at the Ohio State University's veterinary teaching hospital is seeking
deceased cavaliers and candidates for euthanasia, with or without PSOM, for a
study of the muscles which open the Eustachian tube. The study will include
dissections of the Eustachian tube, its muscles, and the inner ear, and imaging
with advanced MRI. The veterinary research is in conjunction with an OSU medical
school otolaryngology study of secretory otitis media in humans. The
otolaryngologists are looking for abnormalities within the muscles that open
Eustachian tube, that prevent secretions from being removed from the tube,
thereby causing a build-up of the mucus causing secretory otitis media.
Dr. Cole asks: "If at all possible, I would prefer to have the cavalier brought
to me at the Ohio State University for euthanasia. Please contact me prior to
make proper arrangements. If that is not possible, please have your veterinarian
refrigerate the dog after euthanasia, and then have your veterinarian contact
me." Contact Dr. Cole at telephone number 614-292-3551, email
cole.143@osu.edu
4September 2009: Drs. Andrew Hillier and Lynette Cole and others 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 (CT scan, tympanic bulla ultrasonography, BAER test, impedance audiometry, otoscopic examination, and pneumotoscopy), and methods of treatment. The diagnostic tests will be compared to the results of the CT scan for the diagnosis of PSOM, to determine which test or group of tests are the best to use for the diagnosis of PSOM.
In their August 2007 interim report to the American Cavalier King Charles Spaniel Club's charitable trust, Dr. Cole reports that 75 Cavaliers are to be "enrolled, placed under general anesthesia, and the following diagnostics performed: CT scan, tympanic bulla ultrasonography, BAER test, impedance audiometry, otoscopic examination, and pneumotoscopy. If the CT scan is suggestive of otitis media (i.e. a soft tissue density present in the tympanic bulla-the bony part of the middle ear), then a myringotomy (incision into the ear drum) will be performed and the mucus flushed out of the middle ear. Cytology and bacterial cultures will be performed on the mucus from the middle ear. A BAER and CT scan will be performed post-middle ear flush on those CKCS with PSOM."
Dr. Cole states that as of August 2007, 13 CKCS have been examined, with ages ranging from 5 months to 9 years of age. Of those, 8 (62%) cavaliers had PSOM (6 had PSOM in both ears, 2 had PSOM in one ear) and 5 (38%) did not have PSOM.
The doctors still are seeking cavaliers to participate in this study. They may be reached by telephone at 614-292-3551 and email Dr. Hillier at hillier.4@osu.edu and Dr. Cole at cole.143@osu.edu and website www.vet.ohio-state.edu/876.htm The American Cavalier King Charles Spaniel Club's charitable trust has contributed a grant to help underwrite this project.
Related Links
Syringomyelia
Deafness
Brachycephalic Airway
Obstruction Syndrome (BAOS)
American College of Veterinary
Dermatology
Dr. Lynette Cole
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.Sm.Anim.Prac., Sept. 1989;30(9):517-519. Quote: "In this paper, a case of otitis media with effusion ('glue ear') is described in a Cavalier King Charles spaniel. Its presentation, diagnosis and surgical management by the insertion of a trans-tympanic ventilation tube (grommet) is discussed."
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). Quote: "Sixty-one episodes of primary secretory otitis media (PSOM) were diagnosed in 43 Cavalier King Charles spaniels over a 10-year period. The principal findings were signs of moderate to severe pain localised to the head or cervical area, and/or neurological signs. Diagnosis was made by examination of the tympanic membrane and middle ear with the aid of an operating microscope under general anaesthesia. A bulging, but intact, tympanic membrane was found in most cases. Following myringotomy, a highly viscous mucus plug was found filling the middle ear. Treatment, consisting of removal of the mucus plug, flushing of the middle ear, and local and systemic medical therapy, had to be repeated between one and five times. The prognosis was good in all cases. PSOM is an important differential diagnosis in Cavalier King Charles spaniels with signs of pain involving the head and neck, and/or neurological signs."
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. Quote: "The aim of this study was to determine the prevalence and potential significance of finding material in the middle ear of dogs having magnetic resonance (MR) imaging. Of 466 MR studies reviewed, an increased signal was identified in the tympanic bulla in 32 (7%) dogs. Cavalier King Charles spaniels, Cocker spaniels, Bulldogs, and Boxers were over-represented compared to the population of dogs having MR imaging. Five (16%) dogs had definite otitis media and one (3%) had a meningioma invading the middle ear. Of the remaining dogs, 13 (41%) had possible otitis media and 13 (41%) had neurologic conditions apparently unrelated to otitis media. The most common appearance of material in the middle ear was isointense in T1-weighted images and hyperintense in T2-weighted images. There was no apparent correlation between the signal characteristics of the material and the diagnosis. Enhanced signal after gadolinium administration was observed affecting the lining of the bulla in dogs with otitis media and in dogs with unrelated neurologic conditions. In dogs without clinical signs of otitis media, finding an increased signal in the middle ear during MR imaging may reflect subclinical otitis media or fluid accumulation unrelated to inflammation. Brachycephalic dogs may be predisposed to this condition."
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.
Contrast-enhanced Computed Tomographic Imaging of the Auditory Tube in Mesaticephalic Dogs. Lynette K. Cole, Valerie F. Samii. Vet. Radiology & Ultrasound, Vol 48(2): 125-128, Mar 2007. Quote: "Auditory tube dysfunction has been speculated as the cause of primary secretory otitis media (PSOM), reported recently in the Cavalier King Charles spaniel. A simple, noninvasive technique is needed for evaluation of the canine auditory tube."
The method of application and short term results of tympanostomy tubes for the treatment of primary secretory otitis media in three Cavalier King Charles Spaniel dogs. Corfield GS, Burrows AK, Imani P, Bryden SL. Aust Vet J. 2008 Mar;86(3):88-94. Quote: "Primary secretory otitis media is an uncommon disease affecting predominantly Cavalier King Charles Spaniel dogs. Current treatment recommendations include repeated manual removal of the mucoid effusion from the tympanic cavity through a myringotomy incision and topical or systemic corticosteroids. The aim of this study was to assess the efficacy of tympanostomy tubes to provide continual tympanic cavity ventilation and drainage for the treatment of primary secretory otitis media in three dogs. Tympanostomy tubes were placed within a myringotomy incision in the pars tensa with the aid of an operating microscope. Clinical signs resolved rapidly in all cases following the procedure and all cases were asymptomatic at the time of follow-up, 8, 6 and 4 months later. Results of this study indicate that tympanostomy tubes provide continual tympanic cavity ventilation and drainage and may be an acceptable alternative to repeated myringotomy for the treatment of primary secretory otitis media."
A Practical Guide to Canine and Feline Neurology. Curtis W. Dewey. John Wiley & Sons; 2008; 273.
Effect of Middle Ear Effusion On The Brainstem Auditory Response Of Cavalier King Charles Spaniels. T. R. Harcourt-Brown, J. E. Parker, N. D. Jeffery. 22nd ESVN Annual Symposium, Sept. 2009; J Vet Intern Med, Jan/Feb 2010;24(1):242. Quote: "The purpose of this study was to investigate the effect of middle ear effusion on the Brainstem Auditory Evoked Reponses (BAER) of [23] cavalier king charles spaniels. BAER’s were obtained from dogs following Magnetic Resonance (MR) imaging screening for syringomyelia. Middle ear effusion was diagnosed if the auditory bulla was completely filled with material that was isontinense to brain parenchyma on T1 weighted images and hyperintense on T2 weighted images. Dogs with otitis externa were excluded from the study. BAER’s were obtained at sound intensities ranging from 10 to 100 dB nHL (normal hearing level). The BAER threshold was determined for each ear as the last trace that showed a recognisable wave V. The latency of wave V was recorded for each intensity where it was identified and the interwave latency between waves I and V was calculated at 90 dB nHL. ... Each dog’s hearing was considered normal by their owner. The median BAER threshold was 60 dB for ears with effusion and 30 dB for those without. The proportion of ears with abnormal BAER thresholds (4 30 dB nHL) was greater for ears with effusion (11/16) than those without (8/30) (Fishers exact test, p = 0.011). Severity of hearing loss for ears with effusion was calculated by linear regression of wave V latencies to be 23 dB (95% confidence 18 to 31 dB). The mean interwave latency between waves I and V at 90 dB for ears with and without effusion was not significantly different (Students t-test, p > 0.05). These data show that middle ear effusion is associated with conductive hearing loss of 21–30 dB in affected ears."
Relationship between pharyngeal conformation and otitis media with effusion in Cavalier King Charles spaniels. Hayes GM, Friend EJ, Jeffery ND. Vet Rec. 2010 Jul 10;167(2):55-8. Quote: "Otitis media with effusion (OME) is a common incidental finding in otherwise normal Cavalier King Charles spaniels (CKCS). ... The incidence of OME as an incidental finding in a sample of 68 CKCS undergoing MRI was 54 per cent in this study, which is comparable to previously reported incidences of 47 per cent ... and 28 per cent ... in this breed. The CKCS in this study were reported to be ‘clinically normal’ by their owners, who did not report clinical signs of neurological disease or otitis in these dogs. ... In this study, measurements made on MRI were used to determine whether there was an association between OME and brachycephalic conformation. The results confirm that association and also demonstrate that, in CKCS, greater thickness of the soft palate and reduced naso-pharyngeal aperture are significantly associated with OME. ... An overlong soft palate has long been accepted as contributing to the [brachycephalic airway] syndrome, but more recently the importance of abnormally thick soft palates has also been recognised ... [B]rachycephalic airway syndrome may occur as a consequence of the selection for morphological neotony in this breed ... Although the aetiology is probably multifactorial, OME is more frequently found in patients with more severe anomalies of nasopharyngeal conformation. Changes within the nasopharynx may impair auditory tube drainage. ... These results suggest that auditory tube dysfunction and OME may represent a previously overlooked consequence of brachycephalic conformation in dogs."
Breed Predispositions to Disease in Dogs & Cats (2d Ed.). Alex Gough, Alison Thomas. 2010; Wiley-Blackwell Publ. 53.
Progression of Otitis Media with Effusion in the Cavalier King Charles Spaniel. S.J. McGuinness, E.J. Friend, C. Rusbridge, P. Knowler and N. D. Jeffery. Abstract at 23d ECVN symposium, Sept. 2010. Investigation of 34 MRI scans of CKCS having 2 scans as part of CMSM screening. Interpreted by the same author (S.J. McGuinness). The scans were classified according to negative, unilateral or bilateral OME based on the absence or presence of hyperintense material on T2 weighted MRI images. ... A total of 34 dogs had 2 MRI scans a median of 20 months apart (range 1 to 46); the incidence of OME at the first MRI was 32%, which increased to 50% at the time of the second MRI, which is comparable with previous studies. At the time of the first MRI, 23 CKCS had no effusion, 10 had unilateral effusion and 1 had bilateral effusion. By the second MRI, 3 cases had progressed from unilateral to bilateral; 5 had progressed from no effusion to effusion being present (4 negative to unilateral, 1 negative to bilateral) and 8 of those having effusion at the first scan remained the same. No cases that had OME at the first MRI had resolved at the time of the second MRI and no case had clinical signs that could be associated with OME. This study demonstrates that OME is a progressive condition in the CKCS and can progress from absent to unilateral or bilateral; or from unilateral to bilateral on sequential scans. It also suggests that OME is an acquired condition in the CKCS and will not resolve spontaneously once it has developed."
Human evolutionary history: Consequences for the pathogenesis of otitis media. Charles D Bluestone, J. Douglas Swarts. Otolaryngology -- Head & Neck Surgery; Dec 2010; 143(6):739-744. Quote: "Among veterinarians, chronic ME effusion (termed primary secretory otitis media) is a well-known disease in the Cavalier King Charles Spaniel. It has been reported to be present in up to 40 percent of these animals. The effusion is mucoid and fills the entire ME. Diagnosis is made by operating microscopic examination, computed tomography scanning, or magnetic resonance imaging (MRI), and has been confirmed at the time of myringotomy. Myringotomy and tympanostomy tube placement has been recommended for treatment. This breed has been artificially selected to have a shortened front-to-back diameter of the skull, a shape termed brachycephaly, which arises due to premature fusion of the coronal sutures. The term neotenous (retention of juvenile characteristics into adulthood) is also appropriate for these breeds. The Cavalier snores habitually like other brachycephalic dogs, including the English Bulldog, a breed that has been reported to be the only animal known to develop obstructive sleep apnea. The snoring is undoubtedly secondary to its constricted pharynx, a consequence of the shortening of the snout. ... Figure 5 compares the head shape of a Cavalier King Charles Spaniel, with its extremely short face, to that of a Golden Retriever, which has a classic prognathic snout. The Cavalier King Charles Spaniel is an animal model of chronic OM with effusion. It has been “artificially selected” (Charles Darwin's term) for its short snout and globular head, but an unintended consequence of breeding for this characteristic is the propensity for chronic OM with effusion. In a recently reported study using MRI, veterinarians from England found that not only did the Cavalier have OM (54%), but another brachycephalic breed, the Boxer, also had ME disease (32%), which was not present in Cocker Spaniels, a mesaticephalic breed. The investigators suggested that the reduced nasopharyngeal space in the Cavalier and Boxers, when compared with the Cocker Spaniel, predisposed them to OM. It might be that one or both of the paratubal muscles is dysfunctional due to the abnormal palatal anatomy in these breeds and is the cause of their OM. The underlying pathogenesis of the Cavalier's ME disease is currently under investigation in our laboratory. Analogously, one could speculate that with the loss of their prognathic face, humans became susceptible to OM, an unintended consequence of “natural selection” for another adaptation (again, Darwin's term), as described above."
Middle ear effusions in dogs: An incidental finding? H.A. Volk, E.S. Davies. Vet.J. June 2011; 188(3):256-257.
Effect of middle ear effusion on the brain-stem auditory evoked response of Cavalier King Charles Spaniels. Thomas R. Harcourt-Brown, John E. Parker, Nicolas Granger, and Nick D. Jeffery. Vet.J. June 2011; 188(3):341-345. Quote: "Brain-stem auditory evoked responses (BAER) were assessed in 23 Cavalier King Charles Spaniels with and without middle ear effusion at sound intensities ranging from 10 to 100 dB nHL. Significant differences were found between the median BAER threshold for ears where effusions were present (60 dB nHL), compared to those without (30 dB nHL) (P = 0.001). The slopes of latency–intensity functions from both groups did not differ, but the y-axis intercept when the x value was zero was greater in dogs with effusions (P = 0.009), consistent with conductive hearing loss. Analysis of latency–intensity functions suggested the degree of hearing loss due to middle ear effusion was 21 dB (95% confidence between 10 and 33 dB). Waves I–V inter-wave latency at 90 dB nHL was not significantly different between the two groups. These findings demonstrate that middle ear effusion is associated with a conductive hearing loss of 10–33 dB in affected dogs despite the fact that all animals studied were considered to have normal hearing by their owners."
