glue ear, otitis media with effusion

häufige Diagnose bei Cavalier King Charles Spaniels

muköser Plug der das Mittelohr anfüllt

It consists of a highly viscous mucus plug which fills the dog’s middle ear and

may cause the tympanic membrane to bulge. The mucus has also been referred to as

“hyperintense material “.

PSOM has been reported almost exclusively in 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 may have mis-diagnosed SM in

cavaliers which actually have PSOM and not SM. Other breeds in which PSOM has been

diagnosed are boxers, dachshund, and shih tzu.

What it is

The cause of PSOM is unknown. Dr. Lynette Cole reports that it is speculated to be due

to a dysfunction of the middle ear or the Eustachian (auditory) tube: either (a) the increased

production of mucus in the middle ear, or (b) decreased drainage of the middle ear through the

auditory tube, or © both.

The auditory 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, Lennart Sjöström, and Nils Wallin-Håkanson, 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 PSOM mucus plugs removed from cavalier. Downs

Veterinary Practice, Bristol, UK. http://www.downsvets.co.uk/the Eustachian tube of

Page 2 of 6

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. “ Photo above shows mucus plugs removed from a cavalier. Courtesy,

Downs Veterinary Practice, Bristol, UK.

In a 2010 study (and a 2013 report of the same 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.

Relation to Other Disorders

In a 2010 report, UK researchers found an association between PSOM and

brachycephalic conformation in cavaliers. They stated: “in CKCS, greater thickness of the soft

palate and reduced nasopharyngeal aperture are significantly associated with OME [otitis media

with effusion, meaning PSOM]. “ However, they did not explain why PSOM is so nearly limited

to the cavalier, while so many other breeds are brachycephalic. They also concluded that

bilateral PSOM was associated with CKCS with more extreme nasopharyngeal conformation,

than unaffected CKCS.

In an October 2010 presentation before a meeting of the UK’s Association of Veterinary

Soft Tissue Surgeons, Robert N. White, a board certified veterinary soft tissue surgeon practicing

at Willows Veterinary Centre and Referral Service in Solihull, West Midlands, observed that the

cavalier does not appear to be a classically brachycephalic breed, despite the extent of BAOS in

the breed, and that the extent of both PSOM and SM in the breed suggests that the CKCS may

suffer from a combination syndrome of the three disorders, all associated with Chiari-like

malformation.

EDITOR’S NOTE: A uniqueness of the CKCS’s morphology is that the breed was

created in the 1920s from a more extreme snub-nosed English toy spaniel – the King

Charles spaniel – by breeding to elongate the muzzle, rather than to shorten it. It is as if

the cavalier’s muzzle has been treated like an accordion – first compressed to create the

Page 3 of 6

predecessor King Charles spaniel, and then stretched.

Infection as a cause of PSOM in the cavalier has been discounted by the researchers.

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,

itchy ears, head tilt, head rubbing, excessive yawning, crying out in pain, ataxia, drooping ear or

lip, inability to blink an eye, rapid eyeball movement, facial paralysis or nerve palsy, Vestibular

disease, 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.

In an April 2015 report involving 27 cavaliers affected with PSOM, the researcher found

that:

“In 74% (20/27) of the cases the dogs were deaf, 15% (4/27) of the dogs showed ataxia,

7% (2/27) showed a head tilt and 7% (2/27) showed a facial paralysis of the affected side.

In 59% (16/27) of the cases the dogs were scratching, 52% (14/27) of the dogs were

rubbing and 56% (15/27) were shaking their heads. In 19% (5/27) of the cases the dogs

seemed to experience pain localized to the head or ears according to the owners.

Gradations of these symptoms were divided in mild, moderate, severe and extreme. …

“In the 27 dogs in this study, 14 of the 27 dogs were rubbing their head. Head rubbing

(against the floor or other surfaces) has, with the exception of dermatitis and allergies

(Bruet, Bourdeau et al. 2012), only been associated with syringomyelia and CM and an

unknown syndrome of behavioral signs of discomfort in the CKCS in former literature

(Rusbridge 2005, Rusbridge, Carruthers et al. 2007). Only 7 of these 14 dogs were also

diagnosed with CM/SM at the moment of the occurring clinical signs. After the

myringotomy procedure, all clinical signs, including the head rubbing, were resolved in

all 14 dogs for a period varying from four weeks to years. It seems that in these cases, the

head rubbing was caused by the overfilled bulla(e) tympanica(e) and therefore this

clinical sign can also be associated with PSOM. “

Diagnosis

The standard means of detecting PSOM by veterinary dermatology (preferably) or

neurology specialists is by either computed tomography (CT) or a magnetic resonance imaging

Page 4 of 6

(MRI) scan. Both require that the dog be under general anesthesia. However, if the case is severe

enough that the pars flaccida, the top portion of the dog’s tympanic membrane (ear drum), is

bulging, the condition may be visible on x-rays and even diagnosed manually with an otoscope.

In extreme cases, the tympanic membrane may have ruptured and the mucus plug clearly seen. It

also may be observed by using an operating microscope with good lighting and at a suitable

magnification.

Tympanometry (impedance audiometry) is a noninvasive method of examining the

function of the Otometermiddle ear while varying the atmospheric pressure in the external ear

canal and inferring the amount of sound energy that is transmitted through the tympanum by

measuring the reflected sound energy. In a February 2015 study, Dr. George Strain reported that

the sensitivity and specificity of tympanometry for the diagnosis of PSOM in cavaliers were 84

and 47%, respectively. He recommended that clinical studies of conscious dogs with PSOM need

to be performed to validate the clinical usefulness of these recordings. (See tympanometer at

right.)

However, in an August 2015 report, Dr. Lynette Cole examined 60 cavalier King Charles

spaniels which had clinical signs suggesting PSOM. To diagnose the disorder, they used

otoscopy, tympanometry, pneumotoscopy and tympanic bulla ultrasonography, in addition to

using computed tomography (CT), which they stated was “the gold standard for the diagnosis of

PSOM in the CKCS. “

All of the methods diagnosed PSOM in ears with large bulging “pars flaccida “ (the

triangular, flaccid portion of the eardrum). However, cavaliers may have PSOM even though

their pars flaccida is flat rather than bulging. She found that tympanometry detected the PSOM

in only 47% of ears with a flat pars flaccida. She concluded that, in cavaliers with a flat pars

flaccida, only the CT scan can reliably detect PSOM in the CKCS.

Other possible alternative instruments for diagnosis of PSOM include pneumotoscopy,

tympanic bulla ultrasonography, and the brain-stem auditory evoked response test (BAER).

However, in the August 2015 report described above, the researchers found that pneumotoscopy

detected the PSOM in only 79% of ears with a flat pars flaccida, and tympanic bulla

ultrasonography detected the PSOM in only 47% of ears with a flat pars flaccida.

Veterinary dermatologists in the United States may be located on the American College

of Veterinary Dermatology website.

Treatment

– myringotomy

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 Cavaliers with Syringomyelia Symptoms on YouTubeclose up

Page 5 of 6

video of a myringotomy actually being performed on a cavalier named Baylee on YouTube.

Following the myringotomy, the specialist typically will repeat the CT scan, to see if all

of the mucus has been removed, and then a BAER test to determine if hearing has been restored.

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 an April 2015 report involving 31 myringotomies and 5 tympanostomies (see below)

on 27 cavaliers affected with PSOM, the researcher found that:

“[A]fter a single myringotomy procedure the mean recurrence time is 19.9 months with a

median of 13 months and a recurrence rate of 61%. After tympanostomy the time to

recurrence was shorter then after myringotomy (p = 0.022), which is contrary to the

theory which describes that the continual tympanic cavity ventilation by using ventilation

tubes may provide a longer symptom-free period. No signs of progression from unilateral

to bilateral PSOM were seen. “

– tympanostomy

In a March 2008 study conducted by Australian researchers, they inserted tympanostomy

tubes (right) 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. However, Dr. Cole reports that “no long-term prospective studies have been

published on the outcome after extrusion of the tympanostomy tubes as far as the length of time

the bulla remains effusion free. In addition, no studies have reported on the efficacy of a more

“permanent “ or long-term tympanostomy tube for treatment of PSOM. “ In a February 2013

report, a team of UK researchers also have questioned the effectiveness of repeated

tympanostomies.

In an April 2015 report involving 31 myringotomies (see above) and 5 tympanostomies

on 27 cavaliers affected with PSOM, the researcher found that:

“[A]fter a single myringotomy procedure the mean recurrence time is 19.9 months with a

median of 13 months and a recurrence rate of 61%. After tympanostomy the time to

recurrence was shorter then after myringotomy (p = 0.022), which is contrary to the

theory which describes that the continual tympanic cavity ventilation by using ventilation

tubes may provide a longer symptom-free period. No signs of progression from unilateral

to bilateral PSOM were seen. “

In an August 2015 study of 12 cavalier King Charles spaniels with PSOM, a team of UK

clinicians report on the results of 22 video-otoscopy-guided tympanostomy tube placements from

2012 to 2014 at The Royal Veterinary College. The tympanostomy tubes were successfully

placed in the tympanic membrane in the cavaliers, under video-otoscopic guidance using a rigid

endoscope and grasping forceps. Outcomes were reported by telephonic answers to

Page 6 of 6