I enjoyed the last dermatology meeting I attended so much, that I thought I should sign up for another one.
Turns out that the ear has its own self-cleaning mechanism. A recently discovered concept is "epithelial migration" within the ear. Cells in the center of the tympanic membrane migrate outwards to the walls of the ear canal, and from there, toward the entrance of the ear canal. This allows cerumen, cornified keratinocytes, debris and organisms to be transported upwards and out of the canal (comparable to the mucocilary escalator). This also serves as a repair mechanism, both for the tympanic membrane and the ear canal.
How on earth did a bored scientist figure that out? By placing tiny ink dots on the tympanic membrane and then by following their onward migration weekly. The journey occurs at a rate similar to that of the growth of fingernails.
Why should we care? This is actually critical information, because when we treat chronic otitis, we must do so until the epithelial migration has normalized.
Sadly, this may never occur, for example if the tympanic membrane is permanently damaged or ear canal stenosis is severe. In fact, hyperplasia and stenosis of the canal not only impede epithelial migration, but they can reverse it.
Here are a few more pearls of Palmerian wisdom from the conference:
• Culturing the external ear canal, although often performed, is not often useful when trying to determine the most appropriate treatment. This is because levels of antibiotic achievable with topical therapy in the canal far exceed (often by greater than 1000x) the MIC values reported on sensitivity panel.
• Culturing the middle ear should be done in all chronic otitis cases. If the ear drum is intact, this requires performing a myringotomy (or a bulla osteotomy.
• Culture results from the middle ear are similar to that of the external canal in only 10 percent of the cases.
• Both middle ears should be cultured, as bacterial findings are often different.
• A hand held otoscope used in a conscious patient with chronic otitis externa is misleading at best. A video-otoscope is far superior.
• Acute otitis externa should be treated with topical medications for five to 14 days.
• Chronic otitis externa should be treated for at least six weeks and sometimes months (four to six months is not unusual in Dr. Palmeiro's world).
• A dog can lose 90 percent of his hearing capacity before the owner notices.
• Up to 90 percent of dogs with chronic otitis externa have otitis media.
And here are a few classic Palmerian quotes:
• A condition that no veterinarian likes to deal with is the "OIHSLOFMOD Syndrome," which stands for "Oh I Had Some Left Over From My Other Dog."
• "If you try to do a favor to an owner by cleaning their cat's ears during an exam, the cat WILL develop Horner's syndrome."
• "Pretending to count drops when the dropper is inside the ear canal in a moving patient is delusional."
Are there preventive things you can do to decrease (or eliminate?) the risk of otitis, for example in a cocker?
At the first sign of allergic skin disease or ear disease, consider referring the patient to a dermatologist to manage the underlying allergies. This will help slow down the progression of ear disease. There is no reason to test a normal dog, but when the first signs of allergies are noticed, then allergy testing may be indicated.
Is the etiology of ear disease always allergies in cockers?
Close to 100 percent. Dr. Palmeiro rarely finds a cocker who needs a Total Ear Canal Ablation (TECA) who doesn't have signs of allergic skin disease. This is especially true in cockers, which seem to be overly reactive to otitis in the way of mineralization and stenosis. Long, pendulous ears are often blamed. That surely doesn't help, but it is definitely not the sole cause in most cockers.
So should we refer every single cocker who undergoes a TECA to a dermatologist for an allergy work up?
If their only sign is otitis, than there may be no need. However, if there are other dermatological issues, he would recommend a referral. And if a dog has one ear affected and one healthy ear, then he would definitely work this patient up for allergies.