When Taquka-aq, the 12-year-old golden retriever, presented with a complaint of unilateral nasal discharge, my first thought was, “Uh-oh, nasal tumor.” If your pet has a runny nose, you probably think he has a cold, or maybe allergies. Cancer is not your first thought. But veterinarians know that certain breeds of dogs are prone to certain disorders. Doberman pinschers get wobbler’s syndrome, an instability in the neck causing neurological problems. Portuguese water dogs and standard poodles get Addison’s disease, a serious adrenal gland malfunction. Boxers and golden retrievers? Cancer. Of course these are generalizations, but when trying to make a diagnosis, we often use a pet’s breed, gender, and age to steer us in the right direction, based on probabilities. As the old medical adage says, “When you hear hoofbeats, don’t look for zebras.”
What first sent up a red flag was that Taq’s nasal discharge was “unilateral.” That means “one-sided.” His right nostril was occluded with dry, crusty green goo. His left nostril, completely normal. One-sided discharge typically has a different set of causes than bilateral, i.e., two-sided, discharge. What were the likely differentials? A growth inside the nasal passage, benign or malignant. An irritating foreign body, such as a blade of grass or wood splinter, lodged in the nasal lining. Bacterial or fungal infections usually cause bilateral discharge, but something like an infected tooth root might cause one-sided symptoms.
“Definitive diagnosis in these cases often requires referral to a specialist,” I advised. “A CT scan of his head, then rhinoscopy. In other words, looking up his nose with a fiberoptic endoscope.” I suggested we do skull x-rays and basic blood work before sending them off-Island. Odds were these wouldn’t yield definitive diagnosis, but if we saw massive abnormalities, it might affect our next steps. His owners also mentioned a brief episode recently during which Taq appeared “off balance.” There were no signs of that now. He had been stiff for many years. Maybe his arthritis was acting up? Maybe he had “geriatric vestibular syndrome,” a benign balance disorder that can strike suddenly, then resolve? Or maybe, perish the thought, a tumor in his nasal passage was eating through the cribriform plate into his brain.
Taq’s x-rays and blood tests were normal. After trying a course of empirical antibiotics, which didn’t help, his owners agreed to consult a specialist. I started making calls to arrange the referral and get an estimate of cost. Cape Cod Veterinary Specialists’ CT machine was on the fritz, so they directed me to VCA South Shore Animal Hospital. Their referral coordinator called Dr. Cornetta, board-certified internal medicine specialist, to the phone. We discussed Faq’s case at length. “We usually do the CT scan and rhinoscopy sequentially as one procedure,” she said. They would anesthetize Taq, do the CT, then go right to rhinoscopy while he was still under, taking biopsies and/or cultures as indicated. A rough estimate? Three grand.
“Take chest x-rays before sending him,” she said. “Just because he’s an older golden.” I completely understood what she was implying. Before spending $3,000 working up a nasal discharge, it made sense to check he didn’t have life-threatening cancer anywhere else. Then, as we were about to sign off, she threw out one final thought: “And check for neurogenic KCS. I’ve seen a few cases in old goldens.”
Keratoconjunctivitis sicca, commonly known as “dry eye.” It is the result of decreased production of tears, which are made primarily by glands found in the third eyelid. Most cases are immune-mediated, meaning that for unknown reasons, the dog’s immune system attacks and destroys its own tear glands. Immune-mediated KCS can usually be treated with topical medications that stimulate tear production. Neurogenic KCS is a horse of a different color. The production of tears in the eye and lubricating fluids inside the nasal passages and nostrils is controlled by the autonomic nervous system, specifically by parasympathetic fibers of the eighth cranial nerve, a.k.a. the facial nerve. If something happens to damage transmission of nerve impulses anywhere along that nerve’s path, it can result in loss of function of these lubricating glands. I had Taq come back to measure his tear production with a simple procedure called a Schirmer tear test. His left eye produced a normal amount. His right eye, almost none. Taq’s right nostril was stuffy and dry because the tear and nasal glands on that side weren’t making the secretions necessary to keep everything nice and moist. Kudos to Dr. Cornetta for diagnosing this zebra over the phone!
Neurogenic KCS can present with a variety of other neurological deficits, depending on the exact location of the lesion. Examining Taq carefully, he did in fact have very mild unilateral facial paralysis. Even his transient loss of balance could be explained by the neurogenic KCS diagnosis, as incoordination is an uncommon but reported symptom. Underlying causes may include inner- or middle-ear infections or trauma, but most cases are “idiopathic,” meaning no explanation can be found. We started Taq on topical cyclosporine to promote tear production, but neurogenic KCS often does not respond to this drug in the same way that immune-mediated KCS does. If the ointment doesn’t help, the next step is to give oral pilocarpine, a drug that basically will mimic the action of the malfunctioning parasympathetic nervous system.
We hope Taq will respond to treatment within a few weeks with improved tear and nasal-moisture production, though some dogs take months to respond. Some can eventually be weaned off medication. Others need lifelong treatment. There is still a remote possibility the underlying cause is something serious, like a tumor. If Taq develops additional clinical signs, he may yet visit Dr. Cornetta and her CT scan, but odds are, even though this did turn out to be a bit of a zebra, it’s still just your average zebra. Seventy-five percent of cases of facial nerve paralysis and neurogenic KCS like Taquka-aq’s are idiopathic and neither progressive nor life-threatening. No ferry ride required.