There’s a common axiom among medical people that urges clinicians to expect horses at the sound of hoofbeats…not zebras.

Translated, this means that common things happen commonly and clinicians would do well to keep this in mind when faced with an unknown disease process. So, for example, when a young dog has a cough, we should place kennel cough at the top of our list of possibilities, allergic bronchitis in the middle, and cancer closer to the bottom.

It’s a good basic principle. But sometimes I get so overwhelmed by my zebras that I lose faith in my horses. In other words, tough cases have a way of arriving all at once and making me see zebras everywhere I look.

Yesterday was one such day. My first case was a critical case transferred from an emergency hospital across town. She was unresponsive due to the meds used to relieve her of her all-night-long seizures. Adding up all the doses I had a hard time determining whether her brain activity had been erased by the meds or from whatever might have caused her seizures in the first place.

Six hours later, when I visited her at the internist’s practice (I had transferred her almost immediately) she was no better—worse, even. A young dog with no history of seizures should be an easy enough diagnosis of epilepsy or toxins—if we were looking for horses. But a day-long coma? We suspect weirder toxins, bizarre drug reactions or strange infections. We were in full-blown zebra mode by late afternoon.

How about the cross-country consult on a family member’s dog? I had urged my relative to see a neurologist after his regular vet found little amiss with a slightly indented area in his dog’s facial musculature. The neurologist had ruled out the commonest ailments and had ordered an MRI to seek out a brain tumor. No luck there by day’s end. Another zebra.

Next up, coincidentally, another neuro case I had referred to our local neurologist. This young-ish kitty had suddenly begun twitching and tremoring, especially in her facial muscles. Three weeks had gone by and the owner was finally ready to see the specialist after antibiotics helped (why, I have no idea, but I figured it was worth a try and was grateful they made any difference) and phenobarbital (a seizure drug) worked somewhat, but both failed to resolve the issue. So far, the CT scan and spinal tap were unremarkable. “Thank you for your referral of this challenging case,” was the message I received from the specialist when no diagnosis could be reached.

Finally, a nasty reaction to a sedative late in the day had me calling up cardiologists after hours. I had feared the worst. Thankfully, this one had a welcome equine ending: a happy, healthy dog who will never, ever receive said sedative ever again. Thank God for horses!