Elwood, a 9 year old neutered and slightly overweight short haired cat, cowered in the back of his kennel, his lanky frame hunkered down and his head tucked beneath a blanket. “He is normally so outgoing! I’m really worried” Ms. Jackson’s voice wavered. Elwood was Ms. Jackson’s late mother’s cat and Ms. Jackson was afraid of losing this loved one as well. As I peered into Elwood’s kennel, Ms. Jackson continued “He hides all day now, and wants attention all night. I just don’t understand. He won’t even come out for his meals anymore.” I gently scratched around Elwood’s left ear and a rumbling purr arose from under the blanket and Elwood raised his head to look at me. I slid my hand beneath his chest and started to bring him out into the light, at which point Elwood desperately scrambled for the back of his kennel. “Ms. Jackson, when did Elwood start hiding?” “It started last week; I thought he just wasn’t feeling well, but that he would come back out in a day or so!” Elwood peered at me a again and gave a sad, plaintive ‘meow.’ I stared into his very wide eyes and wondered if he had really just turned into a night owl or if he was experiencing photophobia, a painful sensitivity to light. I reached out and flicked off the lights, then crooned to Elwood who emerged from his kennel and butted my chin with his head.

“I think Elwood’s eyes are hurting in the light.” I asked Ms. Jackson about any changes at home; no litter changes, no food changes, monthly Revolution to prevent fleas and heartworm disease, no access to the outdoors, no new pets or plants in the house, and Elwood didn’t have access to human medicines. Normally I start physical exams with the face by shining a light in the throat, eyes, and ears, but this time I worked my way from the rear end to the head. Elwood tolerated my fingers probing his abdomen and hands stretching his joints. He purred enthusiastically as my stethoscope delivered the notes of his heart and lungs. His temperature, pulse, and respiratory rate were all mildly elevated. I picked up my pen light and took a quick look in Elwood’s clean ears, then checked his teeth and throat. Finally, I shined my light in Elwood’s wide dilated eyes, a condition known as mydriasis. In a darkened room, I expect Elwood’s eyes to be wide, but when I shined a light into his eyes his pupils should contract. They did, slightly, before rebounding to their full widened gaze. Elwood tried to wrench his head away and I lowered the light for a moment. My nurse stepped in to cradle Elwood, gently gripping his jaw and skull. I reached into my pocket and withdrew a single lens, about the size of a small drink coaster, then rested my finger’s just below Elwood’s right eye, bracing the lens a few inches from his eye before raising the light to line up with my own eye and directing it through the lens.

This light shined through the lens in my hand, through the cornea and lens of Elwood’s eye, and onto the structures in the back of Elwood’s eye, letting me look at the vessels, nerve, and retina that enabled Elwood to see. Slightly off center was a creamy white egg shape known as the optic disc. Viewing the optic disc is similar to looking at a river flowing into the ocean; the disc is the visible end of the optic nerve that courses from the brain to spread into a thin sheet of nerve cells, called the retina, that collect visual information entering the eye. If the optic disc appears enlarged, much like a river overflowing after a storm, I worry about inflammation or high blood pressures. A small optic disc may indicate damage to the nerve or lack of use. The shape of the optic disc varies with some appearing almost triangular and others perfectly round. From the optic disc blood vessels project outwards like uneven spokes of a wagon wheel. I look to see if any of these vessels appear normal; larger vessels are at risk for putting pressure on surrounding tissues or even bleeding into the tissues while smaller vessels may not supply adequate blood to the tissues. Then I look at the retina stretched across the fundus, a fancy word for the back part of the inside of an organ, which can vary in color and texture. Some are stunningly beautiful like a bowl of sparkling blue, green, and yellow confetti while others are reddened and reminiscent of the eyes favored by horror film directors. Elwood’s fundus was a lovely glowing green that would match a firefly’s light on a dusky evening. I peered intensely, looking for cracks or bubbles, changes in color or texture that could represent damage to the retina. The inside of Elwood’s eye looked perfect and an examination of his left eye provided a perfect match.

Eyes really can be a window into the health of a creature by offering a platform to view nerves and vessels. Changes in other parts of the body, such as increased blood pressure from a straining heart, or an infection with certain viruses, are often visible in the eyes. Elwood’s wide-eyed gaze had alarmed Ms. Jackson and brought him to my examination table, but such an evident symptom wasn’t going to reveal a cause right away. We talked about what tests we could run to determine what was wrong with Elwood. We started out with blood work to check indicators of organ function, blood cell health, and response to infections. Elwood’s blood work was unremarkable; none of those values were outside of normal ranges. Next we took Elwood’s blood pressure using a smaller cuff, one that is used on newborn babies, but instead of wrapping it around a baby’s arm, we placed it around the base of Elwood’s tail. Elwood, being such a charming fellow, accepted this test with grace and his blood pressure was slightly above normal range. These could be signs of illness or stress from the visit to our hospital. Next we performed a test to see if Elwood’s irises had atrophied, or weakened and thinned, preventing Elwood from constricting his pupils. We test for iris atrophy by applying different concentrations of a drug called pilocarpine to one of his eyes. By responding to the pilocarpine, Elwood’s eyes showed us that the irises weren’t the issue; his issue was somewhere in his brain.

By this time, I noticed that Elwood was drooling a bit and seemed a bit twitchy. I was worried that Elwood had a disease that affected his brain or a cancerous tumor within his skull. We took a series of x-rays, which revealed nothing awry. With my mind whirling, I sat down with Ms. Jackson again. We discussed every visitor to her house, every cleaning product she had purchased, and every grocery item that came in the house. I asked Ms. Jackson to go through a detailed account of her day, and as I listened to her recount her morning coffee and afternoon walk I realized that she was giving Elwood treats every few hours, but that I had not noted treats on my previous history. My mind raced; could the treats be toxic? Was there a defect in the manufacturing process? A cruel hoaxer that found a way to add poison to the treats at the store in a manner reminiscent of the Tylenol tampering of 1982? I asked Ms. Jackson for the name of the treats, but she couldn’t remember, so I sent her home after the package. She returned with a package labeled ‘calming treats.’ Working with patients who have behavior problems, I recognized a key ingredient; L-tryptophan, which is a precursor to serotonin, a neurotransmitter. Ms. Jackson started using the treats because she was working longer hours and thought they would help keep Elwood calm while she was away. He was receiving 8-10x as many treats as the package indicated. I couldn’t be sure, but I feared Elwood was experiencing Serotonin Syndrome. I explained my concern to Ms. Jackson, noting that I didn’t have any way of testing my theory other than treating Elwood for Serotonin Syndrome and monitoring his response and that there were other diagnostics we could try to rule out other causes such as testing Elwood for toxoplasmosis and bartonella, performing a cerebral spinal fluid tap to look for infectious agents, or sending him to a veterinary university for a CT scan or MRI. Ms. Jackson explained that her savings were limited and she wanted to try treating for Serotonin Syndrome first.

We hospitalized Elwood, put him on fluids and monitored his vital signs, and gave him a drug called cyproheptadine, which competes with serotonin for spots on receptors in the brain, kind of like adding a whole bunch of extra people to a game a musical chairs. The chairs are the receptors, the original players are the molecules of serotonin, and new players are the molecule of cyproheptadine. We don’t know for certain, but we assume that fewer serotonin molecules can grab receptor seats if cyproheptadine is present. Meanwhile we monitored Elwood; if his condition worsened, the muscles supporting his lungs could stop functioning and we would need to provide him with respiratory support or he could have a series of seizures which we might need to treat with emergency drugs. I knew we should see improvements within 24 hours, but the total affects might last for 36 hours. Elwood continued to hide, the fluids helped bring his fever down, he never experienced trouble breathing or seizures. On his second day of treatment, his twitches stopped and his eyes returned to normal. Elwood returned home with Ms. Jackson, who promised not to use calming treats again! Now, I am not certain that Elwood had serotonin syndrome or that the treats caused it, but I am grateful Elwood returned to good health. Ms. Jackson is refraining from feeding calming treats to change behavior, instead she is sticking to Elwood’s flavorful favorites!

What’s your wide-eyed pet story?