Medical Mystery: Why did cat suddenly lose her balance?

Angel Hoefer is a 14-year-old domestic shorthair with controlled hyperthyroidism and a mild heart murmur, but otherwise is a happy elderly cat.

Her owner grew concerned when she recently started to lose her balance. Her back legs seemed unsteady, resulting in her standing with them wide apart, as if to gain balance. She stopped climbing onto the top of the couch and was eating a little less. She seemed to fall over to one side at times, and her owner wasn't sure if she was fainting. She also had two episodes of vomiting and diarrhea within a week.

My team arranged a full cardiac workup with a specialist to make sure that Angel's murmur wasn't causing weakness or syncope (fainting) and determine if she needed heart medication.

The test results showed that the murmur was not significant, nor the cause of her symptoms. Blood work was also normal for her age.

An abdominal ultrasound was performed, and that, too, came back normal, ruling out any obvious intestinal disease and metabolic issues.

A few weeks later, Angel started to shake her head and developed a slight head tilt to her right. She had vomited overnight and was eating a little less than normal.

I returned to Angel's home for a follow-up examination, as her symptoms had worsened.  During the exam, I noted minor ear discharge, close to her ear drum. Along with her moderate head tilt to the right, Angel's eyes had a slight horizontal movement, which snapped more quickly to the left.

What was causing Angel's neurologic symptoms?

Angel was showing signs of vestibular disease.

Normally, the vestibular system helps animals maintain balance by adapting the position of their eyes, head, and body with respect to gravity. Symptoms can be dramatic and distressing, ranging from a head tilt, falling, rolling, leaning, circling, incoordination, and abnormal nystagmus (eye movements). Some patients will develop a wide-legged hind-limb stance to gain balance. There are no breed predilections, but older cats are more commonly affected.

Two types of underlying lesions may cause the condition.

Peripheral VD results from lesions either in parts of the inner ear or the vestibular portion of the eighth cranial nerve, which helps with equilibrium. These lesions have a better prognosis and can often be treated.

Central VD involves lesions in the brain (vestibular nuclei or cerebellar vestibular centers) and often have a poor prognosis.

Angel had horizontal nystagmus, but some patients can have a rotatory, or circular, reflexive eye movement. Her symptoms were largely one-sided but can occur on both sides.

MRI imaging can distinguish between central and peripheral VD, but is often cost-prohibitive, as was the case with Angel.

I treated Angel's ear infection, which allowed me to see that her eardrum was not perforated. Still, inner ear disease or infection may not be visible during an exam and still be present.

She was treated with local and oral antibiotics and anti-inflammatory medications for her ear, and given anti-nausea and anti-vertigo medication to help with her appetite and balance.

Her signs significantly diminished a month later. Angel's positive response to medication was a clinical indicator of peripheral VD.

She regained her appetite and most of her balance, and has only occasional head shakes now. She is being weaned off medications gradually and is back to sitting happily on the top of the couch.

Dawn Filos is a veterinarian and owner of Bucks Mercer Mobile Vet, a house-call mobile practice in Bucks and Mercer Counties. She blogs at askthepetvet.com and can be contacted at Info@askthepetvet.com.