Facial Nerve Paralysis in Horses: Drooping Ear, Eyelid, and Lip Causes

Facial nerve paralysis means the facial nerve (cranial nerve VII) is not working normally on one or both sides of the face. In horses, this most often shows up as a drooping ear, a sagging eyelid, reduced blinking, a hanging lip, or feed and water falling from one side of the mouth. The muzzle may look pulled toward the normal side because muscle tone is reduced on the affected side.

This problem can happen when the nerve itself is bruised, stretched, compressed, inflamed, or damaged near the skull. It can also happen when a deeper disease affects the structures around the nerve, such as the middle or inner ear, guttural pouch region, or the temporohyoid joint. In some horses, facial paralysis is part of a broader neurologic problem rather than an isolated nerve injury.

For many pet parents, the first thing they notice is the eye. A horse that cannot blink well may not spread tears normally across the cornea, which raises the risk of dryness and ulceration. That is why even a horse that seems bright and comfortable still deserves prompt attention from your vet.

One of the most common causes is trauma. A horse may injure the facial nerve after a fall, trailer incident, kick, poll injury, or getting the head caught. Pressure on the nerve can also happen during prolonged recumbency, from tight equipment, or after anesthesia. In these cases, the nerve may be bruised or compressed rather than permanently severed, so some horses improve with time and supportive care.

Another important cause is temporohyoid osteoarthropathy (THO), a disorder involving the joint between the hyoid apparatus and the skull near the ear. THO can affect the facial and vestibulocochlear nerves, so horses may have facial droop along with head tilt, ear pain, or balance problems. Inner ear disease, middle ear disease, and guttural pouch infection can also affect nearby nerves and create similar signs.

Your vet may also consider neurologic diseases such as equine protozoal myeloencephalitis (EPM), less commonly viral encephalitis, and other brainstem disorders. In some horses, no clear cause is found even after a thorough workup. That does not mean the signs are minor. It means the next step is matching the diagnostic plan to your horse's full exam findings, risks, and practical goals.

Diagnosis starts with a physical and neurologic exam. Your vet will look at blink strength, eyelid closure, ear and lip movement, tear production, corneal health, swallowing, balance, and whether any other cranial nerves seem affected. A fluorescein stain may be used to check for a corneal ulcer if the eye is exposed or painful.

From there, testing depends on what your vet suspects. Horses with isolated mild signs after obvious trauma may need a focused exam and monitoring. Horses with head tilt, ataxia, swallowing trouble, or chronic signs often need a broader workup. This can include endoscopy of the guttural pouches, skull radiographs, ultrasound, bloodwork, cerebrospinal fluid testing, and in referral settings CT or MRI. Electromyography and electrical stimulation of the facial nerve may help define the location and severity of injury in some cases.

The goal is not only to confirm that the facial nerve is affected, but to find the underlying cause and identify complications that need attention now, especially corneal ulceration and aspiration risk. Recheck neurologic exams over time are often part of the plan because nerve recovery can be slow, and the pattern of improvement helps guide prognosis.

Not every case can be prevented, but you can lower risk by focusing on head safety, prompt ear and neurologic evaluation, and eye protection when signs first appear. Reduce trauma risks where possible by checking trailers, fencing, stall hardware, and turnout areas for places a horse could strike or trap the head. Make sure halters and other equipment fit correctly and are not left on in situations where snagging is likely.

Because some cases are linked to temporohyoid osteoarthropathy, ear-region disease, or guttural pouch problems, early veterinary attention for head shaking, ear sensitivity, head tilt, unexplained facial asymmetry, or balance changes matters. Horses recovering from anesthesia, illness, or prolonged recumbency should also be monitored closely for pressure-related nerve injury.

Vaccination and routine preventive care also play a role. Keeping your horse current on vaccines your vet recommends for your region, including mosquito-borne neurologic disease prevention where appropriate, can reduce some infectious neurologic risks. Most importantly, if you notice reduced blinking or a new facial droop, do not wait to see if the eye stays comfortable. Early care is often the best prevention for painful secondary complications.