Leg Paralysis in Horses

Radial nerve paralysis can occur from trauma to the radial nerve. The nerve may also be damaged when it is compressed when a horse under goes general anesthesia. In addition, certain plants can be toxic to horses and may cause paralysis, making it important to know what plants grow in your horse’s pasture.  The ingestion of toxic plants can also be fatal to your horse.  Hyperkalemic periodic paralysis (HYPP) is a genetic disease that causes attacks of paralysis, which occur when the horse’s potassium level fluctuate. Paralysis attacks may occur while the horse is at rest or while he is being ridden.

Leg paralysis in horses is the complete or partial loss of the ability to move the limb.  Usually, paralysis is a consequence of trauma, poisoning, or illness.

Radial Nerve Paralysis

• Horse is unable to walk
• Shoulder is slumped
• Weakness
• Collapse

Hyperkalemic Periodic Paralysis (HYPP)

• Trembling
• The appearance of the third eyelid
• Excessive sweating
• Respiratory distress
• Weakness in hindquarters

Toxic Plants (such as sweet pea vine and coyotillo shrub)

• Weakness
• Convulsions
• Respiratory distress
• Hind leg paralysis

Radial nerve paralysis may be caused by:

• The horse is kicked by another horse on the radial nerve; the radial nerve is located in the horse’s shoulder
• Trauma such as the horse accidently running into a barn door or tree post
• The nerve is compressed during general anesthesia 

 Hyperkalemic Periodic Paralysis (HYPP) is a genetic inherited disorder. Leaves, flowers, berries or seeds of a toxic plant may be ingested while the horse forages, causing paralysis and other symptoms of a serious nature.

To begin the diagnostic process, advise your veterinarian if your horse has had any recent injuries or trauma. The veterinarian may also want to take a look at where the horse grazes.

The veterinarian will then perform a physical examination of your horse, listening to the equine’s heart, lungs and gastrointestinal tract with a stethoscope.  The veterinarian will also palpate the abdomen, limbs and muscles. The color of your horse’s gums may be checked. The physical exam may also include taking the horse’s temperature, examining the eyes, and evaluating the blood pressure and pulse. Reflex testing and hoof testing may be done as well. By doing so, the veterinarian can evaluate the patient’s overall condition.

After the physical exam the veterinarian may suggest a complete blood count, to make sure the markers are all within the normal range. Another blood test he may suggest is the serum chemistry profile. In this test, the blood is spun down in a centrifuge to obtain the serum. The serum chemistry test checks the levels of proteins, enzymes, and electrolytes.  If the veterinarian suspects hyperkalemic periodic paralysis disease he may recommend DNA testing. Additionally, the veterinarian may want to take x-rays of the limbs.

If the patient has radial nerve paralysis, the veterinarian will recommend stall rest and may prescribe nonsteroidal anti-inflammatory medication, which will also help with pain relief.  He may apply support wraps to the affected leg.  The veterinarian may also recommend DMSO cream, to be applied to the shoulder of the patient.  Other treatment plans that the veterinarian may suggest are massage therapy, electrostimulation, electro-acupuncture and hydrotherapy.

If your horse was diagnosed with hyperkalemic periodic paralysis disease, the veterinarian will discuss with you a dietary management plan. Horses with HYPP must not eat feed with high potassium levels.  Feed that has high potassium includes soybean meal, alfalfa hay, bromegrass, and sugar or beet molasses.  Feeding should be done on a regular schedule a few times a day.  The veterinarian may recommend the medication acetazolamide to prevent the further paralysis attacks.

Patients that ingested toxic plants will need supportive therapy, which may mean a hospital stay. The horse may also have a gastric lavage whereby the stomach is pumped.  This is done to help clean out the toxic content.  An intravenous line may be started to keep the horse hydrated and to administer medication.

Most horses recover from radial leg paralysis within a few months of stall rest and therapy. Patients with hyperkalemic periodic paralysis can live full lives.  They will need to be on medication and continue to be on a restrictive diet. Horses with HYPP should not be bred. Some horses can make full recovery after they are treated for plant toxins. Young horses and foal that ingest toxic plants often have a grave prognosis.