There are many different types of genetic, infectious, viral and even toxicity issues that can result in permanent or temporary paralysis of horses. Since there are so many possible triggers to a horse's inability to move it is critical to try to decide what has caused the condition before treatment is started. Keeping good records of feeds, pastures, vaccinations as well as contact with other horses or any changes in exercise or behavior prior to the paralysis is essential to help the vet in knowing what the most likely causes are.
Paralysis in horses can affect one leg, both front or both back legs or the whole body. Depending on which limbs are affected the paralysis may be severely debilitating or it may be manageable. Temporary paralysis of one back leg may not be a paralysis at all, rather it may be a condition known as locked stifle where a ligament has simply caught on the stifle, preventing the horse from bending the leg. This type of condition is usually corrected by massaging of the stifle and manipulation of the limb to correct the lock.
Paralysis of the hindquarters may be due to a problem in the spine or central nervous system. This can be a result of a minor misalignment of the back due to a abnormal movement or disc problem that can be corrected with anti-inflammatories, therapy and rest, or it may be a degenerative disease within the central nervous system that is either genetic or caused by a viral infection. In cases where the central nervous system is affected, the chances for recovery to full movement are less optimistic.
Hyperkalemic periodic paralysis or HYPP is known to be problematic in some Quarter Horse lines. In this genetic condition the absorption and movement of sodium in the muscle cells is affected, resulting in sudden and random episodes of paralysis that may be either muscle weakness or spasms. In mild cases the movement will be disrupted, but in severe cases the horse may collapse and die from cardiac and respiratory failure. Since this is a testable genetic condition horses in bredding lines descending from the Quarter Horse stallion "Impressive" should have all foals tested. This lineage will also appear in the American Paint and Appaloosa Horse Club. Careful management of feed, sodium and potassium levels as well as monitoring of exercise can help horses diagnosed with HYPP. Medications are also effective in horses that have had an episode of HYPP or foals that are tested as positive for the genetic condition.
Occasionally toxins can cause signs of paralysis in horses. These toxins may be in plants in the pasture or in supplements or additives to the feed, chemicals used in stables or even improper use of medicines, vaccines and drugs. Carefully reading all instructions and following all dosage recommendations is essential when using any type of chemicals around horses or other animals.