What is Muscle Tremor Disorder?
This condition affects the muscular and nervous systems in your horse. There is a noticeable weight loss and a tendency to shiver or tremble. Currently it is not known what causes this condition. Sometimes your horse may stabilise on its own but it may never be the same again in strength or exercise capability. As it is a progressive disease, the prognosis is poor as the condition deteriorates.
A muscle tremor disorder can be described as a progressive neuromuscular disorder that may affect your horse causing muscle tremors or shivers, difficulty in standing and an unusual walk.
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Symptoms of Muscle Tremor Disorder in Horses
- Facial tremors or odd facial movements
- Muscle wasting on one or both sides of your horse’s body
- Restless moving from side to side of the rear limbs
- Unsteadiness during standing or walking
- Jerking motions and elevation of the tail
- Lack of energy
- Reduced strength
- Shivers or tremors of the muscles
- Rapid blinking of the eyes
- Reluctance to exercise
- Lowered head
- Foot dragging
- Hyperkalemic Periodic Paralysis (HYPP) is a rare genetic disorder that seems to affect the American Quarter Horse breed; it affects the way your horse’s digestion handles the sodium and potassium ions within the diet and the resultant muscle tremors and side effects have no known cure although a change in the diet of your horse may help
- Rhabdomyolysis, or tying-up, is a muscle disorder brought on by exercise intolerance or abnormal muscle contraction
- Myotonia arises from increased muscle use with the decreased power of the muscle to relax after contraction
Causes of Muscle Tremor Disorder in Horses
- Currently unknown, but with ongoing testing, there seems to be a range of causes that may trigger this condition
- It could be a dietary cause, such as your horse’s inability to absorb vital nutrients
- Genetic basis such as HYPP that affects the American Quarter Horse breed
- Mutations caused by genetics that affect the muscle development
- Glycogen-branching enzyme deficiencies (GBED)
- Mitochondrial myopathy
- Malignant hyperthermia
Diagnosis of Muscle Tremor Disorder in Horses
Often an electromyography is used to assist diagnosis although there is no special or totally effective test to confirm this condition. Your horse may have mild elevations of the enzymes CPK and AST which may show in tests. Usually it is clinical signs, the EMG findings and enzyme reports that provide the strongest evidence of this debilitating disease. Experimental testing has not discovered any signs of toxins, and infectious agents don’t seem to be the candidate due to the sporadic habit of the disease.
In the past, it was thought that this condition may have been caused by a single symptom, but the more the scientists try to isolate the cause, the more clinical indicators arise. There are even some plants that may cause this condition such as white snakeroot. Isolating the cause of your horse’s condition is a very long drawn out process which in the end may not be able to come to a conclusive answer, let alone come up with a cure.
Treatment of Muscle Tremor Disorder in Horses
Your veterinarian will explain that there is no treatment at present that can produce a cure for your horse if he develops muscle tremor disorder. Additional vitamins such as Vitamin E and selenium added to the diet have been proven to be helpful and are worth trying. There are medications to provide relief for your horse, but this condition is progressive and eventually if muscle wasting and the tremors worsen, then euthanasia is the kindest solution due to the poor quality of life that your horse will be experiencing.
Even when the condition is arrested your horse will fail to gain weight even though they are eating normally, and they will be reluctant to exercise. There is ongoing clinical testing for this condition as veterinarian specialists strive to understand and find a solution for this debilitating disorder. Once the causes can be isolated, then a cure may be able to be devised, but with so many variables at present the prognosis is still guarded.
Recovery of Muscle Tremor Disorder in Horses
To date, the recovery process prognosis is poor. Management of the disorder is the only the option available if your horse is in the early stages of the disorder, as he may have a few years of quality life left. Allowing rest interspersed with gentle walking exercise, and allowing your horse to retire to a quiet life may help. It is worth talking to your veterinarian to discuss diet including selenium and Vitamin E additives. There are some foods that should be avoided, such as bran, sugar beet, and molasses and some have even suggested avoiding alfalfa. The reason is that these foods contain too much potassium which upsets the balance in between sodium and potassium ions.