Most cases of stringhalt are associated with nerve degeneration. The specific cause this degeneration is unclear, but it might be caused by ingestion of certain plants such as vetch and sweet peas, which contain compounds that damage peripheral nerves. Australian stringhalt commonly involves groups of horses and is thought to be caused by ingestion of flatweed (Hypochoeris radica). Trauma to the dorsal hock or dorsal metatarsal regions can also cause the abnormality by damaging nerves or causing adhesions to tendons.
Some cases of stringhalt may resolve without treatment, often requiring months. Affected horses should be removed from pasture and the pasture should be inspected for toxic plants known to cause stringhalt. Sedative medications may reduce anxiety and improve the condition. A surgical procedure, which involves removing a section of one of the tendons crossing the outer portion of the hock, will bring about improvement in some cases. The prognosis for recovery from stringhalt is guarded to fair; some horses never recover from the condition regardless of treatment.
Friday, December 2, 2011
More about Stringhalt
Stringhalt is an abnormal gait that involves exaggerated flexion of one or both hock joints, resulting in a rapid elevation of the hind limb. The abnormality might be subtle--such as minor upward jerking of the hind leg, or so severe that the canon bone and fetlock are pulled violently against the horse's belly. Some severely affected horses have difficulty moving forward because of the over-flexion at every step. Signs could be exaggerated in nervous or agitated horses, or when they are backed. There is no breed or age predilection. Other syndromes that can cause somewhat similar gait abnormalities include shivers, fibrotic myopathy, intermittent upward fixation of the patella, and peripheral neuropathy (nerve degeneration) due to equine protozoal myelitis (EPM).
The Myster of Stringhalt
Veterinarian Carolyn R. Simmelink explains what is behind a condition that makes it difficult for a horse to control his hind legs.
Question: My horse Bridget, a former jumper, was 18 years old when I bought her. Within two months, I learned she had stringhalt. I gradually put her back into work and was successful in doing Introductory Level dressage before she again became lame. I had her hocks injected and later elected to have surgery performed, but the problem returned. Can you tell me more about stringhalt?
Answer: Stringhalt is a rare lameness that causes a horse to lift his hind legs higher and more rapidly than usual when he's moving. One or both hind legs may be affected, and the lameness varies from mild (just a muscle spasm) to so severe that the horse actually kicks himself in the belly when he tries to move. Conditions that make any horse's gaits more animated, such as cold weather and competing, can exacerbate the signs. There does not seem to be pain involved with the lameness, yet it is difficult to ride a horse that cannot control the actions of his hind legs.
Veterinarians don't know what causes most cases of stringhalt. We do know that the nerve controlling the lateral digital extensor muscle probably is damaged. This muscle lies on the outside of the hind leg, just above the hock, so a kick to this area is the most likely culprit. For horses with bilateral stringhalt--both hind legs are affected--a more central location of nerve damage, either in the spinal cord or brain, is likely.
Treatment is surgical and involves removing a portion of the lateral digital extensor muscle and tendon to restore a more normal gait. Without the action of the lateral digital extensor muscle, the hind leg cannot be brought forward with as much force.
I suspect that in your mare's case, the primary lesion was in the spinal cord because her stringhalt was bilateral and she had no other behavior that would suggest a brain lesion. That also would explain why surgery brought only temporary relief. I could speculate that she had trauma to her spine from her former jumping career that predisposed her to arthritis in her spine and nerve damage to her back legs that happened to develop after you purchased her. The dressage work probably kept her flexible enough until the nerve damage became too severe for her to be ridden.
Question: My horse Bridget, a former jumper, was 18 years old when I bought her. Within two months, I learned she had stringhalt. I gradually put her back into work and was successful in doing Introductory Level dressage before she again became lame. I had her hocks injected and later elected to have surgery performed, but the problem returned. Can you tell me more about stringhalt?
Answer: Stringhalt is a rare lameness that causes a horse to lift his hind legs higher and more rapidly than usual when he's moving. One or both hind legs may be affected, and the lameness varies from mild (just a muscle spasm) to so severe that the horse actually kicks himself in the belly when he tries to move. Conditions that make any horse's gaits more animated, such as cold weather and competing, can exacerbate the signs. There does not seem to be pain involved with the lameness, yet it is difficult to ride a horse that cannot control the actions of his hind legs.
Veterinarians don't know what causes most cases of stringhalt. We do know that the nerve controlling the lateral digital extensor muscle probably is damaged. This muscle lies on the outside of the hind leg, just above the hock, so a kick to this area is the most likely culprit. For horses with bilateral stringhalt--both hind legs are affected--a more central location of nerve damage, either in the spinal cord or brain, is likely.
Treatment is surgical and involves removing a portion of the lateral digital extensor muscle and tendon to restore a more normal gait. Without the action of the lateral digital extensor muscle, the hind leg cannot be brought forward with as much force.
I suspect that in your mare's case, the primary lesion was in the spinal cord because her stringhalt was bilateral and she had no other behavior that would suggest a brain lesion. That also would explain why surgery brought only temporary relief. I could speculate that she had trauma to her spine from her former jumping career that predisposed her to arthritis in her spine and nerve damage to her back legs that happened to develop after you purchased her. The dressage work probably kept her flexible enough until the nerve damage became too severe for her to be ridden.
Stringhalt - What is it?
Stringhalt is a myoclonic affliction of one or both hindlimbs seen as spasmodic overflexion of the joints. The etiology is unknown, but lesions of a peripheral neuropathy have been identified in the sciatic, peroneal, and tibial nerves. Severe forms of the condition have been attributed to lathyrism (sweet pea poisoning) in the USA and possibly to flat weed intoxication in Australia. Horses of any breed may be affected; it is rare in foals.
All degrees of hyperflexion are seen, from the mild, spasmodic lifting and grounding of the foot, to the extreme case in which the foot is drawn sharply up until it touches the belly and is then struck violently on the ground. In severe cases, there is atrophy of the lateral thigh muscles. In Australian stringhalt and lathyrism, the condition may be progressive, and the gait abnormality may become so severe that euthanasia is warranted.
Mild stringhalt may be intermittent. The signs are most obvious when the horse is sharply turned or backed. In some cases, the condition is seen only on the first few steps after moving the horse out of its stall. The signs are often less intense or even absent during warmer weather. Although it is regarded as unsoundness, stringhalt may not materially hinder the horse’s ability to work, except in severe cases when the constant concussion gives rise to secondary complications. The condition may also make the horse unsuitable for equestrian sports (eg, dressage).
Diagnosis is based on clinical signs but can be confirmed by electromyography. If the diagnosis is in doubt, the horse should be observed as it is backed out of the stall after hard work for 1-2 days. False stringhalt sometimes appears as a result of some temporary irritation to the lower pastern area or even a painful lesion in the foot. The occasional horse with momentary upward fixation of the patella may exhibit a stringhalt-like gait.
When intoxication is suspected, removal to another paddock may be all that is required. Many of these cases apparently recover spontaneously. In chronic cases, tenectomy of the lateral extensor of the digit, including removal of a portion of the muscle, has given best results. Improvement may not be evident until 2-3 wk after surgery. Prognosis after surgery is guarded—not all cases respond. This is not surprising because the condition is a distal axonopathy. Other methods of treatment include large doses of thiamine and phenytoin.
All degrees of hyperflexion are seen, from the mild, spasmodic lifting and grounding of the foot, to the extreme case in which the foot is drawn sharply up until it touches the belly and is then struck violently on the ground. In severe cases, there is atrophy of the lateral thigh muscles. In Australian stringhalt and lathyrism, the condition may be progressive, and the gait abnormality may become so severe that euthanasia is warranted.
Mild stringhalt may be intermittent. The signs are most obvious when the horse is sharply turned or backed. In some cases, the condition is seen only on the first few steps after moving the horse out of its stall. The signs are often less intense or even absent during warmer weather. Although it is regarded as unsoundness, stringhalt may not materially hinder the horse’s ability to work, except in severe cases when the constant concussion gives rise to secondary complications. The condition may also make the horse unsuitable for equestrian sports (eg, dressage).
Diagnosis is based on clinical signs but can be confirmed by electromyography. If the diagnosis is in doubt, the horse should be observed as it is backed out of the stall after hard work for 1-2 days. False stringhalt sometimes appears as a result of some temporary irritation to the lower pastern area or even a painful lesion in the foot. The occasional horse with momentary upward fixation of the patella may exhibit a stringhalt-like gait.
When intoxication is suspected, removal to another paddock may be all that is required. Many of these cases apparently recover spontaneously. In chronic cases, tenectomy of the lateral extensor of the digit, including removal of a portion of the muscle, has given best results. Improvement may not be evident until 2-3 wk after surgery. Prognosis after surgery is guarded—not all cases respond. This is not surprising because the condition is a distal axonopathy. Other methods of treatment include large doses of thiamine and phenytoin.
Buddy is here
We are glad to get this old guy - but he does have some baggage. We think he has Stringhalt. We will post an article on this disease. We have agreed to give him some time to settle in and then try some holistic treatments. Perhaps some TLC and a few prayers will be all that is needed.
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