Stringhalt refers to a muscle and/or nerve disorder in which one or both hind limbs travels upward in a vertical snapping motion, coming very far off the ground. Severity can range from subtle to a gait in which the fetlocks hit the abdomen with each step. Stringhalt requires that the hock and stifle joints are hyper-flexed.
“Australian Stringhalt” is a poorly understood condition thought to result from degeneration of the nerves that supply the hind limbs, caused by the ingestion of plant toxins. The specific plant implicated in Australia is the perennial Hypochaeris radicata (a/k/a Flatweed, Catsear, False Dandelion). A similar condition has arisen in West Coastal areas of North and South America.
Other forms of stringhalt “aka Classic Stringhalt” may result from other causes of spinal or neurologic injury.
A high stepping stringhalt-like gait can also occur following injury to the lower hind limb and scarring, especially from old wounds on the front of the cannon involving the extensor tendons. This gait can also result from other underlying hindlimb lameness and neurologic conditions.
Diagnosis is by clinical exam, correlated to a history of eating the appropriate plants or the presence of a compatible scar or injury of the lower limb. Lameness conditions must also be ruled out as thoroughly as possible.
Treatment of Stringhalt depends on the assumed cause. Treatment of so called Australian Stringhalt involves removal of the animal’s access to the plants. Once the horse is no longer eating the plants, signs usually gradually improve over weeks to months. For single-limbed stringhalt, a surgical procedure can sometimes be used in which the lateral extensor tendon of the affected limb is cut.
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Prognosis & Relevant Factors
The prognosis is guarded to fair. A horse may recover after being removed from the pasture containing the plant toxins, but recovery could take several months to a year. Muscle relaxing drugs have been used to treat the Australian form, with mostly poor results.
Surgery may help minimize the exaggerated gait in certain types of cases. There is no proven treatment for the Australian form of the condition.
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