Rhythm & Balance: Part Two

Part Two: Abnormal Rhythm & Balance

In my earlier post, I covered normal equine rhythm and balance in the 3 main gaits: walk, trot, & canter/lope. Now I’ll explain about gaitedness and common disorders.

GAITEDNESS

Researchers have found that gaited horses (such as Icelandic horses, Standardbreds, & Tennessee Walkers), have a mutation in the DMRT3 gene which permits alternate gaits.  This gene doesn’t guarantee that a horse will have alternate gaits like the tӧlt or running walk, it merely configures spinal circuits controlling gaitedness in a way that allows the legs on one side to move together laterally at a faster speed like in the Standardbred’s pace or Icelandic’s tӧlt. Researchers haven’t found any link between conformation and gaitedness.

STRINGHALT

Horses have muscle spindles with sensors for controlling magnitude and length of muscle contractions.  When these go awry, a horse can develop Stringhalt with rapid hyperflexion usually of the hind legs.  Often this is caused by ingesting toxic false dandelions (Hypchaeris radicata).  When caused by ingestion of the toxic weed and detected early enough, the condition is reseverible with treatment. However, stringhalt can be caused by trauma to a limb and sometimes the only option is to surgically cut the lateral digital extensor tendon to provide some relief.  

“WOBBLERS’ vs. EPM vs. EDM

Commonly known as “Wobblers” Syndrome, Equine CompressiveMyelopathy refers to compression of the spinal cord which causes nerve damage and resulting  incoordination of limbs (ataxia) and stumbling.  Wobblers is most often found in geldings and horses who experienced rapid growth. Symptoms are usually symmetrical, unlike in Equine Protozoal Myeloencephalitis (EPM), a disease caused by a parasite in wildlife feces, typically opossums and affecting 1% of horses.

EDM also causes symmetrical ataxia and incoordination in particular of the hind legs. It is usually diagnosed in foals or yearlings when severe, however it may go undetected for years if symptoms are minor.  EDM is often related to Vitamin E deficiency in utero, so it is wide to measure a broodmare’s Vitamin E levels and supplement if necessary. 

CEREBELLAR ABIOTROPHY

Found primarily in Arabians, Cerebellar Abiotrophy, is characterized by a head tremor where affected horses shake their heads left and right.  This head tremor and ataxia is often diagnosed between 6 weeks to 4 months of age. Depending on the severity, horses diagnosed with Cerebellar Abiotrophy may be prone to accidents and are not safe to be ridden and are frequently euthanized. 

“SHIVERS”

Most common in draft horses or extremely tall Warmbloods (16.3+), Shivers is typically seen in geldings and usually noticed by an unwillingness to back up.  This occurs because horses with this condition have difficulty with the coordination of flexion & extension, especially of their hind limbs.

Although these are some scary neurological conditions, the good news is that they are fairly rare and sometimes preventable (avoid toxic false dandelion ingestion, supplement pregnant mares with Vitamin E if necessary, etc.).

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