What is Equine Motor Neurone Disease?

My newsfeed has been completely taken over by all the 'Ice Bucket' challenges, which is raising money for ALS (which is commonly known as Motor Neurone Disease). Amazingly it was reported yesterday that €900,000 has been raised so for the Irish Motor Neurone Disease Association. It's brilliant that so many people have rallied together in support of a charity trying to research and eradicate a horrible disease.

Interestingly enough, horses too can be affected by this condition. It is called Equine Motor Neurone Disease (EMND). It was first discovered in 1990. EMND is very similar to human motor neurone disease (MTD), but EMND is the only naturally occurring animal model for motor neurone disease.

EMND occurs as a result of the degeneration of motor neurones in the spinal cord and brain stem (similar to human motor neuron disease (MND). Clinical signs of EMND begin to develop once the horse has lost 30% of their somatic motor neurones (nerves that are not part of the spine and brain..

Signs and Symptoms

The disease can be divided into sub-acute and chronic forms.
 
Signs for the sub-acute form include:

• Acute onset of trembling and twitching
• Lying down
• Shifting of weight on the rear legs and/or holding all 4 legs closer together
• Symmetrical muscle atrophy/wastage
• Symmetrical buckling of forelimbs while standing
• Abnormal sweating
• Low head carriage
• Inability to lock the stifles
• Loss of muscle mass symmetrically throughout the body for one month prior to the trembling. 
• Horses are not uncoordinated, but walking is easier than standing

Signs for the chronic form:

• Trembling and twitching decrease
• Varying degrees of muscle atrophy
• Extreme weight loss 
• Tail usually is elevated
• Excessive lying down
• Abnormal gait - stumbling, string-halt like symptoms in several limbs

Causes

A definitive cause for EMND has not been determined. There is a strong link between EMND and a Vitamin E deficiency. Other minerals (whether is is a lack of or overdose) likely to be involved as some horses with EMND have normal levels of vitamin E.
Horses which are deprived or have no access to grass or green, high-quality hay, and are not supplemented with vitamin E are at greatest risk of EMND.
Vitamin E is a dietary antioxidant which may be useful in halting the progression of the disease.


Diagnosis

There is no definitive diagnostic test available for EMND, the clinical signs, changes in muscle enzymes and EMG (electromyography: a technique that detects electrical activity in muscles) findings provide strong support for the diagnosis of EMND.

Elevated Tail Position

Prognosis

The condition usually progresses with continued muscle atrophy and weakening over the course of one to several month. Sometimes the condition will stabilse or possibly even seem to improve one to two months after onset. A few horses have stablilised for as long as three years, however, none returned to effective use. The condition becomes progressive, eventually requiting euthanasia.