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Lameness and neurology: it's not always a pain in the neck

by
01 October 2016, at 1:00am

Marion McCullagh reports on the "lame or neurological" session at the 2016 Congress of the British Equine Veterinary Association in Birmingham this month.

THE BEVA HELD ITS 55TH CONGRESS in Birmingham’s ICC from 7th to 10th September with a substantial attendance from many countries.

The session on “Lame or Neurological” was moderated by Kevin Corley of Anglesey Lodge Equine Hospital, Kildare, and began with Martin Furr of the Center for Veterinary Health Sciences at Oklahoma State University describing how he goes about differentiating lameness and neurological disease.

Lameness and neurological disease can exist together and they are hard to sort out. Nowadays, there is more awareness of the neurological component.

Take the time to get a detailed history and signalment; a horse presented to Martin as a complicated lameness turned out to have a simple injection abscess. The clinician’s hands and eyes, backed up by brain and experience are the most important instruments for diagnosis.

Observing response

Observe the horse at rest and in motion. How responsive is it? Is it standing base wide? Does it know where its limbs are in space? Observe the rate, range and direction of movement, where the foot is placed and whether it is placed fast or slowly.

To confuse the issue, a horse with bilateral hind limb lameness or muscle soreness may look ataxic. Orthopaedic lameness is confirmed by response to nerve blocks. It is essential to record all findings at the time of examination.

Once the horse is moving, a neurological gait deficit is irregular from step to step because the horse has poor control of the limb movement. This pattern is even more marked on turns and transitions: the horse may “fall apart” on the trot to walk change.

The irregularity does not increase or decrease throughout the examination, whereas the musculo-skeletal lameness may warm out or show up on moving up or down an incline or on a different surface.

Time can clarify a confusing situation; a mild neurological difficulty can progress into a full-blown neurological disease whereas musculo-skeletal lameness may reduce on rest and anti-inflammatories which would not influence a neurological condition.

Is the horse safe to ride?

Martin continued with “How to decide if the neurological horse is safe to ride”. Riding is risky. Riding accidents topped a survey in New Zealand, ahead of sports such as snowboarding and swimming.

There are several aspects to consider in advising the owner. First, there is the safety of the rider, the horse and everyone who is in contact with the animal.

The level of use needs to be determined; the horse may be t to ride on the at in a sand school but not across country over fixed obstacles. What does the owner want? What is fair to the horse from the welfare point of view?

Then there is the matter of suitability for insurance and, finally, legal implications which vary between countries and between states. The clinician needs to evaluate the severity of the de cit and how it is likely to progress.

Is it static or likely to increase slowly or is it episodic and unpredictable? How is the horse in itself? How does the owner rate on skill, knowledge and experience?

It is the veterinary surgeon’s responsibility to assess the risk and provide clear, unambiguous, written instructions to everyone involved with the horse. If you consider the horse unfit to ride, say so. Always get advice from appropriate professionals regarding legality.

Horses with low grade spinal ataxia may still be t to ride. Horses with seizures should not be ridden until they have been off medication, without seizuring, for at least 30 and preferably 60 days. If they have a history of long intervals between seizures then they should have a break of at least three times the seizure interval.

Neck lesions

Sue Dyson of the Animal Health Trust discussed neck lesions as a cause of lameness or poor performance.

Neck lesions are a rare cause of lameness but if the limbs do not provide an answer to the clinical problem or neck signs such as stiffness, abnormal positioning, local pain or patchy sweating, then the neck needs to have a thorough clinical examination backed up by accurate interpretation of radiographs.

Pain in the brachiocephalicus muscle can cause forelimb lameness. A poor rider or badly fitting tack can also initiate muscle pain causing forelimb lameness. A badly-fitting collar may make a driving horse show lameness only when it is pulling.

Locking up

“Neck locking” is a syndrome of severe episodic neck pain which can last for hours or days. The horse may hold its neck in a low position or show severe forelimb lameness, holding the leg semi- exed at rest. It can be relieved by careful manipulation of the caudal neck region.

Definite cause has not been established but the caudal cervical articular process joints (APJs) are enlarged so that the intervertebral foramen is narrowed, causing nerve root compression, hence pain.

Benefits of medication are unproved because of the sporadic occurrence of the pain. Nerve root compression also occurs if there is osteoarthritis of the APJs where the considerable amount of new bone growth impinges on the intervertebral foramen. This can cause patchy sweating, lameness and either local or referred pain.

There can be alteration of the nerve supply to the muscle so that there is muscle atrophy which reduces limb control and so alters gait. The patchy dermatomal sweating follows upset to the local autonomic nerve fibres. It may be accompanied by local hypoaesthesia. In severe cases the vertebrae can fuse so that the neck stiffens permanently.

Lymphocytic infiltration of nerve roots and a positive PCR for Borrelia burgdofreri in cerebrospinal fluid has occurred in a horse presenting with central neurological signs and neck stiffness but generally B. burgdorferi seems to be commonly incidental to, rather than causal of, neck problems.

Sometimes the first rib may be congenitally abnormal or it may be injured with consequent damage to the eighth cervical nerve. This can be the cause of muscle atrophy and forelimb lameness.

Neck problems are generally rather intransigent; in a study* of 59 horses, 32% returned to full function, 31% improved more than 50% but follow-up showed poor long-term resolution with 55% losing improvement by one to six months’ post-treatment.

  • Birmingham, A., Reed, S., Mattoon, J. and Saville, W. (2010) Qualitative assessment of corticosteroid cervical facet injection in symptomatic horses. Equine Vet Educ 22: 77-82.