WOBBLER Syndrome or ‘Cervical Vertebral Malformation’ is a neurological condition seen in young horses which causes them to have an abnormal ‘wobbling’ gait.

In a normal horse, a message is generated in the brain and is transmitted through the spinal cord. The spinal cord travels through the spinal canal which is formed by the adjacent vertebrae of the neck and back.

There are nerves branching off the length of the spinal cord which transmit the message to the specific muscle groups responsible for movement. ‘Wobblers’ will exhibit an abnormal gait due to disruption of the neurological messages sent from the brain to the muscles controlling the limbs.

The neurological messages become disrupted due to malformation of the vertebrae in the neck, narrowing of the spinal canal and compression of the spinal cord.

The exact reason why horses develop Wobbler Syndrome is not fully understood. Affected horses will often experience a rapid growth spurt and male horses are more commonly affected than female horses.

Wobblers can be diagnosed using a combination of clinical signs and radiographs.

A neurological exam should be performed, firstly to establish if the horse has a neurological problem and, secondly, to attempt to localise the affected area.

At rest the horse may stand with a wide-based gait and when walking will display weakness manifested by stumbling and toe-dragging.

Specific neurological tests will include:

• Neck mobility: A normal horse should be able to easily bend its neck around to its shoulder. If the horse is unable to do so, it can be an indication of pain or discomfort.

• Placement tests: The front legs are taken one at a time and crossed over the front of the other leg or placed in a wide stance. Normal horses should be able to immediately replace their legs to the correct position.

Horses with spinal cord problems will not correct themselves immediately and take a long time to recognise their awkward stance.

• Tail pull: As the horse is being walked, the tail is pulled to each side.

A normal horse will resent pulling on the tail. Wobblers are easily pulled to the side while walking and when the tail is released, they will often sway to the other side.

• Tight circles: This test is performed by turning the horse in a very tight circle. Wobblers will often pivot on the inside leg, swing their hind legs widely or even trip and fall.

• Walking up and down hills: Wobblers will walk awkwardly downhill as though they have been sedated and will knuckle over on their hind fetlocks. When walked uphill, they will walk on their toes. If you elevate the head while the horse is being walked, it will make the deficits more obvious in an affected horse.

• Reversing: A Wobbler will delay moving his hind legs or drag his toes when reversed at walk.

GRADING SCALE

Once the neurological examination is performed the horse can be graded. The scale ranges from 0-5, 0 being a normal horse and five being a severely uncoordinated horse which will struggle to stand unaided.

The next step in diagnosis of a Wobbler is to take a series of neck radiographs. These should be taken beginning at the poll working sequentially down to the base of the neck.

Radiographs may show bony changes associated with the vertebrae which can cause compression of the spinal cord.

If there is a suspicion of spinal cord compression on standard radiographs then a myelogram may be performed.

A myelogram involves injecting an iodine-based dye into the spinal canal. This dye will show up on X-rays, outlining the spinal cord and show any areas where the spinal cord is compressed.

Unfortunately there are limited options for treating Wobblers.

If the condition is identified in foals then a change in diet is advised. They should be fed reduced levels of carbohydrates and proteins whilst maintaining normal mineral and vitamin levels.

The aim of this is alter bone growth, allowing the spinal canal to enlarge and so relieving compression on the spinal cord.

All Wobblers should be given systemic anti-inflammatories to prevent or reduce any oedema around the area of compression. Reducing oedema may improve neurological symptoms.

There are also surgical options for the treatment of Wobblers. These include fusing adjacent vertebrae or removing the upper portion of the affected vertebrae. These are complicated surgeries which are not commonly performed.

The prognosis for Wobblers depends on the degree to which they are affected by the condition.

Many horses which are affected only mildly by the condition can continue to race successfully. Horses which are more severely affected have a poor prognosis. In many cases they can become dangerous to ride or handle and owners and veterinary surgeons are often left with euthanasia as the only option.

John Martin from Stradbally, Co Laois, graduated from University College Dublin and is in practice at Mark Johnston Racing. The article first appeared in the Kingsley Klarion, published by Mark Johnston Racing.