What to Expect
Comprehensive Physical Examination:
- A thorough history will be obtained, including duration of clinical signs, whether there is a history of trauma, and your horse's vaccination history for certain diseases.
- Observation of your horse in its stall. This gives the veterinarian the ability to assess your horse's demeanor. If your horse appears dull and lethargic, it may be an indication of brain involvement. If the neurologic abnormalities are confined to the fore and hind limbs and your horse is bright and alert otherwise, then there may only be spinal cord involvement. The examination may also reveal whether there is abnormal wear of your horse's toes caused by toe-dragging, which is seen with certain neurologic diseases.
- Close evaluation of your horse's body muscling for any muscle wasting or atrophy.
- Assessment of your horse's tail and anal tone will also be assessed to determine if the tail portion of the spinal cord is affected.
- Observation of your horse during urination and defecation.
Evaluation of the cranial nerves: These are 12 nerves that originate from the brain and govern various functions of the head and face, such as the ability to prehend and swallow, the ability to move the facial muscles (blink response, muzzle, ear movement), and the response of the pupils to light. Identification of any cranial nerve abnormalities may aid in localizing which part of the brain is involved. The examination involves close examination of the entire head, including the eyes. Your veterinarian will also assess various reflexes - the most important ones are the menace, palpebral, and pupillary light reflexes.
- To perform the menace reflex, the examiner abruptly moves a hand toward the horse's eye. The appropriate response is to blink the eye, and perhaps move the head away. This helps determine if your horse can see.
- To perform the palpebral reflex, the examiner lightly touches the eyelid, and the horse should close his eye. This helps to determine if the horse has skin sensation, and if he has control of the muscles of the face.
- To perform the pupillary light reflex, the examiner brings the horse into dim lighting, and shines a penlight first into one eye, then the other. The pupils of the eye should constrict. This helps to assess pathways in the brain that control eye function.
Evaluation of the neck: The neck is then examined for any muscle wasting and any signs of neck pain. Neck pain may be evidenced by a pain response upon deep palpation of the vertebrae in the neck. A reluctance or inability of the horse to move its head/neck towards either flank, or to the ground or up in the air may indicate a component of neck pain. An inability to perform these maneuvers may indicate arthritis of the vertebrae of the neck, Wobblers syndrome or neck trauma.
Analysis of gait: The next portion of the exam involves analysis of your horse's gait. The entails observing your horse at the walk and trot, walking up and down an incline, backing up and turning in tight circles. When walking or trotting in a straight line your horse is observed for any stumbling, dragging of its toes (sign of weakness), inconsistent placement of its feet, and outswinging of its legs during the anterior phase of its stride (circumduction). When being circled tightly, your horse is observed for any excessive outswinging of the outer hind limb (circumduction), any pivoting on any of its feet, or any interference of any of its feet. While being circled the tail is also pulled to ascertain any weakness of the hind limbs. To maintain an intact normal gait, the nerve impulses must be able to get from the brain, to the spinal cord, and to the nerves that govern the muscles. If the circuit is interrupted at any point along this line, your horse will likely exhibit gait abnormalities. Abnormal placement of your horse's feet by your veterinarian to determine if your horse will properly replace them should also be performed to determine if your horse has the ability to know where its feet are (proprioception).
Diagnostic Tests: Based upon the clinical exam findings certain tests may be recommended. If compression of the spinal cord in the neck is suspected (cervical vertebral malformation or wobblers) then X-rays of your horse's neck are warranted to look for any fractures, abnormalities with respect to alignment of the vertebrae or evidence of degenerative joint disease or arthritis of the joints (articular facets) of the neck. These X-rays do not allow for visualization of the spinal cord, so if spinal cord compression is suspected then a myelogram will need to be performed to confirm the site of compression.
If a disease such as Equine Protozoal Myeloencephalitis (EPM) is suspected, a standing lumbosacral spinal tap is warranted to obtain spinal fluid for testing. This procedure is performed with your horse standing while mildly sedated. Spinal fluid can then be submitted for testing for EPM. Cytological analysis of the fluid should be performed to evaluate the cell population and protein concentration. The spinal fluid may be grossly abnormal with diseases such as Equine Herpesvirus Myeloencephalopathy.
If fevers accompany the neurologic signs, then bloodwork should also be performed. Fevers may accompany viral diseases such as Eastern Equine Encephalitis (EEE) and West Nile Virus (WNV). Blood can be submitted for determination of viral titers. Blood work is also useful in determining if the neurologic signs are associated with concurrent liver or kidney disease.