When faced with a horse exhibiting neurologic disease, the importance of a thorough physical exam and diagnostic testing cannot be emphasized enough. Stephen Reed, DVM, Dipl. ACVIM, of Rood & Riddle Equine Hospital in Lexington, Ky., described selected equine neurologic diseases during his presentation of the prestigious Milne Lecture at the 2008 American Association of Equine Practitioners Convention, held Dec. 6-10 in San Diego, Calif.

Some elements of the exam include evaluating proprioception (the horse’s awareness of where his feet are in space), gait changes, the presence of unusual gaits, and identifying the neuroanatomical location of an abnormality. He explained that proprioceptive deficits are the first signs of compressive lesions in the spinal cord, while deep pain sensation is the last function lost.

While a horse’s history is important, Reed’s relies on a full exam. He begins with evaluating the horse’s behavior and mental status, and examining the head and cranial nerves. Then he moves systematically along the body and limbs toward the tail, and finally assesses gait. The type of response is important–whether it be a deficiency, a "discharge," such as a stereotypic (continuous, repetitive, and serving no purpose) behavior, seizure, or spasm; or a "release," such as an exaggerated, weak, or ataxic (incoordinated) response. Gait evaluation is a critical part of the exam. All findings should be recorded, signs characterized, and attempts made to localize the lesion to help determine the cause.

The first condition Reed discussed is cervical vertebral stenotic myopathy (CVM), also known as wobbler syndrome. (Stenosis implies a narrowing of the vertebral canal.) This can be a developmental problem in young light-breed horses, or it can be an acquired problem in older horses (over 10 years) from osteoarthritis of the neck vertebral articular process joints (facets). Elongation of the dorsal laminae (the bony plates that form the roof of the vertebral canal) into the intervertebral space (between the vertebrae) can cause stenosis, requiring surgical correction. Compression in a wobbler most commonly occurs between cervical vertebrae 6 and 7 (C6-C7)