This is an excerpt from Equine Disease Quarterly, funded by underwriters at Lloyd’s, London, brokers, and their Kentucky agents.

Horses are afflicted with a number of central nervous system diseases. Diagnosis of these conditions can be challenging both in the live horse and in horses that died or were euthanized due to the neurologic disease. In a clinically affected horse, central nervous system (brain and spinal cord) disease may manifest as altered mental state or behavior, cranial nerve deficits, seizures, abnormal posture, ataxia, paresis or paralysis, muscle atrophy, incontinence, pain, recumbency, or coma. With these varied signs, a systematic neurologic examination is essential for diagnosis.

The goals of the neurologic examination are to establish whether a neurologic problem is truly present and to determine the anatomic location of the process. Likewise, the postmortem examination of a neurologic horse is important to evaluate the clinical diagnosis, establish a diagnosis in undiagnosed cases, provide information that might allow prevention or treatment in herd mates, and monitor for possible zoonotic diseases.

An approach used in the pathological examination of the brain and spinal cord (as well as other body systems) is pathologic pattern recognition. Recognition of the pattern of lesions helps to categorize the condition and allows for consideration of diseases known to produce the pattern. Using both macroscopic and microscopic examination, it can be determined if the lesions affect only a single area of the nervous system or are multifocal or diffuse. Likewise, involvement of specific anatomic structures and symmetry of the pathology are evaluated