Page 1068 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

CHAPTER 10

NERVOUS SYSTEM
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NEUROLOGICAL EXAMINATION

A thorough neurological examination is critical to Arabians are overrepresented in studies of cerebel-
reaching a diagnosis in equine neurological dis- lar abiotrophy and atlanto-occipital malforma-
ease. It can be performed in its entirety in the field tion. Table 10.1 contains a summary of some breed
without any specialised equipment and is quick to predispositions and neurological diseases with a
carry out. It is helpful to develop a logical routine known genetic basis. It is important to take age
so that no phase of the examination is accidentally into account when considering differential diagno-
omitted. The clinical presentation of neurological ses; neoplasia or cauda equina neuritis may be more
disease in the horse is often determined by the ana- likely in older horses, compressive cervical verte-
tomical site of the problem rather than a specific bral disease in young animals, and congenital and
cause. The neurological assessment is therefore developmental diseases are usually apparent from
designed to identify whether there is any dysfunc- birth.
tion in each section of the nervous system, with the It is useful to obtain information on the environ-
goal of being able to pinpoint a single anatomical ment in which the horse lives, its management, any
location that could explain the clinical findings. If recent illness and drug administration, and possible
this is not possible then the assumption is that the exposure to pasture toxins. A history of respiratory
disease process is multifocal. illness or occurrence of abortion would increase the
In summary, the neurological examination helps likelihood of a diagnosis of equine herpesvirus-1
us to answer the following questions: (EHV-1) myeloencephalitis. It is helpful to speak
to the person with the greatest involvement with
• Are my clinical findings likely to be due to the patient, because they are more likely to have
neurological disease? observed subtle changes in the mentation or behav-
• Can the signs be localised to a single iour of the horse.
neuroanatomical location? Seizures are an outward manifestation of dys-
function of the cerebral cortex and are not likely
Once the site, or sites, of the neurological disease to be apparent at the time of the veterinarian’s
have been identified, we can begin to draw up a dif- examination, and so the horse owner’s account of
ferential diagnosis list and decide which additional the event is essential. When owners report the ani-
diagnostic tests are required. mal collapsing or having a seizure, we need to rec-
Detailed information on the interpretation of the ognise that they may not be able to differentiate a
neurological examination and specific neurological generalised seizure (where there is a complete lack
diseases are summarised later in this chapter. of consciousness) from other causes of collapse and
recumbency, such as cardiovascular disease or colic
PHASE 1 – HISTORY (no lack of consciousness). Careful questioning
about the exact nature of the collapsing episode(s)
Some neurological diseases are far more likely in should help to detect when true generalised seizure
particular ages, breeds and genders; for example, events have occurred.