Page 1076 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Nervous system 1051

VetBooks.ir 10.8 10.9

Fig. 10.8 A foal with a fracture of the atlas. Note the
localised sweating at the region of the injury.

from the withers to the lumbar area, and flexion of
the thoracolumbar vertebral column by running the
blunt instrument from croup to tail head.
Most of the spinal reflexes are impossible to test Fig. 10.9 Fracture of C7 and T1, with hypalgesia.
in the adult standing horse. However, in the foal or
recumbent horse some reflexes are possible to assess,
such as the patellar, gastrocnemius and triceps. The voiding and continence can be affected by lesions
response to these tests differentiates upper motor involving the cauda equina.
neuron (UMN; hyperresponsiveness) from lower The spinal cord ends at the level of the first or sec-
motor neuron (LMN; hyporesponsiveness) lesions. ond sacral vertebra. Focal lesions of the vertebrae in
Skin sensation over the limbs should be assessed. the lumbar, sacral and coccygeal regions can affect
This is particularly important in the recumbent the cauda equina and lower motor nerves. There
horse where significant damage to the spinal cord or could be muscle atrophy, hypalgesia, hypotonia and
peripheral nerve damage is suspected. hyporeflexia (Fig. 10.10).
Finally, tail tone and perineal reflexes need to be
assessed. The perineum and tail are innervated by
nerves from the sacral and coccygeal spinal cord seg-
ments. The muscular tone of the tail can be assessed 10.10
by manipulation, and can vary in strength depend-
ing on the horse’s disposition. However, it should
not be difficult to detect true paralysis. The peri-
neal reflex is tested by gently prodding or pinching
the perineum and should normally result in clamp-
ing of the tail and contraction of the anal sphincter.
Abnormal carriage of the tail (elevation or deviation
to one side) could be a natural trait or may suggest
spinal cord disease. Tail rubbing is seen with Oxyuris
equi infestation, but is also a marker of cauda equina
syndrome (polyneuritis equi). It is important to Fig. 10.10 A lack of anal tone is noted in a horse
check bladder fill and tone, because normal bladder suffering from equine herpesvirus-1 myelitis.