SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
c. Placing responses
1) Cross limbs or feet when standing quietly. Horse should resist or
correct stance without stumbling or treading on self.
2) Ask animal to step up onto or down from curb. Should be able to
do so clearly.
d. Hopping, wheelbarrowing – occasionally tried with foals instead of
sway tests.
IV.
Assessment of Tail and Anus
Tail tone can be assessed just prior to testing the perineal reflex. A completely
flaccid tail having no voluntary movement is indicative of a lesion of the
sacrococcygeal segments or nerves. Decreased tail tone can be detected with
lesion cranial to the coccygeal segments, but usually the spinal cord lesion must
be severe for the weakness to be apparent. Some horses are regarded as
natural “tail wringers” and will flick their tails up and down and laterally while
moving. This feature can also be observed with painful musculoskeletal diseases
and has been observed to be acquired by horses that have later been determined
to have spinal cord disease; thus, it is not a reliable neurologic finding.
The perineal reflex is elicited by lightly pricking the skin of the perineum and
observing reflex contraction of the anal sphincter and flexion (clamping down) of
the tail. The sensory fibers are contained within the perineal branches of the
pudendal nerve (S 1 -S 3 ). Contraction of the anal sphincter is mediated via the
caudal rectal branch of the pudendal nerve, and tail flexion by the sacral and
coccygeal segments and nerves (S 1 -C 0 ). An animal with a flaccid tail and anus
due to a lower motor neuron lesion will not have an anal (or tail) reflex although it
may still have normal sensation from the anus and tail if the sensory nerves and
spinal cord and brainstem white matter pathways to the sensory cortex are intact.
Thus, as with all other reflex testing, the sensory perception of the stimulus must
be evaluated separate from the segmental reflex action.
It should be remembered that the spinal cord ends at about the first sacral
vertebrae in the horse. Thus, focal lesions of the last lumbar, sacral, and
coccygeal vertebrae may involve the cauda equina and thus, the lower motor
neurons (spinal nerves) from many sacrocaudal spinal cord segments.
Depending on the level, this will result in varying degrees of hypalgesia, areflexia,
hypotonia, and muscle atrophy of the tail, anus, perineum, hips, and caudal
thighs. A rectal exam may detect space occupying lesions, and fractures or
luxation of the lumbar, sacral, and coccygeal vertebrae. In addition, assessment
should be made of urinary bladder volume and the tone of the bladder wall and
rectum. Adult horses that are recumbent for any reason will often not urinate and
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