Page 1074 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Nervous system 1049

VetBooks.ir 10.6 10.7

Fig. 10.6 Horse with head
tilt to the left secondary to
trauma on the left aspect of
the calvarium.

Fig. 10.7 Blindfolding of a
horse with exaggeration of
vestibular disease. Note the
leaning to the right.

Table 10.3 Neurological causes of dysphagia

SITE OF ABNORMALITY ASPECT OF EATING DISRUPTED TEST TO DIFFERENTIATE
Trigeminal nerve (CN V) Muscles of mastication Facial reflexes
Facial nerve (CN VII) Lip muscle function Other evidence of facial paralysis
Glossopharyngeal nerve (CN IX) Pharyngeal sensation ‘Gag’ reflex
Vagus nerve (X) Pharyngeal musculature Endoscopy of upper respiratory tract
Hypoglossal nerve (CN XII) Tongue musculature Check the tongue for atrophy, pull tongue and
check retraction is sufficient
Supranuclear palsy (cerebral) Severe lesions may depress or prevent the Cranial nerve tests are normal
voluntary effort required for swallowing
Neuromuscular paralysis Lower motor neuron (LMN) (botulism) Accompanying additional signs of LMN disease
(trembling, weakness, ptosis)

Glossopharyngeal nerve (CN IX) and watching for the ‘gag’. Table 10.3 shows neuro-
and vagus nerve (CN X) logical causes of dysphagia.
The glossopharangeal nerve (CN IX) is responsible The vagus nerve (CN X) is also responsible for
for the afferent innervation to the pharynx, and the the afferent and efferent innervation to the larynx.
vagus is responsible for the efferent supply to the The most well-recognised dysfunction of this nerve
pharyngeal musculature. An abnormality of these is the peripheral neuropathy that affects the left
nerves will result in dysphagia, which will be partial recurrent laryngeal nerve, resulting in laryngeal
if a unilateral problem is present. Sensory innerva- hemiplegia and ‘roaring’. The abnormality is best
tion of the pharynx can be assessed by looking for a detected with endoscopy of the upper respiratory
‘gag reflex’ when a nasogastric tube is passed, or by tract (without sedation), but a practical (albeit crude)
touching the wall of the pharynx with an endoscope assessment is the ‘slap’ test, where the withers are