Page 1110 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Nervous system 1085

VetBooks.ir 10.36 10.37

Fig. 10.36 Radiograph of a displaced fracture of Fig. 10.37 Comminuted, displaced fracture of the
the basisphenoid bone. This horse had reared up and occipital protruberance (arrow) as a result of falling
flipped over in the show ring, resulting in temporary over backwards.
unconsciousness followed by seizures, ataxia and
bilateral epistaxis.

Treatment may be pursued as per acute head (50–100 mg i/v for an adult horse), placed in a pad-
injury, listed above. Prognosis depends on the sever- ded stall and treated with dexamethasone (0.02–
ity, complexity and location of neuronal injury, 0.05 mg/kg i/v). Administration of mannitol or
haemorrhage and diffuse axonal injury but is usually other osmotic diuretics should be avoided in the
poor to guarded. first 24 hours because of potential damage to the
blood–brain barrier or active bleeding in the CNS.
INTRACAROTID INJECTION The use of proper injection techniques should
greatly reduce the risk of intracarotid injection.
Inadvertent intracarotid injection in horses is com-
mon because of the close apposition of the jugular FACIAL NERVE TRAUMA
vein and carotid artery in the caudal third of the neck.
It usually results in a generalised seizure, followed The facial nerve (CN VII) innervates the muscles of
by recumbency and degrees of coma. Contralateral facial expression. Among all the peripheral nerves,
facial twitching and a wide-eyed apprehensive facial nerve paralysis is one of the most common
appearance may precede the seizure. Animals may in horses and, depending on the site of damage,
rear or strike violently. The onset of signs is rapid some or all of the facial muscles may be affected.
with viscous or irritant drugs. With water-soluble Unilateral facial paralysis is more common and is
drugs, such as xylazine, recovery usually occurs, evident as deviation of the muzzle towards the nor-
with the horse standing in 5–60 minutes and com- mal side, drooping of the ipsilateral ear, eyelid and
pletely normal in 1–7 days. With insoluble and oil- lip, and reduced flaring of the ipsilateral nostril dur-
based drugs, recovery is usually unsatisfactory, with ing inspiration. Inability to close the eyelid causes
epilepsy, stupor and coma as common sequelae that exposure keratitis. There may also be damage to the
necessitate euthanasia. secretomotor fibres of the facial nerve, leading to
Treatment is not usually necessary with tran- reduced tear production. These fibres may be dam-
quillisers and water-soluble drugs because effects aged at, or proximal to, the geniculate ganglion.
are self-limiting and of reasonably short duration. Bilateral facial nerve paralysis can result in signs of
Violent horses should be sedated with diazepam dysphagia, with dropping of feed and accumulation