Page 1103 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1078 CHAPTER 10

VetBooks.ir literature. Indicators of a poor prognosis include inflammation of the TH joint, or local spread from a
primary otitis interna or media. However, it is usual
recumbency (in adult horses) and respiratory dis-
tress. Additionally, some authors recognise that
with signs of neurological disease, there is no evi-
those affected horses whose clinical signs rapidly in these cases that, at the time these horses present
deteriorate over a 24–48-hour period are less likely dence of any infectious process in any part of the ear.
to survive. Survivors tend to show signs of improve- Sometimes, an extraordinary or repetitive force has
ment over a few days, and cases that survive for lon- occurred just prior to clinical presentation such as
ger than 1 week are highly likely to recover fully. use of a mouth gag, nasogastric intubation or forceful
tongue manipulations. It is also theorised that micro-
Prevention trauma in crib-biters may predispose them to THO.
Tetanus is an easily preventable disease through the Irrespective of the cause, the clinical course often
use of widely available and efficacious toxoid vacci- involves pain, chronic inflammation and reduced
nation programmes. The use of tetanus antitoxin to motion of the TH joint, followed by ankylosis and,
provide immunity is recommended (alongside teta- finally, acute neurological signs associated with frac-
nus toxoid administration) in situations where a foal ture of the petrous temporal bone and damage to
or adult horse is at risk of tetanus infection and has the overlying CNS. The clinical presentation often
not been effectively vaccinated, such as a foal born to relates to damage to the vestibular system (vestibular
an unvaccinated dam or an unvaccinated horse that ataxia and head tilt [Fig. 10.28]) and/or the facial
sustains a wound. Tetanus toxoid manufacturers dif-
fer in their recommendations on the co-administra-
tion of tetanus toxoid alongside tetanus antiserum.
Such recommendations ought to be considered when 10.28
designing exact protocols for administering such
products to an individual at risk of tetanus.
Necrotic or contaminated wounds should be
debrided, lavaged and cleaned. Given the spe-
cies, susceptibility, the potential for contaminated
wounds, increased survival of vaccinated horses and
the widespread availability of highly efficacious vac-
cines, tetanus prophylaxis should be strongly recom-
mended in horses.

TEMPOROHYOID OSTEOARTHROPATHY

Definition/overview
THO is a well-recognised clinical syndrome in the
horse, and regularly seen in middle-aged horses,
although it can affect young horses at a lower fre-
quency. The aetiology is not known at this time, but
some authors have attributed it to chronic infectious
otitis media/interna.

Aetiology/pathophysiology
The disease is characterised by osseous prolifera- Fig. 10.28 Right-sided head tilt and facial and
tion of the proximal styloid bone and juxtaposed vestibulocochlear nerve deficits with right-sided otitis
petrous portion of the temporal bone. The aeti- interna/media and temporohyoid osteoarthropathy.
ology is unknown, and theories include trauma/ Note the muzzle deviation to the left.