Page 264 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Musculoskeletal system: 1.7a The axial skeleton – neck 239

VetBooks.ir There is usually palpable swelling of the muscle, 1.449
although a horse’s distressed behaviour in the acute
stage may make accurate palpation challenging.
A muscle abscess is usually a direct consequence
of a previous intramuscular injection. There is
neck swelling, pain and stiffness (Fig. 1.449).
Ultrasonography usually reveals a thick-walled
unicameral or multicameral structure filled with
anechoic purulent material (Fig. 1.450). Surgical
drainage is sometimes successful, but radical en bloc
resection of the entire abscess may be required.
Jugular vein thrombophlebitis is usually the result
of intravenous medication given via a needle or cath-
eter, or an adverse reaction to a catheter. There is
localised soft-tissue swelling around the vein, thick- Fig. 1.449 A mid right-sided neck swelling due
ening of the wall of the vein and accumulation of to an abscess in the muscles following a vaccination
echogenic material within the vein (Fig. 1.451). If injection. (Photo courtesy Graham Munroe)
severe, the vessel may become transiently or perma-
nently occluded, with obvious palpable thickening 1.450
and firmness of the vein, but with no associated heat,
pain or neck stiffness. Infectious thrombophlebitis
is usually the result of circulating bacteria invad-
ing a thrombus. There is associated heat, pain and
neck stiffness. Diagnosis can be confirmed using
ultrasonography. Systemic antimicrobial therapy
and local injection of antimicrobial drugs into the
infected thrombus may result in complete resolution.
Occasionally, surgical removal of the vein is required. Directly
Rupture of the ligament of the dens is a rare injury, over
which results in dorsal subluxation of the dens, some- mass
times associated with an audible click. The horse
carries its head stiffly in an extended position relative
to the neck. The vertebral canal is wide at this level
and therefore there may be no effect on the spinal
cord, and subsequently no ataxia. The prognosis is
guarded for return to full athletic function.
Acquired torticollis (Fig. 1.452) is believed to be
the result of cerebrospinal Parelaphostrongylus tenuis
migration. Affected horses develop a very obvious
twist in the neck with no associated radiological or
ultrasonographic abnormalities.
A collar or breast plate used particularly in driv-
ing horses may result in forelimb gait abnormalities Fig. 1.450 Ultrasound image of a neck muscle
or unwillingness to work, which can only be repro- abscess showing the circumscribed abscess
duced when the horse is driven. It may not be possible containing speckled hyperechoic foci of pus. Note the
to identify focal areas of pain in the neck region and hyperechoic bony structure deep to the abscess, which
diagnosis is usually dependent on exclusion of other is the edge of the cervical vertebral column. (Photo
potential causes of pain and by changing the tack. courtesy Graham Munroe)