Page 261 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

236 CHAPTER 1

VetBooks.ir 1.7a The axial skeleton – neck

Abnormal head and neck posture, neck cranial aspect of the neck, and cranial neck stiff-
swelling, neck stiffness or reduced range of ness, which may result in adopting an abnormal
motion, difficulties in lowering the head and posture to graze (Fig. 1.444), with or without ataxia.
neck to graze and an abnormal grazing posture, Congenital fusion of other vertebrae may remain
unexplained forelimb lameness, stumbling and undetected unless the horse is evaluated radiographi-
ataxia and weakness are the most common cally. Meningocoele is associated with both forelimb
reasons for considering a problem in the and hindlimb ataxia. If the primary lesion is at the
cervical region of the axial skeleton. cervicothoracic junction, the horse may stand with
an abnormal forelimb posture.
CONGENITAL ABNORMALITIES
Diagnosis
Definition/overview The diagnosis of occipitoatlantoaxial malforma-
Congenital abnormalities of the cervical verte- tion, congenital fusion of other vertebrae and
brae are, by definition, present at birth but may be meningocoele is based on radiographic examina-
overlooked in some horses and become clinically tion (Fig. 1.445). Laterolateral images are usu-
apparent later in life. The most common congenital ally adequate for diagnosis, but ventrodorsal
abnormalities are: occipitoatlantoaxial malforma- images of the occiput, atlas and axis can give addi-
tion, seen most commonly in Arabs in which there tional information about the asymmetry of the
may be a genetic predisposition, but also seen rarely deformities associated with occipitoatlantoaxial
in other breeds; congenital fusions of other verte- malformation.
brae; and meningocoele.
Management
Clinical presentation There is no treatment or management for any of
Occipitoatlantoaxial malformation is usually asso- these conditions.
ciated with visible and palpable deformity of the

1.444 1.445

Ce 2

Figs. 1.444, 1.445 (1.444) A 6-year-old Warmblood showjumper gelding adopting a rather abnormal posture
in order to lower its head to graze. The horse had abnormal stiffness of the cranial aspect of the neck and would
sometimes straddle both forelimbs widely in order to reach the ground with the head. The horse had congenital
occipitoatlantoaxial malformation. (1.445) Laterolateral radiograph of the occiput and first two cervical
vertebrae of the horse in 1.444. Cranial is to the left. There is congenital occipitoatlantoaxial malformation.
Note the truncated atlas and the duplicated odontoid pegs. (Photos courtesy Ana Stela Fonseca)