December 2013 Large animal case

Hanoverian horse 9 Years of age.

Male castrated.

Presented for stiff neck and lameness front left after working in vaulting and sudden, uncontrolled movement.

Radiographs of the neck were taken.

Left to right laterolateral view of the cranial neck.

Radiographic findings and diagnosis

There is a separate, triangular with smooth borders mineral opacity ventral to the occipito-atlanto joint and just dorsally to the caudal part of the stylohyoid (arrow).

Remaing structures are within normal limits.

Two oblique views of the region were taken.

Radiographic examination

Right ventral-left dorsal (top image) and left ventral-right dorsal (bottom image) view of the cranial neck.

Radiographic findings and diagnosis

The separated mineral opacity is a distal fragment of the left fractured paracondylar process (arrow) compared to the right normal one (empty arrow). Mild ventrorostral dislocation is present.

Comments

  • A case serie of fracture of the paracondylar process in 4 hourses has been published in 2005 (Lischer et al., Equine veterinary journal).
  • The horses were referred with different clinical presentations: neurological sign, non-neurological and abscence of clinical signs.
  • The fractures at the base of the paracondylar process may involve the facial canal and stylomastoid foramen where the facial nerve emerges from the skull and then cause neurological signs. In this case, the fracture may not be visible on radiographs (even on oblique views) because of superimposition over other structures of the skull, and CT examination may be necessary.
  • The paracondylar process belongs to the occiput and is the origin of the following muscles in ist rostral edge: Occipitohyoideus, biventer mandibulae and jugulomandibularis, which support deglutition and open the mouth.
  • At its caudal aspect, the rectus capitis lateralis and oblique capitis cranialis muscle are inserted.

Text and Fig. 1 from Lischer et al., 2005 Equine Veterinary Journal.