Acute non-ambulatory tetraparesis with absence of the dens in two large breed dogs: case reports with a radiographic study of relatives

Abstract

BackgroundNon-ambulatory tetraparesis with an absence of the dens of C2 (axis) has not previously been reported in large breed dogs. An absence or hypoplasia of the dens has been reported in both small, medium and large breed dogs, but not in closely related animals.MethodsTwo young large-breed dogs (a German shepherd and a Standard poodle) both with an acute onset of non-ambulatory tetraparesis were subjected to physical, neurological and radiographic examinations. Both dogs were euthanased and submitted for postmortem examination within one week of onset of clinical signs. To investigate possible heritability of dens abnormalities, oblique radiographs of the cranial cervical vertebrae were taken of nine and eighteen dogs related to the German shepherd and the Standard poodle, respectively.ResultsAbsence of the dens, atlantoaxial instability and extensive spinal cord injury was found in both case dogs. Radiographs revealed a normal dens in both parents and in the seven littermates of the German shepherd. An absence or hypoplasia of the dens was diagnosed in six relatives of the Standard poodle.ConclusionsAtlantoaxial subluxation with cervical spinal cord injury should be considered as a differential diagnosis in non-ambulatory tetraparetic young large breed dogs. Absence of the dens and no history of external trauma increase the likelihood for this diagnosis. This study provides evidence to suggest that absence or hypoplasia of the dens is inherited in an autosomal way in Standard poodle dogs.

Biomechanical evaluation of three ventral fixation methods for canine atlantoaxial instability: a cadaveric study

“…AAI has been reported not only in small-sized dogs, but also in large-sized dogs and cats [12, 27, 32, 35]. AAI occurs, because of congenital dysplasia of the atlantoaxial joint (AAJ), including odontoid hypoplasia, non-fusion, incomplete ossification and malformation, as well as acquired trauma-related instability, subluxation or dislocation (fracture or ligament rupture) [6, 16].…”

A review of canine atlantoaxial joint subluxation

“…Complete absence or hypoplasia of the dens is a predisposing congenital anomaly in toy breed dogs and has been recently reported in a family of Standard Poodles (12).…”

Craniocervical junction abnormalities with atlantoaxial subluxation caused by ventral subluxation of C2 in a dog

“…According to these issues, it is suggested that absence of dens allows dorsal angulation of axis by lose their functional ability of alar ligaments. In fact, some AAS patients with dorsal subluxation of C2 with deficit of the dens have been reported (Patton et al, 2010;Stigen et al, 2013). Therefore, the patient who has AAS with absence of dens shows higher opportunity to dorsal subluxation of C2 than normal AAS patients.…”