COMPRESSIVE MYELOPATHY DUE TO CERVICAL
VERTEBRAL CANAL STENOSIS IN THE HORSE:
TWO UNUSUAL CASES
Ann Carstens
University of Pretoria, BVSc, MS, MMedVet (Large Animal Surgery), MMedVet (Diagnostic Imaging), Dipl ECVDI, DTE, PhD,
Mark G Collett, Pathology Section, Institute of Veterinary, Animal and Biomedical Sciences, Massey University,Palmerston
North, New Zealand; N.J. Van Der Merwe, c/o Department of Anatomy, Faculty of Veterinary Science, University of
Pretoria
Abstract Two horses were presented with cervical spinal ataxia.
Case 1: A 6 year old Welsh pony gelding with a 6 month history of progressively
worsening hind limb ataxia was presented. Neurological examination showed grade
1 and grade 31 ataxia in the fore and hindlimbs, respectively. Radiographs revealed
a C5 + C6 block vertebra. Due to the progressive clinical deterioration, the pony was
euthanased. Necropsy revealed a C5 + C6 block vertebra with severe neuronal fibre
degeneration particularly caudal to the block vertebra at C6-7. Block vertebrae are
vertebral synostoses caused by a disturbance in the formation of the vertebrae.
Early in embryonic life 2 cords of paraxial mesoderm are formed lateral to the
notochord in the midline and transverse clefts develop in the paraxial mesoderm to
form somites. Interference with this normal segmentation process can result in a
block vertebra, which may be the result of a genetic predisposition or intra-uterine
disturbance.
Case 2: A 2 year old Thoroughbred colt with a history of having fallen 6 months prior
to referral was presented. The horse had mild proprioceptive defects and grade 2
ataxia of both hind limbs. Radiographs revealed a partial angled fusion of C4 and C5
and with severe changes consistent with osteochondritis dissecans and severe
osteoarthrosis of C5 - C6 articular process joints. On myelography the flexed lateral
view of the neck revealed a total obliteration of the ventral dye column at the C5 - C6
joint with at least a 50% attenuation of the diametrically opposed dorsal contrast
column. A less severe attenuation of the dorsal dye column at C4 - C5 was present.
The horse was euthanased. Necropsy revealed severe osteoarthrosis and Wallerian
degeneration of neuronal fibres in the ventral and superficial lateral funiculi at the site
of compression (C5 - C6) and mild spondyloarthrosis and osseous ankylosis of the
articular processes of C4 - C5. It is possible that the fall may have contributed to the
C4 – 5 articular process ankylosis.
Acknowledgements: We thank Drr G Shear and Dr
Paddy Morgan for their involvement in these two cases.
There is no conflict of interest for any of the authors.
Ann Carstens: cell phone: 0827321709; e-mail address:
[email protected]
References:
1. Reed SM, Andrews FM. Disorders of the neurologic
system. In: Reed SM, Bayly WM, Sellon DC, eds. Equine
internal medicine. 2nd ed. St Louis: WB Saunders Co,
2004;533–665.
Proceedings
of
the
South
African
Equine
Veterinary
Association
Congress
2016
51