South African Equine Veterinary Association Congress 2015 Protea Hotel Stellenbosch
Interpretation of cervical radiographs and other diagnostic imaging for equine
wobbler syndrome
Piercy RJ*
MA VetMB MD PhD DipACVIM MRCVS
Professor of Comparative Neuromuscular Disease
Royal Veterinary College
Summary
Cervical vertebral malformation (CVM) or stenosis (CVS) is the most commonly encountered
neurological problem in horses. In most cases, neurological signs of cervical stenotic myelopathy
(CSM) are characterised by combined pelvic and thoracic limb ataxia and paresis, without central
or cranial nerve deficits, and help localise the problem to the cervical spinal cord segments (C1C5) or sometimes, especially when signs are subtle, to C1-T2. Diagnostic confirmation of
vertebral impairment of the spinal canal is unfortunately hampered by size limitations and the
limits of radiography, myelography and computed tomography in horses. In this presentation I
will discuss my approach to radiography and radiology of the neck in standing horses and the
ancillary diagnostic techniques that can be used when attempting to confirm CVM.
History and Clinical Signs
The clinical signs of spinal cord compression are usually insidious in onset although owners
sometimes report a traumatic incident prior to their recognising any ataxia. Such traumatic
incidents may occur because of mild or previously unrecognised neurological deficits (for
example occasional tripping) that results in a fall. Horses with cervical spinal cord compression
generally have neurological deficits that are recognisable in all limbs characterized by
symmetrical weakness, ataxia, and spasticity. In most instances, the pelvic limbs are more
severely affected than the thoracic limbs likely due to the more superficial location of pelvic limb
tracts in the white matter of the spinal cord. At rest, severely affected horses may have a basewide stance and delayed responses to proprioceptive positioning, whereas at the walk, weakness
may be manifest by stumbling and toe dragging: horses with prolonged clinical signs of cervical
spinal cord compression may therefore have hooves or shoes that are chipped, worn, or squared at
the toe. Ataxia (a sign associated with defective proprioception) is evident as truncal sway at a
walk, inconsistent and erratic foot placement and by circumduction and pivoting on the inside
pelvic limb during circling. Moderate to severely affected horses sometimes have lacerations on
the heel bulbs and medial aspects of the thoracic limbs from overreaching and interference.
Spasticity, characterized by a stiff-legged gait and exaggerated movements, may be observed in
moderately affected horses, especially in the thoracic limbs or in the pelvic limbs when stepping
over curbs or polls. When prompted to back, horses may stand base-wide, lean backward and drag
the thoracic limbs. Occasionally, signs associated with the thoracic limbs may be more severe
than those in the pelvic limbs, particularly in horses with caudal cervical lesions, likely due to
involvement of local spinal cord grey matter associated with the brachial outflow.
A grading scale (0-5) is often used to score horses with signs of spinal ataxia and weakness:
0:normal; 1: very mild deficits detectable only with complex movements (e.g. walking with head
elevated, on an incline, or when circling); 2:mild-moderate deficits that are detectable at the walk;
3: marked deficits obvious at the walk; 4: severe deficits that result in difficulty remaining
standing; (5: recumbent). Some clinicians favour an approach where individual limbs are scored
separately for signs of ataxia and weakness, with a global score being used to summarise the total
neurological deficit. Such an approach is helpful when evaluating disease progression and
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