Cone beam computed tomographic myelography in horses with cervical vertebral compressive myelography

Background: While computed tomographic (CT) myelography is increasingly
available and has been evaluated in alive horses, objective criteria for
diagnosing cervical vertebral compressive myelopathy (CVCM) are lacking.
Objectives: Establish morphometric dimensions of cervical vertebral canal
and spinal cords from horses with CVCM and compare those to unaffected
horses with the use of cone beam CT (CBCT). Study design: Prospective
observational study. Methods: Four control horses and ten horses with CVCM
underwent diagnostic imaging and histopathology. Morphometric measurements
were obtained from cervical radiographs and radiographic and CBCT
myelography. Receiver operating characteristic curves were generated to
establish thresholds of measurements. Results: Intravertebral sagittal
ratios were significantly different between CVCM and control horses.
Dorsal myelographic column reduction was significantly different between
compressed site and non-compressed sites. Full myelographic area (FMA),
dural area (DA), and spinal cord area (SCA) were significantly smaller in
the CVCM horses, and were significantly smaller at compressed sites when
compared to non-compressed sites. Reductions of FMA and DA and ratios of
spinal cord area to full myelographic and dural area were significantly
larger at compressed sites when compared to non-compressed sites.
Diagnostic thresholds to consider for CVCM are FMA<294mm2,
DA<188mm2, and SCA <104mm2. Compressed sites were associated
with thresholds of FMA<274mm2, DA<188mm2, or reduction of
FMA>9%, reduction of DA>14%, SCA:FMA>36.7%, and
SCA:DA>57.9%. Main limitations: Small number of horses. CVCM horses
were younger than control horses. Conclusions: CBCT myelography provides
quantitative parameters that can support a diagnosis of CVCM and should be
used alongside radiographic myelography.