Resumen de Magnetic resonance imaging features of Great Danes with and without clinical signs of cervical spondylomyelopathy
Objective—To characterize and compare the MRI morphological features of the cervical vertebral column of Great Danes with and without clinical signs of cervical spondylomyelopathy (CSM).
Design—Prospective cohort study.
Animals—30 Great Danes (15 clinically normal and 15 CSM-affected).
Procedures—All dogs underwent MRI of the cervical vertebral column (C2–3 through T1–2). Features evaluated included sites of subarachnoid space compression, spinal cord compression, or both; degree, cause, and direction of compression; MRI signal changes of the spinal cord; articular process (facet) joint characteristics; internal vertebral venous plexus visibility; and presence of extradural synovial cysts as well as presence and degree of intervertebral disk degeneration and foraminal stenosis.
Results—Clinically normal and CSM-affected dogs had 11 and 61 compressive sites, respectively, detected with MRI. All CSM-affected dogs had ≥ 1 site of spinal cord compression. No signal changes were observed in spinal cords of normal dogs, whereas 14 sites of hyperintensity were found in 9 CSM-affected dogs. Foraminal stenosis was present in 11 clinically normal and all CSM-affected dogs. The number of stenotic foraminal sites was significantly greater in the CSM-affected group, and severe stenosis appeared to be more common in this group than in the clinically normal group. Significant differences were identified between clinically normal and CSM-affected dogs with regard to amount of synovial fluid evident, regularity of articular surfaces, degree of articular process joint proliferation, and internal vertebral venous plexus visibility.
Conclusions and Clinical Relevance—Abnormalities were detected with MRI in several clinically normal Great Danes. Severe spinal cord compression, number of stenotic foraminal sites, and signal changes within the spinal cord distinguished CSM-affected from clinically normal Great Danes.
Magnetic resonance imaging is the imaging modality of choice for dogs with suspected CSM.1–3 Magnetic resonance imaging is a very sensitive technique for determination of the extent of vertebral canal stenosis and spinal cord compression and yields the most information in regard to the neural tissue.4–7 However, a well-recognized disadvantage of MRI in the human neurology field is the potential for overinterpretation.4,6,7 Several studies4,7–10 have found a high prevalence of abnormal MRI findings in the cervical vertebral column of asymptomatic people, indicating that MRI can display detailed anatomic and pathological changes but cannot directly determine their clinical importance. As such, imaging of clinically normal subjects is important so that clinicians making treatment recommendations can recognize the frequency and spectrum of MRI abnormalities that may be seen in individuals without clinical signs.4,7,9,11 In the veterinary literature, only a few studies3,12 have investigated the presence of cervical vertebral column MRI abnormalities in clinically normal dogs. These studies3,12 focused mostly on Doberman Pinschers, a breed in which disk-associated CSM is common, and revealed that neurologically normal Doberman Pinschers have a high prevalence of abnormalities evident on MRI, including intervertebral disk degeneration, spinal cord compression, and foraminal stenosis, alone or in combination. To our knowledge, no equivalent studies have investigated whether MRI abnormalities are also present in the cervical vertebral columns of clinically normal giant-breed dogs. Giant-breed dogs such as Great Danes commonly have osseous-associated CSM.13 The pathophysiology of osseous-associated CSM differs from that of disk-associated CSM.13 Consequently, results from studies of Doberman Pinschers cannot be extrapolated to Great Danes. In addition, 1 study3 that included 20 clinically normal Doberman Pinschers found that the severity of disk degeneration and disk-associated compression in clinically normal dogs of this breed was significantly associated with increased age. The osseous-associated form of CSM predominantly affects young adult giant dog breeds,13,14 in which an influence of age on MRI findings would not be expected.
To our knowledge, no study has investigated morphological features of the cervical vertebral column via MRI of clinically normal Great Danes or compared morphological features of the cervical vertebral column detectable with MRI between neurologically normal and CSM-affected dogs of this breed. The purpose of the study reported here was to prospectively characterize and compare the morphological features of the cervical vertebral column in Great Danes with and without clinical signs of CSM by means of MRI. We hypothesized that the morphological features of cervical vertebral canal structures would differ between these groups and that abnormalities of these structures would be found by MRI of clinically normal Great Danes.
