History
A 5-year-old castrated male Beagle was referred for evaluation following 3 episodes of signs of neck pain occurring during a 6-week period. Prior to evaluation, the dog was treated with prednisone administration and exercise restriction, which were successful in alleviating the clinical signs after the first and second episode. However, at the time of the third episode, signs of neck pain persisted despite treatment. Consequently, the dog was referred.
No abnormalities were found on physical and neurologic examinations, with the exception of a lowered head carriage and severe signs of pain with manipulation of the neck in any direction. Findings on CBC, serum biochemical analysis, urinalysis, and thoracic radiography were within reference limits. Magnetic resonance imaging of the cervical portion of the vertebral column was performed (Figure 1).
Sagittal T2-weighted image (A), sagittal T1-weighted image (B), and transverse postcontrast T1-weighted image with a chemical fat saturation pulse (C) of the cervical portion of the vertebral column in a 5-year-old castrated male Beagle referred for evaluation of 3 episodes of signs of neck pain occurring during a 6-week period.
Citation: Journal of the American Veterinary Medical Association 243, 7; 10.2460/javma.243.7.959
Sagittal T2-weighted image (A), sagittal T1-weighted image (B), and transverse postcontrast T1-weighted image with a chemical fat saturation pulse (C) of the cervical portion of the vertebral column in a 5-year-old castrated male Beagle referred for evaluation of 3 episodes of signs of neck pain occurring during a 6-week period.
Citation: Journal of the American Veterinary Medical Association 243, 7; 10.2460/javma.243.7.959
Sagittal T2-weighted image (A), sagittal T1-weighted image (B), and transverse postcontrast T1-weighted image with a chemical fat saturation pulse (C) of the cervical portion of the vertebral column in a 5-year-old castrated male Beagle referred for evaluation of 3 episodes of signs of neck pain occurring during a 6-week period.
Citation: Journal of the American Veterinary Medical Association 243, 7; 10.2460/javma.243.7.959
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Diagnostic Imaging Findings and Interpretation
Magnetic resonance imaging was performed with a 1.0-T MRI unit.a The following pulse sequences were performed in the sagittal and transverse planes: T1-weighted, T2-weighted, and T1-weighted images with a chemical fat saturation pulse acquired after IV administration of gadopentetate dimeglumineb (1 mL/4.5 kg [10 lb]).
A focal, well-circumscribed, ventrally located, extradural lesion is evident at the level of the midbody of C4. There is dorsal deviation and compression of the spinal cord as well as attenuation of the dorsal and ventral aspects of the subarachnoid space and epidural fat resulting from the mass. The lesion is hypointense relative to the spinal cord on both T2-weighted and T1-weighted images (Figure 2). In the sagittal T1-weighted images of the cervical vertebral column, the space between C3 and C4 is narrowed and hypointense, compared with the other intervertebral spaces. On the sagittal T2-weighted images, there is decreased signal intensity of the nucleus pulposus of the C2–3, C3–4, C6–7, and C7-T1 disks. This finding is consistent with degenerative disk disease. On postcontrast T1-weighted fat saturation pulse images, the lesion is nonenhancing and centered in the ventral aspect of the extradural space between the right and left segments of the internal vertebral venous plexus. The contrast medium located within the internal vertebral plexus contrasts with the nonenhancing lesion, thus increasing the conspicuity of the lesion. On the basis of MRI findings, differential diagnoses included intervertebral disk disease, tumor, granuloma, or hematoma.
The same MRI images as in Figure 1. A—There is a well-circumscribed ventral extradural lesion (long arrow) centered over the midbody of C4. The lesion is hypointense (signal void) relative to the spinal cord. There is dorsal deviation and compression of the spinal cord along with attenuation of the dorsal and ventral aspects of the subarachnoid space and epidural fat. There is a lack of signal from the C3–4 disk (short arrow) and decreased signal intensity of the nucleus pulposus of the C2–3, C3–4, C6–7, and C7-T1 disks (arrowheads). B—The lesion is hypointense relative to the spinal cord (long arrow), and there is narrowing of the space between C3 and C4 (short arrow). As in the T2-weighted image, there is decreased signal intensity of the nucleus pulposus of C2–3, C6–7, and C7-T1 disks (arrowheads). C—Contrast medium is observed within the internal vertebral venous plexus. The contrast medium increases the conspicuity of the hypointense (signal void) lesion in the ventral aspect of the extradural space (arrow).
Citation: Journal of the American Veterinary Medical Association 243, 7; 10.2460/javma.243.7.959
The same MRI images as in Figure 1. A—There is a well-circumscribed ventral extradural lesion (long arrow) centered over the midbody of C4. The lesion is hypointense (signal void) relative to the spinal cord. There is dorsal deviation and compression of the spinal cord along with attenuation of the dorsal and ventral aspects of the subarachnoid space and epidural fat. There is a lack of signal from the C3–4 disk (short arrow) and decreased signal intensity of the nucleus pulposus of the C2–3, C3–4, C6–7, and C7-T1 disks (arrowheads). B—The lesion is hypointense relative to the spinal cord (long arrow), and there is narrowing of the space between C3 and C4 (short arrow). As in the T2-weighted image, there is decreased signal intensity of the nucleus pulposus of C2–3, C6–7, and C7-T1 disks (arrowheads). C—Contrast medium is observed within the internal vertebral venous plexus. The contrast medium increases the conspicuity of the hypointense (signal void) lesion in the ventral aspect of the extradural space (arrow).
Citation: Journal of the American Veterinary Medical Association 243, 7; 10.2460/javma.243.7.959
The same MRI images as in Figure 1. A—There is a well-circumscribed ventral extradural lesion (long arrow) centered over the midbody of C4. The lesion is hypointense (signal void) relative to the spinal cord. There is dorsal deviation and compression of the spinal cord along with attenuation of the dorsal and ventral aspects of the subarachnoid space and epidural fat. There is a lack of signal from the C3–4 disk (short arrow) and decreased signal intensity of the nucleus pulposus of the C2–3, C3–4, C6–7, and C7-T1 disks (arrowheads). B—The lesion is hypointense relative to the spinal cord (long arrow), and there is narrowing of the space between C3 and C4 (short arrow). As in the T2-weighted image, there is decreased signal intensity of the nucleus pulposus of C2–3, C6–7, and C7-T1 disks (arrowheads). C—Contrast medium is observed within the internal vertebral venous plexus. The contrast medium increases the conspicuity of the hypointense (signal void) lesion in the ventral aspect of the extradural space (arrow).
Citation: Journal of the American Veterinary Medical Association 243, 7; 10.2460/javma.243.7.959
Treatment and Outcome
A ventral slot procedure was performed at the level between C3 and C4. The caudal margin of the slot was extended to the midbody of C4. Upon entering the epidural space, extradural material was identified and removed. Grossly, this material was consistent with mineralized disk material. On histologic evaluation, the extradural material was consistent with degenerative nucleus pulposus.1 The dog recovered from surgery uneventfully and was clinically normal at 2, 4, and 8 weeks after surgery.
Comments
The MRI findings were consistent with caudally displaced extruded intervertebral disk material likely from the space between C3 and C4; however, neoplasia, granuloma, or hematoma could not be excluded from consideration.2 Although most of these differential diagnoses enhance with contrast administration, unlike a typical intervertebral disk herniation, all of these differential diagnoses are valid because contrast enhancement of the extruded disk material has been previously observed.3 The contrast enhancement is thought to be related to neovascularization of the extruded disk material. In addition, degenerative changes in the nucleus pulposus of the C2–3, C3–4, C6–7, and C7–T1 disks were identified, but these disks were likely not the locations where the extruded disk material originated.
Typically, degenerative disk material herniates into the vertebral canal at the intervertebral space or slightly cranial or caudal to it. In the dog of the present report, most of the extruded disk material was centered over the midbody of the vertebra with only a minor component of herniated material being centered over the intervertebral space. Although herniation of intervertebral disk material remained a differential diagnosis for an extradural lesion overlying the midbody of the vertebra, other etiologies such as neoplasia, granuloma, or hematoma are more commonly seen at this site.
Although the signalment and clinical signs of the dog of the present report were typical, the unusual location of the lesion made diagnosis more challenging and the dog a surgical candidate. Prior studies also have documented dispersion of extruded disk material to sites distant to the epidural space overlying the intervertebral space.4,5 Consequently, intervertebral disk extrusion should remain a consideration for extradural lesions in areas other than above the intervertebral space. Ultimately, a presumptive diagnosis of extruded intervertebral disk material should be based not only on the anatomic location of the lesion but also on the signalment, history, and MRI characteristics of the lesion.
Genesis Signa, GE Medical Systems, Milwaukee, Wis.
Magnevist, Bayer HealthCare Pharmaceuticals Inc, Wayne, NJ.
1. Royal AB, Chigerwe M, Coates JR, et al. Cytologic and histopathologic evaluation of extruded canine degenerate disks. Vet Surg 2009; 38: 798–802.
2. Levitski RE, Lipsitz D, Chauvet AE. Magnetic resonance imaging of the cervical spine in 27 dogs. Vet Radiol Ultrasound 1999; 40: 332–341.
3. Suran JN, Durham A, Mai W, et al. Contrast enhancement of extradural compressive material on magnetic resonance imaging. Vet Radiol Ultrasound 2011; 52: 10–16.
4. Besalti O, Pekcan Z, Sirin YS, et al. Magnetic resonance image findings in dogs with thoracolumbar intervertebral disk disease: 69 cases (1997–2005). J Am Vet Med Assoc 2006; 228: 902–908.
5. Tidwell AS, Specht A, Blaeser L, et al. Magnetic resonance image features of extradural hematomas associated with intervertebral disc herniation in a dog. Vet Radiol Ultrasound 2002; 43: 319–324.
