4-year-old intact male Boxer

• A 4-year-old intact male Boxer presented to the Texas A&M College of Veterinary Medicine’s Emergency Service for being down in the hind end.
• Two months prior to presentation, the patient began dragging the left hind limb and was reluctant to jump.
• The patient was treated with carprofen, gabapentin, and kennel rest, but his signs progressed to a non-ambulatory paraparesis.
• The patient subsequently developed a decreased appetite and weight loss.
• Physical examination revealed absent proprioception in both hind limbs, intact reflexes, and present motor function.
• Diffuse muscle atrophy of the epaxial muscles and hindlimbs was observed during the physical exam.
• The remainder of the physical exam was unremarkable.
• Complete blood count, chemistry panel, and lumbar spinal radiographs showed no significant abnormalities.

– An MRI of the spine was performed for further evaluation of the cause of the patient’s clinical signs.
– The MRI study of the spine included various imaging sequences: sagittal T2W MYELO/HASTE images (single image in carousel above), sagittal and transverse T2W images, dorsal STIR images, transverse T2W fat suppressed images, and sagittal and transverse T1W fat suppressed images pre- and post-contrast medium administration.

Imaging Findings:
– Within the spinal cord, there is a T2W/STIR hyperintense, T1W isointense variably contrast-enhancing, fusiform intramedullary mass that expands the spinal cord from the mid body of T1 through the mid body of T6.
– Multifocal variable T2W hypointensity of the nuclei pulposi of the thoracic intervertebral discs.
– The left subscapularis muscle and mid-thoracic epaxial musculature have patchy T2W/STIR hyperintensity and contrast enhancement.
– There is a T2W hypointense focus in the head of the spleen.

1. Intramedullary mass from the level of T1-T6, with the primary differential being neoplasia such as glioma, lymphoma, histiocytic sarcoma, or metastatic neoplasia.
2. Multifocal chronic intervertebral disc degeneration.
3. Suspected secondary inflammation based on the appearance of the epaxial musculature and left subscapularis muscle.
4. The T2W hypointense splenic focus likely represents benign changes such as extramedullary hematopoiesis or lymphoid hyperplasia.

– The patient’s clinical condition continued to deteriorate, and cytoreductive surgery was not recommended.
– Due to the extent of the mass and poor prognosis, humane euthanasia was elected, and a necropsy was performed.
– At necropsy, a 9 cm gelatinous mass was found expanding the intramedullary space of the spinal cord, which was consistent with a high-grade oligodendroglioma.

Oligodendrogliomas are a type of glial neoplasm derived from oligodendrocytes. They are most frequently reported in brachycephalic breeds such as Boxers, Bulldogs, and Boston Terriers. They are most commonly found in the white and gray matter of the cerebral hemispheres and more rarely the brainstem and the spinal cord (1). In a retrospective study examining intramedullary spinal cord neoplasms, oligodendrogliomas made up only 3 of the 53 cases. Of spinal cord tumors in dogs, intramedullary tumors are noted to be the least common with a reported distribution of 15-16%. This incidence is noted to be similarly low in humans. Historically, large breed dogs have been noted to develop intramedullary spinal neoplasms more frequently than small breed dogs, and dogs with primary tumors (mean of 5.9 years) were found to be significantly younger than dogs with secondary tumors (mean of 10.8 years) (4). Patients with intramedullary spinal cord tumors, such as an oligodendroglioma, frequently present with clinical signs of hyperpathia and ataxia due to the space occupying effect of the tumor (3,4). In humans with primary intramedullary tumors, pain is the most common symptom, followed by motor, sensory, and urinary dysfunction (1). In dogs with intramedullary spinal cord tumors, the range of duration of clinical signs prior to presentation is 3 to 236 days with a median of 18 days (4). Intramedullary masses have been found to be most consistently identified by magnetic resonance imaging (MRI) compared to vertebral column radiography, myelography, and CT-myelography (1). A study on the differentiation of intradural spinal cord lesions in dogs using MRI found that the sensitivity for diagnosing an intramedullary tumor with MRI was 83.3% and the specificity was 78.8% (2). The primary differentials in this patient’s case, once the mass was visualized on MRI, included neoplasias such as glioma, lymphoma, histiocytic sarcoma, or less likely metastatic neoplasia. MRI findings for oligodendrogliomas are characterized by ovoid to elliptical mass lesions that are well marginated, located eccentrically in the spinal cord, and associated with variable degrees of spinal cord expansion. They are typically T1W isointense to hypointense, T2W and STIR hyperintense, and moderately contrast enhancing (4). A case report on an intramedullary oligodendroglioma in the spinal cord that had metastasized to the brain in a Toy Poodle reports that the spinal cord mass was T1W hyperintense, T2W hyperintense, and contrast enhancing (5). Astrocytomas had very similar MRI findings and should also be considered as a differential when facing a lesion with these characteristics (4). Dogs with intramedullary tumors have a median survival time of 20 days, though treatment varies highly among reported cases, making it difficult to assess whether any one treatment is best (1). Cytoreductive surgery is infrequently performed on intramedullary tumors due to the difficulty resecting these neoplasms without damaging the spinal cord (2). Both primary and secondary intramedullary tumors are associated with a poor prognosis (4). Although rare, oligodendrogliomas are a potential differential diagnosis for the patient presenting with ataxia and hyperpathia with an intramedullary mass of the spinal cord. On MRI, oligodendrogliomas are reported to most frequently be T2W and STIR hyperintense and contrast enhancing, with T1W hypointensity, isointensity, and hyperintensity all possible (4,5). Oligodendrogliomas can be definitively diagnosed by histopathology, but the prognosis is similarly poor no matter the type of intramedullary tumor due to the location.

References:

1. Koestner A, Higgins RJ. Primary tumors of the central nervous system. In: Tumors in Domestic Animals, ed. Meuten DJ, Iowa State Press, IA. 2002; 4th ed.:699-707.

2. Krasnow MS, Griffin IV JF, Levine JM, Mai W, Pancotto TE, Kent M, Harcourt-Brown TR, Carrera-Justiz SC, Gilmour LJ, Masciarelli AE, Jeffery ND. Agreement and differentiation of intradural spinal cord lesions in dogs using magnetic resonance imaging. J Vet Intern Med 2022; 36:171-178. DOI: 10.1111/jvim.16327.

3. Mamom T, Meyer-Lindenberg A, Hewicker-Trautwein M, Baumgartner W. Oligodendroglioma in the cervical spinal cord of a dog. J Vet Pathol 2004; 41:524-526. DOI: 10.1354/vp.41-5-524.

4. Pancotto, TE, Rossmeisl JH, Zimmerman K, Robertson JL, Were SR. Intramedullary spinal cord neoplasia in 53 dogs (1990-2010): distribution; clinicopathologic characteristics, and clinical behavior. J Vet Intern Med 2013; 27:1500-1508. DOI: 10.1111/jvim.12182.

5. Schkeeper AE, Moon R, Shrader S, Koehler JW, Linden D, Taylor AR. Imaging diagnosis: magnetic resonance imaging features of a multifocal oligodendroglioma in the spinal cord and brain of a dog. J Vet Radiol & Ultrasound 2017; 58(5):E49-E54. DOI: 10.1111/vru.12401