A 9.7-year-old 33.3-kg (73.3-lb) neutered female Labrador Retriever was referred to the Neurology and Neurosurgery Service at the Hospital for Small Animals of the Royal (Dick) School of Veterinary Studies for evaluation of progressive exercise intolerance of 3 months' duration and loss of balance and apparent generalized discomfort of 1 month's duration. The dog was treated with meloxicam and gabapentin for 3 weeks without perceived improvement in its level of comfort, and the neurologic deficits progressed to left hemiparesis.
What is the problem? Where is the lesion? What are the most probable causes of this problem? What is your plan to establish a diagnosis? Please turn the page.
Assessment Anatomic diagnosis
| Problem | Rule out location |
|---|---|
| Left hemiparesis and dragging of the left forefoot Left C1-C5 or C6-T2 spinal cord lesion | Left C1-C5 or C6-T2 spinal cord lesion |
| Diminished flexor reflex left thoracic limb with normal muscle tone and mass | Left C6-T2 spinal cord lesion or most likely secondary to pain given that muscle tone and mass were apparently normal, which is incompatible with a lower motor neuron lesion |
| Decreased range of motion of the neck and vocalization while hopping on the left thoracic limb | Left C1-C5 or C6-T2 spinal cord lesion |
Likely location of 1 lesion
Left C1-C5 or C6-T2 spinal cord lesion
Etiologic diagnosis—Intervertebral disk disease (IVDD; most likely a Hansen type 2 intervertebral disk protrusion) and neoplasia (either primary [eg, meningioma, glial cell tumor, peripheral nerve sheath tumor, or vertebral tumors including osteosarcoma and hematopoietic tumors such as lymphoma] or metastatic disease) are differential diagnoses for progressive cervical myelopathy associated with pain. The lateralization of clinical signs in this dog was also an important factor to consider. Both IVDD and neoplasia may cause lateralization of clinical signs because of the focal nature of these diseases, which may affect one side more severely than the other. The larger diameter of the spinal canal in the cervical region could also have a role in the lateralization of clinical signs given that more severe compression is needed to affect both sides of the spinal cord. Inflammatory or infectious processes (eg, meningomyelitis or diskospondylitis causing vertebral instability or intervertebral disk protrusion) and some vertebral anomalies leading to degenerative changes of the articular facets or intervertebral disk (eg, cervical spondylomyelopathy) may also cause lateralized signs, but develop with low frequency in geriatric dogs. A CBC and serum biochemical analyses (including assessment of serum thyroxine concentration and thyroid-stimulating hormone activity) had been performed 2 weeks prior to the referral evaluation and revealed mildly high hepatic enzyme activities most likely associated with previous treatment with an NSAID. The diagnostic plan included MRI and CSF analysis (to rule out IVDD, neoplasia, or meningomyelitis).
Diagnostic test findings—Magnetic resonance imaging was performed with a 1.5-T permanent magnet.a The dog was positioned in dorsal recumbency, and sagittal and transverse T1- and T2-weighted images, transverse and dorsal T1-weighted images after contrast medium (gadolinium) administration, dorsal short tau inversion recovery images, and transverse T1-weigthed fast field echo images of the cervical portion of the vertebral column were obtained. The MRI examination revealed a focal, intradural extramedullary lesion within the spinal canal on the left side, centered over the cranial endplate of C4. The lesion was hyperintense on T2-weighted images and isointense on T1-weighted images, compared with the gray matter of the spinal cord. After the administration of the gadolium-based contrast medium, there was a strong enhancement of the lesion on T1-weighted images (Figure 2). The lesion's width, height, and length were 7, 7, and 23 mm, respectively, and it occupied > 50% of the spinal canal at the level of the C3-4 intervertebral disk space. A dural tail sign (thickening of the enhanced dura mater that resembles a tail) was detected extending cranially from the mass. Taking into consideration the dog's signalment, progression of clinical signs, and MRI findings, a neoplastic process, such as spinal meningioma or other mesenchymal or round cell tumor, was considered most likely. Cytoreductive surgery with a dorsolateral laminectomy approach was performed to decompress the spinal cord and obtain a definitive diagnosis. Histologic examination of specimens of the mass confirmed the presence of a spindle cell tumor; immunohistochemical analysis revealed that the tumor was S100 positive and synaptophysin negative and therefore most likely a spinal meningioma. The dog made a good recovery after surgery, and was treated with tapering doses of prednisolone and gabapentin for 1 month. At a recheck examination 6 weeks after surgery, the dog had marked improvement with only residual mild proprioceptive deficits of the left pelvic limb. Radiation therapy was offered, but declined by the client.
Comments
Meningioma is the most common primary spinal cord neoplasm and the most commonly reported intradural extramedullary spinal mass in dogs.b Meningiomas are usually slow-growing tumors, causing a progressive and compressive myelopathy, and, as in the case described in the present report, more commonly affect the cervical portion of the spinal cord.1 The clinical signs include proprioceptive deficits, proprioceptive ataxia, variable grades of paresis, and signs of paraspinal or radicular pain.2 Meningiomas may be associated with lateralized and focal clinical signs, as evident in the dog of this report.
For the diagnosis of spinal meningiomas, MRI is considered the gold standard imaging modality because of the high-quality definition of CNS images, compared with that of CNS images obtained with other techniques, although myelography or CT with contrast medium administration may also be used.3 Characteristically, compared with the gray matter of the spinal cord, spinal meningiomas are isointense to hypointense on T1-weighted MRI images and slightly hyperintense on T2-weighted MRI images; contrast enhancement of the mass is typically intense and uniform on MRI images.2,3 Another common feature is the dural tail sign resulting from thickening and enhancement of the dura. The dural tail sign is often associated with intracranial meningiomas in dogs and humans, and has also been described in association with spinal meningiomas in humans.3 Cytoreductive surgery alone or followed by radiation therapy is considered an effective treatment in controlling the progression of spinal meningioma-related clinical signs. In a recent study,4 17 of 24 (71%) dogs with intraspinal meningiomas that underwent surgery had considerable improvement in clinical signs, similar to the postoperative findings for the dog of the present report. In that study,4 the mean survival time was 17.2 months with surgery alone and 39.4 months with surgery followed by radiotherapy.4 These results indicate that cytoreductive surgery and radiotherapy should be recommended for the treatment of spinal meningiomas in dogs.
Transverse T2-weighted (A), T1-weighted (B), and T1-weighted after contrast medium administration (C) MRI images of the vertebral column at the level of the C3-4 intervertebral disk space in a dog with progressive exercise intolerance of 3 months' duration and loss of balance and apparent generalized discomfort of 1 month's duration. A left-sided intradural-extramedullary lesion is present (white arrows). The lesion is hyperintense on T2-weighted and isointense on T1-weighted images, compared with the gray matter of the spinal cord. After contrast medium administration, marked contrast enhancement of the mass is visible on a T1-weighted image.
Citation: Journal of the American Veterinary Medical Association 250, 10; 10.2460/javma.250.10.1097
Transverse T2-weighted (A), T1-weighted (B), and T1-weighted after contrast medium administration (C) MRI images of the vertebral column at the level of the C3-4 intervertebral disk space in a dog with progressive exercise intolerance of 3 months' duration and loss of balance and apparent generalized discomfort of 1 month's duration. A left-sided intradural-extramedullary lesion is present (white arrows). The lesion is hyperintense on T2-weighted and isointense on T1-weighted images, compared with the gray matter of the spinal cord. After contrast medium administration, marked contrast enhancement of the mass is visible on a T1-weighted image.
Citation: Journal of the American Veterinary Medical Association 250, 10; 10.2460/javma.250.10.1097
Transverse T2-weighted (A), T1-weighted (B), and T1-weighted after contrast medium administration (C) MRI images of the vertebral column at the level of the C3-4 intervertebral disk space in a dog with progressive exercise intolerance of 3 months' duration and loss of balance and apparent generalized discomfort of 1 month's duration. A left-sided intradural-extramedullary lesion is present (white arrows). The lesion is hyperintense on T2-weighted and isointense on T1-weighted images, compared with the gray matter of the spinal cord. After contrast medium administration, marked contrast enhancement of the mass is visible on a T1-weighted image.
Citation: Journal of the American Veterinary Medical Association 250, 10; 10.2460/javma.250.10.1097
Footnotes
Philips Intera 1.5-T Pulsar System, Philips Medical Systems, Guildford, Surrey, England.
Petersen SA, Sturges BK, Vernau KM, et al. Spinal cord disease in dogs with neoplasia arising from the central nervous system (abstr). J Vet Intern Med 2006;20:735.
References
1. McEntee MC, Dewey CW. Tumors of the nervous system. In: Withrow SJ, Vail DM, Page RL, eds. Small animal clinical oncology. 5th ed. St Louis: WB Saunders Co, 2013; 583–596.
2. Lorenz MD, Coates JR, Kent M. Pelvic limb paresis, paralysis, and ataxia. In: Lorenz MD, Coates JR, Kent M, eds. Handbook of veterinary neurology. 5th ed. St Louis: Saunders, 2011; 109–161.
3. McDonnell JJ, Amy ST, Faissler D, et al. Magnetic resonance imaging features of cervical spinal cord meningiomas. Vet Radiol Ultrasound 2005; 46: 368–374.
4. Petersen SA, Sturges BK, Dickinson PJ, et al. Canine intraspinal meningiomas: imaging features, histopathologic classification, and long-term outcome in 34 dogs. J Vet Intern Med 2008; 22: 946–953.
