CT/MRI Society Case of the Month
January 2006
Sponsored by Eklin Medical Systems
Patient Identification Number: CTMRSOC1
Patient Surname Code: CTMRSOC
Patient First Name Code: ZWINGENBERGER
Accession Number: JAN06
Contributor: Allison Zwingenberger
Contributor’s Affiliation: University of California - Davis
Species: Canine
Breed: Rottweiler
Age at exam: 11 months
Gender: Male neutered
Presenting signs and pertinent history: Presented to the emergency service with a several month history of progressive hind limb lameness.
Clinical/Neuro exam findings: Ataxia, hind limb paresis, urinary incontinence.
Relevant Laboratory data: No significant abnormalities.
Primary clinical rule-out pre imaging: T3-L3 spinal cord lesion, congenital or developmental
Modality: MR
Manufacturer: GE Genesis Signa
Model/Field Strength: 1.5 T
Sequences Acquired:
Axial T1
Sagittal T1
Axial T2
Sagittal T2
Axial T1 post contrast
Sagittal T1 post contrast
CT/MR Findings: There is a mass at the level of T11, which is approximately half the length of a vertebral body. At the cranial aspect, the mass is broad based peripherally and extends into or compresses the spinal cord. This suggests an intradural-extramedullary lesion. More caudally, the mass appears intramedullary. The mass is hypointense on T2, slightly hyperintense on T1, and is mildly contrast enhancing. There is hyperintensity of the spinal cord on T2 cranial and caudal to the lesion.
CT/MR Assessment: Differential diagnosis for a young dog with an intradural-extramedullary or intramedullary mass are nephroblastoma and lymphosarcoma. T11 is the classic site for nephroblastoma, and is the most likely diagnosis. The hyperintensity of the spinal cord surrounding the lesion may be due to gliosis, edema or syringohydromyelia.
Post Imaging Management: The dog was taken to surgery, and the mass was biopsied and debulked. The mass was infiltrating the spinal cord and little tissue was able to be removed.
Outcome: The dog recovered from anesthesia without motor function to the hind limbs, but retained deep pain sensation. He was discharged with a poor prognosis and instructions for supportive care.
Final Diagnosis based on all diagnostic tests and outcome: Nephroblastoma
Comments:
Nephroblastomas are remainders of renal tissue. They occur between T10-L2 and are intradural-extramedullary. Nephroblastomas arise peripherally with a multilobular shape. They compress the cord and may infiltrate it, as in this case.
It may be difficult to determine whether the tumor is intradural-extramedullary or intramedullary on myelography and MR if the tumor is subpial. MR is better than myelography at distinguishing between these locations. Invasion of the cord may also complicate identification of the origin of the mass. Signs of an intradural-extramedullary tumor include widening of the subarachnoid space and outward displacement of epidural fat, which were not visible in this case. Another reported sign in people is a T1 hypointense band between the mass and the spinal cord which may represent tumor capsule and trapped CSF.
Intradural-extramedullary masses in the spinal cord of dogs have been reported as nephroblastoma, ependymoma, medulloepithelioma, neuroepithelioma, embryonal nephroma, embryonal adenosarcoma, renal adenocarcinoma and Wilms tumor. Immunohistochemical staining has recently supported the theory that all of these originate from renal tissue.
McConnell JF, Garosi LS, Dennis R, et al. Imaging of a spinal nephroblastoma in a dog. Vet Radiol Ultrasound 2003;44:537-541.