A Case Study from Our Neurology Department - MRI or CT?

Posted July 12, 2016 in Articles

A Case Study from Our Neurologist, Heather Jones, DVM, MS, DACVIM 

A 2 year old male-castrated Greyhound-mix was presented to me for evaluation of a 3 week history of hind limb weakness. Neurologic exam found mildly reduced hind limb proprioception with normal reflexes, normal thoracic limbs, normal cranial nerves and a normal cutaneous trunci reflex. Neuroanatomic localization: T3-L3 spinal cord segments.

A CBC/Chem was unremarkable. Radiographs of the thoracolumbar spine revealed questionable lysis of the 9th vertebral body and spinous process and a misshapen T10 pedicle and caudal articular process with wide T10-T11 dorsal articulation. A CT was then performed, which demonstrated a predominantly right-sided hypaxial/vertebral mass with aggressive lysis of the T9 and T10 vertebrae and with vertebral canal invasion and spinal cord compression. Cytology of fine needle aspirates of this mass was consistent with spindle cell neoplasia, with histiocytic sarcoma the most likely diagnosis. The patient’s owners met with our Oncologist, Doctor Carrie Wood, and decided to pursue chemotherapy with CCNU and prednisone.

Histiocytic sarcoma is uncommon in patients as young as in this present case, occurring more typically in patients 6-9 years of age. When it occurs in young dogs, histiocytic sarcoma tends to be more aggressive. The prognosis for this patient is, therefore, quite grave. Palliative radiation therapy can be considered. In cases that respond to CCNU therapy, average survival is estimated at 3-6 months.

MRI is the imaging modality of choice for the vast majority of neurologic cases due to its superior soft tissue (ie. brain, spinal cord) detail compared to CT. The present case exemplifies a scenario in which CT can be used without detracting from the ability to arrive at a diagnosis or to visualize the extent of disease. Compared to MRI, CT carries the benefits of reduced anesthesia time (usually 5-10 minutes vs. 45-60 minutes for MRI), reduced cost to the owner, and superior bony detail. We’re proud to now be able to offer both MRI and CT to our patients so the best imaging modality can be chosen for any specific case. Please contact me if you are a referring veterinarian and have case questions.