Case 171208-1

Seven-year-old, male castrated, Yorkshire terrier mix

The patient presented to the UC Davis neurologic service following acute onset of tetraparesis. The patient had signs of Horners syndrome, decreased motor function and absent reflexes in the pelvic limbs, absent cutaneous trunci reflex, and questionable mentation. Deep pain perception was intact. An MRI on the following day showed an intrinsic lesion extending from C6 to T4. On the second day of hospitalization, deep pain was noted to be absent in the pelvic limbs and the patient developed hematuria. Complete blood count and chemistry panel were unremarkable. CSF tap demonstrated marked inflammation. .

The bladder was diffusely dark red; both serosal and mucosal surfaces were affected. The bladder contained a large amount of red-tinged urine.

No significant findings were noted that related to the patients altered neurologic status.

This slide has three sections of similarly affected spinal cord, in which multiple vessels within the meninges and the cord, are variably occluded by pale, amphophilic, acellular material (fibrocartilaginous emboli). Both the grey and white matter have multifocal to coalescing regions of severe vacuolation and cavitation, with the side of the emboli being more severely affected. Throughout the vacuolated regions, axons are swollen and hypereosinophilic (spheroids), and there are multifocal digestion chambers noted.

No special stains.

Spinal cord (cervical and thoracic): severe, multifocal, asymmetric, acute myleomalacia with spheroids and multiple intravascular fibrocartilinous embolism (FCE)

The most significant finding in this case was acute, multifocal, myelomalacia affecting both the white and gray matter of the spinal cord within the cervical and thoracic spinal cord. Three fibrocartilaginous emboli (FCE) were identified within sections examined and are interpreted to be causal for the lesions within the cord.

Myelopathy due to FCE is considered a common lesion in dogs but is uncommon in other species. It is most common in large breed, young adults but can occur as young as 3 months of age. The pathogenesis is still poorly understood. Embolic fibrocartilage is thought to arise from degenerating discs. FCEs may be found in arteries (more commonly) or veins. Three potential pathways have been proposed for fibrocartilage gaining vascular access. 1. Revascularization of the inter-vertebral disc, which occurs with age in people or following degeneration of the disc. 2. Formation of Schmors nodes, a structure where disc material protrudes into the vertebral body. However, this is rare in canine patients. 3. Inter-vertebral disc vasculature persists from the neonatal state. Collateral circulation to the spinal cord is extensive and it is thought that there must be a shower of emboli in order to lead to severe infarction and subsequent clinical signs. Lesions are generally focal and asymmetric.

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