3.0 Discussion
Lymphoma affecting the spinal cord, meninges, or vertebrae is reported
to be a rare cause of ataxia in the horse (Morrison et al. 2008).
The colt presented in this case report is younger than the typical
4–10-year-old age range often diagnosed with multicentric lymphoma
(Taintor and Schleis 2011). He was examined by a veterinarian nine days
prior to presentation and no neurologic deficits were noted at that
time, thus the ataxia was acute and had progressed significantly by the
time of presentation. An antemortem diagnosis of lymphoma was not
obtained in this horse. For safety reasons the neurologic examination
was not completed and the horse was humanely euthanized. Gross
examination of the spinal vertebrae revealed changes in the articular
facets multifocally was consistent with a diagnosis of vertebral
osteochondrosis dissecans (OCD). The OCD was initially thought to be a
cause for the ataxia, however histology and immunohistochemistry
confirmed a diagnosis of multicentric diffuse large B cell lymphoma.
Microscopic examination of the spinal epidural tissues in this case
revealed extensive local infiltration by neoplastic B lymphocytes. In
this case, both the epidural lymphoma and the vertebral OCD may have
contributed to the horse’s neurologic presentation. However, the lack of
histologic evidence of axonal Wallerian degeneration within the spinal
cord at the time of death suggests that the neoplastic infiltrates are
more likely to be the cause of the clinically noted ataxia than the
vertebral OCD.
Neurologic signs including ataxia and paresis may be present if the
central nervous system is affected, however lymphoma involving the
brain, spinal cord and meninges causing ataxia is rarely reported
(Morrison et al. 2008). Achieving an antemortem diagnosis of lymphoma is
a significant challenge for veterinarians and horses are often diagnosed
during post- mortem examination (Sheard and McGovern 2021). Spinal cord
compression due to neoplasia in horses has been diagnosed ante mortem
with myelography (Hirsch et al. 2009). Two cases of spinal
lymphoma have been diagnosed ante mortem with one miniature horse
surviving to 16 months with treatment until the time of the case report
being written (Hirsch et al. 2009; Finding et al. 2014).
In the present case there was no evidence of spinal cord compression and
myelography would not have been helpful in achieving an ante mortem
diagnosis of meningeal lymphoma. It has been suggested that lymphoma
should be considered as a differential diagnosis in horses presenting
with non-specific clinical signs or those horses who are unresponsive to
treatment (Sheard and McGovern 2021).