Clinical History
Three weeks prior to presentation the owner noticed hind limb lameness and discomfort when touching the leg. This progressed to bilateral hind limb lameness and a difficulty in sitting normally.

Physical and Neurological Examination
On examination, the dog was ambulatory but had marked hind limb ataxia. Conscious proprioceptive deficits were present in both hind limbs, and hind limb local myotactic reflexes were reduced. Some discomfort was noted on palpation of the caudal lumbar spine. A neuromuscular disease was suspected.

Diagnostic Testing

CBC and Serum Chemistry:  No abnormalities

Serum antibody titer for Toxoplasma gondii and Neospora caninum:  Negative

MRI Thoracic/lumbar/sacral spine: No abnormalities

Thyroid: Mildly decreased T4 at 7.1 nmol/l (reference 13-52 nmol/l)

Muscle and Nerve biopsy: The only abnormality identified within a limb muscle biopsy was scattered angular atrophied fibers of both fiber types supporting mild or early denervation. Mononuclear cell infiltrates were present within fresh frozen (modified Gomori trichrome stain, upper left) and plastic embedded (Toluidine blue-basic fuchsin stain, upper right) peripheral nerve specimens consistent with neuritis, arrows point to cellular infiltrates. The cellular infiltrates were composed of CD8+ (brown stain, lower left) and CD4+ (brown stain, lower right) T lymphocytes.

Diagnosis and Outcome
The cellular infiltrates within the peripheral nerve specimens were consistent with neuritis of possible immune origin or less likely a lymphoma affecting peripheral nerves. Clinical evaluations did not reveal evidence of lymphoma in any other organ systems. Prednisolone therapy was initiated at an anti-inflammatory dosage. The dog was treated for 3 months and was off all medication for one month at the time of follow-up examination. The dog had begun to gradually improve prior to starting the medication and there was slow general improvement over the following few months. The ataxia was largely resolved and spinal pain was no longer evident. Proprioception was normal in the right hind limb and slightly slowed in the left hind limb. There was also mild muscle atrophy in the left hind. Myotactic reflexes were still reduced in both hind limbs. The dog is currently receiving no medication. The owner reports that the dog is about 85% back to normal.