Neck Pain in a Young Beagle

A 1-year-old, 27.3-lb (12.4-kg) neutered male beagle was previously presented for cervical hyperesthesia of 1 week’s duration. There was no known history of trauma and no similar prior episodes. The primary care clinician identified apparent neck pain and discharged the dog with carprofen (2 mg/kg PO every 12 hours) and tramadol (3 mg/kg PO every 12 hours) to be administered at home. Activity restriction was also recommended. Because the dog did not improve during the first week of treatment, he was subsequently presented to an emergency hospital.

At this emergency visit, physical examination is unremarkable, except for an elevated rectal temperature of 105.4°F (40.8°C). Neurologic examination reveals marked cervical hyperpathia on palpation and manipulation of the head and neck. CBC and serum chemistry profile results and MRI of the cervical spine are unremarkable. Lumbar CSF analysis (Figure 1) demonstrates elevated total protein (36.7 mg/dL; normal, <25 mg/dL), markedly elevated WBCs (512 cells/µL; normal, <3 cells/µL), and normal RBCs (2 cells/µL; normal, 0-2 cells/µL). Differential cytology reveals 62% nondegenerate neutrophils, 28% macrophages, and 10% small lymphocytes. There are no observed organisms or atypical cells.

Possible causes of CSF neutrophilic pleocytosis in patients of any age include inflammatory conditions (eg, steroid-responsive meningitis-arteritis [SRMA], granulomatous meningoencephalomyelitis [GME]), infectious meningitis (eg, bacterial, protozoal, fungal, rickettsial), neoplasia (eg, meningioma), degenerative disk disease, cerebrovascular accident, acute noncompressive nucleus pulposus extrusion, fibrocartilaginous embolic myelopathy, syringomyelia, and blood contamination of the sample. 

Intervertebral disk herniation, neoplasia, acute noncompressive nucleus pulposus extrusion, and fibrocartilaginous embolic myelopathy are uncommon to rare in dogs younger than 2 to 3 years of age; thus, vertebral column pain with or without concurrent paresis or ataxia should prompt early diagnostic investigation for the more common disorders that affect young dogs (eg, SRMA, diskospondylitis, immune-mediated polyarthropathy, trauma, atlantoaxial instability). 

SRMA is the primary differential diagnosis in this patient based on signalment, fever, cervical hyperpathia, normal MRI (which ruled out diskospondylitis), and CSF neutrophilic pleocytosis. GME and infectious meningitis could be possible but are considered less likely. MRI ruled out structural causes of neck pain. CSF culture and a neurologic infectious disease panel, including tests for borreliosis, anaplasmosis, Rocky Mountain spotted fever, blastomycosis, histoplasmosis, cryptococcosis, toxoplasmosis, and neosporosis, are negative. A presumptive diagnosis of SRMA is thus made. 

Although not performed in this case, elevated CSF immunoglobulin A levels would further support the presumptive diagnosis of SRMA. In addition, monitoring decreasing levels of nonspecific inflammatory marker C-reactive protein during treatment has been used as a clinical indicator of resolving disease.

FIGURE 1

CSF cytospin showing marked neutrophilic pleocytosis

GME = granulomatous meningoencephalomyelitis, SRMA = steroid-responsive meningitis-arteritis