Milo
2021
MEET MILO
Milo is an 8-month-old neutered male Boxer.
Milo presented to BVNS Woodstock in July of 2019 for a 3-day history of neck pain and lethargy. Neurologic exam findings included a dull / depressed mentation, low head carriage, and cervical hyperesthesia (neck pain) appreciated during direct palpation and range of motion testing. Cranial nerve examination, spinal reflexes, and proprioceptive testing were normal.
Differential Diagnoses
SRMA
GME / MUE
Diskospondylitis
Infectious meningomyelitis
Neoplasia
Recommendations
Cervical spinal MRI
CSF analysis
+/- Infectious disease testing (serum, CSF, urine)
+/- C-reactive protein
Diagnostic Results
Cervical Spinal MRI
Meningeal thickening / contrast enhancement
CSF Analysis
Appearance: Xanthochromic, turbid / cloudy
Protein: 100-300 mg/dL (normal < 30 mg/dL)
Cytology: 93% non-degenerative neutrophils
Neutrophilic pleocytosis
CSF Bacterial Culture
Negative
Toxoplasma / Neospora Serology
Negative
Cryptococcus Antigen
Negative
C-reactive Protein
128.0 mg/L (H), Range 0-12.0 mg/L
Diagnostic Conclusions: MRI / CSF analyses combined with signalment and clinical findings were consistent with steroid responsive meningitis arteritis (SRMA).
Steroid-Responsive Meningitis-Arteritis (SRMA)
Steroid-responsive meningitis-arteritis, also known as sterile meningitis, immune-mediated meningitis, and beagle pain syndrome, is a common cause of meningitis in young large breed dogs. Dogs typically are less than 2 years of age, with the majority (>75%) being less than 12 months old. Commonly affected breeds include Boxers, Bernese Mountain Dogs, Beagles, and Golden Retrievers among others. Clinical signs usually include an acute onset of neck pain and fever with an otherwise unremarkable neurologic examination. Diagnosis is achieved through a spinal fluid analysis and exclusion of other infectious and neoplastic etiologies with advanced imaging (i.e., MRI). Typical spinal fluid in these patients includes an increased number of white blood cells (pleocytosis), more specifically neutrophils, and an elevated CSF protein. Serum and CSF IgA is often elevated in SRMA.
This disorder is thought to arise from an aberrant immune response in which histopathology shows inflammatory infiltration of the leptomeninges and associated meningeal arteries. Treatment for this disease includes immunosuppression with corticosteroids and symptomatic treatment of pain with analgesics. Prognosis is generally good; however, clinical recurrence / relapse is not uncommon (up to 48% of patients). Azathioprine has recently been studied in cases of treatment-naïve SRMA. In this particular study, the relapse rate was lower than previously published cases (19%). C-reactive protein (CRP), an acute phase serum protein, is released from the liver in response to systemic inflammation. This biochemical marker is often elevated in dogs with SRMA, and may be monitored to track the disease progression, response to therapy, and evaluate suspected clinical relapses. Additionally, persistently elevated CRP levels warrant continuation of therapy.
Treatment
Prednisone: 2 mg/kg BID for 2 days, then 1 mg/kg BID for 2 weeks, with further tapering every 6 weeks
Doxycycline: 10 mg/kg SID
Clindamycin: 15 mg/kg BID (Discontinued with negative protozoal serology)
Gabapentin: 10 mg/kg TID as needed for pain
Final Diagnosis: Steroid-Responsive Meningitis-Arteritis
Clinical Follow-Up: Clinically normal at 2 weeks, 1 month, 3 months, and 6 months. Prednisone taper completed at 6 months.
Take-Home Points
Cervical spinal pain and fever are hallmark clinical findings in SRMA in large breed dogs under 2 years of age.
Elevated neutrophils in the CSF (neutrophilic pleocytosis) are common in autoimmune and infectious conditions of the spinal cord. CSF bacterial culture is essential to rule out bacterial meningitis before starting immunosuppressive doses of steroids.
C-reactive protein (CRP) is a marker of inflammation that is often markedly elevated in dogs with SRMA.
Azathioprine may be helpful as an adjunct therapy in SRMA.
