Bacterial Myositis Presenting with Severe Lumbosacral Pain and Neurological Deficits
Contributed by Drs. Peter Brofman and Pam Parnell
Veterinary Surgical Care, Mt. Pleasant, SC and Professional Veterinary Pathology Services
Columbia, SC
Clinical History
An 8y MC Pomeranian presented with an acute onset of paraparesis and severe pain. He had previously been on 1mg prednisone (0.25mg/kg) a day chronically for inflammatory bowel disease.
Physical and Neurological Examination
No abnormalities were noted on general physical examination. Neurological examination demonstrated good motor function in all four limbs. The only significant abnormalities noted on neurological examination were severe lumbosacral spinal hyperpathia and decreased withdrawal strength of both pelvic limbs.
Diagnostic Tests
Routine laboratory testing including biochemistry (I-STAT EC8) and hematology (PCV/TS) were normal. An MRI of the lumbar spine was performed (Figure 1). There is increased T2 signal noted within the sub-lumbar region extending along the ventral aspect of the sacrum. This area also shows intense contrast enhancement. There is enhancement noted extending along the nerve roots into the spinal canal at the LS junction and along the ventral aspect of the caudal lumbar and sacral regions. No obvious contrast enhancement of the LS disc space is identified. Obvious discospondylitis was not seen at this time but could not be completely excluded.
Figure 1
Case Progression: Abdominal ultrasonography did not demonstrate any abnormalities other than a slightly enlarged sublumbar lymph node. Urine was submitted for culture and the patient was treated with enrofloxacin and amoxicillin/sublactam, intravenously. The culture was positive for Enterobacter cloacae and was susceptible to enrofloxacin but resistant to amoxicillin/clavulanic acid. Despite 3 days of antibiotic therapy the patient continued to be extremely painful to the point of being unable to stand or walk. Abdominal exploration was pursued to obtain biopsies and culture of the abnormal sublumbar tissue.
Muscle Biopsy: The skeletal muscle interstitium was expanded by fibrin and mixed leuokocytes with neutrophils dominating (Figure 2, arrows point to neutrophils). Myofiber degeneration was mild, with a few individual fibers displaying increased eosinophilia, vacuolization and loss of cross striations. Neither microorganisms nor foreign material was observed. A diagnosis of fibrinopurulent myositis with myofiber degeneration was made.
Figure 2
Culture and Sensitivity:
Enterococcus species; susceptible to enrofloxacin
Conclusion
The patient was maintained on intravenous enrofloxacin 8.5 mgkg IV once a day and a 25 µg/hr Fentanyl patch with continual improvement over 5 days. The dog was discharged with oral enrofloxacin 8.5mg/kg po once a day and maintained on this dosage of antibiotic for 6 weeks. Analgesics (amantadine and gabapentin) were tapered off over 3 weeks. Ten weeks postoperatively the dog was pain free with minimal paraparesis and slightly decreased withdrawal reflex strength in both pelvic limb