A 43-year-old man, with history of intravenous drug use (IVDU), presents to the emergency department (ED) with 2 weeks of fever, back pain, and progressive weakness in his legs bilaterally. He denies any history of trauma or prior surgery. His blood pressure (BP) is 130/75 mm Hg, heart rate (HR) is 106 beats/minute, respiratory rate (RR) is 16 breaths/minute, and temperature is 103°F. On physical examination, he has tenderness to palpation in the mid-lumbar spine, increased patellar reflexes, and decreased strength in the lower extremities bilaterally, with normal range of motion. Laboratory results reveal a white blood cell (WBC) count of 15,500/μL, hematocrit 40%, and platelets 225/μL. Urinalysis and lumbar spine X-rays are unremarkable. Which of the following is the most likely diagnosis?
b. Ankylosing spondylitis
c. Spinal epidural abscess
d. Vertebral compression fracture
e. Spinal metastatic lesion
The answer is c. Epidural abscesses are most commonly found in immunocompromised patients, IV DU, and the elderly. Signs and symptoms of epidural abscess usually develop over 1 to 2 weeks and include fever, localized pain, and progressive weakness, often localized to the lower extremities. An elevated WBC count, along with elevated inflammatory markers (ESR and CRP), are also commonly seen. MRI is the most useful diagnostic test. Unfortunately, X-ray and even CT may lack appropriate sensitivity for the diagnosis. S. aureus is the most common causative organism, followed by gram-negative bacilli and tuberculosis bacillus.
Fibromyalgia (a) is a common cause of chronic back pain, but one would not expect the physical findings (weakness and/or hyperreflexia) or laboratory abnormalities. Fibromyalgia should be a diagnosis of exclusion after other more emergent conditions are ruled-out. Inflammatory conditions, including ankylosing spondylitis (b), may cause back pain. The key findings in this disease include gradual onset of morning stiffness improved with exercise in a patient younger than 40 years. On physical examination, these patients may have limited back flexion, reduced chest expansion, and sacroiliac joint tenderness, all of which are nonspecific. Fever and weakness would not be expected. Back pain may result from vertebral compression fractures (d). These may be secondary to trauma or may be atraumatic in a patient with osteoporosis. Osteoporotic compression fractures usually involve patients older than 70 years or patients with acquired bone weakness (eg, prolonged steroid use). X-ray may miss some compression fractures. CT is a more sensitive diagnostic modality. Metastatic lesions (e) invade the spinal bone marrow, leading to compression of the spinal cord. Most common primary tumors include the breast, lung, thyroid, kidney, prostate (easily remembered by the acronym “BLT with Kosher pickles”), as well as lymphoma and multiple myeloma. Maintain a high level of suspicion for any ...