EMS brought in a 67-year-old man after they found him lying supine by a tree. His girlfriend, who was at the scene, said he had been lying in the same position by the tree for the past five days. She described him as typically “lively and animated,” but said he had become more confused recently. EMS knew of him because of prior calls for alcohol intoxication, but his girlfriend said he had not had a drink for two to three days. The patient said he fell five days earlier and complained only of shoulder pain.
He was noted to be lethargic with slurred speech and significant apathy. He was covered in leaves and other debris. He was able to assist when rolled to the side to examine his back, but he did not appear to be moving his right leg. Strength exam revealed 4/5 strength in all extremities but 0/5 strength in his right lower extremity without pain response. A significant workup was started to determine the cause of the patient's symptoms.
He was taken immediately for a head CT that was unremarkable. A lumbar puncture was performed given the altered mentation, low-grade fever (99.5°F), leukocytosis (13.7), tachycardia (108 bpm), hypotension (94/78 mm Hg), and elevated lactate (3.2 mmol/L) without other source of infection (negative urine and chest x-ray). The CSF showed obvious xanthochromia with 0 RBC and 2 nucleated cells in tube 4 with protein 556 mg/dl and glucose 36 mg/dl. An MRI was obtained to evaluate for epidural abscess that could be causing possible pseudo-xanthochromia and neurologic deficit. The MRI revealed a large epidural abscess extending from C6-T6. The patient went to the OR with orthopedic surgery for a washout, and cultures showed methicillin-susceptible Staphylococcus aureus (MSSA). Further physical exam and searching for the source found a concerning area on his right elbow that showed abscess and osteomyelitis that was also positive for MSSA. He was discharged home after OR washouts and IV antibiotics. His mental status returned to baseline and was felt to be secondary to infection and metabolic response because it improved quickly after fluids and antibiotics. What is his diagnosis?
Find the diagnosis and case discussion on p. 18.
Diagnosis: Spinal Epidural Abscess
Spinal epidural abscess is a rare but potentially devastating infection most commonly found in the lumbar spine. Spinal epidural abscess formation occurs either from hematogenous spread (45%) or direct inoculation (55%) secondary to trauma or surgery. Risk factors for epidural abscess formation include immunocompromised status, diabetes mellitus, intravenous drug use, HIV/AIDS, malignancy, chronic steroid usage, renal failure, intravascular devices, and spinal surgery. (J Am Acad Orthop Surg 2016;24:11.) Staphylococcus aureus causes about two-thirds of cases. Less common causative pathogens include coagulase-negative staphylococci and gram-negative bacteria, particularly Escherichia coli and Pseudomonas aeruginosa. (N Engl J Med 2006;355:2012.)
Patients with spinal epidural abscesses generally present with back pain, fever, or a neurologic deficit. Only about one-third of patients are noted to have a neurologic deficit at the time of presentation. (N Engl J Med 2006;355:2012.) A retrospective case-control study examining 63 patients with spinal epidural abscesses and 126 controls showed the classic triad of back pain, fever, and neurological deficit was present in only 13 percent of patients. (J Emerg Med 2004;26:285.)
Leukocytosis is present in less than 45 percent of patients, while erythrocyte sedimentation rate and C-reactive protein are almost uniformly elevated. (J Am Acad Orthop Surg 2016;24:11.) CSF analysis typically shows a high level of protein and pleocytosis. A CSF gram stain is usually negative, and CSF cultures are positive in less than 25 percent of patients. (N Engl J Med 2006;355:2012.)
Spinal epidural abscess is a rare condition that may appear with nonspecific findings such as back pain, fever, leukocytosis, or elevated inflammatory markers, and is often misdiagnosed on presentation, particularly in neurologically intact patients. (N Engl J Med 2006;355:2012.)
MRI is the imaging modality of choice when epidural abscess is suspected. MRI has a reported sensitivity of 96% and specificity of 94% in diagnosing spinal infections. Imaging should be obtained with and without gadolinium contrast unless medically contraindicated because the use of gadolinium increases the ability to detect extradural fluid collections. (J Spinal Disord Tech 2015;28:E316.) Spinal epidural abscesses generally extend over three to four vertebrae (N Engl J Med 2006;355:2012), and imaging should include the entire spine to evaluate for noncontiguous abscesses, which may be present in 10 percent or more of patients with epidural abscesses. (J Spinal Disord Tech 2015;28:E316.)
Surgical drainage with systemic antibiotics is the treatment of choice for epidural abscess. Initial antibiotic therapy should include coverage for methicillin-resistant Staphylococcus aureus and gram-negative organisms. (N Engl J Med 2006;355:2012.) Guided percutaneous drainage can be used, but may not be possible to perform safely depending on the particular situation. Along with treatment of the spinal abscess, eradication of the primary infection site is essential. (J Am Acad Orthop Surg 2016;24:11.)
The usual duration of antibiotic therapy is at least six weeks because vertebral osteomyelitis exists in most patients with spinal epidural abscess. Intravenous antibiotic administration is preferred. (N Engl J Med 2006;355:2012.)
The most important predictor of the final neurologic outcome is the patient's neurologic status immediately before surgery. Irreversible paralysis, the most feared complication of spinal epidural abscess, affects four to 22 percent of patients, and is associated with delayed diagnosis. (N Engl J Med 2006;355:20128.) The current mortality rate of spinal epidural abscesses is approximately five percent, with death usually resulting from uncontrolled sepsis, evolution of meningitis, or other underlying comorbidities. (J Spinal Disord Tech 2015;28:E316.) This case highlights the importance of keeping a wide differential when encountering frequent flyers in the emergency department rather than anchoring on past visits. A full physical exam on every patient should be performed and any abnormalities deserve an appropriate workup to determine the cause in a timely manner.
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