Malpractice Counsel: Pain in the Back, Pain in the Butt(ocks)

Discussion

Spinal epidural abscesses (SEAs) are an uncommon but serious infection that must be recognized and treated promptly to avoid permanent neurological complications. These abscesses occur most commonly in the thoracolumbar area, where the epidural space is larger. Since the epidural space is a vertical sheath, an abscess that begins at one level commonly extends to multiple levels; SEAs frequently range three to five spinal cord segments.¹ The median age of onset for an SEA is approximately 50 years, and they are more common in men.¹ Risk factors for the development of an SEA include epidural catheter placement, paraspinal injections of glucocorticoids or analgesics, IV drug abuse, human immunodeficiency virus infection, diabetes mellitus, alcohol abuse, trauma, tattoos, acupuncture, and hemodialysis.^1,2 The most common pathogens causing an SEA are Staphylococcus aureus, gram-negative bacilli, and Streptococci.² The percentage of S aureus that are methicillin-resistant (ie, MRSA) varies by geographic location, ranging from 40% to 68%.^3,4

Signs and Symptoms

Typically, patients with an SEA initially present with fever, malaise, and nonspecific symptoms and, as seen in this case, generally present several times to a physician before the correct diagnosis is made.¹ Unfortunately, the classic triad of fever, spinal pain, and neurological deficits is only infrequently observed. Fever is present in approximately two-thirds of patients, and spinal pain is present approximately 90% of the time.²

There are four stages of disease progression associated with SEAs. A typical scenario involves the initial complaint of back pain (stage I); followed by pain in the distribution of an affected nerve root (stage II); then motor weakness, sensory changes, and bladder or bowel dysfunction (stage III); and, finally, paralysis (stage IV).^1,2

Diagnosis

Laboratory studies typically are not helpful in making the diagnosis. A complete blood count may show leukocytosis, but values can also be within the normal reference range. Acute phase reactants like erythrocyte sedimentation rate and C-reactive protein are commonly elevated with an SEA, but are neither sensitive nor specific.¹

To make the diagnosis, the best test is a gadolinium-enhanced MRI of the spine.² It may be prudent to image the entire spine because multiple skip lesions are common, and a patient may not have pain or tenderness in all affected areas. If MRI is not available, a CT scan of the spine with IV contrast is an acceptable alternative.¹

Once an SEA is identified, it is important to determine the organism(s) responsible for the infection. The best culture source is from the abscess itself (90%) followed by blood cultures (62%) and cerebrospinal fluid, which are positive only 19% of the time.¹

Treatment

Once an SEA is diagnosed, a multidisciplinary approach involving hospitalists, interventional radiology, neurosurgery, and/or orthopedics is best. The most effective management is to treat patients with a combination of surgical decompression and drainage with systemic antibiotic therapy, typically for a minimum of 4 weeks. A minority of select patients may be treated with antibiotics alone.

References

1. Sexton, DJ, Sampson JH. Spinal epidural abscess. UpToDate Web site. https://www.uptodate.com/contents/spinal-epidural-abscess. Updated June 23, 2016. Accessed January 9, 2017.
2. Darouiche RO. Spinal epidural abscess. N Engl J Med. 2006;355(19):2012-2020. doi:10.1056/NEJMra055111.
3. Chen WC, Wang JL, Wang JT, Chen YC, Chang SC. Spinal epidural abscess due to Staphylococcus aureus: clinical manifestations and outcomes. J Microbiol Immunol Infect. 2008;41(3):215-221.
4. Krishnamohan P, Berger JR. Spinal epidural abscess. Curr Infect Dis Rep. 2014;16(11):436. doi:10.1007/s11908-014-0436-7.