Three Factors May Predict Patients at Greatest Risk for Concomitant Epidural Abscesses
To help determine which spinal abscess patients are at the greatest risk for having another abscess in the spine, Ju et al. have created a predictive algorithm. They performed a retrospective review on 233 patients with spinal epidural abscesses who were treated at Brigham and Women’s Hospital in Boston from 1993 to 2011 and who had undergone imaging of the whole spine.
A single spinal epidural abscess is a serious condition that can be difficult to diagnose. Abscesses elsewhere on the spine that are not contiguous with the first abscess found are even harder to diagnose as typically the whole spine is not imaged, but rather the cervical, thoracic or lumbar spine is usually targeted, sometimes looking at two of these but rarely all three regions at the same time. These concurrent noncontiguous abscesses can be easy to miss if the whole spine has not been imaged.
Nonspecific back or neck pain is typically a presenting feature of spinal epidural abscess. The condition is misdiagnosed up to three-quarters of the time because it can resemble degenerative disc disease, osteomyelitis, meningitis, or endocarditis. Red flags include unexplained fevers, immunosuppression or concomitant diabetes.
A diagnosis of a spinal epidural abscess may be made with regional imaging of the spine, but unless there are neurological symptoms that point to the presence of another abscess at another region of the spine—a skip lesion—whole spine imaging is not routinely performed. Missing other lesions means the patient may require a second surgery and may have a secondary infection site that has not been optimally treated, which may result in major morbidity such as paralysis or even death.
About the Study
By comparing clinical results of the 22 patients who were found to have skip lesions to those with only one lesion, they identified three factors that are significantly different when a skip lesion is present. They are:
- A delay in presentation, defined as symptoms for more than seven days before hospitalization;
- A concomitant area of infection somewhere else in the body but outside the spine and paraspinal region; and,
- An erythrocyte sedimentation rate of greater than 95 mm/h at presentation.
Each of these factors was associated with a greater likelihood of having another noncontiguous spinal abscess.
- 91% of patients with a skip lesion had a delay in presentation of 7 or more days compared with only 40% of patients with a single abscess.
- 91% of patients with skip lesions had an infection somewhere outside of the spine compared with only 24% of patients with a single abscess.
- 83% of skip lesion patients had an erythrocyte sedimentation rate greater than 95 mm/h compared to only 30% of patients with a single abscess.
These factors allowed the authors to create a predictive algorithm. “According to this simplified algorithm, the predicted probability of a skip lesion was 73% for patients satisfying all three predictors, 13% for two, 2% for one, and 0% for zero predictors,” they stated.
“Low-risk patients (ie, those with zero or one predictor) likely do not require entire spinal column imaging at the time of presentation and, thus, can undergo imaging of the one symptomatic spinal region. On the other hand, those who possess all three predictors are at high risk of having a skip lesion and, thus, warrant imaging of the entire spine. Finally, considering the ramifications of missing a SEA [spinal epidural abscess] lesion, patients who possess two predictors should also undergo entire spinal column imaging.”
There are few case reports of noncontiguous spinal epidural abscesses in the medical literature, but Ju and his colleagues have attempted to validate their algorithm by applying it to some of these reports. They found that their algorithm would have shown that the patients were at increased risk of another abscess elsewhere on the spine.
The incidence of spinal epidural abscesses has been increasing, rising in recent years to 12.5 cases per 10,000 hospital admissions. This rise may be due to an aging population, a greater incidence of diabetes and immunosuppression, and rising rates of intravenous drug use and alcoholism. This study highlights the uncommon but potentially devastating scenario of noncontiguous spinal epidural abscess with three factors thought to suggest it’s probable occurrence.