Nonoperative Management of a Multi-Regional Epidural Abscess with Neurological Dysfunction

Discussion

SEA is a rare condition first described in the literature in 1761 by Morgagni and involves a collection affecting the epidural space in the spinal canal.⁴ Although rare, with an estimated incidence of 0.2-2 cases per 10,000 hospital admissions, this incidence of SEA increasing¹ and it is estimated to have almost doubled in the last decade. This increase is thought to be due to several factors, including increasing age of the population, rising intravenous drug use and an increase in the number of invasive spinal procedures.^5–8

Despite this increase, the number of multi-regional spinal abscesses reported in the literature remains small.

SEA can affect patients of any age group, and large case series have shown a male to female ratio of 2:1.⁹ Although some cases occur in patients with no predisposing factors, epidural abscesses occur more commonly in those with co-morbidities. Individuals with any cause for immunocompromise, including diabetes mellitus, human immunodeficiency virus, intravenous drug use, chronic renal disease, malignancy and long term steroid use are at increased risk of developing SEA in comparison to the general population.¹⁰

The development of an epidural abscess can occur by several mechanisms. In approximately 50% of cases the cause is haematogeneous seeding.

Iatrogenic inoculation from either invasive spinal procedures, diagnostic or therapeutic percutaneous injections can result in the formation of an abscess. Finally, contiguous spread can lead to extension and formation of SEA, most often from an adjacent vertebral body osteomyelitis or discitis.^{5, 11, 12}

Early recognition and treatment is the most important determinant in reducing the associated neurological morbidity and potential mortality.

Patients with SEA usually present with back pain, symptoms of systemic upset, with or without accompanying neurological symptoms. Physical examination will often reveal spinal tenderness to palpation and pyrexia. Neurological deficit, if present, can be extremely variable, ranging from radiculopathy to paraplegia or quadriplegia.^13–15

As in our case, patients with SEA often first present to the accident and emergency department; it is therefore important for clinicians to have a high index of suspicion in this patient group in order to appropriately investigate and instigate treatment as quickly as possible.

Blood parameters will show raised inflammatory markers. CRP and ESR are perhaps the most helpful markers and are more often raised in cases of SEA compared to white cell count.¹⁵ Blood cultures are positive in up to 60% of cases; the identification of the infecting organism is important in order to tailor antimicrobial therapy.^16–18 Patients should also be investigated for a possible primary source of bacteraemia. By far the most common infecting organism is Staphylococcus aureus, being isolated in up to 70% of cases; this is followed by Streptococcus in 7%. Although uncommon overall, gram negative bacilli are often seen in intravenous drug users.^{9, 19}

Gadolinium-enhanced magnetic resonance imaging of the whole spine is the investigation of choice for diagnosis and determining the extent and location of the abscess.^{8, 20, 21}

Even with a rising incidence of SEA, there is currently no clear consensus regarding treatment; the use of nonoperative versus surgical management remains widely debated. Early reviews strongly favoured surgical evacuation in all patients with epidural abscesses. However, a recent systematic review has shown an increasing number of patients being managed nonoperatively when presenting with back pain in the absence of neurology, compared to previously published literature, with no statistically significant difference in outcomes between those in the different treatment groups.²²

Primary nonoperative treatment with antibiotics has been described in the literature.^{3, 22} Several factors to favour medical management have been identified, including patients over 50 years old or with significant co-morbidities; the absence of neurology, or conversely, neurological dysfunction that has been persistent for more than 36 hours. As in our case, extensive multi-regional SEA has also been described as an indication for conservative management.^{22, 23}

Strong indications for emergency surgery include clinical or neurological deterioration despite intravenous antibiotic therapy targeted to the infecting organism, spinal instability or progressive deformity. The aims of surgical intervention are to reduce and eradicate the infective load, decompression and preservation spinal stability.²⁴

Patient outcomes have markedly improved in recent years, with improved awareness and better diagnostic tools to allow early recognition and treatment. However, there is still a significant associated morbidity and mortality. This is largely dependent on patient factors; poorer outcomes are seen in patients with overt sepsis at the time of presentation as well as significant immunocompromise or multiple comorbidities. Infection with methicillin resistant staphylococci species is also linked with poor prognosis. ^{25, 26}

Neurological prognosis is also variable. Important factors in neurological outcomes include the severity of dysfunction at the time of presentation and the duration between onset of neurological symptoms and commencement of treatment.^{27, 28}

Despite the increasing incidence of spinal epidural abscesses, multiregional abscesses continue to be a rare problem with very few cases reported in the literature. Treatment remains debated and different authors have described successful treatment with both operative and nonoperative management, depending on patient factors and presenting symptoms.

This case emphasises the importance of early clinical recognition of patients exhibiting signs and symptoms of SEA as well as early treatment with antibiotics. Despite the presence of neurological dysfunction, which has previously been described as an indication for surgery, we have demonstrated that widespread multiregional epidural abscesses can be successfully treated nonoperatively with antibiotics, provided there is early clinical improvement. Complete resolution of neurology and radiological findings occurred in this case with antibiotics alone.