AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

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• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
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INTRODUCTION

Section 2 of 11  

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Background

Epidural and subdural infections are similar in that both are suppurative infections that may cause clinical problems by extrinsic compression of CNS structures. They differ in almost all other ways. Both are uncommon and are often discovered in the course of investigation for other, more common, clinical entities.

Approximately 90% of epidural infections are located along the spinal neuraxis and cause symptoms referable to the spinal cord. Intracranial epidural infection frequently is associated with a subdural infection. In contrast, 95% of subdural infections are located intracranially with a predilection for frontal lobe involvement. For purposes of this discussion, epidural infection is considered synonymous with spinal epidural abscess, and subdural infection is considered synonymous with intracranial subdural empyema.

Pathophysiology

Epidural infection, by definition, involves the epidural space between the bone and dura. This is a true space in the spinal canal that posteriorly is filled with epidural fat, small arteries, and a venous plexus. Infections tend to spread over several vertebral levels. Anteriorly, the spinal epidural space is a potential space because the dura adheres tightly to the vertebral body. Abscesses are more frequent in the larger posterior epidural space.

Hematogenous spread with seeding of the epidural space is the suspected source of infection in most children and is thought to occur in many adult cases as well. Reported sources of seeding are numerous and include endocarditis, infected indwelling catheters, urinary tract infections, abdominal infections, and others. Direct extension of infection from vertebral osteomyelitis occurs in adults but rarely in children. A source of infection is not identified in many patients. Spinal epidural abscess following epidural steroid injection and epidural catheter placement has been reported.

The effects of epidural abscess are often from involvement of the vascular supply to the spinal cord and subsequent infarction rather than from direct compression.

Subdural infections (eg, subdural empyema) occur beneath the dura. Infection spreads over the brain and may penetrate into the parenchyma of the brain or may cause diffuse cerebral edema.

Frequency

United States

Epidural abscesses seem to be increasing in frequency, possibly related to an increase in intravenous drug abuse or an increase in spinal operative procedures. Reported incidence ranges from 0.2-1.2 cases per 10,000 hospital admissions up to 12.5 cases per 10,000 admissions at a tertiary care center.¹

No clear estimate of frequency for subdural empyema exists, but it is uncommon. Subdural empyema is said to account for 15-25% of pyogenic intracranial infections. Extrapolating from frequency figures for brain abscess yields roughly 1-2 cases per 10,000 admissions to a tertiary care center.

Mortality/Morbidity

• Spinal epidural abscesses are, in themselves, not fatal. However, with complications and associated conditions, mortality rates of 5-23% are reported.² Paraplegia or quadriplegia is a frequent sequela. Disability seems related to severity and duration of symptoms prior to institution of therapy.
• Most case series of subdural empyema report mortality in the 30% range. About 40% of survivors develop a seizure disorder. This disorder was uniformly fatal in the preantibiotic era.

Sex

• No predilection exists with epidural abscess.
• In subdural empyema, men are 3-4 times more commonly affected than women.

Age

• Spinal epidural abscess may be found in all age groups; on average, patients are older than 50 years. Intravenous drug users with spinal epidural abscesses are, on average, aged 35 years.
• Subdural empyema may occur at any age but is most frequent in the second and third decades of life.

CLINICAL

Section 3 of 11  

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• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
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History

• Spinal epidural abscess
• • Early presentations may be subtle, and diagnosis may be difficult, if not impossible, at early stages.
  • History of fever is often but not invariably present.
  • Localized back pain may be present.
  • Neurologic deficit is consistent with a spinal cord syndrome.
  • History may suggest a source or cause of infection (eg, soft tissue infection, intravenous drug abuse, recent epidural injections, neurosurgical procedures or other instrumentation).
  • Duration of symptoms is typically a few days but may extend over weeks. Symptom onset may also be abrupt.
  • Radicular pain consistent with nerve root irritation may be present and confound evaluation, particularly if the pain occurs in the abdomen or the chest.
  • Progressive sensory disturbances in the extremities, weakness, and incontinence suggest progression to spinal cord involvement.
  • An immunosuppressive condition, such as diabetes, alcoholism, or HIV infection, is often present.
• Subdural empyema
• • Headaches may be initially unilateral but then become generalized.
  • Fever and vomiting may be present.
  • Focal or generalized seizures may be present.
  • Tempo of clinical course usually is fulminant with rapid deterioration.
  • Uncommon indolent courses may follow neurosurgical procedures.
  • A history of recent sinusitis or otitis media may be present.
  • Antibiotic therapy may lessen systemic symptoms.

Physical

• Spinal epidural abscess
• • Localized tenderness to percussion or palpation over the involved region may be present.
  • Signs of spinal cord dysfunction, such as loss of sphincter tone, sensory loss, or localized motor weakness, may be present.
  • Reflexes may vary from hypoactive or absent to brisk and spastic.
• Subdural empyema
• • Focal neurologic deficit or focal seizures may be present in a patient with signs of meningeal irritation.
  • Altered mental status is present in most patients.
  • Focal neurologic signs, such as hemiparesis or aphasia, may precede further alteration in consciousness.
  • Papilledema is absent in most patients, reflecting a short duration of increased intracranial pressure.

Causes

• Spinal epidural abscess
• • Most cases arise from hematogenous seeding of the epidural space from a distant source of infection.
  • Another etiology is extension of infection from adjacent vertebral osteomyelitis.
  • Penetrating trauma, recent neurosurgical procedures, or recent epidural injections or catheter placements are other causes.
  • Staphylococcus aureus is the most frequent bacteriologic cause, with methicillin-resistant S aureus (MRSA) being increasingly reported.
• Subdural empyema
• • Most cases are extensions of infections from the paranasal sinuses.
  • Otitis media or mastoiditis also may extend into the subdural space.
  • Recent neurosurgical procedures and penetrating trauma cause other cases.
  • Hematogenous spread of infection from a pulmonary source also has been reported.

DIFFERENTIALS

Section 4 of 11  

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• Clinical
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• Workup
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• Follow-up
• Miscellaneous
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WORKUP

Section 5 of 11  

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• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
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Lab Studies

• Sedimentation rate is often elevated and advocated by some as a screening laboratory test.
• CBC may reveal a high WBC count (but normal WBC counts reported as well).
• Other tests may include blood cultures, electrolyte levels, and preoperative laboratory studies (as needed by neurosurgery, eg, prothrombin time [PT], activated partial thromboplastin time [aPTT], ECG, chest radiograph [CXR]).

Imaging Studies

• Spinal epidural abscess
• • Immediate imaging of the spinal canal is needed. Techniques that are immediately available vary at different institutions.
  • MRI is the procedure of choice because of the noninvasive nature of the test. It also delineates the extent of the abscess, which frequently extends over several levels.
  • CT scan myelography or conventional myelography may be used if MRI is unavailable.
• Subdural empyema: Cranial CT scan is the modality of choice.

Procedures

• Lumbar puncture
• • Lumbar puncture (LP) is relatively contraindicated in both conditions because of the risk of precipitating shifts of CNS content in the presence of a mass lesion. However, LP often is performed in the course of patient evaluation, particularly since meningitis is in the differential diagnosis.
  • A typical cerebrospinal fluid (CSF) profile for parameningeal infections would reveal only a few inflammatory cells with elevated protein level and decreased glucose level.

TREATMENT

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Prehospital Care

• Supportive care, including intravenous access, oxygen, and monitoring, as indicated

Emergency Department Care

• Stabilization procedures may be needed. Most efforts are directed at examination and appropriate imaging for definitive diagnosis. Do not delay antibiotic therapy for imaging procedures or other workup in toxic patients or in those patients with a high likelihood of these disorders or when meningitis remains a possibility in the differential diagnosis. For nontoxic and stable patients, antibiotic therapy is ideally guided by results of abscess aspiration or drainage.
• Spinal epidural abscess
• • Treatment is medical and surgical, with surgery frequently necessary if signs of spinal cord compression are present.
  • Empiric antibiotic coverage should include an antistaphylococcal penicillin or a cephalosporin.
  • Empirical antibiotic therapy in most cases should provide coverage against MRSA with vancomycin.³
• Subdural empyema
• • Immediate surgical evacuation of the empyema is necessary.
  • Some controversy exists as to whether a craniotomy flap or multiple burr holes are the superior therapy.
  • Direct antibiotic therapy against S aureus, the most common pathogen.
  • If a neurosurgical procedure has recently occurred, combination therapy, as described above, is recommended.

Consultations

• Expeditious neurosurgical consultation should be initiated when either of these entities is suspected.

MEDICATION

Section 7 of 11  

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Initiate antibiotic treatment as soon as possible in conjunction with surgical therapy.

Drug Category: Antibiotics

S aureus is a common pathogen in these conditions, although subdural empyema is often polymicrobial with streptococcal species. Antistaphylococcal therapy should be included in any regimen. For spinal epidural abscess, vancomycin can be used pending culture results. For subdural empyema, recommendations vary, but reasonable empiric therapy would include vancomycin, a third-generation cephalosporin, and metronidazole pending bacterial identification with drug sensitivities.

FOLLOW-UP

Section 8 of 11  

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Further Inpatient Care

• Spinal epidural abscess: Once diagnosed, further inpatient and outpatient care will be under the direction of the neurosurgeon and/or infectious disease consultant. Generally, if signs of spinal cord compression are present, the treatment includes immediate surgical drainage with antibiotic treatment. If spinal cord compression is not present, some advocate CT-guided abscess aspiration and a prolonged antibiotic course or antibiotic medication alone. Patients must be carefully monitored, and should neurologic dysfunction develop, immediate surgical decompression is recommended.
• Subdural empyema: Immediate surgical evacuation is recommended as discussed above. Initiate antibiotic therapy as early as possible and continue through the postoperative period. Antibiotics and duration are at the discretion of the admitting physician.

Transfer

• Transfer to a facility with appropriate resources (neurosurgical and neuroimaging), if necessary. If these infections are suspected, antibiotic therapy should be initiated prior to transfer. Physician-to-physician contact is necessary to coordinate care.

Complications

• Spinal epidural abscess may impair spinal cord function through compression, although current thinking is that thrombosis of vertebral vessels with secondary infarction of the cord may be the mechanism of injury.
• Subdural empyema may precipitate cerebral venous thrombosis or cause increased intracranial pressure, resulting in decreased cerebral perfusion and diffuse cerebral edema. Seizures are common.

Prognosis

• An epidural abscess has primary complications of paraplegia or quadriplegia, including all sequelae associated with those conditions. A spinal rehabilitation program may be necessary to minimize long-term problems.
• Acute subdural empyema fatality rate is about 40%. Survivors of subdural empyema may develop seizures either in the acute phase or during convalescence.

MISCELLANEOUS

Section 9 of 11  

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• Miscellaneous
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Medical/Legal Pitfalls

• Spinal epidural abscess
• • Failure to promptly diagnose this condition is the greatest pitfall. Given the multitudes of patients who present to the ED for treatment of back pain, the challenge is to distinguish this rare needle in the enormous haystack.
  • Neurologic findings or complaints, such as a sensory loss, weakness in the extremities, or abnormal reflexes, should prompt further evaluation.
  • Localized spinal tenderness or tenderness to percussion may suggest local inflammation.
  • Fever, if present, may help to distinguish these patients.
  • High-risk behavior, such as intravenous drug abuse, should heighten suspicion.
• Subdural empyema
• • Sinusitis is common. Subdural empyema as a complication of sinusitis is rare.
  • Neurologic findings, altered level of consciousness, general toxic appearance, or worsening symptoms in spite of antibiotic treatment might prompt further investigation.
  • This uncommon and serious complication develops in a few rare patients treated as outpatients for common infections.

MULTIMEDIA

Section 10 of 11  

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Media file 1:  Spinal epidural abscess with cord edema and compression. Abscess extends into paravertebral tissues.
	View Full Size Image
Media type:  MRI

REFERENCES

Section 11 of 11

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1. Bluman EM, Palumbo MA, Lucas PR. Spinal epidural abscess in adults. J Am Acad Orthop Surg. May-Jun 2004;12(3):155-63. [Medline].
2. Tunkel AR. Subdural empyema, epidural abscess, and suppurative intracranial thrombophlebitis. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Disease. Vol 1. Elsevier Churchill Livingstone Inc; 2005:1164-1171.
3. Darouiche RO. Spinal epidural abscess. N Engl J Med. Nov 9 2006;355(19):2012-20. [Medline].
4. Davis DP, Wold RM, Patel RJ, Tran AJ, Tokhi RN, Chan TC, et al. The clinical presentation and impact of diagnostic delays on emergency department patients with spinal epidural abscess. J Emerg Med. Apr 2004;26(3):285-91. [Medline].
5. Grewal S, Hocking G, Wildsmith JA. Epidural abscesses. Br J Anaesth. Mar 2006;96(3):292-302. [Medline].
6. Hooten WM, Kinney MO, Huntoon MA. Epidural abscess and meningitis after epidural corticosteroid injection. Mayo Clin Proc. May 2004;79(5):682-6. [Medline].
7. Joshi SM, Hatfield RH, Martin J, Taylor W. Spinal epidural abscess: a diagnostic challenge. Br J Neurosurg. Apr 2003;17(2):160-3. [Medline].
8. Prendergast H, Jerrard D, O'Connell J. Atypical presentations of epidural abscess in intravenous drug abusers. Am J Emerg Med. Mar 1997;15(2):158-60. [Medline].
9. Reihsaus E, Waldbaur H, Seeling W. Spinal epidural abscess: a meta-analysis of 915 patients. Neurosurg Rev. Dec 2000;23(4):175-204; discussion 205. [Medline].
10. Rigamonti D, Liem L, Sampath P, Knoller N, Namaguchi Y, Schreibman DL, et al. Spinal epidural abscess: contemporary trends in etiology, evaluation, and management. Surg Neurol. Aug 1999;52(2):189-96; discussion 197. [Medline].
11. Siddiq F, Chowfin A, Tight R, Sahmoun AE, Smego RA Jr. Medical vs surgical management of spinal epidural abscess. Arch Intern Med. Dec 13-27 2004;164(22):2409-12. [Medline].
12. Soehle M, Wallenfang T. Spinal epidural abscesses: clinical manifestations, prognostic factors, and outcomes. Neurosurgery. Jul 2002;51(1):79-85; discussion 86-7. [Medline].

Article Last Updated: Sep 18, 2007