Epidural abscess overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]; Anthony Gallo, B.S. [3]
Overview
An epidural abscess is a rare suppurative infection of the central nervous system, a collection of pus localised in the epidural space lying outside the dura mater, which accounts for less than 2% of focal CNS infections. [1] It may occur in two different places: intracranially or in the spinal canal. Due to the fact that the initial symptoms and clinical characteristics are not always identical and are similar to other diseases, along with the fact that they are both rare conditions, the final diagnosis might be delayed in time. This late diagnosis comes at great cost to the patient, since it is usually accompanied by a bad prognosis and severe complications with a potential fatal outcome. According to the location of the collection, the abscess may have different origins, different organisms involved, symptoms, evolutions, complications and therapeutical techniques. [2] With the advent of antibiotics, along with accurate imaging studies and surgical techniques, prognosis and outcome of epidural abscess have greatly improved.
Historical Perspective
In general, abscesses were first described by Hippocrates between 400-370 B.C. Despite scientific advances, both epidural abscesses remain a serious health condition, with significant risks for patients. However, diagnosis, management and outcome have been considerably improved due to more accurate imaging studies, better antibiotics, and improved surgical techniques.[2]
Classification
Epidural abscess may be classified according to the location of the infection into 2 groups: intracranial and spinal.[2] Additionally, spinal epidural abscess can be further classified based on the duration of symptoms into either acute or chronic.
Pathophysiology
Epidural abscess pathophysiology differs based on the location of the infection and responsible organism. Intracranial epidural abscess occurs most frequently as a complication of cranial surgical procedures and sinusitis.[3] Spinal epidural abscess occurs most frequently as a result of spinal instrumentation, vascular access, and IV drug use.[4]
Causes
Common causes of intracranial epidural abscess include paranasal sinusitis, osteomyelitis of the skull, and extension of infection from otitis, mastoiditis or orbit. Common causes of spinal epidural abscess include spinal instrumentation, vascular access, and IV drug use. Irrespective of cause, epidural abscess is a life-threatening, but treatable, condition.
Differentiating Epidural Abscess from Other Diseases
Intracranial epidural abscess must be differentiated from epidural hematoma, subdural empyema, brain abscess, tuberculous meningitis, and other intracranial mass lesions. Spinal epidural abscess must be differentiated from other conditions that cause back pain, motor weakness, and/or spinal tenderness, such as arthritis, osteoarthritis, intervertebral disc disease, vertebral osteomyelitis, primary or metastatic tumors, and musculoskeletal pain.
Epidemiology and Demographics
In general, epidural abscess is rare. Intracranial epidural abscess is the more rare type of epidural abscess and the 3rd most common focal intracranial infection. Spinal epidural abscess is more common than intracranial epidural abscess, however is still rare in the general population, accounting for 2.5 to 3 cases per 10,000 hospital admissions per year.[5] Estimates of the incidence after central nerve block vary from 1 per 1,000 hospital admissions to 1 per 100,000 hospital admissions.[6] Prevalence of epidural abscess is greatest between the fifth and seventh decades of life.[7]
Risk Factors
Common risk factors in the development of intracranial epidural abscess include trauma, neurosurgical procedures, and infections such as sinusitis, otitis, and mastoiditis. Common risk factors for the development of spinal epidural abscess include diabetes mellitus, trauma, and bacteremia.[3]
Natural History, Complications, and Prognosis
If left untreated, intracranial epidural abscess may cause headache, fever, and seizures. If left untreated, spinal epidural abscess may cause back pain, nerve root pain, and paralysis. Complications of epidural abscess include neurological deficits, meningitis, and sepsis. If treated timely, the prognosis for epidural abscess is generally good.
Diagnosis
History and Symptoms
A detailed and thorough history from the patient is necessary. Specific areas of focus when obtaining a history from the patient include immunodeficiency, intravenous drug use, and spinal procedure or trauma. Common symptoms of intracranial epidural abscess include headache, fever, and vomiting. Common symptoms of spinal epidural abscess include back pain, weakness, and persistent pins and needles.
Physical Examination
Physical examination of patients with epidural abscess is usually remarkable for fever, back pain, and generally well appearance, often contributing to misdiagnosis.
Laboratory Findings
Laboratory findings consistent with the diagnosis of epidural abscess include elevated inflammatory markers, abnormal platelet count, and presence of Staphylococcus aureus. Laboratory results, while helpful, are not diagnostic of epidural abscess. Laboratory findings should supplement clinical and imaging findings to aid in the diagnosis.[8]
MRI
MRI may be helpful in the diagnosis of epidural abscess, as it is the preferred imaging study. Epidural abscess appearance varies depending on the location of the disease. On MRI, intracranial epidural abscess appears as a lentiform or crescent-shaped fluid collection. On T2-weighted images, epidural abscesses appear hyperintense compared to the cerebrospinal fluid. On T1-weighted images, epidural abscesses appear isointense or hypointense when compared to the brain. After administration of gadolinium contrast, the dura mater is enhanced on T1-weighted images.[9] On MRI, spinal epidural abscess is characterized by low or intermediate intensity on T1-weighted MR sequences and high or intermediate intensity on T2-weighted images.
CT
Computed tomography may be helpful as a secondary method of imaging in the diagnosis of epidural abscess. If MRI is not available, CT scan may serve as the primary imaging technique. Findings on CT scan suggestive of intracranial epidural abscess include the appearance of an intracranial epidural abscess resembling a crescent-shaped hypodense extraaxial lesion or a lens.[10]
Other Imaging Findings
X ray is likely not helpful in the diagnosis of epidural abscess. Myelography may be helpful in the diagnosis of epidural abscess, however it is now considered obsolete.
Other Diagnostic Studies
Lumbar puncture is likely not helpful in the diagnosis of epidural abscess. Cerebrospinal fluid study is not routinely performed because it offers little information, and has high associated risks. It should be analyzed only when myelography is performed.
Treatment
Medical Therapy
Epidural abscess is a medical emergency and requires prompt treatment. The treatment of epidural abscess generally involves a combined medical and surgical approach. Antimicrobial therapy for intracranial epidural abscess includes metronidazole, a third generation cephalosporin, and either penicillin or vancomycin. Antimicrobial therapy for spinal epidural abscess includes vancomycin, cefepime, ceftazidime, and meropenem.
Surgery
A combination of surgical drainage and prolonged systemic antibiotics (6-12 weeks, IV followed by PO) is the mainstay of therapy for either intracranial or spinal epidural abscess.[11] Due to the importance of preoperative neurologic status, along with the unpredictable progression of neurologic impairment, for the neurological outcome of the patient, surgical therapy varies depending on the location of the abscess. In intracranial epidural abscess cases, burr hole placement or craniotomy should occur as early as possible. In spinal epidural abscess cases, decompressive laminectomy and debridement of infected tissues should occur as early as possible.[8][12]
Primary Prevention
Effective measures for the primary prevention of epidural abscess include rapid treatment of inflammatory diseases of the head, prevention of trauma, and decreased IV drug use.
Secondary Prevention
Secondary prevention strategies following epidural abscess include treatment and management of existing infection.
References
- ↑ Longo, Dan L. (Dan Louis) (2012). Harrison's principles of internal medici. New York: McGraw-Hill. ISBN 978-0-07-174889-6.
- ↑ 2.0 2.1 2.2 Danner, R. L.; Hartman, B. J. (1987). "Update of Spinal Epidural Abscess: 35 Cases and Review of the Literature". Clinical Infectious Diseases. 9 (2): 265–274. doi:10.1093/clinids/9.2.265. ISSN 1058-4838.
- ↑ 3.0 3.1 Fountas KN, Duwayri Y, Kapsalaki E, Dimopoulos VG, Johnston KW, Peppard SB; et al. (2004). "Epidural intracranial abscess as a complication of frontal sinusitis: case report and review of the literature". South Med J. 97 (3): 279–82, quiz 283. PMID 15043336.
- ↑ Strauss I, Carmi-Oren N, Hassner A, Shapiro M, Giladi M, Lidar Z (2013). "Spinal epidural abscess: in search of reasons for an increased incidence". Isr Med Assoc J. 15 (9): 493–6. PMID 24340840.
- ↑ Sampath P, Rigamonti D (1999). "Spinal epidural abscess: a review of epidemiology, diagnosis, and treatment". J Spinal Disord. 12 (2): 89–93. PMID 10229519.
|access-date=requires|url=(help) - ↑ Grewal S, Hocking G, Wildsmith JA (2006). "Epidural abscesses". Br J Anaesth. 96 (3): 292–302. doi:10.1093/bja/ael006. PMID 16431882.
|access-date=requires|url=(help) - ↑ Danner RL, Hartman BJ (1987). "Update on spinal epidural abscess: 35 cases and review of the literature". Rev. Infect. Dis. 9 (2): 265–74. PMID 3589332.
|access-date=requires|url=(help) - ↑ 8.0 8.1 Darouiche, Rabih O. (2006). "Spinal Epidural Abscess". New England Journal of Medicine. 355 (19): 2012–2020. doi:10.1056/NEJMra055111. ISSN 0028-4793.
- ↑ Longo, Dan L. (Dan Louis) (2012). Harrison's principles of internal medici. New York: McGraw-Hill. ISBN 978-0-07-174889-6.
- ↑ Longo, Dan L. (Dan Louis) (2012). Harrison's principles of internal medici. New York: McGraw-Hill. ISBN 978-0-07-174889-6.
- ↑ Grewal, S. (2006). "Epidural abscesses". British Journal of Anaesthesia. 96 (3): 292–302. doi:10.1093/bja/ael006. ISSN 0007-0912.
- ↑ Darouiche RO, Hamill RJ, Greenberg SB, Weathers SW, Musher DM (1992). "Bacterial spinal epidural abscess. Review of 43 cases and literature survey". Medicine (Baltimore). 71 (6): 369–85. PMID 1359381.