Epidural abscess

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]

An epidural abscess is an infection that forms in the epidural space. Specifically, intracranial epidural abscess is limited on the inner side by the cranial dura mater and on the outer side by the cranial bone.^[1] Spinal epidural abscess is limited on the inner side by the spinal dura mater and on the outer side, by the spinal canal.^[2] Spinal epidural abscess is the more common type of epidural abscess. Staphylococcus aureus is responsible for approximately 2/3 of the reported cases.^[3][4] Prevalence is greatest between the fifth and seventh decades of life, with a male predominance.^[5][6] 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. Generally, epidural abscess is a medical emergency and requires prompt treatment. If treated timely, the prognosis for epidural abscess is generally good. Physical examination of patients with epidural abscess is usually remarkable for fever, back pain, and generally well appearance, often contributing to misdiagnosis. MRI is the primary imaging study of epidural abscess, with CT scan as a secondary alternative. 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.^[7] 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 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.^[5]

Epidural abscess may be classified according to the location of the infection into 2 groups: intracranial and spinal.^[5] Additionally, spinal epidural abscess can be further classified based on the duration of symptoms into either acute or chronic.

Epidural abscess pathophysiology differs based on the location of the infection and responsible organism. The majority of intracranial epidural abscess cases occur as a complication of cranial surgical procedures and sinusitis.^[1] The majority of spinal epidural abscess cases occur as a result of spinal instrumentation, vascular access, and IV drug use.^[2]

Common causes of intracranial epidural abscess include paranasal sinusitis, osteomyelitis of the skull, and extension of infection from concurrent otitis or mastoiditis. 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.

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, weakness, and spinal tenderness, such as arthritis, osteoarthritis, intervertebral disc disease, vertebral osteomyelitis, primary or metastatic tumors, and musculoskeletal pain.

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 it is still rare in the general population, accounting for 2.5 to 3 cases per 10,000 hospital admissions per year.^[8] Estimates of the incidence following central nerve block vary from 1 per 1,000 hospital admissions to 1 per 100,000 hospital admissions.^[7] Prevalence of epidural abscess is greatest between the fifth and seventh decades of life.^[5]

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.^[1]

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.

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, spinal procedure, and 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 of patients with epidural abscess is usually remarkable for fever, back pain, and generally well appearance, often contributing to misdiagnosis.

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.^[3]

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 a crescent-shaped, hypodense, extraaxial lesion or a lens.^[9]

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. Following 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.

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.

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.

Epidural abscess is generally 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.

A combination of surgical drainage and prolonged systemic antibiotics (6-12 weeks, IV followed by PO) is the mainstay of therapy for both intracranial and spinal epidural abscess.^[7] 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.^[3][6]

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 strategies following epidural abscess include treatment and management of existing infection.

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]

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.^[1]

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 considerablly improved due to more accurate imaging studies, better antibiotics, and improved surgical techniques.^[1]

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]

Epidural abscess may be classified according to the location of the infection into 2 groups: intracranial and spinal.^[1] Additionally, spinal epidural abscess can be further classified based on the duration of symptoms into either acute or chronic.

Epidural abscess may be classified according to the location of the infection into 2 groups: intracranial and spinal.^[1]

The abscess is limited on the inner side by the cranial dura mater and on the outer side by the cranial bone.^[2]

The abscess is limited on the inner side by the spinal dura mater and on the outer side, by the spinal canal.^[3] Spinal epidural abscess can be further classified based on the duration of symptoms into either acute or chronic.

• Fever
• Systemic toxicity
• Peripheral leukocytosis
• Usually posterior to spinal cord

• Fever absent
• No elevated inflammation markers
• Usually anterior to spinal cord

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]

Epidural abscess pathophysiology differs based on the location of the infection and responsible organism. The majority of intracranial epidural abscess cases occur as a complication of cranial surgical procedures and sinusitis.^[1] The majority of spinal epidural abscess cases occur as a result of spinal instrumentation, vascular access, and IV drug use.^[2]

Epidural abscess pathophysiology differs based on the location of the infection and responsible organism.

Intracranial epidural abscess is the result of sequelae of cranial surgical procedures, sinusitis, and mastoiditis. Cranial dura mater is adherent to the inner table of the skull in the epidural space. This virtual space can become a real space by increasing pressure from a liquid, such as pus or blood, or a solid mass, such as a tumor. A tight adherence contributes to the slow progression and typical round-shape appearance of the abscess. Because the dura mater is tightly attached to the skull in the foramen magnum, intracranial epidural abscesses are usually restricted to the cranial cavity. On the periphery of the pus collection is a wall of inflammation, which may calcify and is identifiable in imaging studies.^[1][3]

Pathophysiological pathways for the progression of intracranial epidural abscess include:^[1]

• Thrombophlebitis of diploic veins, facilitated by the valveless nature of these vessels, allowing for retrograde flow of bacteria
• Direct extension from osteomyelitis of the skull
• Congenital defect, such as communication between sinuses and areas of lesion
• Osteomyelitis of the skull
• Extension of infection from otitis or mastoiditis
• Direct inoculation, during a surgical procedure or trauma
• Remote infection sites, through haematological spread, such as respiratory and urinary tract infections

The majority of spinal epidural abscess cases occur as a result of spinal instrumentation, vascular access, and IV drug use.^[2] Unlike the virtual intracranial epidural space, the spinal epidural space is a real space; more specifically, the sequelae occurs in the areas posterior and lateral to the spinal cord, extending down the length of the spinal canal. This epidural space, which is larger at the sacral region, contains fat, arteries and venous plexus. Because the dura mater is more adherent to the bony surface of the vertebral bodies, from the foramen magnum down to the level of L1, the majority of spinal epidural abscesses are located posteriorly, extending to multiple levels.^[4][5][6]

Pathophysiological pathways for the progression of intracranial epidural abscess include:^[7]

• Neurosurgical procedures
• Trauma
• Skin flora entering open wounds
  • Staphylococcus epidermidis
  • Escherichia coli
  • Pseudomonas aeruginosa
  • Haemophilus influenzae
  • Klebsiella pneumoniae
  • Listeria monocytogenes

As the inflammation progresses, the extension of the abscess also increases, on average by 3 to 5 spinal cord segments. However, the degree of damage, associated neurological symptoms, and sequelae are not directly related to the extension of the abscess, as even small abscesses may cause severe sequelae. The abscess may contain pus, often observed in acute cases, or granulation tissue, often observed following the surgical intervention.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]; Ogheneochuko Ajari, MB.BS, MS [3]; Anthony Gallo, B.S. [4]

Common causes of intracranial epidural abscess include paranasal sinusitis, osteomyelitis of the skull, and extension of infection from concurrent otitis or mastoiditis. 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.

Staphylococcus aureus is responsible for almost two thirds of the reported cases.^[1][2] Due to the generalized use of antibiotics through the years, the number of reported cases of spinal epidural abscess due to MRSA has increased exponentially, reaching up to 40% of the cases in some institutions, particularly in patients with spinal or vascular implanted devices.^[1] Other less common, but still important organisms are:^[1][3][4]

• Escherichia coli
• Pseudomonas aeruginosa
• Anaerobic bacteria
• Mycobacteria
• Fungi
• Parasites

Although some infectious organisms might be responsible for either type of epidural abscess, others are more common of one of those.^{[1][5][6][7][8][9]}

• If infection following sinusitis case:

• Microaerophilic organisms
• Anaerobic streptococci
• Propionibacterium
• Other anaerobic bacteria and fungi

• If infection following neurosurgery:

• Staphylococcus aureus
• Gram-negative bacteria

• Osteomyelitis of the skull

• Staphylococcus aureus
• MRSA
• Mycobacterium tuberculosis

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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]

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, weakness, and spinal tenderness, such as arthritis, osteoarthritis, intervertebral disc disease, vertebral osteomyelitis, primary or metastatic tumors, and musculoskeletal pain.

Intracranial epidural abscess must be differentiated from other diseases that cause headache, vomiting, fever, altered mental status, seizures, cranial nerve abnormalities, and paresis.^[1] Intracranial epidural abscess must be differentiated from:

Spinal epidural abscess must be differentiated from other diseases that cause back pain, fever, weakness, and spinal tenderness.^[2][3][4][5] Therefore, spinal epidural abscess must be differentiated from:

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]

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 it is still rare in the general population, accounting for 2.5 to 3 cases per 10,000 hospital admissions per year.^[1] Estimates of the incidence following central nerve block vary from 1 per 1,000 hospital admissions to 1 per 100,000 hospital admissions.^[2] Prevalence of epidural abscess is greatest between the fifth and seventh decades of life.^[3]

Intracranial epidural abscess is the more rare type of epidural abscess, accounting for 1 out of 10 cases of the disease. However, it is the 3rd most common focal intracranial infection, following brain abscess and subdural empyema. Today it occurs most often following neurosurgical procedures and in IV drug users. Approximately 2% of patients with sinusitis develop intracranial epidural abscess as a complication.^[4]

Spinal epidural abscess is the most common type of epidural abscess. Prevalence is greatest between the fifth and seventh decades of life, with a male predominance.^[3][5] Spinal epidural abscess is rare, accounting for 2.5 to 3 cases per 10,000 hospital admissions per year.^[1] The mortality rate of spinal epidural abscess has not changed significantly over the last 25 years, remaining at < 5%.^[6][7]

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]

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.^[1]

Common risk factors in the development of intracranial epidural abscess include:^[1][2][3]

• Sinusitis
• Otitis
• Mastoiditis
• Trauma
• Neurosurgical procedures
• Exposure to expanded polytetrafluethylene
• Scalp venous catheters in infants
• HIV

Common risk factors in the development of spinal epidural abscess include:^[1][2][3]

• Diabetes mellitus
• Trauma
• HIV infection
• Bacteremia
• IV drug abuse
• Tattoo
• Acupuncture
• Alcoholism
• Chronic bone infection
• Chronic soft tissue infection

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]

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.

If left untreated, intracranial epidural abscess may cause headache, fever, and seizures. If left untreated, the condition will aggravate and severe complications will arise, possibly leading to a fatal outcome. Proper diagnosis and treatment are therefore necessary. Treatment usually involves aggressive antibiotic therapy and surgical drainage.

If left untreated, spinal epidural abscess may cause the following sequelae, which is classified into 4 stages:^[1][2][3][4]

1. Back and focal vertebral pain, with tenderness; fever; neurologic deficits
2. Nerve root pain, described as being “electric-shock” like, radiating from affected areas, sometimes accompanied by paresthesia
3. Dysfunction of the spinal cord, presenting by motor and sensory deficits and sphincter incompetence
4. Paralysis, which may quickly become irreversible

Complications from epidural abscess include:

• Neurological deficits
• Meningitis
• Sepsis
• Irreversible paralysis
• Sepsis
• Spinal cord injury
• Pressure sores
• Urinary tract infection
• Thrombophlebitis
• Pneumonia
• Thrombosis
• Thrombophlebitis of adjacent veins
• Ischemia
• Bacterial toxins
• Inflammatory response and its mediators

The rate of complications rises with the increase of time to reach the proper diagnosis and begin therapy.

If treated timely, the prognosis of epidural abscess is generally good. Full recovery is common among survivors and the mortality rate is low (<5%). Mortality is usually due to sepsis, prolonged immobility, or the development of meningitis.^[5] Positive outcomes are generally associated with:

• Presence of purulent material, instead of granulation tissue, indicating a more acute case
• Absence of paralysis or its presence for < 36 hours, indicating increased chances of returning to normal function

The most important factor to predict the final outcome is the patient’s neurological status prior to neurosurgery. The stages are:^[2]

Poor outcomes are generally associated with three factors:^[6]

• Age
• Degree of thecal sac compression
• Duration of symptoms