Subdural empyema

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]

Subdural empyema is a life-threatening infection, consisting of a localized collection of purulent material, usually unilateral, between the dura mater and the arachnoid mater. Subdural empyema may be classified according to location of the infection into 2 groups: intracranial and spinal, with intracranial being the more common of the two groups, accounting for 95% of subdural empyema patients.^[1][2] Subdural empyema accounts for approximately 15-25% of focal central nervous system infections. In 2014, the incidence of subdural empyema was estimated to be less than 1 case case per 100,000 individuals, with a male predominance.^[3] The most common pathogens in intracranial subdural empyema are anaerobic and microaerophilic Streptococci, compared to spinal subdural epmyema, which can be caused by either Streptococci or Staphylococcus aureus.^[2] If left untreated, subdural empyema frequently evolves into severe fever, headache, nausea, vomiting, seizures, coma, and subsequent mortality. Complications to subdural empyema include status epilepticus, neurological deficits, and thrombosis. Prognosis is generally good with antimicrobial therapy. Physical examination of patients with subdural empyema is usually remarkable for fever, facial pain, and altered mental status.^[4][5][6] MRI is the primary imaging study of epidural abscess, with CT scan as a secondary alternative. Treatment of subdural empyema requires a combined medical and surgical approach. In order to evacuate the pus, burr hole placement or craniotomy may be used to treat the subdural empyema. The preferred surgical mainstay of treatment for subdural empyema is craniotomy.

In 1869, subdural empyema was first operated on by François Gigot de la Peyronie.^[7] The first detailed description of the disease was by Cyril Brian Courville in 1939.

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

Subdural empyema is a localized collection of pus between the dura mater and arachnoid mater, occurring in either the intracranial space or the spinal canal.^[8][1][2] Subdural empyema generally follows the same progression for both intracranial and spinal subtypes, spreading via blood or from nearby infection. Bacterial infections of the skull or air sinuses can spread to the subdural space, producing a subdural empyema. The underlying arachnoid and subarachnoid spaces are usually unaffected, but a large subdural empyema may produce a mass effect.

Common causes of subdural empyema include Streptococci, Staphylococci, and other Gram-negative bacilli.^[1] In children, the majority of cases of subdural empyema occur due to meningitis, while in adults the most common causes are sinusitis, otitis media, mastoiditis, and trauma.^[1][9]

Subdural empyema must be differentiated from other diseases that cause fever, headache, focal neurological signs, seizures, and altered mental status, such as subdural hematoma, brain abscess, and bacterial meningitis. These conditions may be distinguished from subdural empyema by their clinical findings, brain imaging findings, and laboratory studies.

Subdural empyema accounts for approximately 15-25% of focal central nervous system infections. In 2014, the incidence of subdural empyema was estimated to be less than 1 case per 100,000 individuals.^[3] Prior to antibiotics, the case fatality rate of subdural empyema was estimated to be near 100%. However, with antibiotics, the current rate is estimated between 10-20%.^[10] The disease usually occurs in children and young adults (70% cases occurring in the second and third decades of life), being more frequent in men than women, possibly due to sex-related differences in sinus anatomy.

Common risk factors in the development of subdural empyema are meningitis, sinusitis, otitis, mastoiditis, immunodeficiency, head trauma, and lumbar puncture.

If left untreated, subdural empyema frequently evolves into severe fever, headache, nausea, vomiting, seizures, coma, and subsequent mortality. Complications to subdural empyema include status epilepticus, neurological deficits, and thrombosis. Prognosis is generally good with antimicrobial therapy.

If possible, a detailed and thorough history from the patient is necessary. Specific areas of focus when obtaining a history from the patient include prior neurosurgery, sinusitis, or mastoiditis. Common symptoms of subdural empyema include headache, altered mental status, vomiting, and seizures.

Physical examination of patients with subdural empyema is usually remarkable for fever, facial pain, and altered mental status.^[4][5][6]

Laboratory findings associated with subdural empyema are generally unspecific. Often, elevated inflammatory markers are present, including:^[1][4]

• Leukocytes
• Erythrocyte sedimentation rate
• C-reactive protein

Lumbar puncture is not diagnostic of subdural empyema. Lumbar puncture is an invasive procedure which is contraindicated in case of suspicion of subdural empyema and increased intracranial pressure, due to risk of brain herniation, and mortality.^[2]

Generally, x ray is not helpful in the diagnosis of subdural empyema.

Head CT scan may be helpful in the diagnosis of subdural empyema. CT scan is secondary to MRI for subdural empyema imaging. Findings on CT scan suggestive of subdural empyema include a crescentic shape, although collection pockets may appear bi-convex. A surrounding membrane that enhances intensely and uniformly following contrast administration is typically identified.^[11]

MRI in the optimal imaging study in the diagnosis of subdural empyema. Findings on MRI suggestive of subdural empyema are similar to those on CT scan, and include a crescent or bi-convex shaped collection. A surrounding membrane that enhances intensely and uniformly following gadolinium enhancement is typically identified and may also demonstrate restricted diffusion.^[11]

Subdural empyema is a medical emergency and requires prompt treatment. Treatment of subdural empyema requires a combined medical and surgical approach. Empiric antimicrobial therapy depends on the location of the infection (intracranial vs. spinal) and whether it was community-acquired or hospital-acquired. The clinical symptoms may be mild and unspecific initially.

Subdural empyema is a neurosurgical condition, which requires emergency surgical drainage and subsequent medical therapy. In order to evacuate the pus, burr hole placement or craniotomy may be used to treat the subdural empyema. The preferred surgical mainstay of treatment for subdural empyema is craniotomy. A wide craniotomy allows a wide exposure of the area, adequate exploration, and better evacuation of the infected material and decompression of the underlying cerebral hemisphere, thereby improving the outcome.^[1][2]

Effective measures for the primary prevention of subdural empyema include rapid treatment of inflammatory diseases of the head and prevention of trauma. Secondary prevention strategies following subdural empyema include treatment and management of existing infection.

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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]

In 1869, subdural empyema was first operated on by François Gigot de la Peyronie.^[1] The first attempted detailed description of the disease was by Cyril Brian Courville in 1939.

• In 1869, subdural empyema was first operated on by François Gigot de la Peyronie^[1]
• In 1939, the first attempted detailed description of the disease was by Cyril Brian Courville, who additionally referred to the disease as subdural abscess, pachymeningitis interna, purulent pachymeningitis, and circumscript meningitis^[2]
• Historically, treatment was surgical, contrary to the present antimicrobial approach. Before the discovery of antibiotics, the mortality rate of patients with subdural empyema was near 100%, however the development of antimicrobial therapies have dramatically decreased the estimate to between 6-35%.^[2]

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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]

Subdural empyema may be classified according to location of the infection into 2 groups: intracranial and spinal.

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

• 95% of patients with subdural empyema present within this group^[1][2]

• 5% of patients with subdural empyema present within this group^[1][2]

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]

Subdural empyema is a localized collection of pus between the dura mater and arachnoid mater, which occurs in either the intracranial space or the spinal canal.^[1][2][3] Subdural empyema generally follows the same progression for both intracranial and spinal subtypes, spreading via blood or from nearby infection.

Subdural empyema is a localized collection of pus between the dura mater and arachnoid mater, which occurs in either the intracranial space or the spinal canal.^[1][2][3]

Intracranial subdural empyema is usually unilateral, and affects the base of the brain, its convexity, the inter-hemispheric fissure along the falx cerebri, or the posterior fossa. The anatomy of the meningeal membranes dictate the course and characteristics of the disease. The dura mater and the arachnoid mater, which define the initial limits of the empyema, are joined only at the base of the brain, along the falx cerebri and at the tentorium cerebelli. This virtual space between these two meningeal membranes creates the potential for the infection to spread along the cerebral hemisphere, inter-hemispheric fissure, and posterior cranial fossa.

Intracranial subdural empyema’s origin generally depends on the age of the individual. In younger children, the empyema most commonly results from complications of purulent meningitis, while in older children and adults, it most commonly results from complications of sinusitis, otitis media, or mastoiditis. In the case of sinusitis, the frontal sinus is the most commonly affected sinus, followed by the ethmoidal, sphenoidal, and maxillary sinuses. The infection may then spread in two ways:^{[1][2][3][4][5][6]}

• Blood, via retrograde infection, from thrombophlebitis of mucosal veins, which drain the sinuses
• Direct contact via:
  • Bone erosion and Haversian canals in bone, as a complication of osteomyelitis
  • Mastoid and middle ear by erosion of the tegmen tympani
  • Frontal air sinus by erosion in its posterior wall
• Neurosurgical procedures, such as subdural hematoma drainage, craniotomy, and intracranial pressure monitoring
• Head trauma
• Bacteremic seeding of an previous subdural hematoma

The subdural empyema causes an inflammatory reaction in the subdural space, which may be accompanied by cerebrospinal fluid pleocytosis and encephalitis. The venous extension of the infection may lead to hemorrhagic infarction or superficial abscess. Next, cerebral edema and hydrocephalus may develop, which combined with the empyema, creates a mass effect that increases intracranial pressure, and leads to transtentorial herniation, brainstem compression, and death.^[3][6] The most common pathogens in the intracranial type are:

• Anaerobic and microaerophilic Streptococci
• Escherichia coli
• Bacteroides

Spinal subdural empyema is more rare compared to intracranial. This type of infection follows a similar pathophysiology to intracranial subdural empyema. Potential sources of spread of infection include:

• Blood
• Osteomyelitis
• Meningitis
• Lumbar puncture

Spinal subdural empyemas are generally caused by Streptococci or Staphylococcus aureus.^[3]

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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]

Common causes of subdural empyema include Streptococci, Staphylococci, and other Gram-negative bacilli.^[1] In children, the majority of cases of subdural empyema occur due to meningitis, while in adults the most common causes are sinusitis, otitis media, mastoiditis, and trauma.^[1][2]

Subdural empyema is a life-threatening condition and must be treated as such irrespective of the causes. Life-threatening conditions may result in mortality or permanent disability within 24 hours if left untreated.

Intracranial subdural empyema ^[1][3][4]

The most common cause of subdural empyema in adults is the complication of an infection of the air sinuses: frontal, ethmoid, sphenoid, and maxillary. The causative organisms of the empyema are similar to those causing the infection of the sinuses. Generally multiple organisms are present in the empyema, where anaerobes are almost always an important agent.^[3][4] Common causative agents include:

• Anaerobes
• Aerobic Streptococci
  • Streptococcus milleri
  • Streptococcus anginosus
  • Streptococcus pneumoniae
• Staphylococci
• Haemophilus influenzae
• Gram-negative bacilli

Spinal Subdural Empyema ^[1][3]

• Staphylococcus aureus
• Streptococci

The most common cause of subdural empyema in children is occurs as a complication of meningitis. The agents isolated from the pus, are usually similar to the ones causing the meningitis.^[3][5] Common causative agents include:

• Haemophilus influenzae
• Streptococcus pneumoniae
• Nontyphoidal Salmonella

Common causative agents in trauma include:

• Coagulase negative strains of Staphylococcus
• Anaerobes
• Gram-negative microbes

Common causative agents in neurosurgical procedures include:

• Pseudomonas aeruginosa
• Clostridium

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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]

Subdural empyema must be differentiated from other diseases that cause fever, headache, focal neurological signs, seizures, and altered mental status, such as subdural hematoma, brain abscess, and bacterial meningitis. These conditions may be distinguished from subdural empyema by their clinical findings, brain imaging findings, and laboratory studies.

Subdural empyema must be differentiated from other diseases that cause fever, headache, focal neurological signs, seizures, and altered mental status, including:^[1][2]

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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]

Subdural empyema accounts for approximately 15-25% of focal central nervous system infections. In 2014, the incidence of subdural empyema was estimated to be less than 1 case per 100,000 individuals.^[1] Prior to antibiotics, the case fatality rate of subdural empyema was estimated to be near 100%. However, with antibiotics, the current rate is estimated between 10-20%.^[2] The disease usually occurs in children and young adults (70% cases occurring in the second and third decades of life), being more frequent in men than women, possibly due to sex-related differences in sinus anatomy.

In 2014, the incidence of subdural empyema was estimated to be less than 1 case per 100,000 individuals.^[1]

Prior to antibiotics, the case fatality rate of subdural empyema was estimated to be near 100%. However, with antibiotics, the current rate is estimated between 10-20%.^[2]

Subdural empyema may affect patients of any age group.^[1] Subdural empyema most commonly affects individuals younger than 20 years of age, as approximately 70% of cases occur in the second and third decades of life.^[3]

Males are more commonly affected with subdural empyema name than females. The male to female ratio is approximately 6 to 1.^[2]

There is no racial predilection to subdural empyema.

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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]

Common risk factors in the development of subdural empyema are meningitis, sinusitis, otitis, mastoiditis, immunodeficiency, head trauma, and lumbar puncture.

Common risk factors in the development of subdural empyema include:^[1][2]

• Meningitis
• Sinusitis
• Otitis
• Mastoiditis
• Immunodeficiency
• Head trauma
• Lumbar puncture
• Neurosurgery

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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]

If left untreated, patients with subdural empyema may develop severe fever, headache, nausea, vomiting, and seizures. Untreated subdural empyema may also lead to coma and subsequent mortality. Complications of subdural empyema include status epilepticus, neurological deficits, and thrombosis. Prognosis is generally good with antimicrobial therapy.

Subdural empyema is considered a neurosurgical emergency. If left untreated, subdural empyema frequently evolves into severe fever, headache, nausea, vomiting, seizures, coma, and subsequent mortality.

Complications to subdural empyema include:^[1]

• Status epilepticus
• Neurological deficits
• Thrombosis
• Cerebritis
• Cerebral edema
• Cerebral infarction
• Hydrocephalus
• Osteomyelitis
• Damage to the bridging veins

Prognosis is generally good with antimicrobial thearpy. The outcome is dependent on:^[1]

• Preoperative level of consciousness
• Commencement of treatment
• Treatment duration
• Disease progression

Patient education is imperative as failure to follow antibiotic therapy will adversely affect the outcome of the treatment. Identified prognostic factors associated with subdural empyema include:^[1]

Unfavorable Prognostic Factors

• Presentation with encephalopathy or coma
• Age: younger than 10 years or elderly
• Delayed commencement of antibiotics
• Burr hole placement
• Sterile cultures

Favorable Prognostic Factors

• Craniotomy
• Early treatment
• Young age (optimal between 10-20 years)
• Patient presents awake, alert and oriented
• Source of infection: paranasal sinuses
• Aerobic Streptococci isolated in culture
• Aerobic Streptococci as single pathogen

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