History
Spinal epidural abscess
Most symptoms of a spinal epidural abscess are due to enlargement of the abscess and surrounding inflammation, which can lead to tissue compression and spinal cord ischemia. Onset of symptoms usually occurs within hours to days but may be more chronic in nature, presenting with weeks to months of symptoms. The microbiology often dictates the pace of progression. [1, 11]
Back or neck pain is the most common symptom in individuals with spinal epidural abscess, occurring in 70%-100% of cases.
The classic diagnostic triad of fever, spinal pain, and neurological deficits is present in only 8-15% of cases at first physician contact and must not be relied on for diagnosis. Significant back or neck pain coupled neurologic deficits, Staphylococcus aureus bacteremia, recent surgery/injections, or unexplained elevated C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) should prompt an MRI without delay to facilitate diagnosis. [8, 15]
If left untreated, the progression of symptoms is usually sequential and forms the basis for the staging of spinal epidural abscess (see Staging): (1) back pain; (2) radicular irritation; (3) motor weakness, sphincter dysfunction, sensory changes; and, finally, (4) paralysis. Note that this progression may occur very rapidly, and some symptoms may be skipped.
The patient's neurological status at the time of diagnosis is the most accurate predictor of outcome and prognosis.
Intracranial epidural abscess
The symptoms of intracranial epidural abscess are generally more acute but may be difficult to discern from the inciting process (eg, sinusitis, postoperative infection). When intracranial epidural abscess is combined with a subdural empyema, as is often the case, the course is compressed. [12, 13]
Signs and symptoms are due to both infection and the slowly expanding intracranial mass. Fever, headache, malaise, lethargy, nausea, and vomiting may be present. Intracranial epidural abscesses due to sinus infections can cause purulent drainage from the nose or ear.
Patients without a history of recent cranial manipulation who develop intracranial epidural abscess present with encephalopathy and focal neurological deficits. Most patients who have undergone craniotomy (67%) tend to be afebrile at presentation, and their neurological deficits are often less severe and less acute, with more than 90% showing evidence of wound infection.
Physical
Findings associated with spinal epidural abscess from multiple studies include the following [1] :
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Fever (range, 13%-95%; median, 32%) (However, note that many patients with spinal epidural abscess are afebrile.)
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Spinal tenderness (range, 17%-98%; median, 58%)
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Weakness of the extremities (range, 26%-87%; median, 40%)
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Sensory abnormalities (range, 13%-45%; median, 36%)
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Paralysis (range, 5%-39%; median, 27%)
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Reflex abnormalities (up to 40% of cases) (Early hyperreflexia may give way to diminished or absent reflexes.)
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Respiratory compromise (with cervical lesions)
Findings associated with intracranial epidural abscess include the following [12, 13] :
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Fever (However, fewer than half of patients are febrile, so this symptom is unreliable.)
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Headache (50%-73%)
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Altered mental status (44%-50%)
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Sinus tenderness (32%-90%)
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Focal neurological deficits
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Evidence of wound infection (>90% of patients who have undergone craniotomy)
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Seizure (4%-63%)
Causes
The microbiologic causes of spinal epidural abscess and intracranial epidural abscess are considered separately.
S aureus infection causes most cases of spinal epidural abscess. This is followed in frequency by streptococcal and Enterobacteriaceae infections. Coagulase-negative staphylococcal infections are observed almost exclusively in the context of recent spinal instrumentation or other medical procedures. The most common organisms that cause spinal epidural abscess include the following [1, 11, 16, 17] :
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S aureus (60%; up to 25% may be methicillin-resistant S aureus [MRSA]) [7]
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Enteric gram-negative bacilli, especially Escherichia coli (10%); their incidence is rising in some series
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Coagulase-negative staphylococci (3-5%), primarily involving spinal instrumentation or epidural anesthesia/injections
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Bacteroides species and other anaerobes (2%) [18]
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Pseudomonas species (2%)
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Streptococci, including Streptococcus viridans, group B streptococci, and pneumococcus (10%)
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Pasteurella multocida-few case reports [19]
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Mycobacteria, usually Mycobacterium tuberculosis (< 1% in Western countries but much more common in developing countries). Do not forget to send acid-fast bacilli (AFB) stains and cultures.
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Less-common organisms - Acinetobacter , enterococci, Actinomyces species, Nocardia species, [20] Brucella species, and fungi, including Candida, Coccidioides, Aspergillus, [21] Blastomyces, and Sporothrix species
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Exserohilum rostratum was a common cause in 2012 due to the use of contaminated methylprednisolone injections
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Polymicrobial (possibly 5%-10%)
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Unknown (6%-10%)
In intracranial epidural abscess, upper-respiratory bacterial pathogens predominate in sinus-associated disease, whereas nosocomial pathogens are of concern in cases that develop after craniotomy. The most common causative organisms include the following:
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Staphylococci, both coagulase-positive and coagulase-negative
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Streptococci, including anaerobic and microaerophilic species
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Aerobic gram-negative bacilli
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Other anaerobes
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Can be polymicrobial
Physical Examination
Fever is helpful if present, but half or more patients are afebrile.
Respiratory compromise is possible if intracranial or cervical spinal epidural abscess is present.
Always check for spinal tenderness-top to bottom-pressing firmly on each spinous process.
Perform a full neurologic examination-mental status, motor, sensory, reflexes. The neuro exam needs to be repeated daily (or more often), as rapid changes in the examination may have major management implications.
Complications
Death or permanent neurologic sequelae occur in a substantial proportion of patients with epidural abscess, especially those who present with major neurologic deficits or sepsis. In a large 2017 series, 7% died and 8% were left paralyzed. [7]
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CT scan showing a lenticular-shaped intracranial epidural abscess.
