Medical Care
Early diagnosis and treatment of intracranial epidural abscess (IEA) cannot be overemphasized, as neurologic outcome mainly depends on the patient’s neurologic status immediately prior to surgery.
Prehospital management
Rapid transport and early stabilization (airway, breathing, and circulation) are essential in the prehospital setting. This may include intubation if necessary.
Initial management
Initial management depends on the severity and type of clinical presentation.
After initial evaluation and stabilization, relevant laboratory studies should be drawn, including blood cultures, basic labs, coagulation studies, and type and screen. Neuroimaging (beginning with CT of the head) should be obtained as soon as the patient is adequately stable.
Patients with signs of increased ICP, particularly those with cerebral edema and/or large IEAs, should be given mannitol or hypertonic saline as a temporizing measure. The presence of seizures and focal neurological deficits may require emergent intubation, anticonvulsant therapy, and hemodynamic stabilization before proceeding with diagnostic tests. Patients with sepsis should be treated appropriately, including with fluid resuscitation and pressors if necessary.
Neurologic status should be monitored closely.
Antibiotic therapy
In clinically stable patients without significant neurological deficits, antibiotics should be held until after blood cultures and cultures from the operating room are drawn. Until the culture and sensitivity report of the infectious agent becomes available, the choice of empiric antibiotic therapy should be based on the underlying etiology. For example, when an intracranial abscess is thought to be due to extension of infection from paranasal sinuses involving staphylococcal, aerobic, and anaerobic bacteria, more than one antibiotic is necessary. Likewise, an antistaphylococcal agent would be an appropriate choice for infection occurring after a neurosurgical procedure. A reasonable broad-spectrum regimen is vancomycin, ceftazidime, and metronidazole. Depending on local pathogens and antibiotic resistance patterns, other combinations including meropenem, ertapenem, or linezolid, or possibly antifungal agents, may be considered.
Once cultures have been finalized, the antibiotic regimen can then be narrowed to treat the cultprit organism. The length of therapy is determined by the patient's clinical response to treatment and by radiological resolution of the epidural abscess on follow-up imaging. Generally, antibiotic therapy should be continued for a minimum of 8 weeks if surgery is not undertaken, and for at least 4 weeks if the abscess is drained. In general, follow-up CT scanning or MRI should be obtained 2 weeks after antibiotic therapy has been discontinued.
Seizure therapy
Prophylactic seizure therapy is not generally recommended, but the provider should have a low threshold to administer AEDs if there is any clinical suspicion. If the IEA is not associated with a subdural empyema, seizures are unlikely to ensue. Patients who present with seizures should be given AEDs and then placed on video EEG postoperatively. Neurology consultation should be obtained to determine an appropriate weaning or taper of the AED, which generally would occur over months. Patients with a prior history of seizures who currently take AEDs should continue taking them.
Steroid Therapy
Steroids (eg, dexamethasone) may be considered in certain patients, particularly those with meningitic signs and symptoms.
Surgical Care
The goal of surgical care is to eliminate the source of infection and to prevent further complications. Surgical evacuation, decompression, and debridement, along with antibiotic therapy, are the mainstays of effective treatment in most patients with intracranial epidural abscesses (IEAs). Medical management alone (with antibiotics) may occasionally be considered in patients who are clinically stable, have no neurological deficits, and have a small IEA with no evidence of other radiological sequelae (eg, subdural empyema, cerebral edema, cerebritis).
Surgery should be performed promptly, particularly in neurologically deteriorating patients. Depending on the location and etiology of the IEA, neurosurgical as well as otolaryngological consultations may be required.
The type of surgery for an IEA depends on the size and location of the lesion as well as on involvement of the overlying bone.
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A craniotomy is commonly performed, which involves creating a sufficiently sized bony opening over the IEA, evacuating the purulent material, sending cultures, irrigating copiously with antibiotics, and re-attaching the bone with plates and screws. In cases where a subdural empyema is suspected, the dura should be opened so as to visualize the subdural space. If the dura appears infected, it should be removed and replaced with a dural substitute.
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If the bone appears infected (eg, from imaging or from visualization at the time of the surgery), a craniectomy is performed, in which the bone is discarded and sent to the pathologist for examination. The surgeon may replace the bone electively (cranioplasty) after 6–8 weeks of antibiotics and resolution of the infection. The bone is replaced with artificial materials, which may be 3D printed. If there is a significant cranial defect after the craniectomy, the patient may be advised to wear a helmet when out of bed until the cranioplasty is performed.
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For patients who are presenting with an IEA as a complication of a craniotomy, the bone flap is often discarded if it appears infected. In most cases there is an overlying superficial surgical site infection, which may be closed by a plastic surgeon.
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For smaller IEAs, or those in more difficult locations, minimally invasive burr holes may be attempted to drain the purulent material, although the limited visualization provided by a burr hole may limit sufficient inspection and drainage of the infection.
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ENT consultation is frequently required, such as in the setting of an IEA associated with frontal sinusitis
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An endoscopic endonasal approach may be considered with ENT for IEAs secondary to sinusitis in the anterior skull base, as described by Eviator et al. [20]
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In the setting of an associated CSF leak, a lumbar drain may be placed intraoperatively, and then drained at 10–20 cc/hr over a period of 3–5 days.
Aerobic and anaerobic cultures with gram stain, India ink, and acid-fast bacilli (AFB) of the purulent material should be sent from the operating room.
Noggle et al. report that frontal, supraorbital IEAs of the anterior and middle cranial fossa can be adequately and safely debrided via a minimally invasive supraciliary ("eyebrow") craniotomy. This approach has a cosmetic benefit and may decrease approach-related morbidity. [21]
Postoperatively, most patients should be admitted to the Neuro-Intensive Care Unit (or similar) for close Q1 hour neurological checks. A CT head non-contrast should be performed immediately after surgery. Broad spectrum antibiotics should be started.
Consultations
Immediate neurosurgical consultation is highly warranted.
A multidisciplinary approach involving an otolaryngologist may be necessary if the patient presents with concurrent paranasal sinusitis.
Infectious disease consultation may prove useful as well.
Complications
Complications of intracranial epidural abscess can include the following:
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Subdural empyema
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Cerebritis
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Cerebral edema
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Cerebral venous sinus thrombosis
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Cortical vein thrombosis
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Osteomyelitis
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Intraparenchymal brain abscess
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Cerebral edema
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Stroke
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Seizures
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Intracranial hypertension and brain herniation
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CSF leak
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Coma
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Death
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CT scan showing lenticular-shaped intracranial epidural abscess.
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Intracranial epidural abscess. Enhanced MRI of the brain, axial section, revealing a left temporal epidural abscess with an abscess cavity and a thickened enhancing capsule. Adjacent thickened dura enhances as well. In addition, mass effect is evident.
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Intracranial epidural abscess. A coronal section of the MRI revealing a left temporal epidural abscess with an abscess cavity and a thickened enhancing capsule. Adjacent thickened dura enhances as well. In addition, mass effect is evident.
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Intracranial epidural abscess. MRI of the brain, unenhanced. A T1-weighted image (axial view) showing a left temporal epidural abscess with an abscess cavity, surrounding capsule, and the thickened dura underneath. Mass effect is evident.
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Epidural abscess in the posterior fossa following a suboccipital craniectomy.
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Epidural abscess photo, taken intraoperatively.
