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662 PART 5: Infectious Disorders

otherwise feel well unless the clinical course is complicated (eg, by devel- joint space infection; the response to therapy can also be assessed read-
opment of subdural empyema or involvement of deeper intracranial ily with this technique. 64,68 CT myelography may be performed if MRI is
structures). Because the dura is closely opposed to the inner surface of unavailable or contraindicated.
the cranium, the abscess usually enlarges too slowly to produce sudden ■
major neurologic deficits (in contrast to subdural empyema) unless TREATMENT
there is deeper intracranial extension. However, there may eventually be The therapy of subdural empyema and epidural abscess optimally
development of focal neurologic signs and focal or generalized seizures. requires a combined medical and surgical approach. Surgical therapy is
In the absence of treatment, papilledema and other signs of increased essential for three reasons: because antibiotics do not reliably sterilize
intracranial pressure develop as the abscess enlarges. An epidural these lesions without concurrent drainage; because cultures of purulent
abscess near the petrous bone may present as Gradenigo syndrome, material guide antimicrobial therapy; and because surgical decompres-
characterized by involvement of cranial nerves V and VI, with unilateral sion is useful in controlling increased intracranial pressure or avoiding
facial pain and weakness of the lateral rectus muscle. 64 cord compression.
Spinal epidural abscess may develop within hours to days (after hema-
togenous seeding) or may grow slowly over months (associated more Antimicrobial Therapy: Once purulent material is aspirated in patients
often with vertebral osteomyelitis). 64-68 Most abscesses pass through with cranial subdural empyema, antimicrobial therapy should be initi-
the following stages: focal vertebral pain; root pain; defects of motor, ated; it should be based on a Gram stain and on the site of primary
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sensory, or sphincter function; and paralysis. Pain is the most consistent infection. For suspected S aureus, vancomycin (15 mg/kg every 12 hours)
symptom and is accompanied by local tenderness at the affected level in is recommended pending in vitro susceptibility testing. Metronidazole
70% to 90% of cases. Subsequently, radicular pain develops; it is followed (15 mg/kg loading dose and then 7.5 mg/kg every 6-8 hours) is used when
by progression to weakness and paralysis. Fever occurs in most patients anaerobes (eg, B fragilis) are suspected. For aerobic gram-negative
during the course of the illness. Headache and neck stiffness may also bacilli, a third-generation cephalosporin (cefotaxime or ceftriaxone)
occur. Respiratory function may be impaired if the cervical spinal cord should be used, with ceftazidime or cefepime reserved for cases in which
is involved. The usually irreversible manifestations of cord involvement P aeruginosa is likely. Parenteral antibiotics should be continued for 3 to
include muscle weakness, sensory deficits, and disturbances of sphincter 4 weeks, depending on the patient’s clinical response. Longer periods of
control. At this juncture there may be rapid transition to paralysis (usu- intravenous therapy (and perhaps oral therapy) may be required if an
ally within 24 hours from onset of weakness), indicating the need for associated osteomyelitis is present.
emergent evaluation, diagnosis, and treatment. Presumptive antimicrobial therapy for spinal epidural abscess must
■ DIAGNOSIS include a first-line antistaphylococcal agent (ie, vancomycin); coverage
for gram-negative organisms should be included for any patient with a
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Subdural empyema should be suspected in any patient with meningeal history of a spinal procedure or of injection drug abuse. In addition,
pending culture results, empirical antimicrobial therapy in patients who
signs and a focal neurologic deficit. Lumbar puncture is contraindicated have undergone a spinal procedure should include vancomycin for pre-
in this setting because of the risk of cerebral herniation. When lum- sumed involvement by S epidermidis.
bar puncture is performed, CSF findings are nonspecific and include
elevated opening pressure, moderate neutrophilic pleocytosis, and an Surgical Therapy: The optimal surgical approach for subdural empy-
increased protein concentration. Unless the course is complicated by ema is controversial, and there are several unanswered questions with
bacterial meningitis, CSF Gram stain and cultures are negative. Skull regard to management. 61,64 First, should drainage be performed by
radiographs may demonstrate evidence of concurrent sinusitis or osteo- craniotomy or via burr holes? Previous studies have documented a
myelitis. lower mortality rate in patients undergoing craniotomy, although it
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The diagnostic procedures are CT with contrast enhancement or may be that a larger percentage of gravely ill patients were treated with
MRI. 61-64 The typical CT appearance is a crescentic or elliptical area burr holes because of the greater surgical risk. Burr hole therapy may
of hypodensity below the cranial vault or adjacent to the falx cerebri. be more efficacious in the early stages of subdural empyema, when the
Loculations may also be seen. Depending on the extent of disease, pus is liquid, because thickening occurs as the disease progresses, mak-
there is often an associated mass effect with displacement of midline ing aspiration more difficult. If burr holes are to be placed, they should
structures. After the administration of contrast material, a fine, intense be multiple to allow extensive irrigation. However, craniotomy may be
line of enhancement can be seen between the subdural collection and essential for posterior fossa subdural empyema, and it is also needed in
the cerebral cortex. However, false-negative CT scans do occur. MRI 10% to 20% of patients initially treated with trephination. Thus, burr
provides greater clarity of morphologic detail and may detect empyema hole drainage, even with catheter irrigation, may not adequately drain
not clearly seen on CT; it is of particular value in identifying subdural the empyema. When craniotomy is performed, wide exposure should
empyemas located at the base of the brain, along the falx cerebri, or be afforded to allow adequate exploration of all areas where subdural
in the posterior fossa. On the basis of signal intensity, MRI can dif- pus is suspected. Second, should antibiotics be instilled locally to irri-
ferentiate extraaxial empyemas from most sterile effusions and chronic gate the subdural space? Although antibiotic irrigation has become
hematomas. Based on these findings, MRI is considered the modality common, there are no data on the potential benefits of this practice.
of choice for the diagnosis of subdural empyema. CT and MRI are also Third, should drains, or catheters, be left in the subdural space? This
useful for demonstrating sinusitis and otitis, although CT is better than decision is best made by the neurosurgeon intraoperatively; however,
MRI at imaging bone and should be used in cases of penetrating injury with drains in place, the risk of nosocomial superinfection must be kept
or osteomyelitis. MRI is the diagnostic procedure of choice for spinal in mind. Further, surgical correction of the antecedent otorhinologic
subdural empyema because it more accurately defines the extent of the infection may also be necessary.
lesion than does CT. 64 In patients with spinal epidural abscess, laminectomy with decom-
CT and MRI are also the diagnostic procedures of choice for cranial pression and drainage may need to be performed as a surgical emer-
epidural abscess because both demonstrate a superficial, circumscribed gency to minimize the likelihood of permanent neurologic sequelae. 64,68
area of diminished density. The possibility of adjacent subdural empy- However, in a literature review of 38 patients with spinal epidural
64
ema or other intracranial involvement can also be assessed. MRI should abscess treated with antimicrobial therapy alone, 23 recovered, two
be performed in cases of suspected spinal epidural abscess, and is the died, one worsened, and the rest remained the same or improved. In
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diagnostic procedure of choice because it can visualize the spinal cord contrast, a retrospective analysis of 57 cases revealed that patients could
and epidural space in sagittal and transverse sections and can identify be treated safely and effectively with prolonged intravenous antimi-
accompanying osteomyelitis, intramedullary spinal cord lesions, and crobial therapy alone or combined with percutaneous needle drainage

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