Subdural Empyema

Definition, Etiology, PathogenesisTop

Subdural empyema is an accumulation of purulent material between the dura and arachnoid membranes of the brain.

1. Etiologic factors: Aerobic (35%) or anaerobic (10%) streptococci, Staphylococcus aureus (10%), Staphylococcus epidermidis (2%), aerobic gram-negative bacilli (10%).

2. Risk factors: Sinusitis (>50% of cases), otitis media (30%), head injury (30%), cranial osteitis, surgery.

Clinical Features and Natural HistoryTop

Subdural empyema has a nonspecific clinical course. Initially the only symptoms caused by the formation of empyema are headache and fever. Subsequently the patient develops nausea, vomiting, and signs of meningitis (nuchal rigidity). The progressive accumulation of purulent material in the subdural space leads to worsening features of cranial edema and focal neurologic deficits. Delayed treatment leads to permanent neurologic deficits (most commonly spastic paresis or paralysis, seizures, aphasia) or death, with a mortality rate of 40%.

DiagnosisTop

1. Laboratory tests: Nonspecific findings in cerebrospinal fluid (CSF) analysis (usually moderate pleocytosis with a predominance of granulocytes; ~40% of patients have lymphocyte predominance). CSF culture may be negative.

2. Computed tomography (CT) or magnetic resonance imaging (MRI): The most important diagnostic test. Diagnosis is confirmed by the presence of characteristic lesions in the subdural space, accumulation of liquid matter, and meningeal enhancement, as well as features of compression of the brain (mass effect).

TreatmentTop

1. Empiric antimicrobial therapy: Administer 3 antimicrobial drugs IV in maximum doses: penicillin G (INN benzylpenicillin), a third-generation cephalosporin (eg, cefotaxime, ceftriaxone), and metronidazole (7.5 mg/kg every 6 hours). If you suspect methicillin-resistant S aureus (MRSA) etiology, replace penicillin with vancomycin. Continue antibiotic treatment for 2 to 4 weeks in patients after drainage of the empyema and for 6 to 8 weeks in patients in whom drainage was not performed.

2. Surgical treatment: Surgical drainage is the treatment of choice (especially with thicker empyemas >9 mm)

3. Supportive treatment: see Meningitis.

4. Monitoring: In the course of treatment perform a follow-up CT or MRI of the head every 7 to 14 days.