Brain abscess

Background

• Caused by one of three methods:
  • Hematogenous spread (33%)
  • Contiguous infection from middle ear, sinus, teeth (33%)
  • Direct implantation by surgery or penetrating trauma (10%)
• Microbiology
  • Streptococci in 50% of cases
  • Anaerobes and Gram-negative rods are typical pathogens
  • Staph is involved with direct implantation cases

Clinical Features

• Patients rarely appear acutely ill
• Classic triad of headache, fever, AND focal neuro deficit is present in <33%
  • Headache is most common symptom (present in almost all cases)
  • Fever (~50% of patients)
• Focal neuro symptoms or seizure (~33% of patients)
• Neck stiffness (<50% of patients)
• Signs of increased ICP: papilledema, vomiting, confusion, obtundation (50% of patients)

Differential Diagnosis

• CVA
• Meningitis, encephalitis
• Malignancy

Intracranial Mass

• Intracranial hemorrhage
  • Intra-axial
    • Hemorrhagic stroke (Spontaneous intracerebral hemorrhage)
    • Traumatic intracerebral hemorrhage
  • Extra-axial
    • Epidural hemorrhage
    • Subdural hemorrhage
    • Subarachnoid hemorrhage (aneurysmal intracranial hemorrhage)
• Brain tumor
• Brain abscess
• Subdural empyema
• Epidural abscess (intracranial)

Altered mental status and fever

• Infectious
  • Sepsis
  • Meningitis
  • Encephalitis
  • Cerebral malaria
  • Brain abscess
• Other
  • Neuroleptic malignant syndrome
  • Serotonin syndrome
  • Malignant hyperthermia
  • Sympathomimetic toxicity (cocaine, amphetamine, ketamine)
  • Anticholinergic toxicity
  • Heat stroke
  • Delirium tremens
  • Hypothalamic stroke
  • Pheochromocytoma
  • Thyroid storm

Evaluation

Nocardia brain abscess on MRI. (A) T1-WI shows rim-enhancing lesion with associated edema in the right occipital lobe. (B) The dark signal on T2-WI and consistent thickness of the wall suggest a brain abscess.

• Head CT with contrast
  • Ring enhancing lesion surrounding low-density center surrounded by white matter edema
  • Early in course ring may be less defined; CT may only show area of focal hypodensity
• Blood cultures
• Consider additional workup to evaluate for alternate etiologies/complications of underlying disease process

Management

Antibiotics

Otogenic source

• Cefotaxime 2gm IV q6hr + metronidazole 500mg IV q6hr

Sinogenic or odontogenic source

• Cefotaxime 2gm IV q6hr + metronidazole 500mg IV q6hr

Penetrating trauma or neurosurgical procedures

• Vancomycin 15mg/kg IV q12hr + ceftazidime 2gm IV q8hr

Hematogenous source

• Cefotaxime 2gm IV q6hr + metronidazole 500mg IV q6hr

No obvious source

• Cefotaxime 2gm IV q6hr + metronidazole 500mg IV q6hr

Disposition

• Neurosurgery consultation