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Brain Abscess

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Brain Abscess, Intracranial Abscess

  • Pathophysiology
  1. Frontal, temporal, and Parietal Lobes are most commonly affected
  • Causes
  • Source
  1. Unknown primary source of abscess in 20-40% of cases
  2. Direct Spread
    1. Mastoiditis (due to Chronic Otitis Media)
    2. Frontal Sinusitis or Ethmoid Sinusitis
    3. Dental Infection
    4. Retained Foreign Body such as bullet fragments (abscess development may be years later)
    5. Neurosurgery (abscess development may be >1 year later)
  3. Hematogenous spread
    1. Lung Abscess or empyema in host with chronic lung disease (e.g. Cystic Fibrosis, Bronchiectasis)
    2. Esophageal procedures (e.g. esophageal dilation, Varices management)
    3. Cyanotic Congenital Heart Disease
    4. Bacterial Endocarditis
    5. Pulmonary AV Malformation with right to left shunt
    6. Skin Infections
    7. Intraabdominal and pelvic infections
  • Causes
  • Organisms
  1. Strepotococcus esp. viridans (60-70%)
  2. Staphylococcus, esp. Staphylococcus aureus (10-14%)
  3. Other source site-specific organisms (in addition to Staphylococcus and Streptococcus species)
    1. Actinomyces (lung)
    2. Bacteroides (sinus, dental, ear) in up to 20-40% of cases
    3. Clostridium (penetrating Head Trauma)
    4. Enterobacteriaciae, Gram Negative Rods (ear) in up to 25-33% of cases
    5. Enterobacter (urine, penetrating Head Trauma, neurosurgery)
    6. Fusobacterium (sinus, dental, lung)
    7. Haemophilus (sinus, dental)
    8. Pseudomonas (ear, urine, neurosurgery)
  4. Immunocompromised patients
    1. See Brain Lesion in HIV
    2. Aspergillus
    3. Coccidioides
    4. Cryptococcus
    5. Listeria
    6. Nocardia
    7. Toxoplasma gondii
    8. Other fungus (e.g. Candida)
  5. Immigrants
    1. Cysticercosis (most common)
    2. Entamoeba histolytica
    3. Schistosoma
  • Symptoms
  1. Often initially subacute (results in delayed diagnosis typically >1 week)
  2. Headache (69%), typically unilateral in the region of abscess
  3. Neck Stiffness (15%), associated with posterior abscess (e.g. occiput)
  4. Vomiting (suggests Increased Intracranial Pressure)
  • Signs
  1. Fever (45%)
  2. Focal neurologic deficit (50%, delayed finding >1 week after Headache onset)
    1. Oculomotor findings (CN 3 or CN 6) suggests Increased Intracranial Pressure
  3. Seizure (25%)
  4. Altered Level of Consciousness (associated with significant brain edema and with worse prognosis)
  • Imaging
  1. CT Head with contrast OR
  2. MRI Brain with gadolinium (preferred)
  • Differential Diagnosis
  • Diagnostics
  1. Lumbar Puncture
    1. Contraindicated in focal symptoms/signs, CNS mass, Increased Intracranial Pressure (risk of Herniation)
    2. Obtain CNS imaging prior to Lumbar Puncture
  • Labs
  1. Serology
    1. Blood anti-Toxoplasma IgG
    2. CSF anti-cysticercal Antibody
  2. CT-guided or neurosurgery obtained fluid
    1. Gram Stain
    2. Acid-fast stain and modified acid fast (Mycobacteria, Nocardia)
    3. Fungal stains
    4. Aeorbic and Anaerobic Bacterial cultures
    5. Mycobacterial culture
    6. Fungal Culture
  • Management
  1. See Toxoplasmosis
  2. Bacterial cause (initial empiric therapy)
    1. Cefotaxime 2 g IV q4 hours OR Ceftriaxone 2 g IV every 12 hours (or Pen G 3-4 MU q4h) AND
    2. Metronidazole 7.5 mg/kg every 6 hours
    3. Add Vancomycin for suspected Staphylococcus aureus
  3. Nocardia initial empiric therapy
    1. Trimethoprim-Sulfamethoxazole (or Linezolid 500 mg IV or oral every 12 hours) AND
    2. Imipenem 500 mg IV every 6 hours (or Meropenem 2 g IV every 8 hours)
    3. Add Amikacin 7.5 mg/kg every 12 hours, if multiorgan involvement
  4. Post-Trauma or Post-Surgical
    1. Vancomycin 15-20 mg/kg every 8-12 hours (or Linzeolid 600 mg q12h) AND
    2. Cefepime 2 g IV every 8 hours (or Meropenem 2 g IV every 8 hours)
  • References
  1. (2016) Sanford Guide, accessed 4/9/2016
  2. Southwick in Calderwood (2016) UpToDate, accessed 4/9/2016
  3. Brouwer (2014) N Engl J Med 371:447 [PubMed]