145.1 🎓 醫孞生版

145.1.0.1 📌 䞀頁重點

  • Brain abscess: focal pus collection in parenchyma
  • Empyema: pus in space (subdural / epidural)
  • Source:
    • Contiguous (50%): sinusitis (frontal), otitis (temporal/cerebellar), dental (frontal)
    • Hematogenous (30%): lung (lung abscess, bronchiectasis), heart (IE, congenital R-L shunt), skin
    • Trauma / surgery (10%): open fracture, post-op
  • 病原 (polymicrobial):
    • Streptococcus (viridans, anginosus), Staph aureus, Bacteroides, Prevotella, GN (Enterobacteriaceae, Pseudomonas)
    • Immunocompromised: Toxoplasma, Nocardia, fungi (Aspergillus, Mucor, Cryptococcus), mycobacteria
  • Triad (only 20% complete): headache + fever + focal deficit
  • Imaging: MRI with contrast — ring-enhancing lesion with central necrosis + edema
  • Tx: Antibiotic 6-8 weeks IV + drainage (aspirate or excise) + treat source

145.1.0.2 1⃣ Brain Abscess

145.1.0.2.1 Pathogenesis stages
  1. Early cerebritis (Day 1-3)
  2. Late cerebritis (Day 4-9)
  3. Early capsule (Day 10-13)
  4. Late capsule (Day 14+) — surgical drainage easier here
145.1.0.2.2 Clinical (triad only 20%)
  • Headache (~ 70%)
  • Fever (~ 50%)
  • Focal neuro deficit (~ 50%, depending location)
  • Altered mental status (50%)
  • Seizure (25%)
  • Vomiting, papilledema (↑ ICP)
145.1.0.2.3 Imaging
  • MRI gadolinium: ring-enhancing lesion + central necrosis + surrounding edema; multiple/single
  • DWI: abscess (restricted diffusion) vs tumor (no restriction) — key differentiator
  • MR spectroscopy: amino acids, lactate, acetate
  • CT (faster, less sensitive)
145.1.0.2.4 Etiology by Source
Source Most likely organisms Location
Sinusitis (frontal) Streptococci (anginosus), Staph, anaerobes, Bacteroides Frontal lobe
Otitis media / mastoiditis Streptococci, anaerobes, Pseudomonas, GN Temporal lobe / cerebellum
Dental Streptococci, Fusobacterium, Bacteroides, Prevotella Frontal lobe
Lung (bronchiectasis, abscess) Streptococcus anginosus, anaerobes, Fusobacterium Parietal lobe (MCA territory)
IE (right-to-left shunt / cyanotic congenital) Staph aureus, Streptococcus Multiple lesions
Penetrating trauma S. aureus, Clostridium, GN At injury site
Post-neurosurgery S. aureus, S. epidermidis, GN, Pseudomonas Surgical site
HIV / Immunocompromised Toxoplasma (most), Nocardia, fungi (Aspergillus, Mucor), Cryptococcus, mycobacteria Multiple

145.1.0.3 2⃣ Treatment

145.1.0.3.1 Empirical Antibiotic (until culture)
Source Empirical
Sinusitis / dental / unknown Ceftriaxone + Metronidazole + Vancomycin (cover Strep, anaerobes, MRSA)
Otogenic + Cefepime or Pip-tazo (Pseudomonas)
Post-surgery / trauma Vancomycin + Cefepime / Meropenem (cover MRSA + Pseudomonas + GN)
Immunocompromised + Sulfadiazine + Pyrimethamine + folinic acid (toxo); + TMP-SMX (Nocardia); + ampho B (fungi)
145.1.0.3.2 Duration
  • 6-8 weeks IV standard
  • 可胜延長 to 3 months if large / multiple / immunocompromised
  • Serial MRI to monitor
145.1.0.3.3 Surgery (Indication)
  • Mass effect / brainstem compression
  • Size > 2.5 cm → stereotactic aspiration
  • Refractory to antibiotic alone after 1-2 weeks
  • Fungal / mycobacterial abscess (poor antibiotic penetration)
  • Foreign body (post-trauma)
145.1.0.3.4 Stereotactic Aspiration vs Excision
  • Aspiration: less invasive; preferred for deep / eloquent areas
  • Excision: well-encapsulated, easily accessible, fungal, post-foreign body
145.1.0.3.5 Adjunct
  • Anti-seizure prophylaxis (levetiracetam) for 3 mo at minimum
  • Dexamethasone: ONLY if significant edema / mass effect (otherwise impairs antibiotic penetration + immune response)

145.1.0.4 3⃣ Subdural Empyema

145.1.0.4.1 Pathophysiology
  • Pus in subdural space (between dura + arachnoid)
  • 倚 sinusitis (frontal) extension or otitis (temporal)
  • Rapid progression (faster than abscess) — virulent organisms spread along subdural plane
145.1.0.4.2 Clinical
  • Headache + fever + meningismus + focal deficit + seizure (more rapid than abscess)
  • Mortality 10-20% even with treatment
145.1.0.4.3 Imaging
  • MRI: crescentic extra-axial collection with peripheral enhancement
  • Restricted diffusion on DWI
145.1.0.4.4 Treatment
  • Emergency neurosurgical drainage (craniotomy or burr hole)
  • Antibiotic 4-6 weeks: same as brain abscess empirical
  • Anticonvulsant (high seizure risk)

145.1.0.5 4⃣ Epidural Abscess (Intracranial)

  • Pus between dura + skull
  • Usually post-surgery, trauma, sinusitis
  • Slower progression than subdural
  • Treatment: surgical drainage + antibiotic 4-6 weeks

145.1.0.6 5⃣ Spinal Epidural Abscess

145.1.0.6.1 Risk factors
  • IVDU, DM, immunocompromised, recent epidural injection / surgery
  • Bacteremia source
145.1.0.6.2 Clinical (Classic triad — 完敎 only ~ 15%)
  1. Back pain
  2. Fever
  3. Neuro deficit (radiculopathy → paraplegia/quadriplegia)
145.1.0.6.3 Workup
  • ESR / CRP ↑↑
  • Blood cultures + abscess aspirate culture
  • MRI spine with contrast — diagnostic
  • S. aureus #1 (60-70%) — MRSA increasingly
145.1.0.6.4 Treatment
  • Emergency surgical decompression (laminectomy + drainage) if neuro deficit
  • Antibiotic 6 weeks IV: Vancomycin + 3rd gen cephalosporin / pip-tazo
  • Anti-seizure if cortical lesion
  • Pain control