Neuro Infections

Brain Abscess

• Symptoms:
  • MOST COMMON: Severe headache at site of abscess.
    • Sudden worsening = rupture of abscess into ventricles... high mortality rate (25-85%).
  • Many present with triad:
    • Headache
    • Fever
    • Focal Neuro Deficit
  • Other Symptoms based on location:
    • Neck stiffness only if occipital brain abscess or rupture into ventricle.
    • altered mental status, lethargy, coma.
    • Vomiting associated with incresed CSF pressure.
• Findings:
  • Fever not present in 50%
  • Neuro findings are late.
  • Papilledema - late manifestation (25%)
  • CN VI and III palsies from high ICP.
  • Seizures if frontal brain abscess
• Two causes:
  • 1. Direct spread from middle ear, frontal sinus, or dental infection
  • 2. Hematogenous spread from chronic pulmonary/skin/pelvic/intra-abdo infection, endocarditis, cyanotic heart disease.
  • 20-35% of patients --> do not find cause.
• Cerebritis (infammation and edema) --> necrosis, fibrotic capsule formation.
• Organisms:
  • Organism provides clues on site of infection.
  • Anaerobic bacteria (mouth/genital tract)
    • Bacteroides fagilis, Prevotella, Propionibacterium, fusobacterium...
  • Aerobic gram+ cocci (S. viridans, S. milleri, S. pneumo (rare), S. aureus)
  • Aerobic gram- rods  --> usually with neurosurg
  • Immunocompromised:
    • Toxoplasma, Nocardia, Aspergillus/cryptococcus/coccidioides.
  • Immigrants (parasites)
    • Cysticercosis parasite (85% of brain infections in Mexico City)
    • Entamoeba hystolytica
    • Schistosoma japonicum
    • Paragonimus
• Diagnosis:
  • Space occupying lesion (SOL) suggested by:
    • Focal symptoms (even unilateral headache)
    • signs (neuro deficits)
    • papelledema
  • LP CONTRAINDICATED, unless SOL excluded.  (If papilledema or focal findings --> NO LP!!  CT first)
  • MRI better than CT (more sensitivity in picking up lesions) (Diffusion weighted MRI help discriminate abscess vs. neoplasms).  CT only if unable to do MRI.
    • Stages on CT:
      • Early cerebritis
        • irregular lesion of low density - no contrast enhancement.
      • Later cerebritis
        • Thick diffuse ring enhancement (enlarging) on contract injection.
      • Late cerebritis
        • Necrosis, Pre-contrast: ring of higher density surrounding edematous brain.
        • Contrast: thin ring, non-uniform in thickness.
      • Healed abscess
        • Collagen capsule becomes isodense.  No enhancement on contrast.
• Treatment:
  • Neurosurg consult to drain abcess if >2.5cm lesion.
    • (Excision or stereotactic aspiration), culture specimens. 
  • IV abx 6-8weeks 
          +/- prolongued oral therapy if appropriate agent is available.
          (IV empiric therapy based on predisposing condition and presume pathogensis)
    • Generally:
      • Ceftriaxone (enterobacterciae) + metronidazole (anaerobic lytic due to mouth flora)
    • IF Dental Abscess: use penicillin + metronidazole to cover mouth flora
    • IF concerned of pseudomonas (neurosurg)
      • Use ceftazidime or cefepime
    • IF trauma (worry about S.aureus) add vancomycin (MRSA) or oxacillin/nafcillin (MSSA) depending on resistance patterns... aminoglycosides, erythromycin, tetracycline, 1st gen cefs also used.
    • IF hematogenous spread:
      • Typically vanco + gentamycin for empiric therapy.
  • Steroids:
    • if mass effect + mental status change.
    • IV dexamethasone (load 10mg then 4mg q6h)
    • Do not worry about immunocompromise...
    • DC as soon as possible.
      • Reduce contrast enhancement on CT (hard to monitor)
      • Decrease antibiotic penetration
      • Slow capsule formation (can rutupre into ventricles)
  • Repeat Neuroimaging
    • IMPORTANT*, every other week up to 3months after completing therapy.
    • To monitor for expansion of abscess or failure to respond.
• Prognosis:
  • Depends on stage:
    • 0-30% generally
    • 60-100% if stupor/coma
    • 80-100% if ruptures into ventricle.

Spinal Epidural Abscess

• Spinal canal has anterior and posterior epidural space
• Mechanism: of infection:
  • Spread from osteomyelitis or disk space
  • Spinal surgery or epidural catheter.
  • Hematogenous spread from:
    • Skin
    • UTI
    • IV drug use.
  • Organisms:
    • S. aureus (most common)
    • Can see GN's or anaerobes if GU or GI source.
• 4 stages of clinical presentation:

1. Back Ache and focal vertebral pain
2. Nerve root pain (radiculopathy/parasthesias)
3. Spinal Cord dysfunction
4. Paraplegia

• Symptoms:
  • Low back pain, fever, radicular pain, lower motor deficits, cord compression signs, spinous process tenderness.

• Back pain + fever --> consider epidural abscess MRI is test of choice.

• Diagnosis:
  • MRI with Gadolinium --> procedure of choice!!!
    • Can see spinal cord + epidural space in saggital and transverse sections.
    • Can identify accompanied osteomyelitis, intra-medullary spinal cord lesions and diskitis. 
• Treatment
  • If spinal cord compression:
    • URGENT surgery. 
    • Can return function if done in 24-36hrs following neurological change.
      • Emergency surgical drainage.
  • Empiric Abx:
    • Usually anti-staphylococcal agent (cloxacillin, nafcillin, oxacillin etc..)
      • Usually (in US and MKSAP) vancomycin for empric MRSA coverage pending susceptibility testing. 
            (HIGH MRSA rates > 50% in some cases, vanco considered first line in US and     MKSAP).
      • PLUS + antipseudomonal cephalosporin  or carbapenem (for GN bacilli, esp for IVDU or spinal procedure). 
        (I.e. MKSAP answer is vancomycin + ceftazidime)
    • Usually need prolongued (4-6weeks) tx with nafcillin, oxacillin, metronidazole, ceftriaxone.
  • Antimicrobial therapy alone can be considered in patients without long tract signs (i.e. if only pain and radicular symptoms), frequent follow-up, neuro exams, serial MRI studies to demonstrate abscess resolution are important. 
  • TB can be the cause.

Generalized Neuropathy Causes