Intracranial Abscess

FACTS

  • Often polymicrobial, but Staph aureus #1 (50—70%)
  • S. pneumoniae is a common cause of meningitis but not abscesses
 
Refer to the following article for very similar HPI/physical exam/plans
Discitis / Osteomyelitis

HPI

  • Any IVDU
  • Any prolonged use of lines this hospitalization

PHYSICAL EXAM

evaluate for peripheral neuropathy, venous stasis in LEs
evaluate dentition
evaluate all incisions

IMAGING

  • Evaluate for any IPH, which would prompt you to perform a DSA to evaluate for co-occurring mycotic aneurysms
  • Rim-enhancing, diffusion restricting cerebral abscesses
Figure 1: (LEFT): DWI shows diffusion restriction with (MIDDLE/RIGHT) T1 and T1+c sequences showing classic rim-enhancing
Figure 1: (LEFT): DWI shows diffusion restriction with (MIDDLE/RIGHT) T1 and T1+c sequences showing classic rim-enhancing
 
A/P
  • ID consult for medical management
    • CNS penetrating triple ABx: Vanc to be dosed w/ troughs, flagyl 500, CTX 2q12
    • TEE to evaluate for endocarditis
    • BCx
    • CTAP to ensure to evidence of body abscsses
  • Generally only drain surgically if medical management has failed or if symptoms referrable to mass lesion
  • Consider DSA to evaluate for mycotic aneurysm if IPH is present

AIDS and intracranial lesions

Most common ring-enhancing lesions, occur typically when CD4 < 200
  • Toxoplasmosis is most common
  • Less common: Cryptococcus, Primary CNS Lymphoma (~5% patients)
  • Rare: PML, tuberculosis
 
Lesion
Typical Cause / Organism
Imaging Features
CD4 Level
Notes / Clinical Clues
1. Toxoplasmosis (most common)
Toxoplasma gondii (reactivation)
- Multiple ring-enhancing lesions- Basal ganglia or corticomedullary junction- Surrounding edema, mass effect
<100 cells/µL
Fever, focal deficits, seizures. Improves with anti-toxoplasma therapy (pyrimethamine + sulfadiazine + leucovorin).
2. Primary CNS Lymphoma (PCNSL)
EBV-driven B-cell lymphoma
- Solitary or few ring-enhancing lesions- Often periventricular or corpus callosum- Thallium-201 SPECT positive- Restricted diffusion on MRI
<50 cells/µL
Often mistaken for toxo; diagnosis via biopsy or EBV DNA in CSF. Poor prognosis.
3. Progressive Multifocal Leukoencephalopathy (PML)
JC virus (polyomavirus)
- Non-enhancing white matter lesions- Asymmetric, multifocal- No mass effect
<200 cells/µL
No enhancement! Subacute deficits; not a true abscess.
4. Cryptococcal infection
Cryptococcus neoformans
- May cause gelatinous pseudocysts (non-enhancing) or meningeal enhancement
<100 cells/µL
Often with meningitis; India ink + cryptococcal antigen positive.
5. Tuberculoma
Mycobacterium tuberculosis
- Ring or nodular enhancement, variable- May calcify
Variable (<200 cells/µL)
Common in endemic areas.
6. CNS abscess (bacterial/fungal)
Nocardia, Listeria, Candida, Aspergillus
- Ring-enhancing lesions with restricted diffusion
<100 cells/µL
Nocardia: predilection for brain, often multiple. Aspergillus: angioinvasive.