Thank you, Emily, for presenting an extremely interesting case of an elderly gentleman with afib presenting with subacute right-sided weakness and progressive somnolence found to have multifocal lesions (including a pontine ?abscess) in addition to many arterial and venous clots. While we don’t yet have a unifying diagnosis, we had some really interesting discussions!
- There are a limited number of ways a stroke can cause global CNS depression. Primarily we consider bilateral hemispheric involvement (i.e. from a showering of emboli) or a lesion in the brainstem. Indirectly, significant vasogenic edema resulting in herniation should also always be considered.
- The list of diseases that cause both arterial and venous clots is not very long. As a group, we came up with APS, HIT, PNH, DIC, and hyperhomocystinemia. The only additions are IBD, nephrotic syndrome, and mucinous adenocarcinomas (esp pancreatic cancer). Of course, distinguishing between spontaneous thrombosis of arteries and veins and embolic phenomena is important! Infection and cancer can both cause the latter.
- Bacterial brain abscesses are rare, but serious and life-threatening – duh. See more below about pyogenic infection of the brain.
Brain Abscess Basics – adapted from Patel and Clifford. Bacterial Brain Abscess. Neurohospitalist. 2014; 4(4): 196-204.
- Rare! <1 per 100,000
- Age varies. Mean age ranging from 24-57 years
- Significant male predominance consistent through literature (1.5-4.5:1)
- Risk factors:
- Recent trauma or procedure
- Immunocompromised host
- Contiguous spread from local source – 14-58%
- Primary dental, sinus, ear infection, or mastoiditis
- Hematogenous spread from systemic infection – 9-43%
- Pulmonary infections (PNA, empyema, abscess)
- ** cyanotic heart disease and pulmonary AVMs consistently associated **
- Traumatic brain injury
- Prior neurosurgical procedure – 3-18%
- Cryptogenic (cause not found) in 5-40% of cases!
- Frontal lobe is most common, but can occur anywhere
- Location of source can predict location of abscess
- Otogenic à temporal lobe and cerebellum
- Sinus à frontal lobe
- Focal neurologic symptoms
- Nausea and vomiting
- Menigismus suggests concomitant meningitis or prior intraventricular rupture
- Mean time from onset of Sx to presentation to medical care is 7-25 days.
- Blood culture yield is considered modest (14-50%)
- CSF analysis can show pleocytosis, but is often normal. CSF cultures are also rarely positive. Routine CSF collection is often discouraged due to perception of low yield and significant risk – should be considered on a case-by-case basis.
- MRI is the imaging of choice, specifically looking for ring-enhancing lesion with surrounding vasogenic edema. DWI should show diffusion restriction (which is uncommon in ring-enhancing neoplasms).
- Recently, 1H nuclear MR spectroscopy (to detect products of bacterial metapolism and neutrophil proteolysis) has been shown to improve sensitivity and specificity of MR for brain abscess from 61.9% and 60.9% to 95.2% and 100%!
- Usually a single organism
- Negative cultures in 14-34% of samples (usually attributed to abx administration prior to sample collection)
- Aerobic organisms > Anaerobes
- Aerobes: strep
- Anaerobes: b fragilis, peptostreptococcus
- Often empiric, starting with vanc + cephalosporin + metronidazole.
- Include pseudomonal coverage in any pt with recent neurosurgical procedure.
- Add toxo coverage in pts with HIV
- Consider empiric fungal coverage in pts with neutropenia
- Surgical procures – controversial!
- Stereotactic drainage by CT guidance vs. en bloc excision depending on size/location/degree of concern for malignancy
- Corticosteroids? In general try to avoid and give only when must for vasogenic edema/mass effect.
- May reduce penetration of antimicrobials into abscess, increase risk of intraventricular rupture
- Intraventricular rupture
- Obstructive hydrocephalus – esp common in abscesses within posterior fossa