- Emergency evacuation indications: If multiple ring-enhancing lesions are found, emergency surgery for all abscesses >2.5 cm in diameter or for those causing a marked mass effect should be undertaken, either by excision or preferably by stereotactic aspiration.
- Specimen is needed to direct antibiotic treatment: When there is no identification of the infecting organism that has traveled from a source to cause the abscess, then a specimen is needed. If all abscesses are <2.5 cm and are not causing any mass effect, then the largest abscess should be aspirated for microbiological identification. Antibiotics should be withheld until pathological material is obtained for culture.
- Treat with broad-spectrum antibiotics until cultures identify infecting organism: Broad-spectrum antibiotics should be administered until culture results are available, and then antibiotics can be tailored adequately to these results. Afterward, antibiotics should be continued for a minimum of 6–8 weeks and in immunocompromised patients often for more than 1 year.
- Follow with serial scans: Postoperatively, CT scans or MRI should be obtained weekly or any time the patient shows signs of neurological deterioration. Repeated surgical drainage should be undertaken if there is enlargement of an abscess after 2 weeks of treatment or when clinical deterioration occurs, or if an abscess fails to diminish in size after 4 weeks of antibiotics.
- Size determines degree of surgery: Lesions <2.5 cm in diameter may be managed with antibiotics and stereotactic aspiration for identification of a microorganism, while a diameter >2.5 cm may warrant stereotactic aspiration or surgical excision. Large abscesses with a significant mass effect should be decompressed through the safest treatment modality, such as stereotactic aspiration for abscesses located in eloquent areas.
- Location dictates means of removal: Stereotactic aspiration of deep-seated abscesses may be more appropriate, and judicious management must be used in the treatment of lesions located in critical areas, such as in speech areas and the motor cortex.
- Surgical resection for immediate, definitive management: Cerebellar abscesses are usually resected via craniotomy, especially when the lesion is associated with mass effect, edema, and/or obstructive hydrocephalus. A wide decompression of the posterior fossa has been advocated because of the precarious state of a cerebellar abscess in the small volume of the posterior fossa (2, 61). However, controversy persists over the optimal management, with some neurosurgeons using stereotactic aspiration or surgical extirpation (2).
- Mortality risk greater with aspiration: The mortality rate was 50% among patients treated with aspiration, compared with 15% after surgical excision (11).
- Lower incidence of hydrocephalus with surgical resection: It has been reported that the patients who underwent resection for brain abscess did not need subsequent surgical treatment for hydrocephalus, in contrast to some of those who underwent aspiration (16).
- Mastoidectomy for otogenic abscesses: Cerebellar abscesses caused by otogenic abscesses secondary to chronic otitis media require operative planning for a mastoidectomy with an otolaryngologist to coordinate the timing of treatment for each lesion. Much debate remains as to whether the mastoidectomy should be performed preoperatively, concurrently, or postoperatively in cases in which a craniotomy is performed for the cerebellar abscess (2, 28, 39. 86, 105).
- Rare: Fewer than 1% of brain abscesses are located in the brainstem (10, 72).
- Pons and midbrain: Most brainstem abscesses are in the pons or mesencephalon and rarely occur in the medulla (53).
- Stereotactic aspiration usually used due to critical location: Brainstem abscesses are generally treated with stereotactic aspiration and antibiotic therapy, although there are no concrete data about the optimal management. Stereotactic drainage has been reported to be performed through the right paramedian precoronal frontal or suboccipital transcerebellar approaches (53, 115, 116). Potential problems associated with stereotactic aspiration include incomplete evacuation because of thick purulent materal or multiloculations, and/or hemorrhage of the abscess capsule (62, 134).
- Surgical drainage via thinnest covering: Open microsurgery can reduce mass effect on the brainstem and provides direct visual control of the collapse of the abscess as an indication of complete evacuation of the pus; penetration of the abscess at the point of the highest fluctuation decreases the risk of brainstem damage (62, 76).
- Medical management for high-risk patients: High-risk surgical patients or neurologically stable patients with a brainstem abscess of <2 cm diameter may be treated medically with antibiotic therapy and serial imaging follow-up.
Multiple Brain Abscesses
- Incidence is reported at 10–50%: The occurrence of multiple abscesses is not uncommon, with one study reporting an incidence of 10–50% (30). It is especially common in immunocompromised patients for whom multiple toxoplasma foci have to be considered in the differential diagnosis along with bacterial abscesses. Toxoplasma foci preferentially are deeply located, e.g., in the basal ganglia; however, atypical localizations are possible. The toxoplasmosis cysts typically reveal high “apparent diffusion coefficients” values as compared with abscesses according to the lower viscosity of the hydrous cyst content (56).
- Image-guided stereotactic aspiration: The management of patients with multiple brain abscesses has generated much debate. The stereotactic aspiration procedures of multiple bihemispheric pyogenic brain abscesses are being used with increasing frequency in view of the minimal morbidity risk involved with the use of CT-guided stereotaxy. The possibility of repeating this technique several times is a further advantage (26).
- MCA distribution at gray-white interface: Multiple brain abscesses are usually associated with hematogenous spread and are usually found at the gray-white junction in the distribution of the middle cerebral artery (55).