Published on 25/03/2015 by admin
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Chapter 596 Brain Abscess
Charles G. Prober, LauraLe Dyner
Brain abscesses can occur in children of any age but are most common in children between 4 and 8 yr and neonates. The causes of brain abscess include embolization due to congenital heart disease with right-to-left shunts (especially tetralogy of Fallot), meningitis, chronic otitis media and mastoiditis, sinusitis, soft tissue infection of the face or scalp, orbital cellulitis, dental infections, penetrating head injuries, immunodeficiency states, and infection of ventriculoperitoneal shunts.
Cerebral abscesses are evenly distributed between the 2 hemispheres, and 80% of cases are divided equally between the frontal, parietal, and temporal lobes. Brain abscesses in the occipital lobe, cerebellum, and brainstem account for about 20% of the cases. Most brain abscesses are single, but 30% are multiple and may involve more than 1 lobe. The pathogenesis is undetermined in 10-15% of cases. An abscess in the frontal lobe is often caused by extension from sinusitis or orbital cellulitis, whereas abscesses located in the temporal lobe or cerebellum are frequently associated with chronic otitis media and mastoiditis. Abscesses resulting from penetrating injuries tend to be singular and caused by Staphylococcus aureus, whereas those resulting from septic emboli, congenital heart disease, or meningitis often have several causal organisms.
The responsible bacteria include streptococci (Streptococcus milleri, Streptococcus pyogenes group A or B, Streptococcus pneumoniae, Enterococcus faecalis), anaerobic organisms (gram-positive cocci, Bacteroides spp., Fusobacterium spp., Prevotella spp., Actinomyces spp.), and gram-negative aerobic bacilli (Haemophilus aphrophilus, Haemophilus parainfluenzae, Haemophilus influenzae, Enterobacter, Escherichia coli, Proteus spp.). Citrobacter is most common in neonates. One organism is cultured in 70% of abscesses, 2 in 20%, and 3 or more in 10% of cases. Abscesses associated with mucosal infections (sinusitis) frequently have anaerobic bacteria. Fungal abscesses (Aspergillus, Candida) are more common in immunosuppressed patients.
The early stages of cerebritis and abscess formation are associated with nonspecific symptoms, including low-grade fever, headache, and lethargy. The significance of these symptoms is generally not recognized, and an oral antibiotic is often prescribed with resultant transient relief. As the inflammatory process proceeds, vomiting, severe headache, seizures, papilledema, focal neurologic signs (hemiparesis), and coma may develop. A cerebellar abscess is characterized by nystagmus, ipsilateral ataxia and dysmetria, vomiting, and headache. If the abscess ruptures into the ventricular cavity, overwhelming shock and death usually ensue.
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