Bacterial<unk>  after metastasis treatment. Anaerobic and microaerophilic cocci and gram-negative and gram-positive anaerobic bacilli are the predominant bacterial isolates. Many<unk> es are polymicrobial. The predominant organisms include: Staphylococcus aureus, aerobic and anaerobic streptococci (especially Streptococcus intermedius), Bacteroides, Prevotella, and Fusobacterium species, Enterobacteriaceae, Pseudomonas species, and other anaerobes. Less common organisms include: Haemophillus influenzae, Streptococcus pneumoniae and Neisseria meningitidis. Bacterial abscesses rarely (if ever) arise de novo within the<unk> , although establishing a cause can be difficult in many cases. There is almost always a primary lesion elsewhere in the body that must be sought assiduously, because failure to treat the primary lesion will result in relapse. In cases of trauma, for example in compound skull fractures where fragments of bone are pushed into the substance of the<unk> , the cause of the abscess is obvious. Similarly, bullets and other foreign bodies may become sources of infection if left in place. The location of the primary lesion may be suggested by the location of the abscess: infections of the middle ear result in lesions in the middle and posterior cranial fossae; congenital heart disease with right-to-left shunts often result in abscesses in the distribution of the middle cerebral artery; and infection of the frontal and ethmoid sinuses usually results in collection in the subdural sinuses. Other organisms Fungi and parasites may also cause the disease. Fungi and parasites are especially associated with immunocompromised patients. Other causes include: Nocardia asteroides, Mycobacterium, Fungi (e.g. Aspergillus, Candida, Cryptococcus, Mucorales, Coccidioides, Histoplasma capsulatum, Blastomyces dermatitidis, Bipolaris, Exophiala dermatitidis, Curvularia pallescens, Ochroconis gallopava, Ramichloridium mackenziei, Pseudallescheria boydii), Protozoa (e.g. Toxoplasma gondii, Entamoeba histolytica, Trypanosoma cruzi, Schistosoma, Paragonimus), and Helminths (e.g. Taenia solium). Organisms that are most frequently associated with<unk>  in patients with AIDS are poliovirus, Toxoplasma gondii, and Cryptococcus neoformans, though in infection with the latter organism, symptoms of meningitis generally predominate. These organisms are associated with certain predisposing conditions: * Sinus and dental infections—Aerobic and anaerobic streptococci, anaerobic gram-negative bacilli (e.g. Prevotella, Porphyromonas, Bacteroides), Fusobacterium, S. aureus, and Enterobacteriaceae * Penetrating trauma—S. aureus, aerobic streptococci, Enterobacteriaceae, and Clostridium spp. * Pulmonary infections—Aerobic and anaerobic streptococci, anaerobic gram-negative bacilli (e.g. Prevotella, Porphyromonas, Bacteroides), Fusobacterium, Actinomyces, and Nocardia * Congenital heart disease—Aerobic and microaerophilic streptococci, and S. aureus * HIV infection—T. gondii, Mycobacterium, Nocardia, Cryptococcus, and Listeria monocytogenes * Transplantation—Aspergillus, Candida, Cryptococcus, Mucorales, Nocardia, and T. gondii * Neutropenia—Aerobic gram-negative bacilli, Aspergillus, Candida, and Mucorales
Brain abscess
Epidural hematoma
Brain metastasis
Subdural empyema
Amoebic brain abscess
Leptomeningeal cancer
Meninges
Coma