Otogenic abscesses are usually mixed anaerobic and aerobic. Sinusitis abscesses contain organisms present in sinus, are usually mixed. Congenital heart disease leads to infections with streptococcus, hemophilus. Trauma leads to S. aureus and epidermidis. The majority of brain abscesses arise by direct spread from paranasal sinuses, middle ear or mastoid infections.
Infection spreads by retrograde thrombophlebitis through valveless diploic veins.
Frontal sinusitis Anterior or inferior portions of the frontal lobe. Sphenoid sinusitis Frontal or temporal lobe abscess. Maxillary sinusitis Temporal lobe abscess. Ethmoid sinusitis Frontal lobe abscess. Middle ear infection May erode through tegmen, antri, attic or petrous portions of the temporal bone and spread into the temporal lobe.