Abscess formation in the brain can be a devastating complication of sinus infections or bone infections (osteomyelitis) of the skull. Occasionally, abscesses are seeded from infection occurring in other parts of the body. Brain abscesses are frequently multiple.

     One of the problems in treatment in treatment of brain abscesses relates to the fact that surgically drainage of their contents is often required for cure. Unfortunately, normal brain tissue surrounding the abscess may be unavoidably damaged by such surgery. Fine needle aspiration of the abscesses is being performed with greater frequency to avoid this problem.

     Antibiotics may not penetrate well into brain abscesses. Furthermore, white blood cells, which kill infecting bacteria, may not have enough oxygen to effectively eliminate the infection when functioning deep in the abscess at a distance from their normal blood supply. It is well known that white blood cells require a minimum level of oxygen to kill bacteria.

     Most intracranical abscesses are caused by with anaerobic bacteria (bacteria that function optimally in low oxygen concentrations). Hyperbaric oxygen raises the environmental oxygen level in the region of the abscess, exposing the bacteria to levels which may inhibit or kill them, as well as providing sufficient oxygen for white blood cells to exercise their killing power.

     The average mortality from intracranial abscess reported in six large series was 20% when hyperbaric oxygen (HBO₂) was not used. Among the 48 known cases treated with HBO₂ to date, the mortality has been only 2%. Additionally, most of the patients treated with hyperbaric oxygen have returned to their regular daily activity after recovery, with less apparent brain damage. Therapy with HBO₂ carries minimal risk, so the risk-benefit ratio is not arguable.