Definition and Causes

Uncommon, serious, life-threatening infections

They include brain abscess and subdural or extradural empyema and are classified according to the anatomical location or the etiologic agent.

The term brain abscess is used in this article to represent all types of intracranial abscesses

An intracranial abscess is an accumulation of pus and other matter within the skull.

Depending on the location of the abscess and the severity of inflammation and swelling, pressure against the brain may cause mild or severe neurologic symptoms, coma, or death.

Before the emergence of the AIDS pandemic, the frequency of brain abscesses were estimated to account for 1 per 10,000 hospital admissions, or 1500-2500 cases annually.

The prevalence of brain abscess in patients with AIDS is higher, so the overall rate has thus increased. The frequency of fungal brain abscess has increased because of the frequent administration of broad-spectrum antimicrobials, immunosuppressive agents, and corticosteroids.

Early diagnosis and treatment are key to survival.

Infections of the brain and skull may be caused by a number of different bacteria, in a single strain or mixed, originating within the body, in dental or sinus infections, in chronic or traumatic wounds, or from foreign matter.

Viruses, fungi, parasites, protozoa, and other microbial organisms may also cause intracranial abscess.

With the introduction of antimicrobics and the increasing availability of imaging studies, such as CT scanning and MRI, the mortality rate has decreased to less than 5-15%.

Rupture of a brain abscess, however, is associated with a high mortality rate (up to 80%)

Children with congenital heart disease and people with compromised immune systems due to chronic disease, cancer therapy, HIV, AIDS, and immunosuppressive drugs after organ transplantation face higher risk.

Treatment with Hyperbaric Oxygen Therapy

Hyperbaric oxygen therapy (HBOT) is used as an adjunct to surgery and antibiotic therapy for intracranial abscess. The bacteria involved in brain abscess are mainly anaerobic, meaning they thrive in low-oxygen environments. HBOT inhibits anaerobic and some other bacteria from replicating, spreading, and releasing damaging toxins. Hyperbaric oxygen may also help reduce brain swelling, boost the effect of antibiotics, and enhance the body’s natural defenses against bacteria and other microbial organisms.

Hyperbaric oxygen may be especially useful for multiple abscesses in deep or dominant locations, in patients with immune compromise, and when the infection does not respond well to traditional surgery and antibiotics. UHMS guidelines recommend daily or twice-daily treatment of 60-90 minutes at 2.0 to 2.5 atmospheres of absolute pressure (ATA).

Undersea and Hyperbaric Medical Society

Mechanisms of HBO2

Despite the improving mortality of the disease, the last years, patients with certain conditions and complications pose major therapeutic problems.

These include patients with: (a) multiple abscesses, (b) abscess in a deep or dominant location, (c) immune compromise, and (d) no response or further deterioration in spite of standard surgical and antibiotic treatment.

The use of adjunctive hyperbaric oxygen (HBO2) therapy, in this patients may confer additional therapeutic benefit.

A number of mechanisms can be postulated by which HBO2 could provide benefit in ICA.

First, high partial pressures of oxygen may inhibit the flora found in ICA, the predominance of which are anaerobic.
Second, HBO2 can cause a reduction in perifocal brain swelling.
Third, HBO2 has the potential to enhance host defense mechanisms.
Finally, HBO2 has been reported to be of benefit in cases of concomitant skull osteomyelitis.

Patient Selection Criteria

Adjunct HBO2 should be considered under the following conditions:

    1. Multiple abscesses
    2. Abscesses in a deep or dominant location
    3. Compromised host
    4. In situations where surgery is contraindicated or where the     patient is a poor surgical risk
    5. No response or further deterioration in spite of standard     surgical (e.g. 1-2 needle aspirates) and antibiotic treatment.

Clinical Management

Hyperbaric oxygen treatment is administered at a pressure of 2.0 to 2.5 atmospheres absolute, with oxygen administration from 60 to 90 minutes per treatment. HBO2 treatment may be one or two sessions per day depending on the condition of the individual patient. In the initial phase, twice daily treatment may be considered.

Duration and the optimal number of of the HBO2 course must be individualized, based upon the patient's clinical response as well as radiological findings.


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