Hyperbaric Evaluation and Treatment Of Intracranial Abscess

Hyperbaric oxygen therapy of intracranial abscesses refers to the following disorders: cerebral abscess, subdural empyema, and epidural empyema. It is defined as a focal, encapsulated infection of cerebral parenchyma and is caused by a wide array of microorganisms such as bacteria, mycobacteria, protozoa, fungi, or helminths. It is a relatively rare condition, with the incidence estimated at 0.3 to 1.3 per 100,000.  However, this number is believed to be elevated in particular high-risk groups; for example, patients with human immunodeficiency virus (HIV) infection or acquired immune deficiency syndrome (AIDS). There are multiple mechanisms responsible for the development of intracranial abscesses. The infectious organism can invade the brain by either direct spread, which accounts for 20% to 60% of the cases. This is typically caused by a contiguous infection such as sinusitis, otitis, mastoiditis, or dental infection. Brain abscesses can also arise from hematogenous seeding or cranial trauma, which typically manifests as multiple abscesses. Streptococcus and Staphylococcus are the most frequent causes of brain abscesses, with Viridans streptococci  and Staphylococcus aureus being the most common. Anaerobes are also a common constituent of brain abscesses, which originate from the normal oral flora.  A patient’s immune status is also important when considering the cause of the infection. Bacterial abscesses are typically seen in immunocompetent individuals, while immunocompromised patients can be infected with a wide array of organisms, including fungi. Although it is a rare condition, mortality remains at a high rate for patients with brain abscesses. However, one systematic review and meta-analysis demonstrated that the prognosis of patients with brain abscesses has significantly improved. This study showed that over the past 6 decades, the case fatality rate decreased from 40% to 10%, and the rate of patients with full recovery increased from 33% to 70%. Another study, a report in 289 patients with pyogenic brain abscess treated between 1999 and 2006, showed a mortality rate as low as 2.7%. Several factors have been credited towards these improved outcomes. The introduction of computed tomogram (CT) imaging has been critical in improving treatment results for brain abscesses. One retrospective study demonstrated that intracranial abscess mortality rate dropped from 40% to 20% within the first decade after the invention of CT imaging. This invention has allowed clinicians to make a faster diagnosis and facilitated less invasive, more precise neurosurgical procedures such as stereotactic aspiration of abscesses. Improvements in neurologic surgical techniques and antimicrobial therapy, which are the mainstay of therapy, have also been instrumental in these improved outcomes.
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