The incidence of cerebral abscesses ranges from 0.4 – 0.9 cases per 100 000 people and is more frequent in immunocompromised patients. They account for 1 per 10000 hospital admissions.
Dental infections have occasionally been reported as the source of the microorganisms which can give rise to a brain abscess.
What are they?
A brain abscess is a rare but life-threatening infection in which a localised area of suppuration develops within the brain parenchyma.
The most common sites are the temporal lobes (42%), followed by the cerebellum (30%).
They may occur following:
- cranial trauma
- cranial surgery
- 2nd to a septic focus elsewhere, spread either by direct extension / haematological route.
Brain abscesses occur more frequently in men than in women. Odontogenic brain abscesses in children are virtually unheard of.
In view of the relative rarity of brain abscess, there may be delays in making the diagnosis, so this condition remains a significant challenge for clinicians.
Dental procedures alleged to have caused a brain abscess are very wide ranging. These include:
- Dental extraction
- operative dentistry
- periodontal therapy
- dental local anaesthetic injection
- dental prophylaxis
The range of procedures that can seemingly elicit brain abscesses suggest that the mechanism responsible to produce the bacteræmia that causes the brain abscess is not as critical as the host response.
Within 1 minute of a dental procedure, micro-organisms from the mouth may have reached the heart, lungs and peripheral capillary system. In most individuals, the reticulo-endothelial system eliminates these microbes in a matter of minutes.
This is not the case in immune-compromised populations, for example, organ transplant patients and those with AIDS where there has been a reported increased incidence of brain abscess.
Although certain underlying brain pathologies such as a previous stroke or underlying cancer may serve as a focus for abscess formation, in most cases there is no apparent predisposing brain lesion.
Brain abscess linked to a dental source is a rare occurrence, as in most individuals, the blood-brain barrier along with the immune response will stop the entry of microorganisms into the brain. Direct spread tends to cause solitary abscesses whereas as hæmatogenous spread usually results in multiple abscesses. Anærobic species are responsible for the majority of the cases of odontogenic brain abscesses (78%).
Often the diagnosis has been one of exclusion as opposed to evidence.
One of the major criticisms linking possible odontogenic (dental) infections with brain abscess is identification of the causal organisms in both sites. Since brain abscesses often occur spontaneously, the source of infection is searched for retrospectively. Dental sources of infections, especially periodontal diseases are commonly found in the adult population. Thus, the link may be causal or hypothetical.
Mortality ranges from 0 – 24% for odontogenic brain abscesses.