Brain abscesses tend to occur in men younger than 60 years of age (they are uncommon in children), and the main areas affected are the temporal lobe (42%) and cerebellum (30%) [1, 2]. The 40% of brain abscesses are caused by chronic otitis media or mastoiditis, 10% by maxillary sinusitis or paranasal sinusitis, and 50% through the spread of cardiac or pulmonary infections. In rare cases, brain abscesses can occur after dental treatment or cranial trauma. Therefore, brain abscesses are associated with metastatic foci of infections such as cardiac or pulmonary infections, which need to be evaluated and treated in the early stage of disease course, as well as contiguous foci of infection such as otitis, mastoiditis, and sinusitis for avoiding severe complications [2,3,4]. Metastatic infections mediated by microbes from other parts of the body are transferred through the circulatory system or anatomical fascia. Microorganisms are not limited to the periodontal area. Microorganisms gain access to the blood or circulatory system, and the bacteria can migrate to adjacent tissues or other distant organs to cause infection. When bacteria arrive in the brain, localized encephalitis is established, and white blood cells and inflammatory exudate accumulate, causing infective thrombosis . When conventional antibiotic regimens do not control the infection, as in the present case, diagnosis and examination of persistent bacterial inflow sources are necessary. Antibiotic coverage or removal of infection is not effective in controlling inflammation in the parenchyma region. As seen in this case, simultaneous examination and treatment of the distant site can effectively control inflammation in the parenchyma region.
To diagnose a brain abscess, diagnostic imaging, such as a cephalogram, CT, MRI, or angiography, should be used in addition to a clinical examination to distinguish from a brain tumor or hematoma. The use of CT scanning has provided early diagnosis, exact site, characterization, and staging of the abscess . In addition, MRI can be used for the accurate diagnosis of brain abscesses and for detecting the precise location of abscesses because of its ability to distinguish between brain edema and normal brain tissue and its increased sensitivity compared to CTs for detection of early cerebritis. Lesions in the brain may not be localized and may originate from other parts of the body. Therefore, if a remote infection is suspected, imaging multiple parts of the body with chest radiography and a head and neck evaluation may be necessary. Intra-oral infection is a rare cause of brain abscess, and dental radiography is necessary for proper diagnosis. It is difficult to accurately diagnose odontogenic disease by dental radiography alone because of acute inflammatory progression, which is a chronic disease, and inflammation of the soft tissue around the alveolar bone and formation of the abscess. In the case of cerebral abscess, which does not respond to long-term treatment, a thorough oral clinical examination can be performed concurrently with a radiologic examination to determine the exact cause or it would be better to eliminate the potentially causal odontogenic foci for improvement of oral hygiene . However, further studies about the decision criteria for oral and maxillofacial surgeons to eliminate suspected casual teeth will be necessary.
The brain abscess was caused by poly-micro-organism, and it is difficult to identify accurate pathogens. For brain abscess that does not respond to long-term use of antibiotics or surgical treatment, it is necessary to assess the infection focus of other body parts. In brain abscess with a suspected remote infection, it is reasonable to evaluate the head and neck areas close to the brain carefully and chronic infectious diseases such as odontogenic infection can cause such pathology. It has been reported that the Streptococcus anginosus group (SAG) is sensitive to penicillin, ampicillin, cephalosporin, clindamycin, and erythromycin, no matter the exact species of the bacterium. Recently, however, the appearance of antibiotic-resistant bacteria, especially penicillin-resistant bacteria, is common; for this reason, careful selection of antibiotics is required . In this case, the S. anginosus identified in the abscess fluid from the tooth extraction socket had a tolerance to penicillin, and the bacteria were eliminated with ceftriaxone during the first 20 days of hospitalization. Ceftriaxone and metronidazole administered from day 21 and vancomycin administered from day 34 should have repressed the growth of bacteria even further. However, the symptoms worsened, and it appeared to be because the source of the infection was not removed. Table 1 shows the antibiotic administration during the patient’s hospitalization. The primary treatment goal is to control the infection through the use of antibiotics. However, bacteria that have resistance to frequently used antibiotics have been reported, and bacterial pathogens of periodontal disease and systemic spread could not be controlled with conventional antibiotics. In this case, bacterial cultures were performed for the brain abscess to prescribe antibiotics, but there was no response to the antibiotics or surgical treatment. It indicates that the bacterial culture performed in the abscess around the periodontal tissue can be informative, and the efficacy of the antibiotic prescription was observed according to the results of bacterial culture at the time of extraction. Bacterial culture was performed in periodontal tissue at the same time as tooth extraction, and the brain abscess was effectively controlled using antibiotics as a result of bacterial culture. In conclusion, brain abscesses resulting from the odontogenic origin are rare; however, a multidisciplinary approach to diagnosis and treatment is important to consider the odontogenic infection as a potential cause of brain abscesses.