Ⅰ. INTRODUCTION
Dental abscesses and facial cellulitis are potentially lifethreatening conditions, similar to sepsis or airway occlusion, however, it is difficult for dentists to recognize the potential risk of odontogenic brain abscess in clinical practice1). Despite the introduction of various antibiotics since the First World War, reports in the literature have claimed that the total mortality rate of patients with brain abscess ranges from 36% to 90%, while the prevalence is estimated to be 1 in 100,000 people in the american population2). However, since the year 2000, advances in radiological imaging technology have vastly improved our diagnostic capabilities, with these technologies including CT and MRI. In addition to these advances, the development and clinical application of effective antibiotics has decreased the mortality rate due to brain abscesses to below 10%3).
The most common sites for brain abscess are the temporal lobe (42%) and the cerebellum (30%)4). A brain abscess may be caused by trauma, surgical operation, direct infection around skull, secondary infection from bacteremia, or a hematologic pathway5). Dental infection has been reported as a source of microorganisms that can occasionally cause brain abscesses6). The causative pathogens of a brain abscess are typically polymicrobial pathogens5). The most common causative pathogens found in clinical practice are Viridans streptococci and anaerobic bacteria7). Moreover, depending on the origin of the infection, additional microorganisms, including Staphlococcus aureus and Enterobacteriaceae, have also been reported5).
The author reports a case of a patient who presented with symptoms of oral infection and decreased consciousness due to a brain abscess caused by a dental infection, afterwards, a recovery of consciousness and an improvement in symptoms were achieved by administering surgical and antiobiotic treatments. In addition, the report discusses the importance of the diagnosis and a multidisciplinary treatment approach for brain abscesses caused by dental infection; in reference to the present case and another similar case from the year 2000 involving an intracranial infection caused by a dental infection.
Ⅱ. CASE REPORT
In October 2017, a 65-year-old man was admitted after complaining of left facial edema, limitation of mouth opening, and decreased consciousness. Three weeks earlier, the patient visited a private dental clinic for left mandibular molar pain and was prescribed antibiotics and analgesics, however, he could not take the medication due to stomach discomfort and inability to eat due to limitation of mouth opening. Clinical examination showed an infection in left masticatory space (Fig. 1). His medical history included controlled type II diabetes. His blood tests test results were 1) HbA1c of 6.5; 2) C-reactive protein (CRP) of 144mg/dl; 3) erythrocyte sedimentation rate (ESR) of 126mm/hr; and 4) white blood cell count (WBC) of 17250/mm3. The vital signs were 1) body temperature of 38.1°C; 2) blood pressure (BP) of 100/60 mmHg; 3) pulse of 88 bpm; and 4) respiration rate of 18 breaths per minute.
Panoramic view showed distal caries in tooth #36 and periapical lesion in the distal root. While in tooth #27 distal caries was also observed, but evidence of maxillary sinusitis was hard to observe (Fig. 2). Because the patient was in a state of decreased consciousness, it was determined that a surgical procedure to treat the facial and brain abscess could be problematic. Accordingly, the treatment began with intravenous injection of empirical antibiotics, using third-generation cephalosporin and metronidazole.
At the same time, the patient was referred to the department of neurology at our hospital to undergo an electroencephalography examination to determine the reason for his decreased consciousness, however, the results were inconclusive. Moreover, echocardiography performed by the department of cardiology at our hospital could find no evidence of endocarditis. Although the patient showed a recovery of consciousness, the facial abscess was uncontrolled despite the administration of antibiotics for 1 week. Contrastenhanced CT scan, MRI results showed a contrast enhancement in the left frontal, temporal, masticatory, periorbital space (Fig. 3-4). Moreover, the cone-beam CT scan results showed no evidence of maxillary sinusitis, however, diffuse osteomyelitis with trabecular destruction in the left mandibular molar region was found (Fig. 5), and therefore, a bone scan was performed.
Subsequently, the patient was transferred to the department of neurosurgery in our hospital to undergo post-craniotomy drainage for the brain abscess, and the department of oral maxillofacial surgery in our hospital was consulted to perform the collaborative facial incision and drainage surgery. The neurosurgeon made 3 bur holes, including a key hole, in the frontal bone and craniotomy was performed after detaching the dural layer from the cranium. The abscess was observed in the subdural space in the left frontal-temporal-parietal lobe and the abscess was completely drained (Fig. 6). The oral and maxillofacial surgeon extracted the left mandibular first molar (#36) and the sequestrum below the tooth was removed for biopsy. Moreover, the periosteum of the coronoid process was elevated for empyema drainage and the fascia was detached from the masseteric space. The biopsy on the sequestrum revealed evidence of acute osteomyelitis, while abscess culture test results showed mixed species of oral-resident bacteria.
Follow-up CT and MRI results showed that the size of the masticatory space abscess had decreased significantly, but because a brain abscess pocket had formed across the left frontal and temporal lobes, a secondary neurosurgery was performed. In the second surgery, the approach was made through the temporal region. When the dural layer was dissected after creating a hole in the cranium, a mixture of blood and empyema was drained (Fig. 7). An abscess culture test was positive for Staphylococcus aureus. Since the patient had no history of endocarditis, he was diagnosed with a brain abscess acquired by transmission from an oral infection. After the second surgery, brain and facial abscesses were relieved (Fig. 8), but patient reported experiencing hearing loss. Subsequent CT scan results showed findings of left otitis media and perforation of the ear drum. However, since the patient and their guardian did not want further surgery, the patient was discharged with no other treatment.
When the patient returned 1 month later for an outpatient visit, progressive bone healing was observed in the left mandibular region in a bone scan performed at our department of oral maxillofacial surgery (Fig. 9). Accordingly, further treatment plans were suspended.
Ⅲ. DISCUSSION
Brain abscess due to odontogenic infection are lifethreatening, but rare8,9). In the 17 cases that have been reported between 1940 and 1999 the mortality rate was 30%10). A total of 11 cases were reported between 1960 and 1989, and 5 cases were reported between 2001 and 2007, however, most of these articles only reported the location of the abscess and treatment modalities9). Moazzam8) reported on 60 individual cases of brain abscess between 2000 and 2015, while also reporting the locations of central nervous system (CNS) infection caused by dental pathogenic microorganisms, and the clinical outcomes. Moazzam8) reported that the mortality rate among patients with a brain abscess was found to be 8.3% (5/60).
Ewald11) reported 6 cases of secondary pyogenic infection in the CNS caused by a dental infection. Moreover, the study also pointed out that the exact etiology of infection in the brain or spinal cord was unknown in 25% of the cases, and referred to this as a “cryptic abscess.” The study also claimed that the history of dental treatment must always be considered for the assessment and treatment of such “cryptic abscess” in patients, while recommending that dentists perform panoramic and CT scan imaging, along with clinical assessments11,12).
According to a report by Yang4), Odontogenic infections are a hematogenous cause of brain abscesses, but are only responsible for fewer than 2% of cases. However, according to a report by Neidert13), sources of infection in the CNS originated proportionally from: oral lesions, 23%; maxillary sinusitis, 14%; cardiac pathogens, 14%; and infections of unknown origin, 43%. We think that development of neuroimaging techniques such as CT and MRI scanning improves the diagnostic ability of oral and maxillofacial infections, which may lead more diagnosis of brain abscess caused by dental infection. Although there have been many reports about brain abscess due to odontogenic infection in foreign, it is very rare in Korea. We think that various reports are necessary in Korea.
A report by Ewald11) proposed diagnostic criteria for brain abscess due to odontogenic infections: First, the cause of bacteremia cannot be identified: second, only typical microorganisms are found in the oral cavity in a microbial analysis; and third, distinct clinical or radiological signs of odontogenic or periodontal disease are present. According to a report by Moazzam8), if the origin of a brain abscess is an oral infection, 4 possible microbial pathways could be proposed: First, infection by systemic bacteremia caused by an oral infection; second, infection by venous drainage through facial, cavernous, and paranasal sinuses; third, transmission by introduction of foreign bodies or nearby structures; or fourth, infection by lymphatic drainage. Moreover, Moazzam8) added the following precautions in regards to brain abscess due to odontogenic infection: first, even if specific dental lesions are not found during the initial patient examination, if the patient had received any dental treatment within 1-4 weeks prior to the initial examination, then the patient may develop an infection in the CNS later on; second, not all bacteria present in a CNS lesion can be identified by standard microbial culture techniques; and third, endocarditis must not be present8).
Intracranial infection typically occurs from explosive proliferation of pathogenic microorganisms within a short time or by infection with highly toxic microorganisms. If symptoms of chronic infection are present in the oral cavity or the entire body, conversion to acute infection could also cause intracranial infection14). Transmission of maxillary sinusitis, paranasal sinusitis, and otitis media are also known to cause intracranial infection through a venous path15). As mentioned in the case report by Park16), right maxillary periapical lesion may cause maxillary sinusitis and destroy the right sphenoid bone, leading to transmission of the infection to the nearby temporal bone. However, infection by systemic bacteremia is more common than transmission by the introduction of infection from nearby structures or foreign bodies, and therefore, it is difficult to accurately predict the location of odontogenic infection8,15). To compare the present case to previous cases, articles published after the year 2000 in Korea and abroad were investigated (Table 1).
For the diagnosis of the odontogenic brain abscess of the patient in the present case, other departments were consulted. Chest radiographs showed multiple calcified lesions caused by bronchitis, and accordingly, a follow-up examination was performed by a pulmonologist. However, there were no specific findings that ruled out hematogenous spread through the lungs and upper respiratory tract. Similarly, a cardiologist was able to rule out hematogenous spread by endocarditis. The cause of bacteremia could not be identified in other parts of the body, but oral bacterial strains were identified through microbial tests, and clear signs of a dental infection were found by radiological examination. Therefore, the diagnosis of brain abscess due to odontogenic infection was made, and because both oral infections and brain abscesses are polymicrobial infections, the patient was treated with intravenous administration of empirical antibiotics under the consultation of a neurosurgeon.
In this patient, the primary infection was diagnosed finally to be originated in the mandibular posterior molar. Because there were no evidence of submandibular abscess which is a common path of mandibular posterior infection, early diagnosis was difficult. However, MRI was taken initially, and radiographs such as facial CT and Brain CT were regularly taken to check in the treatment procedure that inflammatory findings progressed through the coronoid process, the temporal space, into the subdural space. In addition, the left masticatory abscesses were controlled after the extraction of the # 36 tooth, which was considered to be a causative teeth at the first operation. In other words, deciding on the treatment of teeth suspected to be a potential source of infection could be helpful for the healing of patient. Empirical antibiotics of ceftriaxone and metronidazole were used with consultation of physician. Ceftriaxone and metronidazole were high sensitive in the abscess cultures performed in two surgical procedures and were used continuously. In cases involving dental patients who show neurological symptoms, such as decreased consciousness, odontogenic brain abscess should be suspected. It is necessary to treat suspected odontogenic abscess patients by consulting with other departments to determine the clinical condition of the patient and to make a differential diagnosis by radiological imaging.
The limitations in the present case report include the fact that molecular biological tests on the oral infection causing pathogens were not performed. There are many difficulties in identifying oral infection causing pathogens. In conventional clinical practice, it is difficult to culture many different types of oral bacteria under strictly anaerobic conditions. Even if culturing is possible, the pathogens must be transported immediately to the laboratory after sampling, and thus, conventional microbial culture in clinical setting is insufficient in identifying the causative pathogen8). In the present case, bacteria from near the brain abscess area were cultured, but only Staphylococcus aureus was found. Mueller17) used traditional bacterial cell culture techniques in an attempt to identify the association between the brain abscess and periapical microorganisms and claimed that oral sources of infection were underestimated for brain abscesses, in consideration of retrospective analysis showing matching bacteria between the oral infection source and the brain abscess should be carried out. Therefore, it is believed that future studies using DNA analysis on bacterial samples from both the oral infection and the brain abscess are required.
