## 4 Discussion
### Differential Diagnosis and Outcome  
In addition to a clinical examination, diagnostic imaging should be used to diagnose BAs. The diagnosis of BAs is sustained by contrast-enhanced MRI, where the abscesses appear as typical ring-like structures surrounded by edema. Differential diagnosis between BA and tumor is of extreme importance, infection being differentiated from neoplastic disease by virtue of hyperintense signals in diffusion-weighted MRI scans [35]. Management of multiple BAs typically involves surgical drainage of at least one of the BAs and simultaneous eradication of the primary odontogenic source of sepsis in association with intravenous administration of high doses of antibiotic agents [28; 31; 34; 37]. Antibiotics are often changed (100% of cases) during the entire hospitalization for multiple BAs in order to find the most appropriate treatment. When antimicrobial sensitivity patterns are determined, treatment is then tailored based on the result. In patients with multiple small BAs who are neurologically intact, the disease is managed medically, with close serial monitoring performed using neuroimaging to determine the response to antibiotic therapy [33]. Otherwise, patients with neurological deficits may require urgent evacuation of the lesion [36; 69]. For single BA, the proportion of patients with good outcomes enabling return to prior occupation rose over time, from 12% in 1970-1989 to 24% in 1990-2012 [48]. Patients with multiple BAs experienced a good recovery (81.3%) with a morbidity rate of 12.5%. There is no definite rule for the treatment of BA. Antibiotics are considered to be the first line of treatment and should be started immediately. It has been reported that the Streptococcus anginosus group is sensitive to penicillin, ampicillin, cephalospororin, clindamycin and erythromycinycin, and that Aaggregatibacter actinomycetemcomitans [31] is sensitive to strong synergistic effects with metronidazoleople in combination with amoxicillin [70]. Medical treatment alone is not recommended for pyogenic BAs greater than 2.5-3 cm in diameter and for refractory smaller BAs [6; 58]. Surgical options include open craniotomy with complete excision and stereotactic aspiration. Open surgery is indicated for large and multiple lesions, cerebellar lesions which obstruct CSF flow and fungal abscesses, and contraindicated in deep-seated lesions [6]. Aspiration is associated with reduced morbidity; however, up to 70% of patients require a repeated procedure due to factors such as incomplete aspiration and inadequate antibiotic coverage [6; 58]. When multiple abscesses are present, a successful strategy dictates aspiration of lesions >2.5 cm and treating other lesions conservatively for 6-8 weeks [6]. Oral pathogens are necessary, but not sufficient for odontogenic BAs. The role of microbiota is strictly connected with the immune system that appears to be the crucial determinant of disease susceptibility and severity [46; 58]. Cardiovascular disease, chronic obstructive respiratory disease, rheumatic disease, diabetes, chronic inflammatory bowel diseases, cancer and organ transplants are factors that affect patients rendering medically immunocompromised and the oral microbiota [46; 71; 72; 73; 74; 75; 76]. BA can result in permanent neurological sequelae such as epilepsy, cranial nerve palsies, intellectual and behavioral disorders, motor deficits, hydrocephalus and death. Early diagnosis and intervention can lead to reduced mortality rates and improved outcomes [6,77]. Poor prognosis is reported in immunocompromised patients, children younger than 1 year of age, in delayed diagnosis, in the case of coma or severe mental status change at the time of diagnosis and when BAs rupture into ventricles [6,78, 79, 80, 81, 82]. Prevention of abscesses by routine dental and oral hygiene care or early removal of abscessed or non-treatable teeth is prudent and appears to be more important in the immunocompromised patient. Our review has several limitations.