Brain Abscess in the Contralateral Frontal Lobe Associated with Frontal Sinusitis that Spread from Odontogenic Maxillary Sinusitis.

We encountered a case involving a brain abscess in the right frontal lobe of a 12-year-old girl who was diagnosed with a chief complaint of headache and nausea. Left maxillary sinusitis, a dental infection related to dental caries and apical periodontitis, was observed in the left maxillary first molar in addition to left frontal sinusitis also being present. In addition to administering antibacterial agents, extraction of the left maxillary first molar and drainage of the paranasal sinuses and brain abscess were performed. Follow-up over the course of 1 year and 5 months indicated that the patient had progressed without any sequelae; therefore, the prognosis was good. In this case, although bone destruction was observed in the posterior wall of the frontal sinus, which could be a route for bacteria to enter the skull, we considered the possibility of direct invasion from the same site to be low because the brain abscess occurred on the opposite side. We believe that a route for hematogenous invasion from apical periodontitis, in addition to sinusitis, is also possible. Regardless of the route, the outset was an infection in the dental field; therefore, this case reaffirmed the importance of dental cavity treatment in childhood.