A 77-year-old woman was admitted to our hospital because of low-grade fever and lightheadedness 7 days after the removal of a carious broken tooth. Neurological examination revealed disturbed consciousness and meningeal sign with mild ophthalmoplegia. Cerebrospinal fluid examination showed elevated levels of polymorphonuclear cells and enhanced magnetic resonance imaging revealed a left masticator space abscess. On the basis of these findings, the diagnosis was meningitis complicated by a masticator space abscess. Although her symptoms were ameliorated after the administration of antibiotics, her consciousness deteriorated accompanied by bilateral total ophthalmoplegia. Enhanced head computed tomography revealed a filling defect of the superior orbital veins with enhancement of the cavernous sinus, suggesting cavernous sinus thrombosis. After the addition of anticoagulants to antibiotic therapy and surgical drainage of the abscess, she recovered without residual neurological impairment. Because cavernous sinus thrombosis is potentially life-threatening, early diagnosis and initiation of appropriate therapy are extremely important.