Brain Abscess Following Definitive Radiotherapy in Patients With External Auditory Canal Carcinoma: Report of Two Cases

While osteoradionecrosis of the temporal bone is a late complication of radiotherapy (RT) for external auditory canal carcinoma (EACC), brain abscesses are rare. We present two cases of EACC treated with definitive RT, both of whom subsequently developed brain abscesses. The first patient, a 65-year-old woman with right EACC invading the sigmoid sinus and dura mater, developed a cerebellar abscess eight years post-RT (60 Gy/30 Fr). This abscess, attributed to infection related to temporal bone osteoradionecrosis, was successfully managed with drainage and antibiotics. The second patient, a 45-year-old man with right EACC and suspected dura mater invasion developed a right temporal lobe abscess two months post-RT (70 Gy/35 Fr). Owing to its persistence despite drainage and antibiotics, the abscess was resected, and the skull base was reinforced with a temporalis muscle flap. Neither patient experienced local recurrence. We hypothesize that the brain abscesses resulted from the vulnerability of the dura mater and skull base. Brain abscesses should be considered a potential adverse outcome following definitive RT for EACC, particularly when tumor invasion of the dura mater or skull base is suspected.