Fig. 7

a–c CT image acquired at the first visit. Medical history of craniotomy, extensive pneumocephalus, defects in the posterior wall and floor of the frontal sinus, and channel formation between the brain and paranasal sinus. The patient refused surgery at this time and was discharged. d and e CT scan acquired during the second visit. Intracranial abscess formation and pneumocephalus can be observed. f The osteotomized anterior wall of the frontal sinus is elevated, and the eroded posterior wall can be observed. Meticulous debridement of the mucosal membrane was performed. The formed channel was identified through the eroded posterior wall. g and h CT scan image acquired during the third visit (four postoperative weeks) shows increased pneumocephalus. i Craniotomy and dural repair were performed. CT, computed tomography