Fig. 4

Images from Case 1. A recurrent olfactory neuroblastoma. a Coronal enhanced magnetic resonance imaging (MRI) reveals a recurrent tumor on the frontal base, which was operated upon by an endoscopic endonasal approach from the left nostril. b Enhanced sagittal MRI shows a mass with irregular margins in the left ethmoid sinus extending to the frontal base bone, dura, and sphenoid sinus. c The tumor can be seen extending into the left side of the sphenoid sinus and nasal cavity. d The right lateral side of the sphenoid sinus wall is left intact to support the pedicle of the PNSF. e The PNSF covers the ASB defect through the bony support of the remnant lateral side of the sphenoid sinus wall. f, g Postoperative coronal and sagittal MRI reveals a well enhanced PNSF and coverage of the ASB defect. h, i One year after the operation, the follow-up coronal and sagittal MRI showed well-healing state of the nasal mucosa and no recurrence of the tumor. j An endoscopic view shows a well-harvested PNSF at 2 weeks after the operation. FS: frontal sinus, CP: cribriform plate, SS: sphenoid sinus, PS: planum sphenoidale, PNSF: pedicled nasoseptal flap, ASB: anterior skull base