Surgical classification of radical temporal bone resection and transcranial tympanotomy: a retrospective study from the neurosurgical perspective.

Objective To review the authors' surgical experience with radical temporal bone resection (TBR) with an emphasis on the classification of skull base osteotomy and transcranial tympanotomy (TCT) that is required for middle ear transection. Methods We reviewed the records of 25 patients who underwent radical TBR at our facilities between 2011 and 2020. Results The osteotomy line of radical TBR was divided into 3 segments: anterior (A), medial (M), and posterior (P). Each segment was further classified as follows: A1, through the glenoid fossa (1 patient); A2, in front of the glenoid fossa (23 patients); A3, through the greater wing of the sphenoid bone (1 patient); M1, through the middle ear (16 patients); M2, through the inner ear (9 patients); P1, through the mastoid (9 patients); and P2, through the posterior cranial fossa (16 patients). The M segment was significantly associated with operation time and intraoperative blood loss. In all patients with M1 osteotomy, TCT was performed; TCT was classified into superior and far posterior approaches. A superior approach was performed in all 16 patients, whereas the far posterior approach was performed in only 7 patients with both M1 and P2 osteotomy. Conclusions Our newly proposed osteotomy classification of radical TBR is suitable for minute but clinically important adjustment of the osteotomy line. TCT is an indispensable technique for M1 osteotomy; our newly proposed classification expands our understanding of TCT and how to incorporate this technique into radical TBR.