INTRAOPERATIVE MICROENDOSCOPY WAS performed for eight patients to acce
ss the fundus of the internal auditory canal after retrosigmoid transm
eatal surgery of vestibular schwannomas. The transmeatal procedure is
usually limited laterally by the labyrinth block. The restricted openi
ng of the internal auditory canal bears a potential risk of incomplete
tumor resection. For eight patients with vestibular schwannomas, intr
aoperative microendoscopy was performed after tumor resection to expos
e the ''blind'' area of the internal auditory canal fundus. An excelle
nt view of the fundus contents was obtained, including Cranial Nerves
VII and VIII and the crista transversa. Tumor remnants were not observ
ed in this series. Microendoscopy was shown to be an ideal adjunct to
hearing-preserving transmeatal surgery of vestibular schwannomas, enab
ling the removal of intracanalicular tumors with direct control of the
lateral intracanalicular nerve portions.