Fluorescence-assisted visualization of facial nerve during mastoidectomy: A novel technique for preventing iatrogenic facial paralysis.

Abstract

Mastoidectomy can be risky due to the chance of iatrogenic facial nerve dysfunction. Avoiding injuries to the mastoid segment of the facial nerve is mandatory when drilling the bone. With advancements in intraoperative near-infrared indocyanine green (ICG) video angiography, we describe the application of a novel fluorescent guidance technique during mastoidectomies to identify the facial canal with safety. Mastoidectomies were performed as the key step in the presigmoid, petrosal or translabyrinthine approaches in 16 patients with different pathologies located at the cerebellopontine angle or petroclival region. After the facial canal was drilled to paper thin, ICG was injected via the central venous catheter. Compared with the dark bony portion, the vessels inside the vasa nervorum were highlighted as a result. The fluorescence guides the operator through the course of the facial nerve and facilitates opening of the internal auditory canal and the dissection of tumors. All 16 facial nerves were recognized during mastoidectomies under fluorescence guidance for varied periods of enhancing time (range, 23-50s). In all, one to four attempts after repeated drilling works to enhance the facial nerve were required before these nerves could be clearly seen. The tumor resection procedure yielded the following results: grossly total removal in seven patients, near total removal in five, and subtotal removal in three. Complete obliteration of a giant vertebral artery aneurysm in one patient was seen in the follow-up angiogram. The post-mastoidectomy facial nerve function, examined by triggered EMG, was preserved in all 16 patients, and no patients had postoperative facial palsy worse than House-Brackmann grade IV after 6 months of follow-up. With this novel technique, the course of the facial nerve can be confirmed during mastoidectomy, which reduces the possibility of iatrogenic facial nerve dysfunction. This fluorescence technique is especially helpful in establishing confidence and shortening the learning curve for beginners at mastoidectomies.