Intraoperative monitoring of the facial nerve

Intraoperative facial nerve monitoring (FNM) was used to assess the anatomical and physiological integrity of the facial nerve during neurotological, otological, and parotid surgeries. Why monitor the facial nerve? There are several reasons to perform FNM. First of all, it alerts the surgeon when something potentially harmful was carried out to the nerve. When the regional anatomy is confusing, it allows positive identification of the nerve. Finally, the integrity of the facial nerve is assessed at the end of the procedure.

Eighty seven patients who underwent intraoperative monitoring of facial nerve between 1991 and 1996 at the King Fahad National Guard Hospital, Riyadh, Kingdom of Saudi Arabia were studied. The device used was the nerve integrity monitor manufactured by Xomed. The device works when a physiologically intact facial nerve is stimulated, the muscles that are innervated by this nerve will contract.

In otologic surgery, FNM signals the unintentional mechanical stimulation of the facial nerve during surgery, it predicts the dehiscence in the bony covering of the nerve and it allows mapping the nerve through soft tissue and bone. Facial nerve injury is the most devastating complication of otologic surgery particularly when anatomy is distorted by previous surgery, granulation tissue or cholesteatoma distorts anatomy, and in rare instances by an anolomous course. However, it is unlikely to be injured when it has been identified. The surgical treatment of recurrent parotid tumor can be challenging. The main aim of surgery is complete removal of tumor and preservation of facial nerve.

Facial nerve monitoring assists early nerve identification and decreases the nerve trauma. However, as an adjunct, it has proved extremely beneficial. In this paper, the facial nerve was monitored intraoperatively in 87 cases with different pathologies. It is certainly helpful in revision mastoid surgery and in removal of recurrent parotid tumor. Intraoperative monitoring of the facial nerve plays an important role in identification and preservation of the facial nerve during otological and parotid surgeries.