The facial nerve is very important as damage to it can cause assymetry in the ability to blink, wink, smile and chew food. The facial nerve unfortunateley lies in the middle of the parotid gland and in a formal parotidectomy is found and preserved.
Thankfully the majority of parotid surgery is performed for benign lesions and so the facial nerve is not significantly at risk. Malignant parotid disease is quite different as often the facial nerve function may have already been affected by the disease process and there may be a need to sacrifice part or all of the nerve.
When looking for the nerve typically the surgeon should have experience with parotid surgery as this will allow him to find it with certainty using normal anatomical landmarks he or she is used to. Once the main trunk is found the nerve should not be handled if at all possible as the less it is touched the less of a chance of weakness postoperativeley will develop.
Inevitably some weakness can ensue even with benign disease and even when the facial nerve is deemed completeley intact at the end of the operation. This sometimes relates to minor trauma to the nerve during the operation and often returns in the few months postoperativeley. One does notice clinically the older a patient is the more sensitive the facial nerve is to this transient weakness postoperativeley and this may be related to a deterioration in the blood supply to the nerve with age. If a nerve is sacrificed the surgeon should be planning or know what to do in this eventuality and it may involve grafting the lost portion of nerve or hitching part of other cranial nerves to the damaged facial nerve for some residual stimulation.
Most importantly for a good result both clinically and for the facial nerve, if a patient is to be operated on for a parotidectomy the surgeon should be well practiced in this surgical technique ie a surgeon with an interest in Head and Neck Surgery.