What determines the integrity of CN VII during acoustic neuroma surgery?

The integrity of cranial nerve VII (CN VII), also known as the facial nerve, during acoustic neuroma surgery is primarily assessed through proximal compound muscle action potentials (CMAPs). Proximal CMAPs are measured closer to the nerve's entry point in the brainstem, which provides critical information about the nerve's functionality and helps neurosurgeons monitor potential injuries during the surgical procedure.

Monitoring proximal CMAPs allows for real-time feedback regarding nerve integrity, facilitating immediate action if any changes are detected. This is crucial during surgery, as maintaining the functionality of the facial nerve is essential for preventing postoperative complications such as facial paralysis.

While distal CMAPs and visual facial observation can offer some insights into nerve condition and recovery potential, they do not provide the same level of real-time and relevant information about the nerve's integrity during the delicate phases of the surgery. Distance from the electrode can affect the amplitude and latency of the recorded CMAPs but is not an indicator of the nerve's actual functional status. Thus, proximal CMAPs serve as the most reliable measure for assessing the integrity of CN VII during this type of surgery.