What is the most likely reason for early changes to CMAPs during exposure of CN VII?

The most likely reason for early changes to compound muscle action potentials (CMAPs) during exposure of cranial nerve VII (CN VII) is related to heating from the electrical cautery device. During surgical procedures, electrical cautery is frequently used for hemostasis and tissue dissection. This device generates heat, which can inadvertently affect nearby neural structures, including the facial nerve. Such heat exposure can lead to temporary impairment of neural function, resulting in observable changes in the amplitude or latency of CMAPs.

When the electrical cautery is used near neural tissues, it can cause localized thermal injury, which is often characterized by an immediate decrease in CMAPs. These changes can include a reduction in signal amplitude, reflecting the compromised conduction through the affected nerve. Detecting these alterations is crucial for neurophysiologists monitoring the status of the cranial nerve during surgery to prevent long-term functional deficits.

While inhalation agents, severe blood loss, or changes in the patient's state of consciousness can also impact neuromuscular function, they typically manifest later in the surgical process or under different circumstances than the immediate effects observed from the application of electrical cautery. Heating from the cautery device provides a direct and immediate cause for the observed changes in CMAP