What is the main concern regarding muscle rigidity associated with NMS?

Muscle rigidity in Neuroleptic Malignant Syndrome (NMS) is a significant concern as it can lead to autonomic instability. Autonomic instability refers to a disruption in the body's autonomic nervous system, which controls involuntary functions such as heart rate, blood pressure, and temperature regulation. The severe muscle rigidity seen in NMS causes a hypermetabolic state and can elevate muscle breakdown, leading to increased levels of creatine phosphokinase (CPK), which can further strain autonomic control.

This can manifest in symptoms such as dramatic fluctuations in blood pressure, heart rate, and respiratory patterns, ultimately endangering the patient's stability. Therefore, addressing and managing muscle rigidity is critical to preventing a cascade of complications arising from autonomic instability during NMS.