Final answer:
Opisthotonos is a late clinical sign associated with malignant hyperthermia. It refers to the rigid body posture with the backward arching of the neck and spine caused by uncontrolled muscular spasms.
Step-by-step explanation:
A late clinical sign associated with malignant hyperthermia is opisthotonos, which is the characteristic symptom of tetanus. Opisthotonos refers to the rigid body posture with the backward arching of the neck and spine. This is caused by uncontrolled muscular spasms.