Certified Emergency Nurse (CEN) Practice Test

Opisthotonos is a spasm of the back muscles that causes the trunk to arch backward, leading to a hyperextended position. This can occur as a protective mechanism in response to certain neurological conditions, such as meningitis or seizures, where muscle contraction forces the body into an exaggerated posture. In this state, the head and heels may touch the ground while the spine is elongated and arched, illustrating the characteristic hyperextension.

In contrast, akathisia involves a subjective feeling of inner restlessness and an overwhelming need to be in constant motion, rather than a specific posture. Neuroleptic malignant syndrome (NMS) encompasses a severe reaction to antipsychotic medications, presenting with muscle rigidity, fever, and autonomic instability, but not necessarily the hyperextended posture seen in opisthotonos. Torticollis, on the other hand, is characterized by an abnormal, asymmetrical head or neck position without the pronounced hyperextension seen in opisthotonos.