Final answer:
Cervical dystonia, also known as spasmodic torticollis, is a painful condition characterized by idiopathic involuntary muscle contractions in the neck leading to abnormal head positions.
Step-by-step explanation:
When a client's head is held in a neutral position, and they exhibit painful limitation of neck movement due to idiopathic global muscle spasm, this condition is termed cervical dystonia or spasmodic torticollis. This neuromuscular disorder is characterized by involuntary muscle contractions in the neck that can cause abnormal positioning, such as tilting or twisting of the head. It can result in sustained muscle contractions or intermittent spasms, affecting daily activities like driving. The accessory nerve controls the movement of the head and neck through the sternocleidomastoid and trapezius muscles, and evaluating these muscles can help diagnose nerve function. Additionally, treating conditions like cervical dystonia may involve the use of botulinum toxin to reduce excessive muscle contraction.