Final answer:
The spinal accessory nerve (Cranial Nerve XI) is a motor nerve responsible for shoulder and head movements. The nerve strength is tested by shoulder shrugging and head rotation against resistance. Ensuring safety is important, and the nerve's function can be remembered using mnemonics, specifically the words 'Marry' or 'Money'.
Step-by-step explanation:
Cranial Nerve XI: Name, Function, Tests
The Cranial Nerve XI is known as the spinal accessory nerve and it is primarily a motor nerve. Its main function is to innervate the sternocleidomastoid and trapezius muscles, which are responsible for movements such as head rotation, neck flexion, and shoulder elevation. A common test for spinal accessory nerve function is to evaluate the strength of these muscles by asking the patient to shrug their shoulders or turn their head against resistance. Positive results for this test would show normal muscle strength and symmetry in movement. As with any clinical examination, safety is paramount; tests should be performed gently to avoid any strain or injury.
Another important aspect to know about Cranial Nerve XI is its mode of innervation (MOI), which involves exiting the skull through the jugular foramen and innervating its target muscles. Understanding the basic functions of the cranial nerves can be aided by mnemonics, such as "Some Say Marry Money But My Brother Says Brains Beauty Matter More", reflecting the sensory, motor, or both functions of each nerve. The spinal accessory, being strictly motor, corresponds with the "Marry" or "Money" part of the mnemonic, depending on its position within the sequence of cranial nerves.