Final answer:
Damage to the facial nerve (cranial nerve VII) results in deficits in facial muscle tone, affecting facial expressions and skin sensations. Directed resistance tests during a cranial nerve examination can diagnose this damage. Repetition of these tests helps confirm the consistency and strength of facial muscle responses.
Step-by-step explanation:
Damage to the facial nerve, also known as cranial nerve VII, can result in deficits in facial muscle tone and control. The facial nerve is responsible for the movement of facial muscles and contributes to the expression of emotions and facial skin sensations. When there is damage to this nerve, it can lead to asymmetry in facial movement, as one side may not move in harmony with the other. Directed tests such as the resistance test mentioned can help to diagnose the integrity of the facial nerve. The examiner may ask a patient to perform an action multiple times to assess consistency and strength of muscle contraction, and to rule out any transient factors that may affect the initial response.