Question

Which of the following would NOT correspond to a right-sided LMN lesion to CN XI?

1) Weakness when turning the head to the left, especially against resistance
2) Right-sided downward and lateral rotation of the scapula
3) Some shoulder drop on the right side
4) Weakness when elevating right arm and shoulder
5) Weakness when performing cervical lateral flexion to the left

Answer 1

Weakness when elevating the right arm and shoulder does not correspond to a typical right-sided LMN lesion of CN XI, as arm elevation above the head is primarily controlled by muscles innervated by the axillary nerve.

Step-by-step explanation:

The student's question is concerned with identifying which symptom would NOT correspond to a right-sided lower motor neuron (LMN) lesion of the eleventh cranial nerve (CN XI), which is also known as the accessory nerve. The CN XI is responsible for innervating the sternocleidomastoid and trapezius muscles, which means that a lesion would typically present with issues in head rotation and shoulder elevation on the side of the injury.

Of the options provided:

1. Weakness when turning the head to the left, especially against resistance
2. Right-sided downward and lateral rotation of the scapula
3. Some shoulder drop on the right side
4. Weakness when elevating right arm and shoulder
5. Weakness when performing cervical lateral flexion to the left

Number 4, 'Weakness when elevating right arm and shoulder,' does NOT correspond to a typical LMN lesion of the right CN XI. This is because elevating the arm above the head primarily involves the shoulder abductor muscles innervated by the axillary nerve (CN XI), not the trapezius.