Advanced Accessory Nerve Quiz

Q1. A right accessory nerve lesion distal to the sternocleidomastoid branch would most strongly produce which deficit?

• Right sternocleidomastoid paralysis with normal trapezius
• Bilateral facial paralysis
• Right tongue paralysis
• Right trapezius weakness with relatively preserved sternocleidomastoid function

Q2. Why does a right sternocleidomastoid weakness impair rotation of the head to the left?

• CN XI crosses completely to innervate the opposite sternocleidomastoid
• The right trapezius is the only muscle that rotates the head left
• The left sternocleidomastoid rotates the face left
• The right sternocleidomastoid normally rotates the face contralaterally

Q3. Why can trapezius paralysis impair abduction of the upper limb above the horizontal plane?

• Trapezius directly flexes the elbow
• Trapezius contributes to upward rotation of the scapula required for full arm elevation
• Trapezius is the primary rotator cuff muscle
• CN XI innervates the deltoid

Q4. Which clinical setting is classically associated with iatrogenic spinal accessory nerve injury?

• Carpal tunnel release
• Surgery or lymph node biopsy in the posterior triangle
• Cataract extraction
• Appendectomy

Q5. Which examination pattern suggests a proximal right CN XI lesion affecting both major muscular targets?

• Weak right shoulder shrug and weak head rotation to the left
• Right ptosis and pupillary dilation
• Weak left shoulder shrug and weak head rotation to the left
• Weak right jaw closure and tongue protrusion

Q6. Why can a lesion near the jugular foramen produce broader deficits than an isolated distal accessory nerve injury?

• All cervical spinal nerves pass through the jugular foramen
• CN IX, CN X, and CN XI share the jugular foramen
• The facial and trigeminal nerves also exit through the jugular foramen
• CN XI merges permanently with CN IX and CN X

Q7. How does the modern anatomical interpretation treat the traditional cranial root of the accessory nerve?

• It arises from the spinal accessory nucleus and supplies trapezius
• It is a sensory root from the trigeminal ganglion
• It forms the entire spinal accessory nerve
• It is generally regarded as vagal in origin and function rather than part of the spinal accessory nerve proper

Q8. Which sequence correctly traces the spinal accessory nerve from its origin to trapezius?

• Facial nucleus to internal acoustic meatus to stylomastoid foramen to sternocleidomastoid
• Nucleus ambiguus to hypoglossal canal to carotid sheath to tongue to trapezius
• Spinal accessory nucleus to cervical rootlets to foramen magnum to jugular foramen to sternocleidomastoid to posterior triangle to trapezius
• Trigeminal motor nucleus to foramen ovale to posterior triangle to trapezius

Q9. Which finding best distinguishes trapezius weakness from serratus anterior weakness when evaluating scapular dysfunction?

• Serratus anterior weakness causes loss of facial expression
• Shoulder droop and weak shrug favor trapezius dysfunction, while prominent medial winging with wall pushing favors serratus anterior dysfunction
• Both muscles are supplied by CN XI, so the findings are identical
• Trapezius weakness causes isolated loss of elbow flexion

Q10. Which statement best integrates accessory nerve anatomy?

• CN XI is a sensory cranial nerve from the medulla that supplies the face
• CN XI is a motor nerve from the upper cervical cord that enters through the foramen magnum, exits the jugular foramen, and supplies sternocleidomastoid and trapezius
• CN XI exits through the hypoglossal canal and innervates the tongue
• CN XI is a parasympathetic nerve to the parotid gland