Accesory Nerve Disorders

Question 1

What is it

Answer 1

Dysfunction of the spinal accessory nerve (cranial nerve XI), which controls the sternocleidomastoid (SCM) and trapezius muscles, leading to weakness in head turning and shoulder elevation.

Question 2

Clinical Features

Answer 2

💪 Motor Impairments:

Weakness in turning the head away from the affected side (SCM dysfunction) 🤷‍♂️
Shoulder droop on the affected side (trapezius dysfunction) ⬇️💪
Difficulty shrugging the shoulder against resistance 🏋️
Winged scapula (if severe trapezius weakness) 🦅

🚫 No sensory loss (purely motor nerve)

Question 3

Epidemiology

Answer 3

Rare disorder overall
Most commonly affected by iatrogenic injury (surgical damage)
Can also be caused by trauma or neurological conditions

Question 4

Age Groups Affected

Answer 4

Any age: Trauma, tumors, infections
Middle-aged to older adults: More likely due to stroke or degenerative diseases
Post-surgical patients (neck, shoulder, or lymph node surgeries): High risk of CN XI injury

Question 5

Risk Factors

Answer 5

✅ Modifiable:
• Surgical procedures (especially neck dissections, carotid surgery, lymph node removal)
• Blunt or penetrating neck trauma
• Repetitive strain injuries (athletes, manual laborers)

🚫 Non-Modifiable:
• Stroke (brainstem or upper cervical spinal cord involvement)
• Neuromuscular diseases (ALS, MS, Guillain-Barré syndrome)
• Congenital CN XI abnormalities (rare)

Question 6

Clinical Presentation

Answer 6

🔹 Unilateral CN XI Palsy:
Weakness in turning head to the opposite side
Shoulder droop + difficulty shrugging
Winging of scapula (if trapezius is severely affected)

🔹 Bilateral CN XI Palsy (Rare but Severe):
Severe difficulty holding head upright
Loss of shoulder stability, making arm movement difficult

Question 7

Prognosis

Answer 7

🔹 Depends on the cause:
Surgical/traumatic injury: Partial to full recovery (months) depending on severity
Stroke-related: May improve with rehab but often incomplete recovery
Neuromuscular disease (ALS, MS): Progressive decline
Mild nerve injuries: Can recover with physical therapy

🔹 Prevention:
Avoid unnecessary surgical trauma to CN XI
Early physical therapy for mild injuries
Proper postural support in neuromuscular diseases

Question 8

Test

Answer 8

SCM test - patient rotates their head against practitioner resistance

Trapezius test - patient shrugs shoulder against practitioners resistance

Outcomes - weakness, muscle wasting