10. The Cervical Plexus

Question 1

Where is the cervical plexus located

Answer 1

Network of nerve fibres located:

• in posterior triangle of neck
• within prevertebral layer of cervical fascia
• superficial to scalenus medius and levator scapulae
• deep to SCM

Question 2

Which spinal cord segments form the cervical plexus

Answer 2

Anterior rami C1-C4

Question 3

Which structures do the sensory branches of cervical plexus provide cutaneous innervation to

Answer 3

1. Posterior scalp: lesser occipital n. (C2-3)
2. External ear + mastoid process: greater auricular n. (C2-3)
3. Anterior neck: transverse cervical nn. (C2-C3)
4. Supraclavicular fossa: supraclavicular nn. (C3-4)

Question 4

What is Erb’s point and what is its clinical relevance

Answer 4

• Area of skin (middle of posterior border of SCM) where sensory nerves of cervical plexus emerge.
• Utilised clinically when performing cervical plexus nerve block - provides regional anaesthesia for surgery in neck region, e.g. Thyroidectomy, cervical lymph node excision

Question 5

Which structures do the motor branches of the cervical plexus innervate

Answer 5

1. Infrahyoids (depress hyoid bone for swallowing and speech): several branches from C1-C3 form a loop - ansa cervicalis - giving off 4 motor branches to these muscles
2. trapezius and SCM: accessory n. (C3-4)
3. Diaphragm: phrenic n. (C3-5)

Question 6

Which clinical signs would suggest accessory n palsy?

Answer 6

• wasting of shoulder muscles
• winging of scapula
• weakened shoulder abduction and external rotation