6.1.2 Sympathetic Innervation of Head and Neck Structures

Question 1

How do sympathetic nerves reach the superior cervical ganglion?

Answer 1

• 1st order neurone descends via brainstem into spinal cord
• Synapses on to cell body of 2nd order neurone (pre-ganglionic)
• Exits at the T1&2 level
• Enters and ascends in sympathetic chain up into neck
• At superior cervical ganglion syanpses on to 3rd order neurone (post-ganglionic)

Question 2

How do sympathetic nerves reach structures of the head & neck?

Answer 2

By hitch-hiking onto blood vessels

Runs on outside of CCA then along its terminal branches (ICA and ECA) to reach target tissues

Sympathetic nerves to eye and orbit run with ICA then into orbit via opthalmic artery & distal branches of Va

(dilator pupillae and smooth muscle of levator palpebrae superiosis)

Nerves to sweat glands run with ECA

Question 3

Where can sympathetic innervation to the head and neck be damaged?

Answer 3

• 1st order neurone- within CNS
• 2nd order neurone- exiting CNS and within sympathetic chain
• 3rd order neurone- running with blood vessels

Question 4

What pathology can interrupt sympathetic innervation to head and neck and involve structures relating to the eye?

Answer 4

CCA or ICA e.g. carotid artery dissection or aneurysm

Apical lung cancer e.g. pancoast’s tumour, may lead to Horner’s Syndrome

Question 5

What is the triad of Horner’s syndrome?

Answer 5

Partial ptosis
Miosis (dilated pupil)
Anhidrosis

may also have enophthalmos (slightly sunken eye)

Question 6

Why does sympathetic interruption only lead to partial ptosis?

Answer 6

Eyelid retraction is controlled by levator palpebrae superioris which consists of two parts

Skeletal muscle -somatic-major
Smooth muscle-autonomic-minor

Therefore only a minority of LPS in sympathetic disruption, majority innervated by CNIII

Question 7

Label the image

Answer 7