H&N 5: ANS of The Head And Neck

Question 1

Where do the sympathetic fibres of the head and neck arise from?

Answer 1

From T1-T6 so they must ascend to reach head and neck
They synapse with cervical ganglia in the sympathetic chain and post ganglionic fibres continue to the head and neck by hitch hiking onto blood vessels before reaching the target tissues

Question 2

What is Horners syndrome?

Answer 2

Lesion to sympathetic fibres of head and neck

Symptoms are partial ptosis, miosis, +/- anhydrosis

Question 3

Why does Horners syndrome present with its characteristic symptoms?

Answer 3

Partial ptosis due to paralysis of superior tarsal muscle
Miosis due to paralysis of dilator pupillae
Anhydrosis due to loss of innervation of sweat glands of the face

Question 4

What are the ganglia within the sympathetic chain?

Answer 4

Superior, middle and inferior cervical ganglia

Question 5

Which cranial nerves are associated with the parasympathetic nervous system?

Answer 5

CN III (oculomotor)
CN VII (facial)
CN IX (glossopharyngeal)
CN X (vagus)

Question 6

What are the 4 parasympathetic ganglia within the head?

Answer 6

Ciliary
Pterygopalatine
Submandibular
Otic

Question 7

Are pre ganglionic nerves longer in the sympathetic or parasympathetic system?

Answer 7

Parasympathetic

Question 8

What is the rough course of parasympathetic fibres in the head and neck?

Answer 8

Parasympathetic fibres arise from ganglia within the brainstem
Hitch hike onto one of 4 cranial nerves
Fibres synapse onto s peripheral ganglia
And then hitch hike onto branches of the trigeminal nerve to go to the target tissues

Question 9

Fibres from the oculomotor nerve synapse to which ganglia?

Answer 9

Ciliary ganglia

Question 10

Where is the ciliary ganglia located?

Answer 10

Within the bony orbit

Question 11

Where do post ganglionic fibres from the ciliary ganglion go to?

Answer 11

Through the SOF to the ciliary body (accommodate for near vision) and sphincter pupillae (contracts the eye)

Question 12

Pre ganglionic fibres associated with the facial nerve synapse to which ganglia?

Answer 12

Pterygopalatine ganglia
(Pre ganglionic fibres travel with greater petrosal nerve)

And submandibular ganglia
(Pre ganglionic fibres are carried with the chorda tympani)

Question 13

Where do post ganglionic fibres from the pterygopalatine ganglia go to?

Answer 13

Hitch hike onto branches of the maxillary nerve (CN V2) to innervate lacrimal, nasal and oral mucosal glands

Question 14

Where do post ganglionic fibres from the submandibular ganglia go to?

Answer 14

Hitch hike onto CN V branches to innervate the submandibular and sublingual glands

Question 15

The Otic ganglion is supplied by pre ganglionic fibres associated with which cranial nerve?

Answer 15

Glossopharyngeal

Pre ganglionic fibres travel with the lesser petrosal nerve, a branch of the glossopharyngeal nerve

Question 16

Where do post ganglionic fibres from the Otic ganglia go to?

Answer 16

Hitch hike with a branch of the mandibular nerve to innervate the parotid gland

Question 17

What does the vagus nerve innervate?

Answer 17

Glands in the larynx, oesophagus, trachea, thorax and abdomen
Pre ganglionic fibres meet at ganglia at, or close to, the target tissue

Question 18

What are some differences between a Horners syndrome and oculomotor nerve lesion?

Answer 18

• oculomotor nerve innervates larger portion of levator palpebrae superioris so ptosis is usually complete, not partial like in Horners
• in Horners miosis is a constricted pupil due to unopposed parasympathetic innervation to the sphincter pupillae, whereas in oculomotor nerve lesion the pupil is dilated due to unapproved action of sympathetic nervous system on dilator pupillae of iris
• CN III innervates most of extra ocular muscles, only lateral rectus and superior oblique are spared, hence eye will be in a down and out position (Horners syndrome would not affect any extra ocular muscles)

Question 19

What determines whether ptosis is partial or complete?

Answer 19

The greater portion of muscles that keep the eyelid open are the somatic muscles fibres of the levator palpebrae superioris, innervated by oculomotor nerve
The lesser portion of muscles that keep the eyelid open are smooth muscle fibres of superior tarsal muscle, controlled by sympathetic fibres from the superior cervical ganglion

Damage to sympathetic fibres causes partial ptosis as they contribute a lesser portion of the muscle fibres
Damage to CN III will lead to more ptosis as it innervates more muscle (and also innervates extra ocular muscles hence down and out eye)

Question 20

What functions of the facial nerve will be impaired if the lesion is just after the geniculate ganglion, but before any further branching?

Answer 20

Greater petrosal nerve has already branched so it’s effector tissues are spared
All other functions of CN VIII could be affected (muscle of facial expression, nerve to stapedius, taste to anterior tongue and parasympathetic to salivary glands)

Question 21

Which nucleus do parasympathetic oculomotor nerve fibres run from?

Answer 21

Edinger westphal nucleus