L4 ENT Emergencies

Question 1

What is the 7th cranial nerve

Answer 1

the facial nerve

Question 2

What function does the facial nerve have?

Answer 2

derived from the second pharyngeal arch
has motor function - muscles of facial expression, posterior belly of the digastric, styohyoid and stapedius mucles
& sensory - a small area around the concha of the external ear and special sensory taste sensation to the anterior 2/3 of the tongue via the chorda tympani

parasympathetic - supplies many of the glands of the head and neck including submandibular & sublingual salivary glands. nasal, palatine and pharyngeal mucous glands. Lacrimal glands.

Question 3

What is the course of the facial nerve?

Answer 3

Intracranial

1. originates in the pons
2. two roots travel through internal acoustic meatus and enter into the facial canal
3. exits the facial canal via the stylomastoid foramen posterior to the styloid process of the temporal bone

Extracranial
1. runs anteriorly to the outer ear
2. 3 branches off; the posterior auricular nerve, nerve to digastric muscle and nerve to stylohyoid muscle
3. main trunk continues anteriorly and inferiorly to the parotid gland where it terminates and splits into 5 branches; temporal, zygomatic, buccal, marginal mandibular, cervical

Question 4

What 3 things happen in the facial canal

Answer 4

“the two roots fuse to form the facial nerve
the nerve forms the geniculate ganglion
gives rise to:
i. greater petrosal nerve
ii. nerve to stapedius (passes through the pyramidal eminence to supply the stapedius muscle in the middle ear)
iii. chorda tympani “

Question 5

What are the 5 branches of the facial nerve?

Answer 5

1. temporal branch
2. zygomatic branch
3. buccal branch
4. marginal mandibular branch
5. Cervical branch

Question 6

What is the main function of the facial nerve?

Answer 6

Innervate the main muscles of facial expression

Question 7

Facial nerve soundbite

Answer 7

“arises in the pons
terminates at the parotid gland and splits into 5 branches (temporal, zygomatic, buccal, marginal mandibular, cervical) which are responsible for the muscles of facial expression
“

Question 8

What’s cranial nerve V?

Answer 8

The trigeminal nerve

Question 9

What is the main function of the trigeminal nerve?

Answer 9

both sensory and motor innervation to the face.

Question 10

What is the sensory function of the trigeminal nerve?

Answer 10

The three terminal branches of CN V innervate the skin, mucous membranes and sinuses of the face. Their distribution pattern is similar to the dermatome supply of spinal nerves (except there is little overlap in the supply of the divisions).

Question 11

Does the trigeminal nerve have motor function?

Answer 11

Only the mandibular branch of CN V has motor fibres. It innervates the muscles of mastication: medial pterygoid, lateral pterygoid, masseter and temporalis. The mandibular nerve also supplies other 1st pharyngeal arch derivatives: anterior belly of digastric, mylohyoid, tensor veli palatini and tensor tympani.

Question 12

Where does cranial root V begin and end?

Answer 12

begins from roots extending from the midbrain to the medulla.

In the middle cranial fossa, the sensory root expands into the trigeminal ganglion. A ganglion (pl. ganglia) refers to a collection of the neurone cell bodies outside the central nervous system. The trigeminal ganglion is located lateral to the cavernous sinus, in a depression of the temporal bone. This depression is known as the trigeminal cave.

The peripheral aspect of the trigeminal ganglion gives rise to 3 divisions: ophthalmic (V1), maxillary (V2) and mandibular (V3).

The motor root passes inferiorly to the sensory root, along the floor of the trigeminal cave. Its fibres are only distributed to the mandibular division.

The ophthalmic nerve and maxillary nerve travel lateral to the cavernous sinus exiting the cranium via the superior orbital fissure and foramen rotundum respectively. The mandibular nerve exits via the foramen ovale entering the infra-temporal fossa.

Question 13

What are the 3 branches of the trigeminal nerve?

Answer 13

1. ophthalmic
2. maxillary
3. mandibular

Question 14

Opthalmic nerve

Answer 14

“3 branches; frontal, lacrimal and nasochiliary
innervate the skin and mucous membrane of derivatives of the frontonasal prominence derivatives:
Forehead and scalp
Frontal and ethmoidal sinus
Upper eyelid and its conjunctiva
Cornea (see clinical relevance)
Dorsum of the nose”

Question 15

Maxillary nerve

Answer 15

“The maxillary nerve arises from the trigeminal ganglion, travels along the lateral wall of the cavernous sinus and then exits the cranium via the foramen rotundum (sphenoid bone).

Maxillary nerve gives rise to 14 terminal branches, which innervate the skin, mucous membranes and sinuses of derivatives of the maxillary prominence of the 1st pharyngeal arch:

Lower eyelid and its conjunctiva
Cheeks and maxillary sinus
Nasal cavity and lateral nose
Upper lip
Upper molar, incisor and canine teeth and the associated gingiva
Superior palate
Parasympathetic Supply:

Lacrimal gland: Post ganglionic fibres from the pterygopalatine ganglion (derived from the facial nerve), travel with the zygomatic branch of V2 and then join the lacrimal branch of V1. The fibres supply parasympathetic innervation to the lacrimal gland.
Nasal glands: Parasympathetic fibres are also carried to the mucous glands of the nasal mucosa. Post-ganglionic fibres travel with the nasopalatine and greater palatine nerves (branches of V2)”

Question 16

Mandibular nerve

Answer 16

“Mandibular nerve gives rise to four terminal branches in the infra-temporal fossa: buccal nerve, inferior alveolar nerve, auriculotemporal nerve and lingual nerve.

These branches innervate the skin, mucous membrane and striated muscle derivatives of the mandibular prominence of the 1st pharyngeal arch.

Sensory supply:

Mucous membranes and floor of the oral cavity
External ear
Lower lip
Chin
Anterior 2/3 of the tongue (only general sensation; special taste sensation supplied by the chorda tympani, a branch of the facial nerve)
Lower molar, incisor and canine teeth and the associated gingiva

Motor Supply:

Muscles of mastication; medial pterygoid, lateral pterygoid, masseter, temporalis
Anterior belly of the digastric muscle and the mylohyoid muscle (these are suprahyoid muscles)
Tensor veli palatini
Tensor tympani

Parasympathetic Supply:

Submandibular and Sublingual glands: Post-ganglionic fibres from the submandibular ganglion (derived from the facial nerve), travel with the lingual nerve to innervate these glands.
Parotid gland: Post-ganglionic fibres from the otic ganglion (derived from the glossopharyngeal nerve, CN IX), travel with the auriculotemporal branch of the V3 to innervate the parotid gland.”

Question 17

Anatomy of the head and neck

Answer 17

Question 18

What are the 3 types of stridor?

Answer 18

Inspiratory
Expiratory
Biphasic

Question 19

Where does an inspiratory stridor suggest a blockage?

Answer 19

Supraglottis (above vocal cords)

Question 20

Where does a biphasic stridor suggest there is a blockage?

Answer 20

suggests something on the glottis