Cranial nerves extra Flashcards
What is the course of the facial nerve and what branches does it give off at which point?
Travels through internal acoustic meatus - gives off greater petrosal nerve
Goes through facial canal, whilst travelling through gives off a branch to the stapedius muscle followed by the chorda tympani
Exits the facial canal through the stylomastoid foramen at which point it gives off a posterior auricular branch and divides into 5 motor branches, temporal, zygomatic, buccal, marginal mandibular and cervical
What does the greater petrosal nerve carry?
Parasympathetic fibres to the lacrimal gland via the pterygopalatine ganglion
What does the chorda tympani nerve from the facial nerve carry?
Fibres that carry taste sensation from the anterior 2/3 of the tongue
Unites with the lingual branch of V3 to supply parasympathetic fibres to the sublingual and submandibular salivary glands via the submandibular ganglion
What 5 motor branches does the facial nerve split into after passing out of the stylomastoid foramen?
1) Temporal
2) Zygomatic
3) Buccal
4) Marginal mandibular
5) Cervical
What 2 muscles are supplied by the temporal branch of the facial nerve?
1) Frontalis
2) Orbicularis Oculi
Which muscle is supplied by the zygomatic branch of the facial nerve?
Orbicularis Oculi
Which 2 muscles are supplied by the buccal branch of the facial nerve?
1) Buccinator
2) Zygomaticus
Which 2 muscles are supplied by the marginal mandibular branch of the facial nerve?
1) Orbicularis oris
2) Mentalis muscle
Which muscle is supplied by the cervical branch of the facial nerve?
Platysma
Inability to swallow foods and regurgitation of liquids is likely due to damage to which cranial nerve?
Vagus CN X
and/or glossopharyngeal CN IX
Hoarseness is often due to damage to which cranial nerve and why?
Vagus CN X
Unable to oppose vocal chords due to weakness/paralysis of intrinsic laryngeal muscles which are supplied by the recurrent laryngeal nerve of the vagus
Unilateral tongue atrophy is likely due to damage of which cranial nerve?
Damage of the hypoglossal nerve on one side
Unilateral trapezius atrophy is likely due to damage to which cranial nerve?
Accessory CN XI
If one pupil was smaller than the other but both pupils reacted to light, what is this likely due to damage to?
The sympathetic trunk
Why does the uvula deviate from the midline on phonation in unilateral vagus nerve damage?
Levator veli palantini is supplied by the vagus nerve (with some influence from CN IX) on phonation failure of this muscle on one side to lift the soft palate results in deviation of the uvula away from the damaged side
Which cranial nerves emerge from the cerebellopontine angle?
Facial CN VII
Vestibulocochlear CN VIII
Which cranial nerve emerges from the interpeduncular fossa?
Oculomotor CN III
Which cranial nerve emerges immediately lateral to the medullary pyramids?
Hypoglossal nerve CN XII
Which cranial nerves emerge from immediately lateral to the medullary olives?
Glossopharyngeal CN IX
Vagus CN X
Which cranial nerve emerges from the dorsal surface of the brain stem?
Trochlear CN IV
Which 2 cranial nerves are not true peripheral nerves, why?
The olfactory (CN I) and optic (CN II) They are actually CNS structures the olfactory bulbs and tracts and the optic tracts
Where are the true peripheral olfactory nerves?
Found in the nasal mucosa
Pass through the ciribiform plate of the ethmoid bone to the olfactory bulb where they synapse
The olfactory nerve is most commonly damaged as a result of head injury, how may such damage occur?
Haemorrhage following head injury
Craniofacial trauma as part of a head injury could also lead to damage of the peripheral olfactory nerves
What is anosmia?
Loss of smell
The optic nerve is formed from what embryonically?
Formed from an outgrowth of the embryonic diencephalon
Sensory components of the trigeminal nerve supply what?
The skin, teeth, mucous membranes of the face plus the anterior scalp and dura
What do motor fibres of the trigeminal nerve supply?
Muscles of mastication
A number of muscles involved in swallowing
Tensor tympani which dampens the amplitude of vibration of the tympanic membrane
What is the innervation and function of the tensor tympani muscle?
Dampens the amplitude of the vibration of the tympanic membrane
Innervated by the trigeminal nerve
Where are the cell bodies of most of the trigeminal sensory fibres located?
Located in the trigeminal ganglion (or semilunar ganglion) located at the convergence of the ophthalmic, maxillary and mandibular nerves
Through which foramina do the 3 divisions of the trigeminal nerve exit the cranial cavity?
Ophthalmic - superior orbital fissure
Maxillary - foramen rotundum
Mandibular - foramen ovale
The mandibular division of trigeminal nerve gives off what 4 important branches?
1) Auriculotemporal nerve
2) Inferior alveolar nerve
3) Buccal nerve
4) Lingual nerve
The maxillary division of the trigeminal nerve gives off what 2 important branches?
1) Infraorbital nerve
3) Superior alveolar nerve
Which 2 nerves from the trigeminal nerve hang from the pterygopalatine ganglion?
Greater and lesser palatine nerves
What do the greater and lesser palatine nerves supply?
Greater palatine -> mucosa, glands and gingiva of hard palate, roof of oral cavity
Lesser palatine -> soft palate
Which 2 reflexes are tested when examining the trigeminal nerve and which other cranial nerves are involve in these?
Jaw jerk
Afferent and Efferent limb = trigeminal nerve
Corneal reflex
Afferent limb = ophthalmic
Efferent limb = facial nerve to orbicularis oculi
What is neuralgia?
Intense burning or stabbing pain which occurs along a damaged nerve
What is trigeminal neuralgia?
Episodes of sharp stabbing pain in the cheek, lips, gums or chin on one side of the face
What kind of fibres does the facial nerve carry?
Sensory, motor and autonomic (parasympathetic)
What kind of fibres does the trigeminal nerve carry?
Sensory, motor and carries autonomic (parasympathetic)
What are the sensory functions of the facial nerve?
Taste from anterior 2/3 of tongue
Floor of mouth and palate
Cutaneous sensation from external ear
Where are the cell bodies of the sensory fibres runnin in the facial nerve located?
In the geniculate ganglion within the facial canal of the petrous temporal bone
What are the parasympathetic functions of the facial nerve?
Innervation of the sublingual and submandibular salivary glands via the submandibular ganglion
PS fibres also to lacrimal gland, nasal and oral mucous membranes via the pterygopalatine ganglion
What is the function of the facial nerve fibres running in the greater petrosal nerve?
Forms the pterygopalatine ganglion
Provides PS fibres to the mucous glands of the oral cavity, nose and pharynx and the lacrimal gland
Motor functions of the facial nerve are tested by asking the patients to do what?
Raise their eyebrows, screw up their eyes, purse their lips and show their teeth
What is Bells palsy?
Paralysis or severe weakness of muscles on one side of the face due to damage to the facial nerve
What is hyperacusis?
Over sensitivity to certain frequencies and volume ranges of sound
Why may damage to the facial nerve lead to hyperacusis?
Because the facial nerve gives off a branch to the stapedius muscle found in the middle ear which prevents excessive movement of the stapes bone, helping to control the amplitude of sound waves from the external environment
How can the vestibular part of the vestibulocochlear nerve be tested?
Weber test - place tuning fork in the center of the forehead and ask if its louder in either ear - it should be the same volume in each
How can the cochlear part of the vestibulocochlear nerve be tested?
Rinne test - place tuning fork on mastoid process and the next to the ear and ask which is louder, it should be louder next to the ear
What is an acoustic neuroma?
A tumour affecting the vestibulocochlear nerve
Dysphagia is caused by damage to which cranial nerves?
Vagus and/or glossopharyngeal
What is dysphagia?
Difficulty swallowing
What is dysphonia?
Difficulty in voice production normally characterised by hoarseness usually
What is dysarthria?
Imperfect articulation due to poor control of muscles
Which nerves are involved in the gag reflex?
Afferent limb = Glossopharyngeal CN IX
Efferent limb = Vagus CN X
Patient gags when posterior pharynx is brushed
Is the glossopharyngeal nerve mostly sensory or motor?
Mostly sensory
What sensory information is carried in the glossopharyngeal nerve?
Posterior 1/3 of tongue and oropharynx
Chemoreceptors in the carotid body and baroceptors in the carotid body
Cutaneous sensation from the ear
The glossopharyngeal nerve also has a parasympathetic component, what does this supply?
PS fibres to the parotid gland via the otic ganglion
The vagus nerve provides PS innervation to what?
Thoracic and abdominal viscera
Aswell as PS fibres, the vagus nerve carries motor fibres to what?
Striated muscle
The vagus nerve is joined by what?
The cranial root of the accessory nerve
The vagus nerve is joined by the cranial root of the accessory nerve, what do they supply together?
Together they supply the striated muscles of the palate, pharynx and larynx
The functioning of the vagus and cranial accessory nerves can be tested by asking the patient to say aah and observing the movements of the soft palate, what normally happens?
The uvula should move anteriorly but should lie centrally and not deviate on movement
Do the spinal and cranial roots of the accessory nerve have the same function?
No they have completely different functions
What is the origin of the spinal part of the accessory nerve?
Rootlets from the upper segments of the cervical cord
How does the spinal part of the accessory nerve enter the cranial cavity?
Through the foramen magnum
What happens once the spinal part of the accessory nerve runs into the cranial cavity?
Once the spinal accessory nerve has entered the cranial cavity through the foramen magnum it briefly joins the cranial accessory nerve to travel through the jugular foramen, then seperates off and runs to supply the sternocleidomastoid and trapezius muscle
How would you test the functioning of the spinal root of the accessory nerve?
As patient to turn head and shrug against resistance
Does the spinal accessory nerve have a sensory component?
No
Where is the spinal accessory nerve particularly at risk of damage?
Posterior cervical neck - the spinal accessory nerve has a superficial course here
Does the hypoglossal nerve have any sensory function?
No, the hypoglossal nerve is purely motor function
What does the hypoglossal nerve supply?
Purely motor to the intrinsic and extrinsic muscles of the tongue
What 3 processes are normal tongue movements necessary for?
1) Articulation
2) Chewing
3) Initiation of swallowing
How would you assess the functioning of the hypoglossal nerve?
Ask patient to protrude tongue and check it doesnt deviate to either side
Other than deviation, what changes may you observe in the tongue in a patient with unilateral hypoglossal nerve damage?
Damage to the tongue from teeth due to poor coordination when chewing
What happens to PS and S fibres in the 4 autonomic ganglia of the head?
Pre and post synaptic parasympathetic fibres synapse here, sympathetic fibres are present, but pass through without synapsing
