Cranial Nerves Flashcards by Brian McCalister

Difference between cranial nerves and spinal nerves?

Different location of cell bodies

Cranial nerves from the brain, spinal nerves from the spinal cord

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What are the two atypical CNs and why?

I and II (olfactory and optic)

True brain tracts, not just nerves

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Where are the structures that the cranial nerves supply derived from?

The same branchial arch from which each cranial nerve is derived from (usually)

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From which surface do all but one exit the brain?

From the inferior surface of the brain

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The number of the cranial nerve gives its rostro-caudal position, but there is an exception, which one?

CNXII (hypoglossal) is just infront of CNXI (accessory)

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Name the cranial nerves

I = olfactory
II = optic
III = occulomotor
IV = trochlear
V = trigeminal
VI = abducens
VII = facial
VIII = auditory vestibulocochlear 
IX = glossopharyngeal
X = vagus
XI = accesory
XII = hypoglossal

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What are the three primary segments/vesicles of the brain called? What can they be further divided into?

Prosencephalon

telencephalon (cortex)
diencephalon (hypothalamus)

Mesencephalon

Rhombencephalon

metencephalon (pons)
myelencephalon (medulla)

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Problems with the foramina of the skull?

Make the base weak - fractures
Can compress nerves
Peripheral nerve diseases and metastases can pass to the brain via the foramina

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Which CNs are sensory?

Some Say Marry Money But My Brother Says Big Brains
Matter More
Olfactory, Optic, Auditory vestibulocochlear,

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Which CNs are motor?

Oculomotor, Trochlear, Abducens, Accessory, Hypoglossal

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Which CNs are both?

Trigeminal
Facial
Glossopharyngeal
Vagus

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What does the olfactory nerve do?

Sensory only

Supplied nasal cavity - sense of smell

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What is the path of the olfactory nerve?

Leaves the nasal cavity to ascend intra-cranially via the cribriform plate of the ethmoid bone where they form the olfactory bulb

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How is the first cranial nerve tested?

Get the patient to identify smells

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What could also cause anosmia?

Infection of the upper respiratory tract

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Functions of CNII?

Optic nerve - sensory only

Vision

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How is CNII tested?

Acuity - Snellen chart
Colour - Ishihara plate
Visual fields - wiggle fingers
Visual reflexes - shine a torch in one eye and check both pupils constrict
Fundoscopy on both eyes

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What can cause damage to the optic nerve?

Direct trauma to eye or orbit
Hypothalamic tumour
Aneurysm of internal carotid near hypothalamus
Increased intracranial pressure causing increased CSF pressure
Fracture of optic canal

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General functions of the oculomotor nerve?

Somatic motor and autonomic

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Somatic motor functions of the oculomotor nerve?

All extraocular muscles except for lateral rectus and superior oblique
Levator palpebrae superioris muscle

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Autonomic function of the oculomotor nerve?

Constrictor pupillae of the eye (parasympathetic)

Ciliary muscles

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What is seen in oculomotor nerve palsy and why?

Eye is down and out due to unopposed action of the lateral rectus and superior oblique
Dilated pupil
Ptosis
Pupillary reflex on the side of the region is lost

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How to test the levator palpebrae superioris?

Look up to see if elevation of the eyelid accompanies effort

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What is oculomotor nerve palsy associated with?

Aneurysm of posterior communicating artery

Cavernous sinus thrombosis

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Where does the trochlear nerve emerge from?

Dorsal aspect of the midbrain

Function of the trochlear nerve?

Supplies the superior oblique muscle

Sign of trochlear nerve damage?

Diplopia when looking down and medially | Difficulty walking downstairs

Divisions of the trigeminal nerve?

Maxillary Mandibular Ophthalmic

Function of the ophthalmic division?

Sensation over forehead | Corneal reflex

What is the route for the corneal reflex?

Ophthalmic sensory division Fibres synapse with facial neurones to orbicularis oris Contracts - blink

How do you know if just the facial nerve is effected when testing the corneal reflex?

If touching the cornea of one eye produces a blink in the other eye only, ophthalmic division not affected

What does the mandibular division of the trigeminal nerve innervate?

``` Anterior two thirds of the tongue (general sensation) Skin, lower teeth and cheek Muscles of mastication including -temporalis -masseter -medial and lateral pterygoids -anterior belly of digastric ```

How is the trigeminal nerve tested?

Assess touch and pain in three regions of face on both sides Corneal reflex Clench teeth and feel bulk of masseter and temporalis muscles Open mouth against resistance Jaw jerk

Function of the maxillary branch?

Sensory innervation of skin and mucous membranes of nose, palate and upper dental arcade

Function of the abducens nerve?

Lateral rectus muscle

Sign of damage to the abducens nerve?

Patient unable to look outwards, squint if they do

Why is the abducens nerve liable to damage if there is increased intra-cranial pressure?

Long intra-cranial course

Sensory function of the facial nerve?

Taste of anterior two thirds of tongue | External acoustic meatus and auricle

Motor functions of the facial nerve?

Muscles of facial expression Parasympathetic secretomotor to submandibular and sublingual salivary glands via chorda tympani Parasymp to glands of nasal mucosa and paranasal sinuses, palate and lacrimal gland

What is seen in damage to the facial nerve in the parotid region

Paralysis of facial muscles Eyes remain open Angle of mouth droops Forehead does not wrinkle

What is seen if there is a fracture of the temporal bone and damage to the facial nerve?

Bell’s Palsy | Involvement of cochlear nerve and chorda tympani; dry cornea; loss of taste in anterior 2/3rds tongue

What is seen because of damage from an intracranial haematoma

Forehead wrinkles because of bilateral innervation of frontalis muscle Paralysis of contralateral facial muscles

How to test the facial nerve?

Crease forehead Close eyes and keep them closed against resistance Puff out cheeks and prod Show teeth

Function of the auditory vestibulocochlear nerve?

Sensory Vestibular branch - balance Cochlear branch - hearing

What can cause auditory vestibulocochlear nerve lesions?

Skull fracture Ear infection Tumour of the nerve (acoustic neuroma)

How to test the auditory vestibulocochlear nerve?

``` Rinne test (mastoid and next to ear, latter should be louder normally) Weber's test (centre of forehead) ```

Sensory function of the glossopharyngeal nerve?

Posterior third of the tongue Pharynx, oropharyngeak isthmus, dorsum of palate, auditory tube, mastoid antrum, mastoid air cells Carotid body and sinus

Motor function of the glossopharyngeal nerve?

Stylopharyngeus | Parotid salivary gland (parasympathetic secretomotor fibres)

How to test function of the glossopharyngeal nerve?

Gag reflex

Motor functions of the vagus nerve?

All muscles of the pharynx except stylopharyngeus Muscles of airways, larynx, heart and GI tract All palate muscles except tensor veli palatine

Sensory function of the vagus nerve?

General sensory of lower pharynx and larynx External auditory meatus Taste to epiglottis

A lesion of which nerve can lead to hoarseness? What can cause it?

Recurrently laryngeal branch of the vagus Paralysis of the vocal cord Left recurrent laryngeal nerve is lower than the right. Bronchial/oesophageal carcinoma or enlarged mediastinal lymph nodes

How can mitral stenosis lead to hoarseness?

Causes an enlarged left atrium, pushed up left pulmonary artery, compresses left recurrent laryngeal against the aortic arch

Which nerve can be damaged in a thyroidectomy and how?

Superior laryngeal nerve, branch of the vagus | Lies close to the superior thyroid artery and can be damaged when lighting the blood vessel

How to test the function of the vagus nerve?

Observe the uvula while the patient says 'aah' Check that it does not deviate Would deviate away from the affected side

Function of the accessory nerve?

Cranial component innervates the pharynx, larynx and soft palate Spinal component innervates the trapezius and SCM (C2-4)

What happens if there is damage to the accessory nerve?

Paralysis of SCM and superior fibres of trapezius | Shoulder droop

How to test the accessory nerve?

Ask patient to shrug shoulders against resistance

Function of the hypoglossal nerve?

All extrinsic and intrinsic muscles of the tongue | -except palatoglossus

What can cause a lesion of the hypoglossal nerve?

Neck laceration | Basal skull fracture

Which way does a protruded tongue deviate if there is damage to the hypoglossal nerve?

Towards the affected side

Cranial Nerves Flashcards

(61 cards)