Lecture 7&8-Cranial Nerves Flashcards by Vibha Shaji

What is CN I?

Olfactory nerve

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Describe the course of the olfactory nerve

Top of nasal epithelium -> cribriform plate in ethmoid bone -> olfactory bulbs -> olfactory tracts -> forebrain -> olfactory cortex in temporal lobe

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How can smells trigger memories?

Olfactory nerve feeds into limbic system

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What is the function of the olfactory nerve?

Smell

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What is the medical term for loss of sense of smell?

Anosmia

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What is CN II?

Optic nerve

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What is the course of the optic nerve?

Retina -> optic canal -> chiasma -> primary visual cortex in occipital lobe

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What is a swollen optic disc called?

Papilloedema

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True or false: lesion before optic chiasm affects both eyes

FALSE - only affects one eye

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What is bitemporal hemianopia?

Tunnel vision

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What is CN III?

Oculomotor nerve

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What is the course of the oculomotor nerve?

Midbrain -> cavernous sinus -> superior orbital fissure -> orbit

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What are the functions of the oculomotor nerve?

supplies most of extra-ocular muscles
supplies LPS which opens eyelid
autonomic fibres innervate sphincter pupillae (constricts pupil) and ciliary muscle (changes lens thickness)

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Why is autonomic function of the oculomotor nerve affected first in damage?

Parasympathetic fibres are on the outside

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What is CN IV?

Trochlear nerve

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What is the course of the trochlear nerve?

Midbrain -> cavernous sinus -> superior orbital fissure -> orbit

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What is the function of the trochlear nerve?

Supplies superior oblique muscle (moves eyeball down)

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True or false: CN IV has the longest intracranial course of the CNs

TRUE

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What is CN V?

Trigeminal nerve

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What is the course of trigeminal nerve?

Pons -> trigeminal ganglion -> 3 divisions:

1) opthalmic branch -> superior orbital fissure -> sensation to cornea of eye
2) maxillary branch -> foramen rotundum -> cheek
3) mandibular branch -> foramen ovale -> mandible (motor and sensory)

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What are the functions of the trigeminal nerve?

Main sensory nerve of the face

Muscles of mastication

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True or false: the trigeminal nerve is the efferent limb of the corneal reflex

FALSE - afferent limb

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Which branch of the maxillary nerve of the trigeminal nerve provides sensation to the cheek?

Infraorbital nerve

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What are the three branches of the mandibular branch of the trigeminal nerve?

Inferior alveolar nerve
Mental nerve
Lingual nerve

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What is CN VI?

Abducens nerve

What is the course of the abducens nerve?

Bottom of pons -> cavernous sinus -> superior orbital fissure

What is the function of the abducens nerve?

Supplies lateral rectus (moves eyeball laterally)

What is CN VII?

Facial nerve

What is the course of the facial nerve?

Pons -> through petrous part of temporal bone -> internal auditory meatus -> 5 branches

What are the functions of the facial nerve?

- muscles of facial expression - taste to anterior 2/3 of tongue (SS) - autonomic - lacrimal gland and some salivary glands

What are the branches of the facial nerve? | HINT: to Zanzibar by motor car

``` Temporal Zygomatic Buccal Mandibular Cervical ```

What is CN VIII?

Vestibulocochlear nerve

What is the course of the vestibulocochlear nerve?

Pons -> internal auditory meatus -> petrous bone -> cochlea -> temporal lobe

What are the functions of the vestibulocochlear nerve?

Hearing and balance

What is presbyacusis?

Old-age related hearing loss (bilateral)

What is acoustic neuroma?

Benign tumour of Schwann cells involving vestibulocochlear nerve

What are the symptoms of acoustic neuroma?

- unilateral hearing loss - tinnitus - vertigo - numbness down one hand of face

What is CN IX?

Glossopharyngeal nerve

What is the course of the glossopharyngeal nerve?

Medulla -> jugular foramen -> down neck -> parts of tongue and pharynx

What are the functions of the glossopharyngeal nerve?

- special sensory to the middle ear, tympanic membrane, carotid body and sinus and taste and general sensory of posterior 1/3 tongue - autonomic to parotid gland - stylopharyngeus muscle

How do you test the function of the glossopharyngeal nerve?

- gag reflex (sensory limb) | - tested with CN X

What is CN X?

Vagus nerve

What is the course of the vagus nerve?

Medulla -> jugular foramen -> down neck through carotid sheath, behind artery and vein -> thorax

What are the functions of the vagus nerve?

- general sensory to lower pharynx and larynx - muscles of soft palate, pharynx and larynx - parasympathetic to thoracic and abdominal viscera

How do you test the function of the vagus nerve?

- note speech - swallow and cough - say “ahh” observing uvula, should equally rise on both sides but will deviate away from lesion if CN X damaged - gag reflex (efferent limb)

What does damage to the recurrent laryngeal branch of the vagus nerve lead to?

Hoarseness and dysphonia

Which artery does the right recurrent laryngeal nerve turn under?

Right subclavian artery

Which artery does the left recurrent laryngeal nerve turn under?

Arch of aorta

What is CN XI?

(Spinal) accessory nerve

What is the course of CN XI?

Medulla -> jugular foramen -> spinal branch goes through foramen magnum

What is the function of the accessory nerve?

Motor to SCM and trapezius muscles

How do you test the function of the accessory nerve?

Shrug shoulders against resistance and turn head against resistance

True or false: the accessory nerve travels through the anterior triangle

FALSE - posterior triangle

What is CN XII?

Hypoglossal nerve

What is the course of the hypoglossal nerve?

Medulla -> hypoglossal canal -> tongue

What does damage to the hypoglossal nerve lead to?

Weakness and atrophy of the tongue muscles on the ipsilateral side

How do you test the function of the optic nerve?

- visual tests - pupil response/reflex - visual acuity tests (eg Snellen chart)

How do you test the function of the oculomotor nerve?

- pupillary light reflexes | - eye movements

How do you test the function of the trigeminal nerve?

- sensation to face: dermatones of Va, Vb, Vc - muscles of mastication - corneal reflex (afferent limb)

How do you test the function of the facial nerve?

- muscles of facial expression | - corneal reflex (efferent limb)

How do you test the function of the vestibulocochlear nerve?

- hearing: Rinnes and Weber’s test | - test balance