Cranial Nerves

Thomas C D Lewis, B.Eng MBBS

Cranial Nerves Revision 27/04/2009 Question 1

a) Sensory to the anterior 2/3 of the tongue b) Efferent cranial nerve in corneal reflex c) Sensory to Posterior most portion of auricle d) Innervates muscles of mastication e) Afferent cranial nerve to Edinger-Westphal brainstem nucleus f)

Innervates stapedius

g) The nerve associated with the third pharangeal arch h) This nerve exits the skull via the foramen rotundum i)

Innervates the motor muscles of the tongue

j)

Efferent cranial nerve in gag reflex

k) Tested in the Rhomberg test Select the most appropriate match from the following list A: Olfactory B: Optic C: Oculomotor D: Trochlear E: Trigeminal (V1) F: Trigeminal (V2) G: Trigeminal (V3) H: Abducens I: Facial J: Vestibulocochlear K: Glossopharangeal L: Vagus M: Accessory (spinal) N: Accesorry (cranial) O: Hypoglossal P: None of the above

Question 2 – clinical scenarios

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Thomas C D Lewis, B.Eng MBBS You have been asked by a colleague to review the findings of a crude vestibulocochlear examination performed by a fellow doctor. The results are as follows: Left Ear Right Ear

Rinne's Test Positive Negative

Weber's Test Away Towards

What is the diagnosis based purely on these results? Select the most appropriate answer from the list below A: Sensorineural deficit in the left ear B: Conductive loss in the left ear C: Sensorineural deficit in the right ear D: Conductive loss in the right ear E: None of the above F: All of the above

Question 3 – Clinical scenarios Mrs. Smith is a 58 year old lady who has come to see you after becoming concerned that her vision isn’t quite what it used to be. Her visual fields were assessed thoroughly and the following was ascertained.

What is the diagnosis based on this result? A: Bitemporal hemianopia B: Lesion to the left optic nerve C: Lesion to the optic chiasm D: Lesion to the right optic nerve E: Left Homonymous Hemianopia F: Lesion to the right optic nerve G: Lesion to the left optic tract H: Lesion to the right optic tract I: None of the above

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Thomas C D Lewis, B.Eng MBBS Question 4 a) , b) and c) are all motor cranial nerves involved in the control of eye muscles. A lesion to d) would cause paralysis to all eye muscles except lateral rectus and superior oblique, so the eye points e) and f). Bell’s palsy involves a lesion to g) causing ipsilateral paralysis to the entire face. An upper motoneurone lesion differs however because h) innervation is bilateral to the lower part of the face. A: Olfactory B: Medial C: Oculomotor D: Trochlear E: Corticobulbar F: Trigeminal (V2) G: Trigeminal (V3) H: Abducens I: Inferior J: Vestibulocochlear K: Glossopharangeal L: Vagus M: Corticospinal N: Accesorry (cranial) O: Red nuclei P: Facial Q: Optic R: Trigeminal (V1) S: Accessory (spinal) T: Laterally U: Hypoglossal Question 5 – Cranial Nerve Reflexes For each of the following select the TWO cranial nerves involved in the afferent and efferent part of the reflex a) Corneal Reflex: Afferent b) Corneal Reflex: Efferent c) Blink Reflex: Afferent d) Blink Reflex: Efferent e) Stapedius Reflex: Afferent

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Thomas C D Lewis, B.Eng MBBS f)

Stapedius Reflex: Efferent

g) Accommodation Reflex: Afferent h) Accommodation Reflex: Efferent A: Olfactory B: Optic C: Oculomotor D: Trochlear E: Trigeminal (V1) F: Trigeminal (V2) G: Trigeminal (V3) H: Abducens I: Facial J: Vestibulocochlear K: Glossopharangeal L: Vagus M: Accessory (spinal) N: Accesorry (cranial) O: Hypoglossal P: None of the above Question 6 Select the answers you believe to be true a) Stylopharangeus is supplied by the glossopharangeal cranial nerve b) Cranial nerve XII passes the jugular foramen c) The temporalis muscle’s motor function is given by the facial nerve d) The lacrimal nerve is a branch of the trigeminal nerve e) Damage to the hypoglossal nerve paralyses the trapezius muscle

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Thomas C D Lewis, B.Eng MBBS Question 7 Label the diagram by selecting the match from the list below

A: Optic radiation B: Nasal fibres C: Optic disc D: Optic Chiasm E: Temporal fibres F: Meyer’s Loop G: Visual Cortex H: Edinger-Westphal I: Optic tract J: Calcarine sulcus K: Optic nerve

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Thomas C D Lewis, B.Eng MBBS

Question 8 Consider the following lesions and match to the correct perimetry chart:

A:

B:

C:

D:

E:

F:

G:

H:

I:

J:

K:

L:

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Thomas C D Lewis, B.Eng MBBS

M:

N:

Question 9 There are three major divisions of the brainstem: midbrain, pons and the medulla. A major component of the brainstem is the cranial nerve nuclei. Select the answers you believe to be true a) Nucleus Ambiguus contains motor nuclei of cranial nerve IX b) Inferior Salivatory nucleus contains motor nuclei of cranial nerve IX c) The chief sensory nuclei is sensory to temperature from the face d) The Edinger-Westphal nucleus is superior to V motor nuclei on the brainstem e) The dorsal nucleus innervates the gall bladder Question 10 – Concerning embryological development Select the answers you believe to be true a) The fifth pharangeal arch is supplied by the recurrent larangeal nerve b) The facial nerve supplies the second pharangeal arch c) Muscles of mastication are derived from the second pharangeal arch d) The sixth pharangeal arch is supplied by a division of the accessory nerve e) Taste sensation comes from both the second and third pharangeal arch Question 11 Upon testing a patient you find that when protruding his tongue, the tongue deviates to the left. Which of the following statements are true: a) The tongue is deviating towards the side of the lesion

b) This kind of lesion will also make chewing impossible c) This is a hypoglossal lesion d) Parasympathetic innervation of the tongue arises from the medulla e) The patients sense of taste will be affects on the anterior 2/3 of the tongue Question 12

a) A mixed sensory and motor cranial nerve involved in mastication b) Zygomatic is a branch of this cranial nerve c) Crosses and divides the parotid gland d) Supplies the submandibular gland

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Thomas C D Lewis, B.Eng MBBS e) Innverates its target gland via the otic ganglion A: Olfactory B: Optic C: Oculomotor D: Trochlear E: Trigeminal (V1) F: Trigeminal (V2) G: Trigeminal (V3) H: Abducens I: Facial J: Vestibulocochlear K: Glossopharangeal L: Vagus M: Accessory (spinal) N: Accesorry (cranial) O: Hypoglossal P: None of the above Question 13 Which of the following statements are true: a) The facial nerve is a mixed cranial nerve b) Two of the cranial nerves also carry parasympathetic preganglionic fibres c) There are three special sensory cranial nerves d) Spinal XI is actually a spinal nerve e) The cranial nerve motor and sensory nuclei are bilateral Question 14 a) Gag Reflex: Afferent b) Gag Reflex: Efferent c) Salivary Reflex: Afferent d) Salivary Reflex: Efferent (Select TWO) e) Jaw-jerk Reflex: Afferent f)

Jaw-Jerk Reflex: Efferent

g) Lacrimal Reflex: Afferent h) Lacrimal Reflex: Efferent A: Olfactory B: Optic C: Oculomotor

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Thomas C D Lewis, B.Eng MBBS D: Trochlear E: Trigeminal (V1) F: Trigeminal (V2) G: Trigeminal (V3) H: Abducens I: Facial J: Vestibulocochlear K: Glossopharangeal L: Vagus M: Accessory (spinal) N: Accesorry (cranial) O: Hypoglossal P: None of the above Question 15 You have been asked by a colleague to review the findings of a crude vestibulocochlear examination performed by a fellow doctor. The results are as follows: Left Ear Right Ear

Rinne's Test Negative Positive

Weber's Test Away Towards

What is the diagnosis based purely on these results? Select the most appropriate answer from the list below A: Sensorineural deficit in the left ear B: Conductive loss in the left ear C: Sensorineural deficit in the right ear D: Conductive loss in the right ear E: None of the above F: All of the above

Answers: Q1 a) G – the anterior 2/3 of the tongue derive from the 1st pharangeal arch b) I – the corneal reflex involves taking a wisp of cotton wool and rubbing this on the patient’s cornea without the patient seeing the stimulus. This causes the patient to blink, with the afferent cranial nerve being V1 and the efferent being the facial nerve

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Thomas C D Lewis, B.Eng MBBS which innervates all muscles of facial expression and in this case is innervating the orbicularis orbit. c) P – the posterior most portion of the auricle (ear) is innervated by C2/C3 dermatomes and not the trigeminal d) G – The four muscles lateral pterygoid, medial pterygoid, masseter and temporalis receive motor function from the mandibular (V3) cranial nerve e) B – the Edinger-Westphal nucleus is involved in pupillary constriction when a light stimulus is given to the patients eye. The afferent cranial nerve is optic and the efferent is the oculomotor nerve. f) I – the stapedius is one of two muscles in the inner ear involved in protecting the ear from persistent loud sounds. Stapedius acts by contracting and dampening the movement of the stapes ossicle (the other muscle is tensor tympani supplied by V3 which tenses the tympanic membrane). g) K h) F – the maxillary part of the trigeminal exits the base of the skull here i) O j) L – the gag reflex involves stimulating the glossopharangeal sensory nerve at the posterior portion of the oropharanynx. The efferent nerve is vagus which supplies the alpha-moto neurons responsible for the gagging response k) J – this tests the vestibule portion of this nerve and involves the patient standing with their eyes shut and feet close together. The doctor must ensure he is in a position to catch the patient should their balance fail. Question 2 D - Rinne’s test involves placing a vibrating 512 tuning fork on the patient’s mastoid bone until they can no longer perceive the sound. The tuning fork is then placed near the ear and a normal ear would still be able to hear the tuning fork’s ‘humm.’ A positive Rinne’s test is normal and indicates that air conductive hearing is more sensitive than bone conduction. Here, there is a negative Rinne’s result in the right ear indicating that air conduction is not as sensitive as bone conduction. To further clarify, Weber’s test tells us where sound lateralises to when the base of a vibrating 512 tuning fork is placed on the patients forehead. If Weber’s test lateralises towards the Rinne’s negative ear, this indicates that the air conductive pathway has been altered (e.g. excess cerumen). If it lateralises away from the Rinne’s negative ear, this indicates a sensorineural deficit (e.g. hair cells damaged by aminoglycoside)

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Thomas C D Lewis, B.Eng MBBS In this case, there are signs that the patient’s right ear air conductive pathway is blocked. Question 3 I – None of the above Right homonymous hemianopia with macula sparing is the diagnosis. This lesion occurs at the visual cortex and is often caused by a posterior stroke which leads to this phenomenon of macula sparing. Question 4 a) C b) D c) H d) C e) I f)

T

g) P h) E Question 5 a) E – crude touch to sclera

b) I – ‘screw’ up eye using orbicularis oculi c) B - light d) I - ‘screw’ up eye using orbicularis oculi e) J – Loud noise f)

I – tightens stapedius muscle to prevent damage from loud noise

g) B - light h) C – moves eye in AND parasympathetic motor constricts pupil Question 6 a) T – Stylopharngeus derives from the third pharangeal arch and is thus supplied by CNIX b) F – The jugular foramen contains the cranial nerves IX , X and XI c) F – This is a muscle of mastication so is innervated by V3 d) T – the lacrimal nerve is sensory to the skin and conjunctiva of the lateral part of the upper eyelid and lacrimal gland, which is a subdivision of the ophthalmic nerve (V1), which is a trigeminal branch. e) F – Damage to CN XI causes this

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Thomas C D Lewis, B.Eng MBBS Question 7 a) D – Nasal fibres decussate at the optic chiasm above the pituitary gland b) K c) I d) F e) A Question 8 a) I – bitemporal hemianopia occurs here as the nasal fibres (which view the more lateral parts of the visual field) are disrupted b) C – this is analogous to blindness in the right eye c) F – Left homonymous hemianopia. The left part of the hemifield is lost. d) H – There is a lesion to Meyer’s loop so the left upper visual field is lost e) A – There is a lesion to the parietal part of the optic radiations meaning left lower visual fields are lost f)

L – Macular sparing of the left hemifield

Question 9 a) T – along with X and XII b) T – it controls the parasympathetic parotid response c) F – the spinal V nucleus receives temperature information from the face (analogous to the anterolateral tract in spinal cord) d) T – Edinger-Westphal is found in the midbrain whereas V motor is found in the pons e) T – along with the lungs and heart (parasympathetic control) Question 10 a) F - The sixth pharangeal arch is supplied by the recurrent larangeal nerve b) T c) F - Muscles of mastication are derived from the first pharangeal arch d) F - The sixth pharangeal arch is supplied by a division of the vagus nerve (recurrent larangeal) e) T- Taste sensation comes from both the second and third pharangeal arch (VII and IX) Question 11 a) T- The tongue is deviating towards the side of the lesion. This is because in a hypoglossal cranial nerve injury there is no innervation to the side of the tongue where the lesion is and it therefore atrophies. This makes the muscles on the opposite side of the tongue stronger and causes deviation.

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Thomas C D Lewis, B.Eng MBBS b) F- Mastication is a trigeminal nerve function c) T- This is a hypoglossal lesion d) F- There is no Parasympathetic innervation of the tongue e) F- The patients sense of taste for the anterior 2/3 of the tongue derives from the facial nerve Question 12 a) G – sensory to lower face and motor to muscles of mastication b) I c) I d) I e) K – parasympathetic innervation of the parotid gland comes via the inferior salivatory nucleus via the otic ganglion Question 13 a) T - The facial nerve is a mixed cranial nerve b) F - Four of the cranial nerves (III VII IX X) also carry parasympathetic preganglionic fibres c) T- There are three special sensory cranial nerves (I II VIII) d) T - Spinal XI is actually a spinal nerve as it attached to the spinal cord not to brainstem or forebrain e) T - The cranial nerve motor and sensory nuclei are bilateral Question 14 a) K – crude touch to back of throat b) L – Vagus motor control to back of throat c) A - Smell d) I & K – Parasympathetic control of saliva e) G f)

G–

g) E - Itch h) I – parasympathetic motor Question 15 A - Rinne’s test involves placing a vibrating 512 tuning fork on the patient’s mastoid bone until they can no longer perceive the sound. The tuning fork is then placed near the ear and a normal ear would still be able to hear the tuning fork’s ‘humm.’

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Thomas C D Lewis, B.Eng MBBS A positive Rinne’s test is normal and indicates that air conductive hearing is more sensitive than bone conduction. Here, there is a negative Rinne’s result in the left ear indicating that air conduction is not as sensitive as bone conduction. To further clarify, Weber’s test tells us where sound lateralises to when the base of a vibrating 512 tuning fork is placed on the patients forehead. If Weber’s test lateralises towards the Rinne’s negative ear, this indicates that the air conductive pathway has been altered (e.g. excess cerumen). If it lateralises away from the Rinne’s negative ear, this indicates a sensorineural deficit (e.g. hair cells damaged by aminoglycoside) In this case, there are signs of a sensorineural defect in the left ear.

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