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BB1 > Anatomy of the Brain > Flashcards

Anatomy of the Brain Flashcards

1
Q

Which cranial nerves originate from the midbrain?

A

Trochlear

Oculomotor

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2
Q

Which cranial nerves originate from the pons?

A

Trigeminal
Vestibulocochlear
Abducent
Facial

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3
Q

Which cranial nerves originate from the medulla?

A

Glossopharyngeal
Medulla
Accessory
Hypoglossal

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4
Q

Despina is experiencing a hoarse voice, which cranial nerve is likely affected?

A

Vagus (X)

The Vagus nerve gives rise to the recurrent laryngeal nerve which innervates the muscles of the larynx (voicebox).

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5
Q

Despina is experiencing vertigo, which cranial nerve is likely affected?

A

Vestibulocochlear (X)
The Vestibulocochlear nerve carries sensations of hearing and balance. A deficit in balance leads to feelings of vertigo.

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6
Q

How can the midbrain be identified?

A

This can be identified by the large cerebral peduncles anteriorly (inferior aspect of image) and small colliculi.

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7
Q

How can the medulla be identified?

A

This section is taken in the superior 1/3 of the medulla, which can be referred to as the open medulla, due to the posterior indent formed by the 4th ventricle.

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8
Q

How can the Pons be identified?

A

Anteriorly the pons bulges forwards, and posteriorly the beginning of the 4th ventricle can be seen.

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9
Q

How else can the medulla be identified?

A

This region of the medulla is referred to as the closed medulla, due to CSF being enclosed within the central canal of the medulla. This cross section is the most similar to a cross section of the spinal cord.

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10
Q

Which arteries supply the brainstem? (from base to top)

A 
Anterior spinal artery
Vertebral artery
Posterior Inferior Cerebellar Artery (PICA)
Anterior Inferior Cerebellar Artery (AICA)
Pontine Branches
Basilar Artery
Superior Cerebellar Artery (SCA) 
Posterior Cerebral Artery (PCA)
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11
Q

Upon examination Despina showed decreased pinprick and temperature sensation across the distribution shown in blue.
Based on this information which spinal tract/s are involved?

A

Spinothalamic

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12
Q

Upon examination Despina showed decreased pinprick and temperature sensation across the distribution shown in blue.
Despina has a lesion to her brainstem. Given the information you have, which of the locations below is most likely?
Trauma to which artery is most likely to have caused this lesion?

A

Vagus and Vestibulocochlear nerve
This is the location of the Vagus nerve and the Vestibulocochlear nerve. The spinothalamic tract is found lateral to the pyramids within the medulla.
Trauma to the vertebral artery
The vertebral arteries supply the lateral aspect of the medulla, and trauma or thrombus of these vessels can lead to lateral medullary syndrome.

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13
Q

What is the retina and what does it do? Which nerves is it innervated by? What are its features?

A

This is the innermost layer of the eye (in yellow on the left) that contains photoreceptive cells including rods, cones and photosensitive ganglion cells. They detect light that passes through the cornea, lens and across the vitreous chamber of the eye.
On the right, a photo of the retina demonstrates the appearance of the full retina. The optic disc is where the optic nerve joins the retina. The macula is the location of maximal photoreceptor density (with therefore highest visual acuity, corresponding to the centre of the visual field). Note the blood vessels emerging from the optic disc, and avoiding obstructing light reception near the macula.

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14
Q

How can the retina be examined?

A

In the 3D model below, look at the left eye, which is illuminated as if being examined with an opthalmoscope. By looking through the pupil with a light, you can examine the retina. Because the apeture you are looking at is small, so you can only see a small portion of the retina, much the same as when examining in real life! In the same way, identify a blood vessel, and follow this to find the optic disc. Examining the appearance of the disc is an important component of a cranial nerve examination.

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15
Q

What is the optic nerve and where is it located?

A

Optic nerve fibres start at the optic disc at the back of the retina. They are special sensory fibres for sight, receiving visual information from retinal photoreceptors. They exit the eye ball and enter cranium through optic canal. The optic nerves are surrounded by extensions of the cranial meninges and subarachnoid space, which is filled with CSF. The nerve passes posteromedially in the orbit, and through a tendinous ring formed by the base of the four rectus muscles to reach the start of the optic canal. Find this by looking at the right eye of the model below, and after appreciating where the common tendinous ring would be, delete the rectus muscles to examine the base of the orbit and find the optic canal and superior orbital fissure.

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16
Q

What are the optic chiasm and tracts and what do they do?

A

After travelling through the canal the nerve enters the middle cranial fossa. Each nerve meets to form the optic chiasm. Fibres from the medial aspect of the eye cross over to the opposite side and then continue on via the optic tracts. As a result the optic tracts contain fibres from the lateral (temporal) retina of the eye on the same side and the nasal retina from the opposite site, thus carrying all information from the same half of the visual field.

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17
Q

What are the optic radiations? What do they do?

A

The paired optic tracts sweep posteriorly and send most axons to synapse in the thalamus, in the lateral geniculate nucleus of the thalamus. Axons of the thalamic neurons project through the internal capsule to form the optic radiations, which project to the primary visual cortex in the occipital lobe, where conscious perception of visual images occurs. Some nerve fibres in the optic tracts send branches to the midbrain, to the superior colliculus which allows a visual reflex centre controlling the extrinsic eye muscles. Some fibres project to the pretectal nuclei in the midbrain to mediate papillary light reflexes. Use the figure below to see how visual information from the left and right halves of the visual fields is conducted along the visual pathway. Note that irrespective of what eye the light comes through, visual information from the left half of the visual field is processed in the right occipital cortex and vica versa.

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18
Q

How can we represent optic pathway defects in visual field perception?

A

Lesions at any point in the optic pathway can cause defects in visual field perception. We can represent this by drawing two circles to represent each visual field, and shading in black the portion of field loss.

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19
Q

What are the types of defects in visual field perception?

A

Complete left/right monocular blindness (complete loss of sight in one eye)
Left/right temporal hemianopia (loss of lateral vision in one eye)
Left-right homonymous hemianopia (complete loss of sight in one side of each eye - same side in both eyes)
Bitemporal hemianopia (tunnel vision)

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20
Q

Which lesions cause which types of blindness?

A

See anatomy e-learning

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21
Q

Joseph can only see through the inner halves of his fields of vision.
What type of visual field defect does Joseph have?
Which bit of the optic pathway has been affected?

A

Bitemporal hemianopia

Decussating fibres at the optic chiasm

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22
Q

You are concerned about the intracranial pathology that may be causing this bitemporal hemianopia, and organise a CT scan of his head. Here is a saggital section of the scan: (mass shown in the brain)

A

Pituitary adenoma

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23
Q

What are pituitary adenomas and what do they cause? How may they be treated?

A

Pituitary adenomas that are non secretory can grow to large sizes and patients present due to compression effects on nearby structures. Jonathan underwent transphenoidal resection of the lesion and made a full recovery. Remind yourself of the relationship between the pituitary, hypothalamus and optic chiasm and how the pituitary might be approached via the nasal cavity and through the sphenoid bone in the 3D model below.

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24
Q

Which cranial nerves cause eye movements?

A

3rd, 4th and 6th

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25
Q

What 3 types of movements is the eye capable of?

A

The eye is capable of vertical, horizontal and rotary movement. The muscles responsible for this movement are known as the extra-ocular eye muscles.

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26
Q

When is rotation of the eyeball used?

A

Whilst you cannot rotate your eyes on demand, if you fix your gaze on one point and tilt your head the eyes rotate to keep your gaze.

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27
Q

Which muscles, and how many, control eye movement?

A 
There are 6 extra-ocular muscles controlling eye movement. Four recti, and two obliques:
Lateral rectus
Medial rectus
Superior rectus
Inferior rectus
Superior oblique
Inferior oblique
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28
Q

Where do the four recti muscles originate from?

A

Four recti muscles arise from a common tendinous ring and insert into the sclera just posterior to the cornea.

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29
Q

What do the levator palpabrae superioris and the tarsal muscles do? How are they innervated?

A

These muscles do not act on the eye, but contract to raise the eyelid. Closing of the lids requires relaxation of the levator palpebral muscle (CN III). Orbicularus oculi (innervated by CN VII) is located in the eyelids and is used to close the eyelids.

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30
Q

What is important to remember about the external ocular muscles?

A

It is important to remember that the external ocular muscles rarely act in isolation. The action of the other muscles is complex, as their primary line of pull is oblique to the axis of the globe.

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31
Q

What does each extraocular muscle do?

A

Superior rectus: look upward and medially
Inferior rectus: look downward and medially
Lateral rectus: look laterally
Medial rectus: look medially
Inferior oblique: look upward and laterally
Superior oblique: look downward and laterally

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32
Q

What is the action of the medial and lateral recti?

A

The action of the medial and lateral recti is straightforward: medial rectus adducts the globe (eyeball) and lateral rectus abducts the globe, without elevation or depression.

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33
Q

What is the action of the superior and inferior recti?

A

The superior and inferior recti act to elevate and depress the globe respectively. However as the orientation of the muscle is not inline with the angle of the orbit, the recti muscles also create secondary actions.

Superior rectus: elevation, adduction and intorsion
Inferior rectus: depression, adduction and extorsion

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34
Q

What is the action of the superior and inferior oblique?

A

The superior and inferior oblique depress and elevate the globe respectively, and as with the recti muscles create secondary actions.

Superior oblique: Depression, abduction and intorsion

Inferior oblique: Elevation, abduction and extorsion

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35
Q

What clinical testing can be done to test the extraocular muscles?

A

So the extraocular muscles work in conjunction to cancel out the accessory movements of each other clinical testing is not straight forward.

The action of the medial and lateral recti is straightforward: medial rectus adducts the eye and can be tested by looking medially. Lateral rectus abducts the globe and can be tested by looking laterally

To test the remaining 4 muscles the eye is abducted or adducted so that only one set of muscles can act.

When the eye is ABDUCTED the superior and inferior recti act to elevate and depress the globe respectively.

When the eye is ADDUCTED the superior and inferior oblique depress and elevate the globe respectively.

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36
Q

Through which skull base foramina do the 3rd, 4th and 6th cranial nerves pass?

A

Superior orbital fissure

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37
Q

Where does the trochlear nerve originate?

A

Posterior midbrain

38
Q

Where does the abducens originate?

A

Medullo-pontine junction

39
Q

Where does the oculomotor nerve originate?

A

Anterior midbrain

40
Q

Where is the oculomotor nerve? What branches/fibres does it give off? Where do these fibres go to?

A

The oculomotor nerves exit the midbrain (medial to cerebral peduncles) and then run anteriorly through the cavernous sinus (on the lateral wall). This nerve divides into superior and inferior branches, which both pass through the superior orbital fissure to innervate the extraocular muscles (excluding lateral rectus and superior oblique) and levator palpebrae superioris. These nerves also send presynaptic parasympathetic fibres to the ciliary ganglion for innervations of the ciliary muscle (accommodation) and sphincter pupillae (constricts pupil).

Motor fibres to:
Superior rectus
Inferior rectus
Medial rectus
Inferior oblique
Levator palpabrae superioris

Parasymathetic fibres to:
Sphincter Pupillae muscle via ciliary ganglion (causes pupillary constriction)
Ciliary muscle via ciliary ganglion (causes accomodation)

41
Q

What do lesions to the oculomotor nerve result in?

A

Lesions to the oculomotor nerve result in a resting ‘down and out’ position of the eye, due to the unopposed actions of lateral rectus and superior oblique. The pupil dilates due to loss of parasympathetic innervation to the pupil. Loss of innervation to levator palpabrae superioris leads to a drooping eyelid (ptosis).

42
Q

What and where is the trochlear nerve?

A

The trochlear nerve is the smallest cranial nerve, but has the longest intracranial course of the cranial nerves. It arises from the posterior (dorsal) surface of the midbrain (the only cranial nerve to do so), passing anteriorly around the brainstem. The trochlear nerve pierces the dura mater at the margin of the tentorium cerebelli and passes on the lateral wall of the cavernous sinus, through the superior orbital fissure to the superior oblique muscle (the only extraocular muscle to use a pulley).

43
Q

What type of injuries may occur in the trochlear nerve? What are typical signs of this?

A

This nerve is rarely paralysed alone, but may be torn when there are severe head injuries due to its long intracranial course. The characteristic sign of this is double vision (diplopia) when looking down. The superior oblique assists the inferior rectus in depressing the pupil and is the only muscle to do so when the eye is adducted (eg when watching feet when going downstairs).

44
Q

Where is the abducens nerve? What can affect this nerve? What can this cause?

A

The abducens nerve emerges from the brainstem, from between the pons and medulla. The nerves then enters the dura and has a very long intradural course to the superior orbital fissure. It courses through the cavernous sinus, surrounded by venous blood adjacent to the internal carotid artery. The abducens is somatic motor to one extraocular muscle, the lateral rectus.

Because of its long intradural course and the sharp bend along the petrosal part of the temporal bone, the abducens can be affected by increased intracranial pressure. Complete paralysis of abducens causes medial deviation due to the unopposed action of medial rectus. Diplopia is present in all ranges of movement, except when looking away from the lesion.

45
Q

Which eye movements test which nerve?

A

Oculomotor: look top left, straight up, and top right
Left abducent/right oculomotor: look left
Right abducent/left oculomotor: look right
Left trochlear/right oculomotor: look bottom left
Right trochlear/left oculomotor: look bottom right
Oculomotor and trochlear: look straight down

46
Q

Why can the cranial nerves become damaged? What effect can examining eye movements have? What must be known to understand nerve palsies of the 3rd, 4th and 6th cranial nerves?

A

To understand the cranial nerve palsies for the 3rd, 4th, and 6th cranial nerves, think about what muscles they innervate, and how the eye would look if these functions were lost.

47
Q

Lesions in each nerve causes which symptoms?

A

Trochlear nerve palsy: Eye looks up and in at rest.
Oculomotor nerve palsy: Eye looks ‘down and out’ at rest. Pupil dilated. Complete eyelid droop (Ptosis)
Abducens nerve palsy: Failure to abduct eye.

48
Q

What would you tell a lorry driver with oculomotor nerve palsy?

A

Advise them they must tell the DVLA immediately

49
Q

From where does the trigeminal nerve arise?

A

Lateral aspect of the pons

50
Q

Which are the major divisions of the trigeminal nerve?

A

Ophthalmic
Maxillary
Mandibular

51
Q

What does the trigeminal nerve supply motor and sensory innervation to? What roots does it have? What are these roots comparable to? Where are these located? What muscles do they supply?

A

The trigeminal nerve arises from the lateral aspect of the pons. The trigeminal nerve provides somatic sensory and motor supply to derivatives of the first pharyngeal arch. It has a large sensory root and a smaller motor root. The roots of CN V are comparable to the dorsal and ventral roots of spinal nerves, i.e. the trigeminal ganglion is comparable to the dorsal root ganglion of spinal nerves. It is housed in a dural recess lateral to the cavernous sinus. The motor root passes inferior to the trigeminal ganglion (just as the ventral roots of spinal nerves do not pass through the DRG). The fibres join the mandibluar division to supply the muscles of mastication.

52
Q

What do the peripheral processes of the trigeminal nerve form? What do the maps of their zones resemble?

A

The peripheral processes form three nerves or divisions, the ophthalmic nerve (V1), the maxillary nerve (V2) and the mandibular nerve (V3). Maps of the zones of cutaneous innervations by the three divisions resemble the dermatome maps for cutaneous innervations by spinal nerves (however there is little overlap in innervations in the head).

53
Q

Which skull base foramina does each trigeminal division pass through?

A

Ophthalmic: superior orbital fissure
Maxillary: foramen rotundem
Mandibular: foramen ovale

54
Q

Which facial bone foramina does each trigeminal division branch pass through?

A

Branches of the opthalmic: supraorbital foramen
Branches of the maxillary: infraorbital foramen
Branches of the mandibular: mental foramen

55
Q

What is the opthalmic division (V1) and what does it do? Where is it located? How can it be tested?

A

This nerve is sensory to the cornea, upper conjunctiva, upper nasal mucosa, frontal and ethmoidal sinus, anterior dura, superior eyelid and forehead/scalp.

The ophthalmic nerve passes anteriorly through the lateral wall of the cavernous sinus and passes through the superior orbital fissure. Note how the ophthalmic nerve divides into the frontal nerve, the nasociliary and the lacrimal nerve. The supraorbital nerve (branch of frontal nerve) passes through the supraorbital notch/foramen as it leaves the orbit to pass onto the forehead. The integrity of this division can be tested specifically? through the corneal reflex. (What is the motor root of this reflex?)

56
Q

What is the maxillary division (V2) and what does it do? Where is it located? How can it be anaesthetised?

A

This provides sensory fibres to the: dura of the middle cranial fossa, inferior conjunctiva, upper dentition and skin and mucous membranes associated with upper jaw. The maxillary branch exits the middle cranial fossa through the foramen rotundum. Note how the maxillary nerve passes through/next to the maxillary air sinus.

The superior alveolar nerves are not accessible to dentists and so anaesthesia is achieved by injecting the agent into tissues surrounding the root of the tooth and allowing the solution to infiltrate to the terminal branches.

57
Q

What is the mandibular division (V3) and what does it do? Where is it located? What are its 2 main branches?

A

This provides sensory innervation to the oral mucosa and anterior 2/3 of the tongue, lower teeth and jaw, temporal regions of face and external ear. It also provides motor supply to the muscles of mastication. The mandibular nerve leaves the middle cranial fossa through the foramen ovale and descends into an area behind the ramus of the mandible. This area is called the infratemporal fossa and it contains the branches of the mandibular nerve, the maxillary artery and its branches, and the lateral and medial pterygoid muscles.

The mandibular nerve has 2 main branches:

The inferior alveolar nerve supplies the lower dentition and gives off the mental nerve which passes through the mental foramen.
The lingual nerve which supplies somatosensory fibres to the anterior 2/3 of the tongue. The chorda tympani is a branch of the facial nerve and“hitches a lift” with the lingual nerve to supply special sensory fibres of tast to the anterior 2/3 of the tongue.

58
Q

How many muscles of mastication are there, what are they called and which nerve are they supplied by? Which other muscles are supplied by this nerve?

A

Name the 4 main muscles of mastication which are all supplied by the mandibular division of the trigeminal nerve: massetter, temporalis, medial pterygoid and lateral pterygoid. (Other muscles supplied by the mandibular nerve include the mylohyoid, the anterior belly of digastric and tensor tympani.)

59
Q

What is the function of each muscle of mastication?

A

Massetter: Elevation and protrusion of mandible
Medial pterygoid: Elevates, depresses and moves mandible from side to side
Lateral pterygoid: Protrudes, depresses and moves mandible from side to side
Temporalis: Elevation and retraction of mandible

60
Q

If a patient has a painful rash over their face, what might be the diagnosis? What causes this and how would you treat it?

A

Shingles
(Trigeminal neuralgia may cause pain in the distribution of the nerve but not a rash)
Reactivation of the herpes simplex virus that can lie dormant in nerves following many years after the initial infection (chicken pox) causes a painful, vesicular rash in the cutaneous distribution of that nerve commonly known as shingles. You prescribe a course of aciclovir and reccomend regular paracetamol and ibuprofen.

61
Q

Which division of the trigeminal has been affected by shingles if the eyes, forehead and nose are affected on one side only?
Which specialist should this be referred to?

A

Ophthalmic (V1)

Maxillofacial surgeon

62
Q

If there is any sign of involvement of the ophthalmic division of the trigeminal (which could include just nasal involvement - see Hutchinson sign) - you must refer to an ophthalmologist. Why?

A

The ophthalmic branch also supplies the cornea which if also involved could impact on eyesight.

63
Q

Where do the facial and vestibulocochlear nerves arise from?

A

The facial nerve (CNVII) arises from the pons, whilst the vestibulocochlear nerve (CNVIII) arises from two separate regions - the vestibular parts is from the pons and medulla, whilst the cochlear component is from the inferior cerebellar peduncle.

64
Q

Through which foramen do the facial nerve (CNVII) and the vestibulocochlear nerve (CNVIII) exit the cranium?

A

Internal acoustic meatus

65
Q

What is special about the facial nerve?

A

The facial nerve has the longest intraosseus course of all the cranial nerves.

66
Q

What types of function does the facial nerve have? Where does it innervate?

A

The facial nerve has both motor and sensory function as well as special sensory and autonomic (parasympathetic) function.

Motor: muscles of facial expression - 5 main terminal branches which can be seen on the image below

General sensory: soft palate

Special sensory: taste to anterior two thirds of tongue

Autonomic (parasympathetic): submandibular, sublingual and lacrimal glands

67
Q

What is the function of the vestibulocochlear nerve?

A

The vestibulocochlear nerve has pure sensory function.

Sensory: balance, hearing

68
Q

What does damage to the facial nerve (CNVII) cause?

A

Paralysis of facial muscles
Altered taste
Dry mouth

69
Q

What does damage to the vestibulocochlear nerve (CNVIII) cause?

A

Vertigo
Tinnitus
Loss of balance

70
Q

What is a likely cause of a right sided mass in the brain (near the centre)?

A

This is most likely an acoustic neuroma (vestibular schwannoma) - a type of tumour.

71
Q

The acoustic neuroma is most likely to affect which cranial nerve first?

A

Acoustic schwannomas are most likely to affect CNVIII (vestibulocochlear) first.

72
Q

Where do the glossopharyngeal nerve (CNIX) and the vagus nerve (CNX) emerge from? What about the accessory nerve (CNXI)?

A

The glossopharyngeal nerve (CNIX) and the vagus nerve (CNX) emerge from the medulla. The [spinal] accessory nerve (CNXI) is technically made up of a cranial portion (which emerges from the medulla) and a spinal portion (which emerges from the upper part of the spinal cord - hence it is sometimes named the spinal accessory nerve).

73
Q

Through which foramen do the glossopharyngeal nerve (CNIX), the vagus nerve (CNX) and the accessory nerve (CNXI) exit the cranium?

A

Jugular foramen
Once they have passed through the jugular foramen, the nerves are in close proximity. Beyond this point, the nerves begin to travel to the respective regions which they innervate.

74
Q

What is the function of the glossopharyngeal nerve (CNIX)?

A

The glossopharyngeal nerve has both motor and sensory function as well as special sensory and autonomic (parasympathetic) function.

Motor: stylopharyngeus

General sensory: pharynx, tonsillar sinus, pharyngotympanic tube and middle ear cavity

Special sensory: taste to posterior third of tongue

Autonomic (parasympathetic): parotid glands

75
Q

What is the function of the vagus nerve (CNX)?

A

The vagus nerve has both motor and sensory function as well as autonomic (parasympathetic) function throughout most of the body. This is the longest cranial nerve, and is sometimes known as the ‘wandering’ nerve (in Latin, vagus means wandering).

Motor: palate, pharynx (except stylopharyngeus) and larynx

General sensory: pharynx and larynx

Autonomic (parasympathetic): trachea, bronchial tree, lungs, heart and GI tract (to left colic flexure)

76
Q

What are the divisions and branches of the vagus nerve?

A

See table on e-learning

77
Q

What is the function of the accessory nerve?

A

The accessory nerve has only pure motor function.

Motor: trapezius and sternocleidomastoid muscles

78
Q

What does damage to the glossopharyngeal nerve cause?

A

Less saliva production

Loss of taste (posterior tongue)

79
Q

What does damage to the vagus nerve cause?

A

Hoarse voice

Decreased parasympathetic outflow

80
Q

What does damage to the accessory nerve cause?

A

Difficulty shrugging shoulder

Difficulty turning head

81
Q

Which muscles are innervated by cranial nerves IX, X and XI?

A

A: muscles of the pharynx and larynx innvervated by fibres of CNX.
B: proximal portion of sternocleidomastoid innervated by CNXI.
C: parotid gland innervated by autonomic (parasympathetic) fibres of CNIX.

82
Q

Which structure may have become enlarged in Eva’s neck causing compression of cranial nerves IX, X and XI?

A 
Abscess
Aneurysm (of carotid artery)
Lymphadenopathy
Thrombus (in jugular vein)
Tumour
83
Q

What is the hypoglossal nerve and where does it emerge from?

A

The hypoglossal nerve is the 12th cranial nerve (CNXII). It emerges from the medulla - depicted on the image on the left.

84
Q

Where does the hypoglossal nerve exit the skull?

A

The hypoglossal nerve (CNXII) exits the skull through the hypoglossal canal.

85
Q

Which structure does the hypoglossal nerve predominantly innervate?

A

The hypoglossal nerve provides innervation to the muscles of the tongue.

86
Q

What are the two sets of muscles in the tongue?

A

The tongue is considered to have two sets of muscles - an intrinsic set of muscles and an extrinsic set of muscles. These are almost all innervated by the hypoglossal nerve (CNXII).

Intrinsic
Superior longitudinal
Transverse
Inferior longitudinal

Extrinsic
Styloglossus
Hyoglossus
Genioglossus
Palatoglossus*

*the palatoglossus is the only of these muscles to be innervated by the vagus nerve (CNX).

87
Q

What is the anatomical course of the hypoglossal nerve (CN XII)?

A

The hypoglossal nerve (CN XII) passes around the external carotid artery to reach the muscles of the tongue which it innervates. The diagram on the left shows a labelled image of the muscles and nerves (with branches). On the right we can see an image from Rohen’s where we can clearly see the hypoglossal nerve extending down and supplying these muscles.

88
Q

Eva’s tongue has deviated to the left side. A lesion of the hypoglossal nerve (CNXII) would cause the tongue to deviate to which side?

A

A lesion of CNXII would cause the tongue to deviate towards the side of the lesion.

89
Q

Which muscles of the tongue/pharynx does the hypoglossal nerve (CNXII) not innervate?

A

Palatoglossus is innervated by the vagus nerve (CNX), and geniohyoid is innervated by the C1 nerve root.

90
Q

Which foramen does the hypoglossal nerve travel through in the skull?

A

The hypoglossal nerve travels through the hypoglossal canal.

BB1 (28 decks)

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