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MD4001 > Cranial Nerves – Sensorimotor to Head and Neck > Flashcards

Cranial Nerves – Sensorimotor to Head and Neck Flashcards

1
Q

Identify all cranial nerves.

A 
Olfactory 
Optic
Oculomotor
Trochlear
Trigeminal (includes ophthalmic, maxillary, mandibular) 
Abducent
Facial 
Vestibulocochlear
Glossopharyngeal 
Vagus
Spinal accessory
Hypoglossal
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2
Q

State the function of the olfactory, optic, and oculomotor nerves.

A

Olfactory- Sensory (smell)
Optic- Sensory (vision)
Oculomotor- Motor (ciliary muscles, sphincter of pupil, all extrinsic muscles of eye except those listed for IV and VI)

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3
Q

State the function of the trochlear, triG, and Abducent nerves.

A

TROCHLEAR
Motor (Superior oblique muscle of eye)

TRIGEMINAL

  • Sensory root: Sensory (skin of face, oral, nasal and sinus mucosa, and teeth, orbital cavities, and tip of the nose and cornea of eye)
  • Motor root: Motor (muscles of mastication by V3 and 4 other muscles)

ABDUCENT
Motor (lateral rectus muscle of eye)

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4
Q

State the function of Facial, Vestibulocochlear, and Glossopharyngeal nerves.

A

FACIAL

  • Primary root: Motor (muscles of facial expression + 3 other muscles)
  • Intermediate nerve: Motor (lacrimal, nasal, palatine, submandibular, and sublingual glands) + Sensory (taste to anterior two thirds of tongue, soft palate)

VESTIBULOCOCHLEAR

  • Vestibular nerve sensory (orientation, motion)
  • Cochlear nerve sensory (hearing)

GLOSSOPHARYNGEAL

  • Motor (stylopharyngeus, PSNS efferents to parotid gland)
  • Sensory (taste fibers from posterior third of tongue + general sensation of oropharynx, tonsillar sinus, pharyngotympanic tube, middle ear cavity + visceral afferent (sensory) supply from the carotid body (chemo) and sinus (baro) for reflex cardiovascular control)
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5
Q

State the function of Vagus, Spinal accessory, and Hypoglossal.

A

VAGUS

  • Motor (PSNS efferents to heart, GI tract, lungs, airways including pharynx, larynx, trachea) + motor to palate
  • Sensory (laryngopharynx, larynx, deep auricle, parts of the external acoustic meatus, reflex sensory from tracheo-bronchial tree, lungs, heart, GI tract to L colic flexure + taste from the vallecula and epiglottis + visceral afferents from blood vessels for control of CVS)

SPINAL ACCESSORY
Motor (sternocleidomastoid and trapezius)

HYPOGLOSSAL
Motor (all intrinsic and extrinsic muscles of tongue, except palatoglossus)
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6
Q

How many modalities do the cranial nerve serve ?

A

7 modalities, each requiring nuclei (clusters of cell bodies) with associated nerve fibers (clustered in nerves or tracts)

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7
Q

Describe the general path of cranial nerves in the head.

A

Cranial nerves arise from the brain or brainstem and exit via fissures or foramina in the skull

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8
Q

How are cranial nerve nuclei arranged ?

A

The nuclei are essentially laid out from medial (basal plate near midline) to lateral (alar plate) in the brainstem:

Efferent (motor) – somatic [1], special visceral (branchial arch derived) [2], general visceral (parasympathetic) [3]

Afferent (sensory) – somatic [4], special visceral (smell and taste) [5],general visceral [6], special somatic (sight, hearing and balance) [7]

The nuclei lie sequentially, longitudinally in the midbrain, pons and medulla.

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9
Q

True or False: you will assess the sense of smell in any patient that you are seeing following a head injury.

A

True.

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10
Q

Describe the path of the olfactory nerve.

A

Olfactory tract and bulb give rise to olfactory nerves that pass through
the cribriform plate of the ethmoid where they are anchored by dura mater.

Project to the limbic system, hypothalamus and reticular formation visceral and behavioural responses to odours

The olfactory nerves are only distributed to the roof and upper aspect of the nose – septum and superior concha

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11
Q

Identify possible pathologies of the olfactory nerve, and their effects.

A

1) Olfactory neuropathy caused by upper resp. tract infection may result in anosmia (as may tumours in the ant. cranial fossa)
2) Trauma, causing the brain and olfactory bulb to move may tear the olfactory nerves to cause anosmia

3) Fractures of the cribriform plate may give CSF rhinorrhoea
(blood stained CSF leaking from nose)

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12
Q

Identify a possible therapeutic use of olfactory nerves.

A

Neuro-regenerative olfactory nerves may be harvested endoscopically, but lie close to the cranial cavity and the optic nerve.

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13
Q

Which nerve is involved in testing for facial sensation ?

A

Trigeminal nerve

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14
Q

Which nerve is involved in testing for sense of smell following head injury ?

A

Olfactory nerve

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15
Q

Where does each branch of the trigeminal nerve reside ?

A

Maxillary: roof of mouth (palate)

Mandibular: floor of mouth

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16
Q

Which nerve is responsible for the muscles of mastication ?

A

The mandibular division has the motor root to supply the muscles of mastication.

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17
Q

Describe the effect of an injury to V3.

A

Deviation to affected side if injured, because mandibular division has motor root to supply muscles of mastication.

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18
Q

Describe the common path of the trigeminal nerve.

A
  • The nerve roots of V emerge from the mid-pons and pass forwards onto the apex of the petrous temporal bone (in the middle cranial fossa), where the trigeminal ganglion (equivalent to a DRG) lies in a cave of dura mater (Meckel’s Cave) on the apex of the petrous temporal bone.
  • The mandibular (V3) division passes through the foramen ovale.
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19
Q

Which part of the neck/head is affected if all three divisions of the trigeminal nerve are affected ?

A

Lesion must be in the pons (CVA) or at the skull base (trauma, tumor)

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20
Q

Describe the path of V1 following the common path of the trigeminal nerve.

A

-V1 pass anteriorly in the lateral wall of the cavernous sinus (in the process of which V1 picks up sympathetic fibers from carotid plexus) to reach the superior orbital fissure.

  • V1 follows:
    1) lacrimal nerve to lacrimal gland, but also skin of lateral, upper eyelid, and forehead
    2) frontal nerve, dividing into supra-orbital and supra-trochlear, to supply skin of upper eyelid and forehead skin to vertex
    3) nasociliary, giving long ciliary nerve(s), ant. and post. ethmoidal nerves, before continuing as infratrochlear to skin of medial, upper eyelid and root of nose (external nasal nerve other continuation of anterior ethmoidal)
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21
Q

What nerve(s) innervate(s) the skin over the angle of the mandible ?

A

Skin over the angle of the mandible is not V, but cervical plexus – great auricular and transverse cervical

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22
Q

Identify the sensory supply of V1.

A
  • Forehead and scalp
  • Frontal, ethmoid and sphenoid sinuses
  • Upper eyelid and its conjunctiva (both on eyelid and over the cornea)
  • Cornea (through nasociliary nerve)
  • Dorsum of the nose (including tip of nose through external branch of the ant. ethmoidal branch of the nasociliary branch of V1)
  • Lacrimal gland
  • Parts of the meninges and tentorium cerebelli
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23
Q

What may shingles at the tip of the nose indicate ?

A

Shingles at the tip of the nose may be a warning that the disease will develop on the cornea (because may mean that ext. nasal branch of the ant. ethmoidal branch of the nasociliary branch of V1 is affected, and nasociliary nerve also supplies sensation to cornea of eye)

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24
Q

What nerve is the first limb of the corneal reflex ?

A

V1

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25
Q

Describe the path of V2 following the common path of the trigeminal nerve.

A

-V2 passes anteriorly in the lateral wall of the cavernous sinus to reach the foramen rotundum, which it passes through, to reach pterygopalatine fossa

-V2 divides to send zygomatic and infra-orbital branches into the orbit via the inferior orbital fissure
These pass through the orbit and emerge through bony foramina to supply skin of parts of the face.

-V2 sends palatine and alveolar branches to the palate and upper teeth

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26
Q

Identify the sensory supply of V2.

A

Skin of the:

  • Lateral forehead
  • Zygomatic region (zygomatic br.)
  • Lower lid
  • Side of nose
  • Cheek (anteriorly)
  • Upper lip (infra-orbital br.)
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27
Q

Describe the path of V3 following the common path of the trigeminal nerve.

A

The mandibular nerve exits via the foramen ovale entering the infra-temporal fossa, branching into four tributaries:

  • Auriculotemporal Nerve (receives a contribution from Glossopharyngea)
  • Inferior Alveolar Nerve
  • Buccal nerve
  • Lingual nerve
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28
Q

Identify the sensory, and motor supply of V3.

A

SENSORY
Skin of:
-Auricle and Temple (auriculotemporal n.)
-Cheek, posteriorly, or laterally (buccal br.)
-Lower lip and Chin (or mental region) (mental n.)

General sensation to:

  • Anterior 2/3 of tongue, and floor of mouth (lingual n.)
  • Lower gums and teeth (inferior alveolar n.)

MOTOR

  • Muscles of mastication (lateral pterygoid, medial pterygoid, masseter, temporalis)
  • Tensor Tympani in middle ear
  • Tensor palati (via branch to medial pterygoid)
  • Mylohyoid and anterior belly of digastric (via inferior alveolar branch)
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29
Q

Describe a pathology affecting V3. How may this happen ?

A

Trigeminal Neuralgia – terrible pain, usually in V3, occasionally V2, which may also be damaged in dental procedures.

30
Q

State the embryonic origin of the muscles supplied by V3.

A

These muscles are all 1st pharyngeal arch derivatives

31
Q

Identify a test for triG nerve.

A

Jaw jerk test

32
Q

Describe the jaw jerk, detailing the nervous pathway involved.

A

Afferent component in the stretch receptors in temporalis and masseter feed back into triG nerve nucleus (mesencephalic nucleus of TriG n) which then feeds into triG motor nucleus, into mandibular nerve to cause contraction of temporalis and masseter through efferent fibers, causing a jaw jerk.

33
Q

Describe the path of facial nerve.

A

• The nerve arises in the pons, an area of the brainstem. It begins as two roots; a large motor root (which emerges (with the nervus intermedius) in the angle between the lower pons and the cerebellum – the cerebellopontine angle), and a small sensory root.
↓
• The two roots travel through the internal acoustic meatus (with nervus intermedius, VIII and labyrinthine artery), a 1cm long opening in the petrous part of the temporal bone. Here, they are in very close proximity to the inner ear.
↓
• Still within the temporal bone, the roots leave the internal acoustic meatus, and enter into the facial canal. Within the facial canal, three important events occur:
1) Firstly the two roots fuse to form the facial nerve.
2) Next, the nerve forms the geniculate ganglion of Facial/Nervus Intermedius (cell bodies for taste fibers are here)
3) Lastly, the nerve gives rise to:
Greater petrosal nerve – parasympathetic fibres
Nerve to stapedius - motor fibres to stapedius muscle of the middle ear (the muscle that dampens the movement of the stapes)
Chorda tympani - special sensory fibers and paraysmpathetic fibers (overall, taste and secretomotor), just before the stylomastoid foramen
↓
The facial nerve then exits the facial canal (and the cranium) via the stylomastoid foramen, just posterior to the styloid process of the temporal bone, to supply facial musculature.
↓
After exiting the skull, the facial nerve turns superiorly to run just anterior to the outer ear.
↓
The first extracranial branch to arise is the posterior auricular nerve. It provides motor innervation to the some of the muscles around the ear (including occipitalis and auricular muscles). Immediately distal to this, motor branches are sent to the posterior belly of the digastric muscle and to the stylohyoid muscle. The main trunk of the nerve, now termed the motor root of the facial nerve, continues anteriorly and inferiorly into the parotid gland
↓
Within the parotid gland, the nerve terminates by splitting into five branches (superficial to the external carotid artery and retromandibular vein) (to the ipsilateral muscles of facial expression)
-Temporal branch
-Zygomatic branch
-Buccal branch
-Marginal mandibular branch
-Cervical branch
These branches are responsible for innervating the muscles of facial expression.

34
Q

Identify the sensory, and motor supply of VII.

A

Sensory: to parts of external acoustic meatus and deep auricle

Motor: muscles of facial expression

35
Q

Describe possible pathologies affecting the facial nerve.

A
  • The nerve is at risk of compression n the internal acoustic meatus– such proximal injury will affect the muscles of facial expression AND stapedius, causing hyperacusis
  • At birth, the mastoid process has not formed and VII is at risk of compression and injury in forceps delivery, leading to paralysis of the facial muscles
  • Facial nerve injury distal to the stylomastoid foramen causes ipsilateral facial muscle paralysis – but think about the affect on the eye and on the mouth/lips if their muscles are weak or paralysed (dry eye, pooling of tears, dribbling saliva etc)
  • If injury is within the petrous temporal bone, or proximal to it (Bell’s palsy, acoustic neuroma) then the above signs occur plus hyperacusis (pain on loud sounds) and taste disturbances. There may also be an affect on adjacent VIII.
  • The facial nerve and its branches are clearly at risk in surgery on the parotid gland and duct, or following facial lacerations
  • The marginal mandibular branch of VII dips inferior to the mandible and overlies the submandibular gland, consequently it is at risk in surgery on the gland. The lower lip muscles maybe paralysed causing saliva to dribble from the mouth
36
Q

State the embryonic origin of the muscles supplied by VII.

A

“All these muscles are derivatives of the second pharyngeal arch.”

37
Q

Identify what each division of the facial nerve in the parotid gland supplies.

A

Temporal to frontalis and orbicularis oculi

Zygomatic to orbicularis oculi and upper lip muscles

Buccal to buccinator (cheek) and lip muscles

Marginal mandibular to lower lip muscles

Cervical to platysma

38
Q

Describe cortical control of facial nerve nuclei, and explain the clinical relevance of this.

A

Bilateral for upper half of face (both R and L side of the brain, therefore upper facial sparing in CVA, upper motor neurone (UMN).

Contralateral for lower half, therefore contralateral weakness or paralysis of lower face in CVA (upper motor neurone).

Lower motor neurone (LMN) lesion – weak or paralysed whole ipsi-lateral half (Bell’s Palsy)

Refer to diagram on slide 25 for further information.

39
Q

Describe the neural pathways behind the corneal reflex.

A

Afferent supply from V (cornea supplied by branch of V1), to the trigeminal nucleus, which then feeds into facial motor nucleus, into efferent from VII (muscles of eyelid cause us to blink)

40
Q

Describe the path of the abducent nerve.

A

Passes upwards on the clivus

41
Q

Describe the path of the oculomotor nerve.

A

Initially just superior and immediately adjacent to the tentorium cerebelli

42
Q

Describe the path of the trochlear nerve.

A

Trochlear (IV), very thin and entering the edge of the tentorium

43
Q

Identify pathologies, affecting the abducens nerve, and the result of an injury to CNVI.

A

May be stretched in increased ICP.

Injury to right CNVI would cause non-synchronous movements when looking right, leading to double vision, diplopia (right eye would not abduct fully), and vice versa.

44
Q

Identify pathologies affecting the oculomotor nerve, and the result of an injury to CNIII.

A
  • May be compressed in increased ICP
  • May be compressed in aneurysms of posterior cerebral, superior cerebellar branches of the circle of Willis, or the posterior communicating artery. Because Oculomotor (III) passes between the posterior cerebral and superior cerebellar branches of the circle of Willis, before lying close to the posterior communicating artery.

Injury to the oculomotor paralyses most of the muscles that move the eye, and that raise the upper eye lid.

45
Q

Describe the motor supply of CNIII.

A

The oculomotor (III) supplies most of the muscles that move the eye, as well as raising the upper eye lid.

  • Levator palpebrae superioris
  • Superior rectus
  • Medial rectus
  • Inferior rectus
  • Inferior oblique
46
Q

To what extent can we move our eyes, following a lesion to the oculomotor nerve ?

A

We can turn the eye downwards (superior oblique supplied by trochlear), and laterally (lateral rectus supplied by abducens), while the upper eye droops (ptosis)

47
Q

Describe the motor supply the CNVI.

A

Lateral rectus (abducts the eye)

48
Q

Describe the motor supply the CNIV.

A

Superior Oblique

49
Q

Describe the result of an injury to CNIV.

A

Injury to IV means that the patient cannot look medially and inferiorly (since trochlear supplies superior oblique)– struggle (diplopia) to walk downstairs or read a book

50
Q

How may we clinically test the nerves and muscles supplying the eye ?

A

Clinically, the “H” test assesses all movements of the eyes, and therefore all muscles and their nerves

51
Q

Describe the modalities and structures supplied by CNXI.

A

XI Accessory – often referred to as the spinal root as it is actually derived from C 1 to 5; it supplies Sternocleidomastoid and Trapezius.

52
Q

Describe the path of CNXI.

A
  • Once formed, the accessory passes up through the foramen magnum, and then through posterior cranial fossa and back out of the skull via the jugular foramen.
  • Outside the cranium, the spinal root of XI descends along the internal carotid artery to reach the sternocleidomastoid muscle, the deep surface of which it enters.
  • It then crosses the posterior triangle of the neck in the investing layer of fascia and surrounded by lymph nodes, to supply motor fibres to the trapezius.
53
Q

What is the clinincal significance of the accessory nerve being surrounded by lymph nodes as it joins the trapezius ?

A

Carcinoma of tongue can spread of those lymph nodes and affect accessory nerve

54
Q

Describe the path of CNXII.

A
  • XII Hypoglossal exits the cranium via hypoglossal (ant.condylar) canal.
  • Descends the neck, passing lateral to both the internal and external carotid arteries and associated with a loop of Cx nerves that supply the strap muscles of the neck
  • Enters oral cavity under the tongue, between mylohyoid and hyoglossus to supply all the tongue muscles except one
55
Q

Describe effects of lesion to CNXII.

A

If hypoglossal nerve injured, ipsilateral tongue weakness, therefore it deviates to the side of the lesion

56
Q

Identify the structures innervated by Hypoglossal n.

A

i) Extrinsic muscles

Genioglossus (makes up the bulk of the tongue)
Hyoglossus
Styloglossus
NOT Palatoglossus (innervated by vagus nerve via pharyngeal plexus)

ii) Intrinsic muscles
Superior longitudinal
Inferior longitudinal
Transverse
Vertical
57
Q

Summarize the nerve supply to the tongue.

A

SENSATION

  • Ant 2/3 is via lingual (V3) for general sensation, with taste from facial (VII, Nervus Intermedius), “which leave the tongue as a part of the lingual nerve, but at the infratemporal fossa they join the chorda tympani”
  • Post 1/3 glossopharyngeal (IX) for both general sensation and taste

MOTOR
-Hypoglossal (XII) to all muscles, except palatoglossus, which is Vagus (X) via the pharyngeal plexus

58
Q

Describe the neural pathways behind the gag reflex.

A

Glossopharyngeal nerve (sensory for posterior 1/3 of tongue) afferents, into nucleus solitaris, which feeds into nucleus ambiguus (both in the brainstem), which sends vagus efferents to either cause relaxation (for swallowing) or contraction (gag reflex).

59
Q

Describe the sensory nerve supply of the pharynx.

A

Nasopharynx – Maxillary (V2)

Oropharynx, palatine tonsil, inferior aspect of soft palate and posterior 1/3 tongue – Glossopharyngeal (IX)
(Referred pain to middle ear)

Laryngopharynx, vallecula and epiglottis - Vagus (X)

Soft palate is a combination of V2 and IX

60
Q

Where might problems with oropharynx and tonsils refer pain ?

A

Middle ear (all supplied by glossopharyngeal n.)

61
Q

Which foramen does IX leave the cranium through ?

A

Emerges from jugular foramen with X and XI (and internal jugular vein)

62
Q

Identify the main branches of CNIX. What does this supply ?

A

Tympanic branch of IX to middle ear, tympanic membrane and mastoid air cells

63
Q

Which nerve damage can affect swallowing and gag reflex ?

A

Defects in IX and X affect swallowing and the gag reflex

64
Q

State the embryonic origin of the striated muscles of the pharynx and larynx. How are they supplied ?

A

Motor supply to the striated muscles of the pharynx and larynx is by Vagus and Cranial component of Accessory n.

Derived from 4th and 6th pharyngeal arches

65
Q

Identify the contents of the carotid canal.

A

Internal carotid artery

Sympathetic plexus

66
Q

Identify the main branches of the vagus nerve in the head, and neck.

A

HEAD
-auricular branch

NECK

  • Pharyngeal branches
  • Superior laryngeal nerve
  • Recurrent laryngeal nerve (right side only)
67
Q

What is the function of the ganglionic swellings on IX and X ?

A

The ganglionic swellings on IX and X house the cell bodies of 1y sensory neurones, like the trigeminal ganglion or dorsal root ganglia.

68
Q

Describe the path of the greater petrosal nerve.

A

Given rise to by the facial nerve.

Escapes from the middle ear and lies on the surface of the petrous temporal bone in the middle cranial fossa

Passes through the foramen lacerum and heads towards the pterygoid canal, then “synapses at the pterygopalatine ganglion.” and goes on to supply lacrimal gland.

69
Q

Describe the general general distribution of the maxillary division (V2) and the pterygopalatine ganglion.

A

Orbit – Lacrimal Gland (also via V1); Maxilla – sinus, upper teeth and gums (superior alveolar branches), and palate; Nasal Cavity via sphenopalatine foramen; Nasopharynx

70
Q

How far down the GI tract does the vagus nerve give parasympathetic motor supply to ?

A

As far as 2/3 along the transverse colon

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