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ESA 4 > Head And Neck Week 4 > Flashcards

Head And Neck Week 4 Flashcards

1
Q

How many cranial nerves are there?

A

12

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2
Q

Which cranial nerves are atypical?

A

CNI and CNII

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3
Q

What makes the olfactory and optic nerves atypical cranial nerves?

A

They are part of the central nervous system

Outgrowths of the brain

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4
Q

What is the clinical relevance of the atypical cranial nerves?

A

They do not regenerate when cut

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5
Q

Which cranial nerves are mixed motor and sensory?

A

Trigeminal (CN V)
Facial (CN VII)
Glossopharyngeal (CN IX)
Vagus (CN X)

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6
Q

Which nerves are purely sensory?

A

Olfactory (CN I) - smell
Optic (CN II) - vision
Vestibulocochlear (CN VIII) - hearing and balance
(Special sensory function as opposed to general sensation)

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7
Q

The special sense taste is carried in which nerves?

A

Facial (CN VII)

Glossopharyngeal (CN IX)

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8
Q

Which five cranial nerves are purely motor?

A 
Oculomotor (CN III)
Trochlear (CN IV)
Abducent (CN VI)
Accessory (CN XI)
Hypoglossal (CN XII)
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9
Q

Which cranial nerves carry efferent autonomic fibres?

A

Oculomotor (CN III)
Facial (CN VII)
Glossopharyngeal (CN IX)
Vagus (CN X)

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10
Q

What is unique about CNI?

A

The only nerve to enter the cerebrum directly

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11
Q

What is the cranial nerve exit foramen of CNI?

A

Cribriform/olfactory foramina of cribriform plate of ethmoid bone

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12
Q

Describe the course of CNI

A

Olfactory receptor neurones found in roof of nasal cavity, nasal septum and medial wall of superior nasal concha
On either side of the nasal septum, receptor neurones pass through cribriform plate by forming 20 olfactory nerves
Reach the olfactory bulb found on orbital surface of frontal lobe, within the anterior cranial fossa
Synapse onto mitral and tufted cells at the glomerulus of the olfactory bulb –> form the olfactory tract
Forms the anterior olfactory nucleus along its route
Which forms medial (passes to the contralateral olfactory bulb and cortex) and lateral striae (projects to primary olfactory cortex)

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13
Q

What is the function of CN I?

A

Smell

Modality - Special visceral sensory - derived from endoderm (taste)

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14
Q

How would you test the olfactory nerve?

A

Enquire about sense of smell, taste (smell is important in detecting flavour)
Use smelling salts
Patients with unilateral anosmia are usually unaware of their condition due to the contralateral nostril compensating - -> each nostril must be tested individually

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15
Q

What is the differential diagnosis of anosmia?

A

Head trauma - cribriform plate
Viruses - damage olfactory neuroepithelium
Obstruction
Parkinson’s/Alzheimer’s - damage to anterior olfactory nucleus
Intracranial lesions of frontal lobe- e.g. meningioma, metastases, meningitis, sarcoidosis - may produce no symptom other than anosmia
Temporal lobe epilepsy - olfactory hallucination due to irritation of lateral olfactory area

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16
Q

What is unique about CNII?

A

It is covered with meninges

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17
Q

What is the cranial nerve exit foramen of the optic nerve?

A

Optic canal

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18
Q

What is the function of CNII?

A

Vision

Modality - Special somatic sensory - derived from ectoderm (sight, sound, balance)

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19
Q

Describe the course of CNII

A

Begins where the unmyelinated axons of retinal ganglion cells pierce the sclera, forming the optic disc
These nerves enter the middle cranial fossa by exiting the optic canal posteromedially
Optic chiasm is formed - decussation occurs - nasal fibres of the retina cross to join the uncrossed temporal fibres –> forming the optic tract
Most fibres terminate in the lateral geniculate body of the thalamus –> where the axons pass to the occipital cortex
Some fibres enter pre-tectal nucleus - act as the afferent limb of pupillary light reflex, control eye movements
Some fibres enter suprachiasmatic nucleus - circadian rhythm

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20
Q

Describe how to test optic nerve function

A

Acuity - Snellen charts - with and without their vision aids
Colour - Ishihara plates
Visual fields - get the patient to look directly at you whilst wiggling one of your fingers in each of the four quadrants - ask patient to identify which finger is moving - visual inattention can be tested by moving both at the same time and checking the patient identifies this
Visual reflexes - block any let from entering the contralateral eye and shine a pen torch into one eye - check the pupils on both sides constrict - repeat on other side
Fundoscopy

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21
Q

What are the differential diagnoses of CNII dysfunction ?

A

Optic neuritis - Multiple sclerosis (spares the PNS but affects CNS), toxic substances such as alcohol, inflammatory disorders - loss of acuity, peripheral vision
Lesions along the length of visual pathway - berry aneurysm, pituitary gland tumour - visual field defect
TIA - occlusion of retinal artery - loss of vision in one eye for brief period of time - marker of impending retinal or cerebral infarct

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22
Q

What is the cranial nerve exit foramen of the oculomotor nerve?

A

Superior orbital fissure

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23
Q

Describe the course of CN III

A

Leaves the midbrain between posterior cerebral and superior cerebellar arteries
Pierces sellar diaphragm over the hypophysis
Upon piercing cavernous sinus - enters superior orbital fissure
Forms the superior (innervates superior rectus and levator palpebrae superioris) and inferior divisions (innervates inferior and medial rectus and inferior oblique)
Within inferior division - ciliary ganglion - parasympathetic fibres - short ciliary nerves innervate ciliary body and sphincter pupillae - efferent motor limb of pupillary light reflex (constriction)

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24
Q

How can the oculomotor nerve be tested?

A

Stand directly in front of the patient
Ask them to keep their head perfectly still
Draw two large joining H’s in front of them using your finger and ask them to follow your finger with their eyes
Ask if experiences any double vision and if so when it is worse

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25
Q

What is the function of CN III?

A

Innervates 4/6 of the extra-orbital muscles (superior, medial and inferior rectus muscles and inferior oblique) and levator palpebrae superioris - modality - general somatic motor (skeletal muscles)
Innervates the pupillary sphincter - parasympathetic efferent motor limb - constriction - modality - general visceral motor (smooth muscles of gut and autonomic motor)

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26
Q

What is the differential diagnosis of CN III dysfunction?

A

Aneurysms in the superior cerebellar, posterior cerebral and posterior communicating artery - parasympathetics more likely to be compressed due to being more medial and superficial
Fracture of the cavernous sinus
Herniating uncus
Cavernous sinus thrombosis
Diabetes/hypertension (pupil-sparing)
Raised intracranial pressure (tumour/haemorrhage)

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27
Q

What are the signs and symptoms of CN III dysfunction?

A

Diplopia (double vision)
Eyes in down and out position because CN IV and VI still working
Ptosis (levator palpebrae superioris)
+/- pupil dilation and loss of reflex (compressive lesions cause pupil dilation, vascular lesions spare the pupil)

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28
Q

What makes CN IV unique?

A

The only cranial nerve to arise from the dorsal aspect of the brainstem
Has the longest intracranial course of all CNs

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29
Q

What cranial nerve exit foramen does CN IV pass through?

A

Superior orbital fissure

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30
Q

What is the function of the trochlear nerve?

A

Innervates the superior oblique

Modality - General somatic motor (skeletal muscle)

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31
Q

Describe the course of CN IV

A

Arises from dorsal brainstem (midbrain)
Loops around brainstem and passes anteriorly within the subarachnoid space
Passes between superior cerebellar and posterior cerebral arteries (like CN III)
Pierces the dura at the tentorium cerebelli - into cavernous sinus - enters superior orbital fissure

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32
Q

How is CNIV tested?

A

Same as CN III and CN VI
Test eye movements by asking to keep head still and follow your finger with their eyes - move finger in two large joining H’s

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33
Q

What are the signs and symptoms of CN IV dysfunction ?

A

Vertical diplopia - worsens when patient looks down and medially
Unopposed inferior oblique can cause eye to drift upward (extorsion)
Rare and subtle - can be corrected with slight tilt of head

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34
Q

What is the differential diagnosis of trochlear nerve dysfunction?

A 
Any raised ICP - susceptible to cerebellar tumour compression due to wrapping around brainstem 
Head injuries most common acute injury- easily damaged by shear injury of head trauma due to being thin and having long intracranial course
Congenital palsies (children)
35
Q

What are the cranial nerve exit foramina of CN V?

A

V1 - ophthalmic nerve - superior orbital fissure
V2 - maxillary nerve - foramen rotundum
V3 - mandibular nerve - foramen ovale

36
Q

What makes the trigeminal nerve unique?

A

Largest cranial nerve

Divides into three nerves

37
Q

What are the functions of the trigeminal nerve?

A

V1 - scalp, forehead, nose - modality - general somatic sensory
V2 - cheeks, lower eyelid, nasal mucosa, upper lip, upper teeth, palate - modality - general sensory somatic
V3 - anterior 2/3 of tongue, skin over mandible, lower teeth - modality - general somatic sensory
- muscles of mastication - modality - special visceral motor - derived from pharyngeal arches

Note - post-ganglionic neurones of parasympathetic ganglia travel with branches of the trigeminal nerve but it is not part of the cranial outflow of PNS supply

38
Q

Describe the course of CN V

A

Originates from 3 sensory and 1 motor nucleus - extending from midbrain to medulla
At the pons - sensory nuclei form a sensory root and motor nucleus forms motor root (analogous to dorsal and ventral roots of spinal cord)
Middle cranial fossa - sensory rot expands into trigeminal ganglion - located lateral to the cavernous sinus, in a depression of the temporal bone (trigeminal or Meckel’s cave)
Divides into v1, v2, v3
Motor root passes inferiorly to sensory root along the floor of trigeminal cave - fibres only distributed to v3
V1 and v2 travel lateral to cavernous sinus and exit via their foramina
V3 exits via foramen ovale and into the infratemporal fossa

39
Q

What is the difference between a nucleus and a ganglion?

A

Nucleus is a collection of nerve cell bodies within the CNS

Ganglion is a collection of nerve cell bodies outside the CNS

40
Q

How can you test the trigeminal nerve?

A

Test the sensory branches by touching the face with a piece of cotton wool and then a blunt pin on each side of the face at the:
- jawline
- cheek
- forehead
The corneal reflex should be examined (sensory supply from cornea is via the ophthalmic, motor via facial nerve) - lightly touch the cornea with cotton wool - patient should close their eyelids
Motor - ask the patient to clench teeth together, observe and feel the bulk of masseter and temporalis
- ask to open mouth against resistance
- open mouth and move jaw left to right to test pterygoid muscles
- jaw jerk - left index finger on chin and strike with a tendon hammer - should cause slight protrusion of the jaw

41
Q

What is the differential diagnosis of trigeminal nerve dysfunction?

A

Trigeminal neuralgia - distribution of v2 and v3 - normally idiopathic - MRI to check for tumours and lesions
Vulnerable to MS because part of trigeminal nerve enters the spinal cord –> can cause neuralgia
Herpes zoster, metastatic disease, trauma and aneurysms of the petrous portion of the internal carotid can all lead to CNV damage

42
Q

What is the cranial nerve exit foramen of CN VI?

A

Superior orbital foramen

43
Q

Describe the course of CN VI

A

Leaves the pontomedullary junction of the pons
Fibres travel within subarachnoid space between pons and clivus, straddling the basilar artery
Exits the dura, enters dorello’s canal -runs between skull and dura
Makes a sharp bend as passes over petrous bone tip to enter cavernous sinus
Enter superior orbital fissure
Innervates the lateral rectus

44
Q

What is the function of the abducens nerve?

A

Innervates the lateral rectus (extraorbital muscle) - abducts/moves eyeball away from midline
Modality - general somatic motor (skeletal muscle)

45
Q

How can we test the abducens nerve?

A

Same as oculomotor and trochlear
Ask patient to follow your finger with their eyes, keeping their head still, whilst drawing two joining H’s in front of them with your index finger
Ask about double vision, blurriness

46
Q

What is the differential diagnosis of CN VI dysfunction?

A

Any pathology leading to downward pressure on the brainstem - stretches nerve along clivus of skull - hydrocephalus, tumour, basilar artery aneurysm, intracranial lesions, rarely Wernicke-Korsakoff syndrome (thiamine deficiency mainly in alcoholics)
Diabetes - microvascular complications and Thrombophlebitis of cavernous sinus - CN VI damage rarely seen in isolation

47
Q

What are the signs and symptoms of CN VI dysfunction?

A

Horizontal diplopia
Medially rotated eye - cannot be abducted past the midline
Patient may attempt to compensate by rotating head to allow eye to look sideways

48
Q

What is the cranial nerve exit foramen of CN VII?

A

Stylomastoid foramen

49
Q

Describe the course of the facial nerve

A

Leaves the pontomedullary junction ventrally as a large motor root and small sensory root- adjacent to abducens nerve
Traverses subarachnoid space - enters internal acoustic meatus within petrous part of temporal bone
Enters facial canal
The two roots fuse to form the facial nerve, forms the geniculate ganglion, gives rise to the greater petrosal nerve, nerve to strapedius and the chorda tympani
Sharp bend - nerve travels inferiorly past middle ear- exits via stylomastoid foramen
After exiting skull runs superiorly anterior to outer ear
Gives off motor branches - posterior auricular nerve, nerve to posterior belly of digastric, nerve to stylohiod
Motor root of the facial nerve passes through the parotid gland - within which splits into 5 terminal branches which innervate muscles of facial expression:
-temporal
-zygomatic
-buccal
-mandibular
-cervical
Parasympathetics carried by the geniculate ganglion along the greater petrosal nerve - enter middle cranial fossa - travels across foramen lacerum - combines with deep petrosal nerve - forms nerve of the pterygoid canal - passes through pterygoid canal - enters pterygopalatine fossa - synapse with pterygopalatine/sphenopalatine ganglion - stimulate the lacrimal glands and mucosal glands of oral cavity, nose and pharynx
Chorda tympani travels across bones of middle ear - exits via petrotympanic fissure - enters infratemporal fossa - hitchhikes with the lingual nerve - parasympathetic fibres stay with lingual nerve forming submandibular ganglion - innervate submandibular and sublingual salivary glands
main body of chorda tympani leaves to provide sensory innervation to anterior 2/3 of tongue

50
Q

What is the function of the facial nerve?

A

Sensation to part of external ear - modality - general somatic sensory
Taste from anterior 2/3 of tongue, hard and soft palate - modality - special visceral sensory
Muscles of facial expression - modality - special visceral motor (derived from second pharyngeal arch)
Lacrimal, submandibular, sublingual and mucosal glands of nose, oral cavity and pharynx - modality - general visceral motor (parasympathetic)

51
Q

How can CN VII be tested?

A

Motor - facial expression - crease up forehead, close eyes, keep eyes closed against resistance, puff out cheeks, reveal teeth (smile)
Sensory - not formally tested

52
Q

What is the differential diagnosis of CN VII dysfunction ?

A

CNVII is the most frequently damaged cranial nerve

Intracranial (proximal to stylomastoid foramen) lesion causes:
- Middle ear pathology - tumour or infection
- Idiopathic - Bell’s palsy
Extracranial lesion causes :
- Trauma - e.g. Compression during forceps delivery due to underdeveloped mastoid process in neonates
- Parotid gland pathology - tumour, parotitis, surgery
- Infection of nerve- herpes virus
- Idiopathic - Bell’s palsy

53
Q

What are the signs and symptoms of facial nerve dysfunction?

A

UMN v.s. LMN - forehead muscles spared in UMN lesion due to bilateral cortices contributing to muscles of forehead - UMN causes contralateral facial weakness
LMN lesion - ipsilateral facial weakness - forehead not spared - Bell’s palsy
Intracranial lesions (proximal to stylomastoid foramen) - muscles of facial expression weakened +/- (chorda tympani) reduced salivation + loss of taste on ipsilateral anterior 2/3 of tongue, (nerve to strapedius) ipsilateral hyperacusis, (greater petrosal nerve) ipsilateral dry eye due to reduced lacrimal fluid
Extracranial - only motor affected (facial expression)

54
Q

What is the cranial nerve exit foramen of CN VIII?

A

Internal acoustic meatus

55
Q

Describe the course of the vestibulocochlear nerve

A

Vestibular component arises from Vestibular nuclei complex in pons and medulla
Cochlear component arises from ventral and dorsal cochlear nuclei in inferior cerebellar peduncle
Combine in pons to form vestibulocochlear nerve - emerges from cerebellopontine angle - pontomedullary junction - lateral to facial nerve
Enters internal acoustic meatus with facial nerve and labyrinthine artery
In the auditory canal splits into vestibular and cochlear nerves
Vestibular nerve - formed of vestibular ganglion - innervates vestibular system of inner ear - detects balance
Cochlear nerve - formed of spiral ganglion - extends around cochlea of inner ear to sense sound

56
Q

What is the function of CN VIII?

A

Hearing and balance

Modality - special somatic sensory (derived from ectoderm)

57
Q

How can CN VIII be tested?

A

Differentiate between conductive and sensory-neural hearing loss using :
Rinne test- sounding tuning fork placed on mastoid process and then next to their ear and asked which is louder - normal patient finds second sound louder
Weber test - place tuning fork base down in centre of patients forehead - ask if louder in either ear - normally heard equally in both ears

58
Q

What is the differential diagnosis of CN VIII dysfunction?

A

Trauma - basilar skull fracture
Acoustic neuroma
Labrynthitis
Vestibular neuritis - herpes simplex

59
Q

What are the signs and symptoms of vestibulocochlear nerve damage?

A

Hearing loss - have to differentiate between conductive (problem with bone conduction) and sensorineural (nerve damage) using the tests
Vestibular neuritis - vertigo, nystagmus, loss of equilibrium (especially in low light), nausea and vomiting
Labrynthitis - same as vestibular neuritis but also include signs of cochlear nerve damage - sensorineural hearing loss, tinnitus
Acoustic neuromas - loss of hearing, disequilibrium, tinnitus - also due to position of CNV and CNVII - facial pain, sensory loss, weakness

60
Q

What is the cranial nerve exit foramen of CN IX?

A

Jugular foramen

61
Q

Describe the course of the glossopharyngeal nerve

A

Leaves the ventrolateral medulla below CNVIII
Moves laterally in the posterior cranial fossa
Leaves the cranium via the jugular foramen
The tympanic nerve arises here - penetrates the temporal bone - enters middle ear
-forms tympanic plexus - sensory - middle ear, internal surface of tympanic membrane, Eustachian tube
-parasympathetic fibres leave tympanic nerve in the middle ear to join the lesser petrosal and then to synapse with the otic ganglion (CNV3) - hitchhike on the auriculotemporal nerve - innervate parotid gland
Exiting the jugular foramen it forms the superior and inferior ganglia - contain the cell bodies of sensory fibres
Descends down the neck anterolateral to internal carotid artery
Gives motor innervation to stylopharyngeus muscle
Gives rise to carotid sinus nerve - provides innervation to carotid sinus and body
Enters the pharynx by passing between superior and middle pharyngeal constrictors
Terminates - dividing into pharyngeal, lingual and tonsil branches
Pharyngeal branch combines with fibres of vagus nerve to form pharyngeal plexus - innervate mucosa of oropharynx
Lingual branch - provides posterior 1/3 of tongues with general taste and sensation
Tonsillar branch - tonsillar plexus - palatine tonsils

62
Q

What is the function of CN IX?

A

post. 1/3 tongue, ext. ear, and middle ear cavity. - modality - general somatic sensory
carotid body and sinus - modality - general visceral sensory
taste from post. 1/3 tongue - modality - special visceral sensory (derived from endoderm)
parotid gland - modality - general visceral motor (parasympathetic)
stylopharyngeus - shortens and widens the pharynx, elevates the larynx during swallowing - special visceral motor (from pharyngeal arch)

63
Q

How can the glossopharyngeal nerve be tested?

A

Gag reflex
Touching arches of the pharynx
Taste not formally tested
Tested with CN X

64
Q

What is the differential diagnosis of CN IX dysfunction?

A 
Isolated lesions uncommon
Tumour
Infection
Trauma
In region of jugular foramen - affects CNIX, X and XI - Jugular foramen syndrome
65
Q

What are the signs and symptoms of CN IX damage?

A

Absence of gag reflex (sensory portion - vagus is the motor portion) (but 25% of population have absence normally so not alone diagnostic)
Taste absent on posterior 1/3 of tongue
Glossopharyngeal neuralgia - throat, ear - worsens during eating - initiated by swallowing

66
Q

What is the cranial nerve exit foramen of CN X?

A

Jugular foramen

67
Q

Describe the course of the vagus nerve

A

Leaves the ventrolateral medulla as several rootlets
Exits the cranium through jugular foramen between CNIX and CNXI
Auricular branch arises in cranium - supplies sensation to posterior external auditory canal and external ear
Upon exiting forms two ganglia:
-superior ganglion - synapses with CN IX and superior cervical ganglion - general sensation
-inferior ganglion - taste and chemoreceptors of aortic arch
Nerve travels in the carotid sheath
Pharyngeal branch arises - motor innervation to majority of muscles of pharynx and soft palate
Superior laryngeal branch arises - splits into internal and external branch - external branch innervates cricothyroid muscle of larynx - internal branch provides sensation to laryngopharynx and superior larynx
Recurrent laryngeal branch arises- right side hooks under right subclavian artery and back up to larynx - innervates most intrinsic muscles of larynx
Right vagus passes anterior to subclavian artery and posterior to sternoclavicular joint to enter thorax - forms posterior vagal trunk
Left vagus passes inferiorly between left common carotid and left subclavian posterior to sternoclavicular joint, entering thorax - forms anterior vagal trunk
Branches form oesophageal plexus - innervate smooth muscle of oesophagus
Left recurrent laryngeal branch arises - hooks under arch of aorta in thorax - both innervate most of intrinsic muscles of larynx
Cardiac branches arise - regulate heart rate and provide visceral sensation to the organ
Vagal trunks enter abdomen through oesophageal hiatus
Terminate by dividing into oesophageal, stomach and small and large bowel (up to splenic flexure) branches

68
Q

What is unique about the vagus nerve?

A

Longest course of all cranial nerves - head to abdomen - extensive distribution - Latin for wanderer

69
Q

What is the function of the vagus nerve?

A

External ear, larynx and pharynx - modality - general somatic sensory
Larynx, pharynx and thoracic and abdominal viscera - modality - general visceral sensory
Taste from epiglottis region of tongue - modality - special visceral sensory (endoderm)
Smooth muscle of pharynx, larynx, most of the GIT, heart - modality - general visceral motor (parasympathetic)
Most muscles of pharynx and larynx - modality - special visceral motor (pharyngeal arches)

70
Q

How can CN X be tested?

A 
Ask the patient to speak
Uvula observed during patient saying "aaah" - lies centrally and does not deviate on movement
Gag reflex (Efferent limb)
Cough (intrinsic laryngeal muscles)
Swallow
71
Q

What is the differential diagnosis of vagus nerve dysfunction?

A

Isolated lesions very uncommon
As result of surgery - both recurrent laryngeal nerves
Cancer of larynx or thyroid gland - both recurrent laryngeal nerves
Patent ductus arteriosus - left recurrent laryngeal
Aortic aneurysm - left recurrent laryngeal
Lung cancer - Recurrent laryngeal
Trauma
Parkinson’s
MS
Infarcts
Cerebellar/brainstem lesion
Alcohol

72
Q

What are the signs and symptoms of CN X damage?

A

Dysphagia- pharyngeal branch
Dysphonia - hoarse voice - one sided recurrent laryngeal nerve damage
Aphonia and stridor - damage to both recurrent laryngeal nerves
Gravelly voice - Parkinson’s disease - interference of basal ganglia dysfunction with articulation
Dysphagia and dysarthria occur together - MS, infarct, cerebellar/brainstem lesion, alcohol
Aspiration pneumonia as complication of dysphagia
Uvula deviation away from affected side
Lack of gag reflex
Tachycardia - due to lack of parasympathetic innervation

73
Q

What is the cranial nerve exit foramen of CN XI?

A

Jugular foramen (but enters through foramen magnum)

74
Q

Describe the course of the accessory nerve

A

Arises from neurones of C1-C5
Rootlets coalesce after leaving the spinal accessory nuclei between dorsal and ventral nerve roots and ascend through foramen magnum
Traverses the posterior cranial fossa
Exits via jugular foramen alongside internal carotid artery, CN IX and CN X
Descends alongside internal carotid artery - superficially - between investing and pre-vertebral layers of fascia
Innervates sternocleidomastoid
Moves across posterior triangle of neck to innervate trapezius
Briefly meets the cranial portion of the accessory nerve (From the medulla ) but this leaves immediately and joins CN X at the inferior ganglion to form the recurrent laryngeal nerve - functionally considered part of the vagus nerve

75
Q

How can the accessory nerve be tested?

A

Ask patient to shrug shoulders and turn their head against resistance
Feel SCM when turning head as other neck muscles will compensate

76
Q

What is the differential diagnosis of CN XI dysfunction?

A

Iatrogenic - cervical lymph node biopsy, cannulation of IJV, carotid endarterectomy
Trauma - stab wound to posterior triangle

77
Q

What are the signs and symptoms of CN XI damage?

A

Muscles wasting of SCM and trapezius - asymmetrical neckline - longstanding nerve damage
Weakness of SCM and trapezius (shrugging and turning head)

78
Q

What is the function of the accessory nerve?

A

Motor innervation of trapezius and SCM - modality - general somatic motor
Cranial accessory nerve - runs with CN X - pharynx and larynx - modality - special visceral motor (pharyngeal arch)

79
Q

What is the cranial exit foramen of CN XII?

A

Hypoglossal canal

80
Q

What is the function of the hypoglossal nerve?

A

Intrinsic and extrinsic tongue muscles (except palatoglossus) - modality - general somatic motor

81
Q

How can CN XII be tested?

A

Observe tongue for signs of wasting or fasciculations
Ask patient to tick tongue out - if deviates to one side suggests weakness of ipsilateral side - LMN damage causes ipsilateral weakness/wasting, UMN damage causes contralateral weakness/wasting
Can also ask patient to push tongue against each cheek and feel for pressure on the external surface of their cheek

82
Q

Describe the course of the hypoglossal nerve

A

Arises from hypoglossal nucleus in medulla oblongata
Passes laterally across posterior cranial fossa
Exits via hypoglossal canal
Receives a branch of the cervical plexus - conducts fibres from c1-2 nerve roots - do not combine - merely travel in sheath
PAsses inferiorly to angle of mandible
Crosses external and internal carotid arteries
Moves in anterior direction to supply the tongue

83
Q

What is the differential diagnosis of CN XII dysfunction?

A

Uncommon
Tumours
Penetrating traumatic injury
Dissection of internal carotid artery

84
Q

What are the signs and symptoms of hypoglossal nerve damage?

A

Tongue muscle wasting, fasiculations (twitching of isolated muscle fibre groups)
Tongue deviates to side of weakness upon protrusion
Acute pain –> internal carotid dissection
UMN lesion causes contralateral weakness and wasting where as LMN lesion causes ipsilateral weakness and wasting

ESA 4 (28 decks)

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