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Neuroanatomy and Clinical Neurology > Cranial Nerves 7-12 > Flashcards

Cranial Nerves 7-12 Flashcards

1
Q

What is cranial nerve 7?

A

Facial nerve

Large motor root supplies muscles of facial expression, arise from facial nerve proper/principle/brachial nucleus – lower pons

Smaller sensory root (intermediate nerve) carries taste, parasympathetic and somatic sensory fibres

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2
Q

What are the functions of cranial nerve 7?

A

Motor to muscles of facial expression, posterior belly of diagastric, stylohyoid and stapedius

General sensation around external acoustic meatus
Taste from anterior 2/3 of tongue and soft palate
Parasympathetic to submandibular gland, sublingual salivary glands, lacrimal gland, and glands of nasal cavity and palate

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3
Q

What is the main motor nucleus of cranial nerve 7?

A

In reticular formation of the lower pons

Medial half of the nucleus supplies the muscles of the upper part of the face. Receives corticonuclear fibres from both cerebral hemispheres.

Lateral half of the nucleus supplies the muscles of the lower half of the face
Receives only corticonuclear fibres from the opposite cerebral hemisphere.

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4
Q

What is the Sensory (Solitary) Nucleus if cranial nerve 7?

A

Lies close to motor nucleus in medulla
Receives taste fibres from geniculate ganglion

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5
Q

Where is the Parasympathetic Nuclei of cranial nerve 7?

A

Lie posterolateral to main motor nucleus

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6
Q

What is the Superior salivatory nucleus of cranial nerve 7?

A

Receives afferent fibres from the hypothalamus through the descending autonomic pathways
Superior salivatory nucleus is the motor component of the greater petrosal and chorda tympani nerves

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7
Q

What is the Lacrimal nucleus of cranial nerve 7?

A

Lacrimal nucleus receives afferent fibres from the hypothalamus for emotional responses
Receives afferent fibres from the trigeminal nerve for reflex lacrimation secondary to irritation of the cornea or conjunctiva

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8
Q

What is the Intracranial Course and Relations of cranial nerve 7?

A

Two roots of CN VII emerge from junction of pons and medulla  both roots pass laterally and forward with CN VIII  enter internal acoustic meatus  pass laterally through inner ear

At lateral extremity of meatus, both parts of CN VII turn posteriorly to enter facial canal and gives a branch to stapedius muscle

On reaching the medial wall of the tympanic cavity, the nerve expands to form the sensory geniculate ganglion

The nerve then turns sharply downwards and laterally to exit the skull through the stylomastoid foramen

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9
Q

What is Greater Petrosal Nerve of cranial nerve 7?

A

Arises at geniculate ganglion
Efferents from superior salivatory nucleus  pterygopalatine ganglion  postganglionic fibres to lacrimal and nasal glands
Afferents from palate to geniculate ganglion, which has central projections to sensory nucleus of CN VII

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10
Q

What is Chorda Tympani Nerve of cranial nerve 7?

A

Arises before CN VII emerges from stylomastoid foramen
Passes anteriorly across tympanic membrane to lingual nerve (CNV3) in infratemporal fossa
Efferents from superior salivatory nucleus  submandibular ganglion  postganglionic fibres to submandibular and sublingual glands
Afferents (taste) from anterior 2/3 of tongue to geniculate ganglion, which has central projections to sensory nucleus of CN VII

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11
Q

What are the Extracranial Course and Branches of cranial nerve 7?

A

Outside stylomastoid foramen CN VII runs forward in parotid gland
Crosses external carotid artery
Divides behind ramus of mandible into branches which unite to form parotid plexus

Five branches emerge from anterior border of parotid gland, which supply the muscles of facial expression :
1. Temporal
2. Zygomatic
3. Buccal
4. Mandibular
5. Cervical

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12
Q

What are the clinical correlations of facial nerve - cranial nerve 7?

A

Ear and Parotid Disease
Due to its close relationship to the temporal bone, middle ear and the parotid gland, it can be affected by ear and parotid disease

Herpes Zoster Virus
May lay dormant in the geniculate ganglion (after an attack of chickenpox)
At a later stage it may cause a vesicular eruption in the small area of skin around the external acoustic meatus supplied by CN VII and on the anterior portion of the tongue

Bell’s Palsy
CN VII swells within facial canal resulting in a lower motor neuron lesion
Usually unilateral and cause is unknown

Paralysis of ipsilateral upper and lower parts of face

Upper Motor Neuron Lesion
Damage of cell bodies in the corticobulbar tract
(e.g. stroke)

Paralysis of contralateral lower part of face

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13
Q

What is the Vestibulocochlear Nerve (CN VIII)?

A

Formed in the internal acoustic meatus by the union of the vestibular and cochlear nerves

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14
Q

What are the functions of Vestibulocochlear Nerve (CN VIII)?

A

Special sensory
(hearing and equilibrium)

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15
Q

What are the Four Vestibular Nuclei of Vestibulocochlear Nerve (CN VIII)?

A

Located at junction of pons and medulla in lateral part of floor of 4th ventricle

  1. Superior vestibular nucleus
  2. Inferior vestibular nucleus
  3. Medial vestibular nucleus
  4. Lateral vestibular nucleus
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16
Q

What are the Two Cochlear Nuclei of Vestibulocochlear Nerve (CN VIII)?

A

In medulla

a. Anterior cochlea nucleus
b. Posterior cochlea nucleus

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17
Q

What is the Vestibular Nerve?

A

Concerned with equilibrium
Pass from utricle, saccule and semicircular ducts to vestibular ganglion
Major links with cerebellum, particularly the flocculonodular lobe

Spinal projections > medial vestibulospinal tract (fibres in medial longitudinal fasciculus) and lateral vestibulospinal tract > alpha motor neurons (to motor end plate of extrafusal muscles) and gamma motor neurons (to intrafusal fibres of the muscle spindle) of mainly the cervical part of spinal cord to innervate muscles to do with head and neck movements

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18
Q

Medial longitudinal fasciculus (MLF) is composed of?

A

Medial vestibulospinal fibres (medial vestibular nucleus)
Tectospinal fibres (superior colliculus of midbrain)
Reticulospinal fibres (Reticular formation)

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19
Q

How does the MLF and tectospinal tract influence cranial nerve 8?

A

MLF ultimately influences motor neurons innervating primarily axial and neck musculature, such as the co-ordinated head and eye movements of watching a tennis ball go back and forth

Tectospinal tract will influence reflex movements of the head and neck to visual and auditory stimuli such as automatically turning to look in the direction of a noise or flashes from camera’s going off

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20
Q

What is the cochlear nerve?

A

Hair cells of organ of Corti > cochlea nerve (cell body in spiral ganglion) > ipsilateral cochlea nuclei

Concerned with hearing

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21
Q

What is the pathway of sound?

A

Hair cells of organ of Corti

Cochlea nerve (cell body in spiral ganglion)

Ipsilateral cochlea nuclei

Superior olivary complex

Lateral lemniscus & nuclei of lateral lemniscus

Inferior colliculus

Medial geniculate nucleus (thalamus)

Auditory cortex

22
Q

What are the clinical correlations of cn 8?

A

Disturbances of vestibular function include vertigo and nystagmus

Disturbances of cochlear function include hearing loss and tinnitus

23
Q

What are the functions of Glossopharyngeal Nerve (CN IX)?

A

Taste from posterior 1/3 of tongue
General sensation from pharynx, palatine tonsils, posterior 1/3 of tongue, pharyngotympanic tube, middle ear, carotid sinus and carotid body

Motor to stylopharyngeus muscle
Parasympathetic to parotid gland and glands in posterior 1/3 of tongue

Carotid sinus reflex involving glossopharyngeal and vagus nerves in regulation of blood pressure

24
Q

What is the Main Motor Nucleus of Glossopharyngeal Nerve (CN IX)?

A

Part of nucleus ambiguus
In superior part medulla oblongata

Receives corticonuclear fibres from both cerebral hemispheres
Efferent fibres supply the stylopharyngeus muscle

25
Q

What is the Inferior Salivatory Nucleus of Glossopharyngeal Nerve (CN IX)?

A

Parasympathetic
Adjacent to nucleus ambiguous in inferior part of pons

Input from hypothalamus through descending autonomic pathways

Input from olfactory system through reticular formation

Input regarding taste from sensory (solitary) nucleus

Efferent preganglionic parasympathetic fibres  tympanic branch of CN IX  tympanic plexus  lesser petrosal nerve  otic ganglion  Postganglionic fibres to parotid gland

26
Q

What is the Sensory Nucleus of Glossopharyngeal Nerve (CN IX)?

A

Part of solitary nucleus

Posterior 1/3rd of tongue, pharynx, carotid body & sinus  via superior and inferior CN IX ganglia  CN IX  solitary nucleus

The solitary nucleus and tract are structures in the brainstem that carry and receive visceral sensation and taste from the facial (VII), glossopharyngeal (IX), vagus (X) cranial nerves, as well as the cranial part of the accessory nerve (XI).

27
Q

What is the Spinal Nucleus of Trigeminal Nerve in Glossopharyngeal Nerve (CN IX)?

A

General sensation from posterior 1/3rd of tongue, pharynx & ear  superior CN IX ganglion  spinal nucleus of trigeminal nerve

28
Q

What is the course and relations of Glossopharyngeal Nerve (CN IX)?

A

Emerges from anterior surface of medulla between olive and inferior cerebellar peduncle  superior ganglion of CN IX
jugular foramen  inferior ganglion of CN IX  upper part of neck, medial to CN X, CN XI and IJV  between internal and external carotid arteries

Branches to:
Stylopharyngeus muscle pharynx, tonsils, posterior 1/3rd of tongue (taste and general sensation), carotid sinus and body

29
Q

What are the clinical correlations of Glossopharyngeal Nerve (CN IX)?

A

Lesions of glossopharyngeal nerve also usually affect the vagus nerve
Bilateral corticonuclear lesions produce severe dysphagia

Neurological deficit involving CN IX can be evaluated by testing for loss of the sensation for touch or taste on the posterior one-third of the tongue

Afferent in gag reflex

30
Q

What is the function of Vagus Nerve (CN X)?

A

Sensory from inferior pharynx, larynx and thoracic and abdominal regions
Sense of taste from root of tongue and taste buds on epiglottis

Motor to soft palate, intrinsic laryngeal muscle and one extrinsic tongue muscle - palatoglossus

Parasympathetic to thoracic and abdominal viscera

31
Q

What is the Main Motor Nucleus of Vagus Nerve (CN X)?

A

Part of nucleus ambiguus
In medulla oblongata

Receives corticonuclear fibres from both cerebral hemispheres

Efferent fibres to constrictor muscles of pharynx and intrinsic muscles of larynx

Motor to pharyngeal and palate muscles involved in swallowing, speech.
Efferent limb pf gag reflex.

32
Q

What is Parasympathetic Nucleus of Vagus Nerve?

A

Also called posterior/dorsal nucleus of vagus

Lies beneath the floor of lower part of 4th ventricle

Receives afferents from hypothalamus and glossopharyngeal nerve
(carotid sinus reflex)

Efferent fibres to involuntary muscle of bronchi, heart, oesophagus, stomach, small intestine and large intestine as far as distal 1/3rd of transverse colon

33
Q

What is the Sensory Nucleus of Vagus nerve?

A

Lower part of solitary nucleus

Taste from pharynx travel  inferior ganglion of CN X  sensory nucleus

General sensation from pharynx and larynx  superior ganglion of CN X  spinal nucleus of trigeminal nerve

34
Q

What is the vagus nerve?

A

Series of rootlets from anterior surface of medulla between olive & inferior cerebellar peduncle  jugular foramen with CN IX and CN XI  superior and inferior sensory ganglia in & below jugular foramen

Below inferior ganglion, cranial root of CN XI joins vagus nerve and is distributed mainly in its pharyngeal and recurrent laryngeal branches

Descends vertically in neck in carotid sheath, posterior to common carotid arteries and IJV  root of neck  mediastinum posterior to SC joint and brachiocephalic vein

35
Q

What is the course of the right vagus nerve?

A

Enters thorax anterior to subclavian artery  gives off right recurrent laryngeal nerve which hooks around right subclavian artery and ascends between trachea & oesophagus to supply larynx  vagus continues posteroinferiorly to right side of trachea  posterior to right brachiocephalic vein, superior vena cava, and root of lung  divides into branches to join pulmonary plexus  leaves plexus as a single nerve  oesophagus  contributes to oesophageal and cardiac nerve plexuses  enters abdomen through oesophageal opening of diaphragm and becomes the posterior vagal trunk  posterior surface of stomach, duodenum, liver, kidneys, and small & large intestines as far as distal 1/3rd of transverse colon via celiac, superior mesenteric & renal plexuses

36
Q

What is the course of the left vagus nerve?

A

Enters thorax between left common carotid & left subclavian arteries  left side of aortic arch  diverges posteriorly from phrenic nerve and is separated laterally from it by left superior intercostal vein  curves medially at inferior border of aortic arch  gives off left recurrent laryngeal nerve which passes inferior to aortic arch lateral to ligamentum arteriosum and ascends to larynx between trachea and oesophagus  vagus passes posterior to root of left lung and divides into branches supplying the left pulmonary plexus  leaves plexus as single nerve  oesophagus  contributes to oesophageal plexus  enters abdomen through oesophageal opening of diaphragm and becomes anterior vagal trunk  stomach, liver, upper part of duodenum & head of pancreas

37
Q

What are the branches of the vagus nerve?

A

Meningeal branch to dura mater
Auricular branch
Receives cranial root of accessory nerve
Pharyngeal nerves
Superior laryngeal nerves
Cardiac nerves
Oesophageal branches
Gastric branches
Pancreatic branches
Branches to gallbladder
Branches to intestine as far as left colic flexure

38
Q

What are the clinical correlations of vagus nerve?

A

Clinical Correlations
Lesions of CN X commonly involve CN IX, CN XI and CN XII due to their close proximity to each other

Pharyngeal Reflex
Tested by touching the lateral wall of the pharynx with a tongue depressor, which causes the patient to gag (pharyngeal muscles contract)
Afferents run in CN IX and efferents run in CN IX (to stylopharyngeus muscle) and CN X (to pharyngeal constrictor muscles)
Unilateral lesions of vagus will show little or no gag reflex on that side

Innervation of the soft palate
Tested by asking the patient to say “Ah”
Normally, the soft palate rises and the uvula moves backward
Lesion of the right vagus nerve causes the uvula to be pulled upward, backward and to the left, since the right muscles are paralysed

Hoarseness or absence of the voice may occur with vagal nerve palsy

39
Q

What is Accessory Nerve (CN XI)?

A

Motor nerve formed by the union of a cranial and a spinal root

40
Q

What is the function of Accessory Nerve (CN XI)?

A

Motor to sternocleidomastoid and trapezius

41
Q

What is the cranial root of Accessory Nerve (CN XI)?

A

Formed by nucleus ambiguus

Receives corticonuclear fibres from both cerebral hemispheres

Efferent fibres of CN XI emerge from anterior surface of medulla oblongata between olive and inferior cerebellar peduncle  joins the spinal root (two roots unite)  jugular foramen  roots separate  cranial root joins CN X and is distributed in its pharyngeal and recurrent laryngeal branches to the muscles of the soft palate, pharynx and larynx and oesophagus

Spinal nucleus in anterior gray column of spinal cord in upper 5 cervical segments

Receives corticospinal fibres from both cerebral hemispheres

Emerges from spinal cord between anterior & posterior cervical nerve roots  form trunk  foramen magnum  joins cranial root  jugular foramen  separates from cranial root  spinal accessory nerve descends with carotid artery  innervates SCM  leaves its posterior border near middle  crosses posterior triangle of neck & innervates trapezius

Joined in the neck by branches of cervical plexus (C2-C4) which conveys sensory fibres to the trapezius and SCM muscles

42
Q

What are the clinical correlations of Accessory Nerve CN11?

A

Lesion of CN XI results in paralysis of the sternocleidomastoid and trapezius muscles

There will be weakness in turning the head to the opposite side (SCM) and shrugging the shoulder (trapezius) and the muscles will atrophy

Damage to spinal root induces torticollis.

43
Q

What is the function of Hypoglossal Nerve (CN XII)?

A

Motor to intrinsic (all) and extrinsic (styloglossus, hyoglossus & genioglossus) muscles of the tongue

Close to midline below floor of lower part of 4th ventricle

Receives corticonuclear fibres from both cerebral hemispheres

Cells responsible for supplying the genioglossus muscle only receive corticonuclear fibres from the opposite cerebral hemisphere

44
Q

What is the course of Hypoglossal Nerve (CN XII)?

A

Emerges from anterior surface of medulla between pyramid & olive  hypoglossal canal  anteroinferiorly in neck between internal carotid artery and IJV until angle of mandible  curves anteriorly to enter tongue  ends in branches to supply muscles of the tongue

45
Q

What are the clinical correlations of Hypoglossal Nerve (CN XII)?

A

UMNL (corticonuclear fibers in internal capsule) → paralysis of genioglossus muscle with deviation of tongue towards contralateral side of lesion on protrusion

In addition, there is contralateral hemiplegia and a drooping of the facial muscles in lower quadrant of contralateral face

LMNL of hypoglossal nerve → tongue deviates to side of lesion (weak side) with no other deficits

46
Q

How do you test CN 7?

A

Muscles of facial expression
Taste (anterior 2/3 of tongue)

47
Q

How do you test CN 8?

A

Crude auditory acuity (watch ticking, rubbing thumb and index finger by ear)
Rinne and Weber test
Otoscope examination (3rd year)

48
Q

How do you test CN 9?

A

Taste (post 2/3 tongue) – Not tested
General sensation (post 2/3 tongue)
Gag reflex

49
Q

How do you test CN 10?

A

Patient to say “AH” – look for palate rising and uvula moving posteriorly

50
Q

How do you test CN 11?

A

Trapezius muscle strength (shrug shoulders against resistance)
Sternocleidomastoid muscle strength (rotate head against resistance)

51
Q

How do you test CN 12?

A

Protrude tongue, push tongue into cheeks

Neuroanatomy and Clinical Neurology (16 decks)

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