22.1 Specific Cranial Nerves Flashcards
CN III
Oculomotor nerve
CN IV
Trochlear nerve
CN VI
Abducens nerve
How can oculomotor, trochlear and abducens nerves be tested to see if they are functional? (Give 2 tests)
Examine
1) pupillary reflexes
2) eye movements
What are the signs of damage to the oculomotor nerve (III)?
- Diplopia (double vision)
- Ptosis
- Pupil dilation
- DOWN and OUT movement of eye (bc unopposed left superior oblique and lateral rectus muscles)
What are the signs of damage to the trochlear nerve (IV)?
Diplopia when looking downward and medially
bc affected eye cannot move in and down
What are the signs of damage to the abducens nerve (VI)?
Loss of lateral movement of eye –> diplopia when looking to affected side
bc lateral rectus paralysed
CN V
Trigeminal nerve
What are the three branches of the trigeminal nerve?
V1: opthalmic
V2: maxillary
V3: mandibular
Where do the three trigeminal branches split off from?
The trigeminal ganglion
Role of CNV1 (ophthalmic)?
Sensory supply to forehead and eyes
Role of CNV2 (maxillary)?
Sensory supply to maxilla and upper teeth
Roles of CNV3 (mandibular)?
- Sensory supply to anterior 2/3 of tongue, jaw, lateral sides of face, dura, tympanic membrane
- Motor supply to tensor tympani and muscles of mastication
What is a good visual way to remember the innervation of the three trigeminal branches?
Knight’s helmet
Where does the opthalmic branch pass through the cranium?
Superior orbital fissure
Where does the maxillary branch pass through the cranium?
Foramen rotundum
Where does the mandibular branch pass through the cranium?
Foramen ovale
How can the ophthalmic and maxillary afferents be unusually involved in coughing and sneezing reflexes?
As they join the trigeminal ganglion along with the mandibular branch, which innervates the muscles of mastication involved in these reflexes
What are the two sensory nuclei in the brainstem next to the trigeminal ganglion that the fibres may travel to?
Primary
Spinal
(Extra: mesencephalic, = proprioceptive)
What are the roles of the primary and spinal sensory nuclei?
Primary: touch
Spinal: nociceptive
Which nucleus do the mandibular motor fibres travel to?
Motor nucleus
What is lateral medullary syndrome?
Acute ischaemic infarct of the lateral medulla, due to occlusion of PICA (posterior inferior cerebellar artery)
What symptoms does lateral medullary syndrome cause? Why?
Loss of pain and temp sensation (bc trigeminal nuclei affected) from ipsilateral face and contralateral body (bc spinothalamic tracts have decussated before this, in the spinal cord)
What are three tests for CN V?
- Touch cornea to induce blink reflex
- Test sensation in face
- Check that jaw closes symmetrically
CN VII
Facial nerve
What are the roles of CN VII (facial)?
- Special sensory: taste to anterior 2/3 of tongue
- Motor: muscles of facial expression and stapedius
- Parasympathetic: supply to salivary glands
Via which nerve and ganglion does CN VII parasympathetically innervate the submandibular and siblingual glands?
Chorda tympani
Submandibular ganglion
Via which ganglion does CN VII parasympathetically innervate the lacrimal glands?
Pterygopalatine ganglion
Which nerve innervates the stapedius?
Facial nerve VII
Via which ganglion and nerve does the facial nerve provide taste sensation to the anterior 2/3 of the tongue?
Geniculate ganglion
Chorda tympani
Where does the motor supply of the facial nerve originate in the brainstem?
In the motor nucleus
Where does the sensory supply of the facial nerve originate in the brainstem?
Nucleus solitarius
Where does the parasympathetic supply of the facial nerve originate in the brainstem?
Superior salivatory nucleus
How is the facial nerve tested?
Examine control of facial muscles
Check symmetry of expression
What are two things that can occur with a facial nerve lesion?
Bell’s palsy
Hyperacusis
What is Bell’s palsy characterised by?
characterised by loss of expression, dry eyes, altered taste, ptosis and uncontrolled salivation/dribbling
What is hyperacusis?
Increased sensitivity to everyday sounds that causes an intolerance
Which number cranial nerve is the vestibulocochlear nerve?
VIII
State a mnemonic to remember if the cranial nerves are sensory, motor or mixed (both)? What is the vestibuloochlear nerve?
Some say money matters, but my brother says big brains matter most
Sensory (CN I)
Sensory (CN II)
Motor (CN III)
Motor (CN IV)
Both (CN V)
Motor (CN VI)
Both (CN VII)
Sensory (CN VIII)
Both (CN IX)
Both (CN X)
Motor (CN XI)
Motor (CN XII)
‘says’ = sensory
Vestibulocochelar carries sensory information
Where is the origin of the vestibulocochlear nerve?
Vestibular area of the Rhomboid fossa of the brainstem (vestibular and cochlear nuclei
What are the two components of the vestibulocochlear nerve? What are their functions?
Vestibular component = balance
Cochlear component = hearing
What is the functional categorisation of the vestibulocochlear nerve?
Special somatic afferent
Describe the course taken by the vestibulocochlear nerve from where it emerges to where it terminates
Emerges from the vestibular and cochlear root
Leaves the brain through the internal acoustic meatus in the posterior cranial fossa
In here it splits into two roots: vestibular cochlear
The vestibular root connects to the vestibular ganglion
The cochlear root reaches the spiral canal of the modlolus where the spiral ganglion is located
Whichh cranial nerve does the vestibulocochlear nerve travel with in the internal acoustic meatus?
Facial nerve (VII)
What is an audiometry exam?
Tests the ability to hear sounds based on frequency (tone) and intensity (loudness)
What is the difference between sensorineural and conductive hearing loss?
Conductive hearing loss is caused by mechanical damage to the outer or middle ear leading to defective condution of sound waves to the endolymph
Sensorineural hearing loss is deafness as a result of disease of the cochlea or vestibulocochlear nerve
How can conductive and sensorineural hearing loss be distinguished?
Usign a tuning fork (Rinne’s and Weber’s) test
What is the Weber’s test? What do the results mean in someone with hearing loss?
Tuning fork striked against knee and placed on high on the midline of the patients forehead
Hearing loss = sound moves to one side more
Unilateral conductive hearing loss = sound heard louder in the deaf ear
Unilateral senorineural hearing loss = sound louder more in normal ear
Normal = sound heard in midline (bilateral hearing loss too)
What is Rinne’s test?
PROCEDURE:
Vibrating fork placed againt mastoid process for 2-3 seconds
Lift fork off mastoid process and place tips 1cm from external auditory meatus
Ask where it was loudest (air or bone)
What would the results of the Rinne’s test look like for an individual with conductive hearing loss?
-Hear best when fork is in the AIR = no conductive hearing loss
-Hear best when fork is on BONE = conductive hearing loss
Normal person has better air conduction (normal everyday life sounds are heard this way)
What may cause sensorineural hearing loss?
Acoustic neuroma
What is an acoustic neuroma? How may it cause sensorineural hearing loss? What other symptoms may it cause?
Benign tumuor compressing CN VIII leading to auditory loss, nausea, vertigo and motion sickness (sometimes facial numbness)
How is conductive hearing loss treated? How is this different to sensorineural hearing loss?
Corrected with hearing aids which help to transmit sound from the outer or middle ear to the vestibulocochlear nerve
Cannot amplify the sound in sensorineural hearing loss = have to use cochlear implants
Give some causes of conductive hearing loss
Cerumen (wax) occluding external auditory meatus
Perforated eardrum
Infections producing fluid in tympanic cavity
Immobilisation of the ossciles
Which tests are used to determine vestibular function?
Caloric or rotational tests
What is vestibular nystagmus?
Dysfunction in the vestibulocochlear reflex leading to involuntary biphasic eye movement with slow and rapid phases of opposite directions and motion sickness and nausea
What is the vestibulo-ocular reflex?
Stimulated when we turn our head quickly
Involves the automatic and synchronised movement of the eyes so we can see where we are rapidly and reorientate ourselves
Becomes faulty in nystagmus- stimulated unecessarily
What is the caloric test? Describe what happens during it
Each ear is irrigated with warm and cool water in turn, for around 30 seconds
This alters the properties of the endolymph within the horizontal canals in order to induce alterations to firing patterns.
If vestibular abnormalities are present, this will typically be associated with reduced ocular movements as the linkage of vestibular stimuli to eye position is reduced.
Dizziness is a typical side effect in all patients
Hot and cold water create convection currents in the opposite direction and therefore horizontal nystagmus
Which way do the eyes move if hot water is irrigated into the ear during the caloric test?
Increased rate of firing of vestibular nerve
Both eyes turn to contralateral ear with quick eye movements to ipsilateral ear
Which way do the eyes move when irrigated with cold water in the caloric test?
Enodlymph falls within semicircualr canals decreasing rate of vestibular firing
Mimics head turn to contralateral side so eyes turn to the ipsilateral ear
What is the rotational test?
Instead of using water, the patient may be placed in a chair moving gently and asked to look at a striped curtain as it moves around. If vestibular nerve or system are damaged, tracking the lines becomes more challenging and the patient eye movements are less regular or predictable
What is cranial nerve IX?
Glossopharyngeal
(On, On, On, They Traveled And Found Voldemort Guarding Very Ancient Horcruxes)
What is cranial nerve X?
Vagus
On, On, On, They Traveled And Found Voldemort Guarding Very Ancient Horcruxes.
What is cranial nerve XI?
(spinal) Accessory nerve (XI)
On, On, On, They Traveled And Found Voldemort Guarding Very Ancient Horcruxes.
What type of nerve is IX?
Mixed nerve
Sensory
Motor
Paraysmpathetic
What type of nerve is X?
Mixed nerve
Sensory
Motor
Parasympathetic
What type of nerve is XI?
Motor
Where does cranial nerve IX originate from?
Laterally from the medulla oblongata
Which nerve is shown below?
Cranial nerve IX
Which embryological strucutres are generally innervated by the glossopharyngeal nerve? List them
Third branchial arch:
Senory innervation to (afferents from)
-Carotid bodies and sinus
-Tympanic membrane and tube
-oropharynx
-mucosa of middle ear
-Mastoid air cells
-General sensation for posterior 1/3 tongue
-Taste sensation for posterior 1/3 tongue
Parasymapthetic:
-innervate salivary parotid gland
Motor:
-Stylopharygeus muscle
-Superior pharyngeal contrictor
What does cranial nerve IX provide parasympathetic innervation to?
Parotid glands
What does cranial nerve IX provide motor input to?
Stylopharyngeus muscle
How many nuclei give rise to the glossopharyngeal nerve?
4
The ambiguous nucleus
The inferior salivary nucleus
The spinal nucleus of the trigeminal nerve
The solitary nucleus
Which nuclei do motor afferents for cranial nerve IX, X and XI come from?
Nucelus ambiguous
Which branch of the glossopharyngeal nerve gives taste to the posterior 1/3 tongue?
Lingual branch
How can the glossopharyngeal nerve and vagus nerve be tested for?
Test the gag reflex on posterior part of tongue
(glossopahryngeal nerve innervates mucosa of pharynx and anastomoses with the vagus)
What is the function of the stylopharygenus muscle?
Elevates the pharynx and larynx so plays an important role in swallowing and speaking
What is the origin of the vagus nerve?
Lateral medulla oblongata of the brainstem
What are the four vagal nuclei?
the dorsal motor nucleus
the nucleus ambiguus
the solitary nucleus
the spinal trigeminal nucleus
Which nuclei provide parasympathetic supply from the vagus nerve? What is this to?
Dorsal motor nucelus - parasymapthetic motor innervation to pharynx, larynx and all of GI tract derived from foregut and midgut
Nucelus ambiguus - (as well as efferent motor) parasympathetic fibres to the heart
What is supplied by the vagus nerve? What type of innervation is each one?
SENSORY:
-Larynx
-External acoustic meatus
-Aortic chemoreceptors and baroreceptors
-Epiglottis taste buds
PARASYMPATHETIC:
-Heart (nucelus ambiguus)
-Smooth muscle of phaynx, larynx, thorax and GI tract
MOTOR:
-Pharyngeal muscles (excluding stylopharyngeal)
-Laynx
-Palatoglossus
Which cranial nerve is respoinsible for palatal movements? Through the action of which muscle?
Vagus nerve supplies the pharyngeal plexus which provides motor innervation for the muscles of the soft palate
-Swallowing (palatoglossus provides depression)
-Speech
-Exhaling
How is the vagus nerve tested?
-Gag reflex
-Check soft palate elevation (say ‘ah’)
-Swallowing
-Vagovagal reflex (massage cartoid baroreceptor and see hypotension)
Which nucleus supplies motor innervaiton to the soft palate, phayrnx and larynx?
Nucelus amiguus
Vagus
Which cranial nerve is this?
Spinal accessory nerve (XI)
What is the origin of the accessory nerve?
Posterior border of the olive below the level of the vagus nerve
What foramen does the glossopharyngeal, vagus and accessory nerves pass through?
Jugular foramen
Which muscles are innervated by the spinal accessory nerve?
Pharyngeal constrictors
Larynx and muscles of soft palate
Trapezius
Sterncelidomastoid
What is the action of sternocleidomastoid when stimulated?
Facilitates turning of the head to the contralateral side
Flexion of the neck to the ispilateral side
What is the action of trapezius when stimulated?
Extension of the neck
Retraction, elevation and rotation of the scapula
Why is spinal accessory nerve not a ‘true’ cranial nerve
Does not necessarily originate in the cranium
Has a cranial division from the medulla at the level of the nucelus ambiguus (cranial nucelus) emerging at posterior border of the olive leaving at jugular foramen where it briefly contacts spinal part of accessory nerve
Roots emerge from C1-6 and pass into the cranium via foramen magnum
How is the spinal accessory nerve tested?
Test sternocleidomastoid and trapezius
-Shrug sholders and rotate head both normally and against resistance
What is the name given to cranial nerve XII?
Hypoglossal
What type of innervation does CN XII supply?
MOTOR
Where is the origin of the hypoglossal nerve?
Hypoglossal nucelus in the medulla oblongata
What is innervated by the hypoglossal nerve?
ALL intrinsic muscles of the tongue
All extrinisc muscles of the tongue but palatoglossus (vagus)
Geniohyoid muscle (one of the suprahyoid muscles between madible and hyoid bone)
How is the hypoglossal nerve involved in swallowing?
Innervates intrinsic and extrinsic muscles of the tongue
Where does the hypoglossal nerve leave the cranium?
Hypoglossal canal
How is the function of the hypoglossal nerve tested?
Asked to protrude the tongue
Observe speech
What would happen if there was a lesion on one side of the hypoglossal nerve and a patient was asked to protrude the tongue?
Tongue deviates towards the side of the lesion
(Normally, simultaneous contraction of the paired genioglossus muscles cause the tongue to protrude straight and forward)
What causes medial medullary syndrome?
Occlusion/Lesion of the anterior spinal artery causing infarction of the medial part of the medulla oblongata
What are the characteristics of medial medullary syndrome?
-a deviation of the tongue to the side of the infarct on attempted protrusion, caused by ipsilateral muscle weakness (hypoglossal)
-loss of discriminative touch, proprioception and vibration on contralateral side (medial lemniscus)
-limb weakness on contralateral side (medullary pyramid and corticospinal tract)
