7: Anatomy - Clinical testing of cranial nerves Flashcards
What is the name and modality of CN I?
Where does it emerge from the skull and where does it connect to the CNS?
Olfactory nerve; Special sensory
Remember the part afterwards is the olfactory tract because CN I synapses at the olfactory bulb
Cribriform plate of the ethmoid bone, goes straight to olfactory areas
What is the name and modality of CN II?
Where does it emerge from the skull and where does it connect to the CNS?
Optic nerve; Special sensory
Optic canal
Diencephalon
What is the name and modality of CN III?
Where does it emerge from the skull and where does it connect to the CNS?
Oculomotor nerve; Motor
Superior orbital fissure
Midbrain
What is the name and modality of CN IV?
Where does it emerge from the skull and where does it connect to the CNS?
Trochlear nerve; Motor
Superior orbital fissure
POSTERIOR aspect of the midbrain
What is the name and modality of CN V?
Where does it emerge from the skull and where does it connect to the CNS?
Trigeminal nerve; Both sensory and motor
Depends on branch - V1 = superior orbital fissure, V2 = foramen rotundum, V3 = foramen ovale (“standing room only”)
Only CN to connect to CNS at the PONS
What is the name and modality of CN VI?
Where does it emerge from the skull and where does it connect to the CNS?
Abducens nerve; Motor
Superior orbital fissure
Ponto-medullary junction
What is the name and modality of CN VII?
Where does it emerge from the skull and where does it connect to the CNS?
Facial nerve; Both
Stylomastoid foramen / Internal acoustic meatus
Ponto-medullary junction
What is the name and modality of CN VIII?
Where does it emerge from the skull and where does it connect to the CNS?
Vestibulocochlear nerve; Sensory (special)
Internal acoustic meatus
Ponto-medullary junction
What is the name and modality of CN IX?
Where does it emerge from the skull and where does it connect to the CNS?
Glossopharyngeal nerve
Jugular foramen
Medulla
What is the name and modality of CN X?
Where does it emerge from the skull and where does it connect to the CNS?
Vagus nerve; Both
Jugular foramen
Medulla
What is the name and modality of CN XI?
Where does it emerge from the skull and where does it connect to the CNS?
Spinal accessory nerve; Motor
Actually ascends through foramen magnum THEN down through jugular foramen
Cervical spinal cord
What is the name and modality of CN XII?
Where does it emerge from the skull and where does it connect to the CNS?
Hypoglossal nerve; Motor
Hypoglossal canal
Medulla
Some people say CN II isn’t a real cranial nerve - why?
It has its own meninges, so arguably it’s an extension of the CNS
Remember increases in intracranial pressure cause compression of CN II – papilloedema
Which cranial nerve(s)
a) emerge from the pons
b) emerge from the ponto-medullary junction
c) emerge from the opposite side of the brainstem to the others?
a) CN V
b) CN VI, VII and VIII
c) CN IV
Where is CN I actually found?
What is everything called proximal to the olfactory bulb?
Olfactory mucosa of nasal cavity
Olfactory tract
Through which hole does CN II reach the brain from the orbit?
Optic canal
What sense are you testing when you test CN II?
Vision
How can CN II be tested?
Visual acuity (Snellen chart)
Colour (Ishihara plates)
Visual fields
Visual reflexes
Direct fundoscopy
Which specific modalities are found in CN III?
Somatic motor for eye movements
Parasympathetics for pupillary constriction
Which blood-filled space in the brain carries the internal carotid arteries, CN III, IV, V and VI?
Cavernous sinus
Which ocular muscles are supplied by CN III?
Medial rectus
Superior rectus
Inferior rectus
Inferior oblique
(Also - LPS, dilator and sphincter pupillae, ciliary muscles)
LR6 SO4 AO3
Which cranial nerves supply
a) lateral rectus
b) levator palpebrae superioris
c) superior oblique?
a) CN VI
b) CN III
c) CN IV
Which cranial nerves connect to the CNS via the
a) pons
b) ponto-medullary junction
c) cervical spinal cord
d) midbrain
e) medulla?
a) CN V
b) CN VI, VII and VIII
c) CN IX
d) CN III, IV (posteriorly)
e) CN IX, X and XII
When the eye is adducted only, which muscle are you testing?
Medial rectus
When the eye is adducted AND
a) elevated
b) depressed?
Which muscles are you testing?
a) Inferior oblique
b) Superior oblique
When the eye is abducted only, which muscle are you testing?
Lateral rectus
When the eye is abducted AND
a) elevated
b) depressed
which muscle are you testing?
a) Superior rectus
b) Inferior rectus
Which special senses does CN VIII control?
Hearing (Cochlear nerve)
Balance (Vestibular nerve)
Where do CN VI, VII and VIII connect to the CNS?
Ponto-medullary junction
How is CN VIII tested?
Rinne-Weber tests
How do you perform Weber’s test?
What are the possible findings?
Ask patient which ear is affected
Use a 512Hz tuning fork (smallest), strike and press to patient’s forehead
LOUDEST ON BOTH SIDES = NORMAL
LOUDEST ON AFFECTED SIDE = CONDUCTIVE HEARING LOSS
LOUDEST ON UNAFFECTED SIDE = SN HEARING LOSS
How do you perform Rinne’s test?
What are the possible findings?
Ask patient which ear is affected
Strike 512Hz (smallest) tuning fork and press to MASTOID PROCESS for bone conduction
Then move in front of ear for air conduction
Ask patient which was louder
AIR CONDUCTION > BONE CONDUCTION = NORMAL
BONE CONDUCTION > AIR CONDUCTION = CONDUCTIVE HEARING LOSS
CN XI has a unique connection to the CNS - where is it?
Cervical spinal cord
What is the function of CN XI?
Somatic motor to trapezius and sternocleidomastoid
CN XI connects to the cervical spinal cord.
How does it
a) enter
b) exit the cranium?
a) Foramen magnum
b) Jugular foramen
Which point in the neck is a point where much of the cervical plexus (C1-4) overlaps?
Erb’s point
At the midpoint of the posterior border of sternocleidomastoid
Keeping in mind that it supplies trapezius and sternocleidomastoid, how do you test CN XI?
Shrug shoulders
Laterally flex neck
Where does CN XII connect to the CNS?
Medulla
CN XII descends through the neck to the carotid sheathe, then turns anteriorly at the level of which bone?
What muscles does CN XII supply?
Hyoid bone
Intrinsic tongue muscles (except palatoglossus, which is CN X)
Which muscles does CN XII supply?
How do you test CN XII?
Intrinsic tongue muscles (exception: palatoglossus CN X)
Ask patient to stick their tongue out
If a patient with unilateral CN XII dysfunction sticks their tongue out, which side will their tongue droop to?
Towards the affected side
REMEMBER: “tongue tells tales”
What are the three divisions of the trigeminal nerve (CN V)?
V1 - ophthalmic division
V2 - maxillary division
V3 - mandibular division
Which nerve modalities are carried in
a) CN V1
b) V2
c) V3?
a) Sensory
b) Sensory
c) Sensory and Motor
Which part of the brainstem does CN V connect to?
Pons
only one which does this, important fact
From which cranial fossa does each branch of CN V exit?
All middle cranial fossa
What is the mnemonic for remembering the cranial foramina that CN V exits from?
Standing room only
CN V1 = superior orbital fissure
CN V2 = foramen rotundum
CN V3 = foramen ovale
Which aspects of the nose are supplied by CN V1?
Bridge
Tip
Which infection follows nerves and can damage the cornea if CN V1 is affected?
Herpes zoster
or ‘Ophthalmic zoster’
Which aspect of the nose is supplied by CN V2?
Alae (sides)
Which nerves supply sensory fibres to
a) the angle of the mandible
b) the TMJ
c) most of the skin of the mandible?
a) Great auricular nerve (C2 and 3)
b) CN V3
c) CN V3
What the named nerves and levels of the cervical plexus?
Lesser occipital (C2)
Greater auricular (C2-3)
Transverse cervical (C2-3)
Supraclavicular (C3-4)
Which aspects of the nasal cavity are given sensory fibres by branches of the trigeminal nerve?
CN V1 - upper, anterior aspect
CN V2 - lower, posterior aspect
Which paranasal sinuses are supplied with sensory fibres by CN V1?
Frontal sinus
Ethmoidal air cells
Sphenoid sinuses
Which paranasal sinus is given sensory fibres by CN V2?
Maxillary sinus
Or ‘maxillary antrum’
CN V3 gives off both sensory AND motor fibres. Which facial muscles are supplied by CN V3?
Muscles of mastication
(Masseter, temporalis, medial and lateral pterygoids)
Which muscles of mastication
a) open
b) close the jaw?
a) Lateral pterygoid OPENS the jaw
b) Masseter, temporalis and medial pterygoid CLOSE the jaw
In addition to the muscles of mastication, CN V3 supplies two other muscles in the head and neck.
What are they called?
TENSOR VELI PALATINI
TENSOR TYMPANI
Trigeminal nerve does the tensors
How do you test the sensory fibres of CN V?
Touch skin in divisions of trigeminal nerve
How do you test the motor fibres of CN V?
Ask patient to CLENCH THEIR TEETH - tests masseter and temporalis
Ask patient to OPEN JAW AGAINST RESISTANCE - tests lateral pterygoid
Which nerve modalities are carried by CN VII?
Somatic motor - to muscles of facial expression AND stapedius
Parasympathetic - to submandibular and sublingual glands
Special sensory - to taste buds of anterior 2/3rds of tongue
Does CN VII supply the parotid gland?
No, but its fibres pass through it
Which bone does CN VII run through?
Temporal bone
IN via the internal acoustic meatus, OUT via the stylomastoid foramen
Which specific part of the temporal bone does CN VII run through?
Petrous part
via the facial canal
Which passage connects the internal acoustic meatus to the stylomastoid foramen?
Facial canal
Through which foramen does most fibres of CN VII exit the temporal bone?
Stylomastoid foramen
What happens to the somatic motor fibres of CN VII which exit the stylomastoid foramen?
Run down into parotid gland
Then split into 5 named nerves to supply the muscles of facial expression
Which branch of CN VII supplies special sensory fibres to the anterior 2/3rds of tongue and parasympathetic fibres to the submandibular and sublingual glands?
Chorda tympani
Which cranial nerve does the chorda tympani hitch a ride with to supply the tongue and salivary glands?
CN V3
Mandibular division of trigeminal nerve
What are some of the muscles of facial expression?
Frontalis
Orbicularis oculi
Orbicularis oris
How can you test the motor fibres of CN VII?
Ask patient to make facial expressions
Which skeletal muscle, the smallest found in the body, is supplied by CN VII?
Stapedius
What is supplied with special sensory fibres by CN IX?
Posterior 1/3rd of tongue
What is supplied with somatic sensory fibres by CN IX?
Pharynx
Tonsils
Posterior 1/3rd of tongue
Eustachian tube
Middle ear
Which muscle is the only one supplied with somatic motor fibres by CN IX?
Stylopharyngeus
Which receptors, found in the carotid sinus, are supplied with visceral afferent fibres by CN IX?
Chemoreceptors
Baroreceptors
Which gland is given parasympathetic fibres by CN IX?
Parotid gland
Which cranial nerves supply the
a) submandibular
b) parotid
c) sublingual glands?
a) CN VII
b) CN IX
c) CN VII
Which cranial nerves supply
a) stylopharyngeus
b) palatoglossus
c) stapedius
d) tensor veli palatini and tensor tympani
e) sternocleidomastoid and trapezius?
a) CN IX
b) CN X
c) CN VII
d) CN V
e) CN XI
Which cranial nerve is also known as the wanderer because it has so many modalities and travels throughout the body?
CN X
Where does CN X extend to?
Midgut
In the neck, CN X runs within the ___ ___.
carotid sheathe
What is the course of the
a) left
b) right recurrent laryngeal nerve?
a) Hooks under arch of aorta
b) Hooks under right subclavian artery
CN X passes (anterior / posterior) to the lung roots.
posterior to lung roots
In what arrangement do the left and right vagus nerves pass along the oesophagus?
At which level does the oesophagus penetrate the diaphragm?
LARP - left anterior, right posterior
T10 (dermatomal level of the umbilicus)
Where in the abdomen do the vagus nerve’s LAST parasympathetic axons go?
Splenic flexure
Where in the abdomen do CN X’s parasympathetic nerves synapse?
Coeliac ganglion
Superior mesenteric ganglion
because it extends to the midgut only
Which muscles are supplied by CN X?
Muscles of palate (except tensor veli palatini, which is CN V)
Pharyngeal muscles
Laryngeal muscles
Plus palatoglossus (the rest are CN XII)
In terms of testing CN X, how do you test
a) the muscles of the palate
b) pharyngeal muscles
c) laryngeal muscles?
a) Say AAAAAH
b) Swallow
c) Speak
If a palatal muscle e.g levator veli palatini isn’t working, which structure will deviate when the patient says ahhh?
Uvula
What side does the uvula deviate to when a palatal muscle isn’t working?
AWAY from dysfunctional side
(Tongue tells tales i.e it deviates to affected side, uvula does the opposite)
