Cranial Nerve Examination Flashcards
Cranial nerve abnormalities may arise from lesions affecting what?
Communicating pathways to and from the cortex, cerebellum and other parts of the brainstem Nerve nucleus Nerve Neuromuscular junction disorders Muscle
List the cranial nerves and their components.
Olfactory - sensory Optic - sensory Occulomotor - motor Trochlear - motor Trigeminal - both Abducens - motor Facial - both Vestibulocochlear - sensory Glossopharyngeal - both Vagus - both Spinal accessory - motor Hypoglossal - motor
Describe the tract of the olfactory cranial nerve.
Olfactory cells of the nasal mucosa
- central processes of primary olfactory neurons pass from the olfactory cells to the olfactory bulb
Olfactory bulbs
Pyriform cortex
Describe the tract of the optic cranial nerve.
Retinal ganglion cells
Optic chiasm
Thalamus
Primary visual cortex in the occiptal lobe
What examining the optic nerve, what examinations are performed?
Optic disc with ophthalmoscope
Pupillary responses
Visual acuity (Snellen chart)
Visual fields and bling spots (confrontation)
Describe optic atrophy appearance on opthalmoscope and causes of it.
Inflammation of the optic nerve makes the optic disc look paler
Caused by optic neuritis (MS symptom) or past damage to the optic nerve
Describe the appearance of papilloedema on opthalmoscope and causes of it.
Optic disc looks blurry with unclear margins
Caused by increased vascularity (possibly raised ICP)
How does pupillary reflexes assess both the third and second cranial nerves?
The second nerve relays the light information from the eye to the optic tract where it splits. Most fibres go to the lateral geniculate nucleus and subsequently to the visual cortex. The other fibres travel to the Oculomotor nucleus where they synapse with neurons which enter the third cranial nerve.
These fibres control pupillary contraction to limit the amount of light entering the eye
What are the important things to remember when testing visual acuity.
Test one eye at a time
We are looking for a problem with the nerve, not the lens, so they are allowed to wear their glasses if they need them
Give an examples of monocular vision loss and a bitemporal hemianopia visual field defect.
Monocular vision loss
- optic neuritis
Bitemporal hemianopia
- pituitary tumour pressing on the chiasm
How do you know if the patient is experiencing visual field loss?
You map their visual field against your own
- you need to site opposite the patient and cover one eye
Which cranial nerves are involved in moving the eyes?
3 - occulomotor
4 - trochlear
6 - abducens
What is the function of the oculomotor nerve?
Movement of the eyeballs, lens accomodation and pupil constriction.
Where are the nuclei for the parasympathetic and motor parts of the oculomotor nerve?
Motor
- midbrain (oculomotor nucleus)
Parasympathetic
- midbrain (Edinger-Westphal)
What does the oculomotor nerve innervate?
Inferior oblique Medial rectus Superior rectus Inferior rectus Levator palpebrae superioris Ciliary muscles Pupillary constrictor muscles
Describe what happens if there is a lesion on the oculomotor nerve.
Ptosis - levator palpebrae superioris is not longer innervated
Eyes turn down and out - superior oblique and lateral rectus muscles still work
Pupil dilation - pupil dilator muscles still work
What is the function (and muscles innervated) of the trochlear nerve.
Moves the eyeball in and down
- innervates the superior oblique muscle of the eye
Where is the nucleus for the trochlear cranial nerve?
Midbrain - inferior colliculus
If someone has double vision, when will it be most exacerbated?
In the direction of action of the muscle supplied by the affected nerve
e.g. trochlear nerve caused double vision is worse when the person looks down and in
Describe the action of the oblique muscles.
Superior oblique - intorsion - pulls eye towards the nose Inferior oblique - extorsion - pulls eye towards the ears
What is the function (and muscles innervated) of the abducens nerve.
Moves eyeball laterally
- innervates the lateral rectus muscle of the eye
Where is the nucleus of the abducens cranial nerve?
Pons
What happens when there is a lesion of the abducens nerve?
Eye gets pulled medially because the medial rectus muscle still works
What palsy is it when you shine a light into someones eye and the pupil remains big, but the other one shrinks?
Oculomotor palsy ipsilateral to the light shining eye
- not optic nerve palsy because the other eye reacted
Describe internuclear opthalmoplegia.
Disorder of conjugate gaze (bilateral fixation on a single object)
- failure of adduction in the affected eye
- nystagmus of lateral gaze in the contralateral eye
Results from lesion of medial longitudinal fasciculus (connects the 3rd and 6th nuclei)
Common in MS
What are the symptoms of Horner’s syndrome?
Miosis
Ptosis
Apparent enopthalmos
Anhidrosis
What can cause Horner’s syndrome?
Ipsilateral disruption of the cervical/thoracic sympathetic chain
- congenital
- brainstem stroke
- cluster headache
- apical lung tumour
- MS
- carotid artery disease
- cervical rib
- syringomyelia
What is the function of the trigeminal nerve?
Sensory input from the face
Mastication
Where are the nuclei for the trigeminal nerve.
Sensory input
- pons & medulla
Motor
- pon
What structures does the Trigeminal nerve supply.
Face (opthalmic, madibular and maxillary divisions)
Anterior 2/3rds of the time
Masseter, temporalis, medial and lateral pterygoids
Describe herpes zoster ophthalmicus.
Pain precedes vesicles
Usually affects V1 (opthalmic branch of the trigeminal nerve) on one side of the face
Treated with oral aciclovir
What are the three components of the facial nerve, and where are their nuclei?
Motor - pons
Sensory - medulla
Parasympathetic - medulla
What is the function of the facial nerve?
Muscles of expression
Taste - innervation of the anterior 2/3rds of the tongue
Salivation and lacrimation
What is the effect of an upper motor neuron lesion of the facial nerve?
Weakness of the inferior facial muscles on one side
What is the effect of an lower motor neuron lesion of the facial nerve?
Weakness of superior and inferior facial muscles on one side
What is Bell’s sign?
Can see the cornea when the patient closes his eyes
How do you test the corneal reflex?
Lightly touch the cornea with cotton wool
- sensory (trigeminal)
- motor (facial)
Test of pontine function
What is the function of the vestibulocochlear nerve?
Balance
- nerve endings within semi-circular canals
Hearing
- cochlear
Where are the nuclei for the balance and hearing parts of the vestibulocochlear nerve located?
Pons and medulla
How can you test the function of the vestibulococholear nerve?
Rinne’s test
- tuning fork held behind the ear
Weber’s test
- tuning fork placed on the forehead
Which nerves (when affected) cause bulbar weakness.
9, 10, 11 and 12
What are the symptoms of bulbar palsy.
Dysphagia Difficulty chewing Nasal regugitation Slurring of speech Choking on liquids Dysphonia Difficulty in handing secretions
What is the function of the Glossopharyngeal nerve?
Taste Proprioception for swallowing Blood pressure receptors Swallow and gag reflex Lacrimation Salvia producation
What is does the glossopharyngeal nerve innervate?
Posterior 1/3rd of the tongue Pharyngeal wall and muscles Carotid sinuses Lacrimal glands Parotid glands
Which way does the uvula deviate in glossopharyngeal pasly, and why?
Away from the side of the lesion
- muscles of the soft palate normally pull the uvula up, so when they are weak, they allow the uvula to drop on one side, swinging it away from the lesion
Where are the nuecli for the motor and sensory parts of the glossopharyngeal nerve found?
Medulla
Where are the nuecli for the motor and sensory parts of the vagus nerve found?
Medulla
What is the function of the Vagus nerve?
Monitors blood oxygen concentration Pain receptor in the dura Sensation of the external ear, larynx and pharynx Heart rate and stroke volume Speech Swallowing Air flow
What does the vagus nerve innervate?
Chemoreceptors Carotid bodies Respiratory and digestive tracts External ear, larynx and pharynx Pacemaker and ventricular muscles
Where is the nucleus for the spinal accessory nerve found?
Medulla
What is the function and innervation of the spinal accessory nerve?
Head rotation and shoulder shrugging
- sternocleidomastoid and trapezius muscles
How is the spinal accessory nerve tested?
Ask patient to turn head against resistance (contraction of the sternocleidomastoid)
Ask patient to shrug against resistance (contraction of the trapezius)
Where is the nucleus of the hypoglossal nerve found?
Medulla
What is the function and innervation of the hypoglossal nerve?
Speech and swallowing
- innervates the tongue
If there is a lesion of the hypoglossal nerve, which way does the tongue deviate and why?
Towards the side of the lesion
- because muscles work to constantly push the tongue out, so any weakness allows the tongue to flop on the side of the lesion
Which cranial nerves are affected if there is a lesion in the cavernous sinus?
III, IV, V1, V2, VI
Can also cause Horner’s syndrome
Which cranial nerves are affected if there is a lesion in the superior orbital fissure.
III, IV, V1 and VI
Which cranial nerves are affected if there is a lesion in the cerebellopontine angle?
V, VII and VIII
Which cranial nerves are affected if there is a lesion in the Jugular foramen?
IX, X, and XI
Which cranial nerves are affected if there is a bulbar palsy?
XI, X, XI and XII
What is the difference between a psudobulbar and a bulba palsy?
Pseudobulbar palsy is an upper motor neuron lesion, involving descending corticoblbar pathways (cortex to nucleus)
Bulbar palsy is an lower motor neuron lesion of the nuclei, cranial nerves or muscles
What are some possible causes of pseudobulbar and bulbar palsy?
Pseudobulbar
- stroke, MS and a space occupying lesion
Bulbar
- brainstem stroke, Guillain-Barree syndrome and myasthenia gravis
