cranial nerve examination Flashcards
Optic tract lesions
-Bitemporal inferior quadrantinopia: Lesion from above (craniopharyngioma)
-Bitemporal superior quadrantinopia: lesion from below (pituitary tumour)
-Lesion between chiasm and eye: unilateral blindness
-Lesion between visual cortex and chiasm: homonymous hemianopia
other than bitemporal hemianopia, what are other signs of pituitary tumour
-Raised ICP, papilloedema on fundoscopy
-Hyperpituitarism
–> If growth hormone: acromegaly-prognathism, enlarged hands and feet, prominent brow
–> if prolactin: increased lactation, loss of libido in men, erectile dysfunction
CN 1: Anatomy and test
Bulbs lie inferior to frontal lobe
Then pass inferiorly to reach nasal mucosa
Test: smelling salts
Causes of loss of smell
Viral infection
Nasal tumour
Frontal cerebral lesions e.g. meningioma
Optic nerve: anatomy
Optic nerve–> optic canal–> optic chiasm–> nasal fibres cross over–> LGN–> visual cortex
- Optic nerve begins at retina
- Exits orbit via optic canal
- Right and left optic nerves come together anterior to pituitary to form optic chiasm
- Nasal fibres from each retina cross over to join temporal fibres that remain uncrossed
- Fibres of optic tract travel to lateral geniculate nucleus in the thalamus
- Optic radiations travel from LGN to visual cortex
Causes of loss of visual acuity
-Cataract
-Refractive errors
Retinal diseases: macular degeneration
Optic nerve pathology eg optic neuritis
Higher lesions
Optic nerve test:
- Acuity (snellen chart)- 6/6 second number is variable
- Fundoscopy
- Fields
- Colour vision
3,4, 6
-3 + 4 originate in midbrain, 6 in pons
-Travel in cavernous sinus before exiting skull via superior orbital fissure
Test:
-Eye movements (H shape)
-Direct and consensual pupillary response
Anatomy of light reflex
Optic nerve –> pretectal nucelus –> efferent fibres to EW nucleus (on both ipsilateral and contralateral)
- Afferent limb: optic nerve
- Synapses in pretectal nucleus: efferent limbs carried to edinger westfall nucleus on both sides brain (ipsilateral and contralateral)
- Efferent fibres of 3 carry light reflex to eye
- Synapses in ciliary ganglion along its course
- Innervates ciliary sphincter
What does direct and consensual pupillary reflex test?
Direct: ipsilateral efferent limb
Consensual: contralateral efferent limb
How would palsy of 3 present?
- Loss of accommodation reflex
- Ptosis
- Pupillary dilatation
- Down and out palsy (unopposed lateral rectus
How would 4 palsy present clinically?
Eye deviated upwards: weakening of superior oblique, impairing ability to look downwards
Unable to walk down stairs, read a book
How would 6 palsy present clinically?
Eye deviated medially (unopposed medial rectus)
Unable to abduct eye
How would you test trigeminal nerve?
- Test all sensory regions with cotton wool
- Test corneal reflex
- Test muscles of mastication: get pt to clench jaw, then feel temple/side of jaw
Facial nerve test:
Muscles of facial expression
What is the difference between UMN and LMN injury to facial nerve?
UMN lesion: preservation of frontalis due to dual innervation from both hemispheres.
LMN: frontalis lost, no raising of eyebrows
Rinne’s
Normal: air conduction better than bone conduction
Sensorineural deafness: air conduction better than bone conduction
Conductive: bone conduction better than air conduction
Weber’s test
Normal: sound head equally both sides
Sensorineural deafness: sound heard better on unaffected side
Conductive: sound heard better on affected side
Vestibulocochlear nerve testing
Supplies: hearing and balance
Test:
-Weber’s
-Rinne’s
Glossopharyngeal nerve supply and testing:
Cranial nerve foramen:
-Jugular foramen
Supply
-Taste posterior 1/3rd tongue
-parasympathetic to parotid gland
-Sensation to palate
To test: touch to each side of uvula and look for gag reflex (i.e. normal sensation): lost on affected side
Vagus nerve: path, supply and how to test
-Exits via jugular foramen
-Travels in carotid sheath
-Travels inferiorly to supply innervation to pharynx, larynx, palate
-Continues, to supply branches to heart, lungs and gut
Supplies: muscles of larynx and pharynx
Parasympathetic supply to gut
To test: ask pt to open mouth and say ‘ah’: uvula deviates to unaffected side
Accessory nerve
Originates from nerves in upper spinal cord. Enters skull via foramen magnum, exits again via jugular foramen
Supplies: trapezius and sternocleidomastoid
Test:
-When testing sternocleidomastoid: ask pt to turn to right, palpate left sternocleidomastoid
Hypoglossal nerve
Supply: all muscles in tongue except palatoglossus (vagus nerve)
Test: stick out tongue: will deviate to affected side (overaction of genioglossus on contralateral side)
AMTS score
Ask pt to remember address, ask them to repeat at the end (42 west street)
Time
-What time is it to nearest hour/what time of day is it?
-What year is it?
Place
-Where are we?
Person
-What is your age?
-What is your date of birth?
General knowledge
-Who is the prime minister/monarch
-In what year did world war 1 begin?
Other
-Can the pt recognise job roles of two members of staff
-Count backwards from 20-1
To complete examination (cranial nerves)
-Full neurological examination including the upper and lower limbs.
-Neuroimaging (e.g. MRI head): if there are concerns about space-occupying lesions or demyelination.
-Formal hearing assessment (including pure tone audiometry): if there are concerns about vestibulocochlear nerve function
-Bitemporal hemianompia: endocrine exam, pituitary profile, referral to endocrine and MDT
cerebello-pontine angle tumour
-Mostly acoustic neuromas
-Most common posterior fossa tumour
-Cranial nerves involved: 5, 7, 8
Describe cause of macular sparing
Lesions affecting the calcarine sulcus of the occipital lobe tend to cause homonymous hemianopia with sparing of the macula.
Macular vision is spared given the dual blood supply to the anterior portion of the visual centre (PCA and MCA).
Name cranial nerve palsy associated with oblique diplopia
Oblique diplopia (images appear at an angle to each other) occurs due to dysfunction of both vertical and horizontal muscles.
This type of diplopia is associated with cranial nerve III palsy.
Name cranial nerve palsy associated with horizontal diplopia
Horizontal diplopia (images appear side-by-side) occurs due to dysfunction of the medial and/or lateral rectus muscles.
This type of diplopia is associated with cranial nerve VI palsy.
Name cranial nerve palsy associated with vertical diplopia
Vertical diplopia (images appear on top of each other) occurs due to dysfunction of the superior and/or inferior oblique muscles.
This type of diplopia is associated with cranial nerve IV palsy.
Describe anatomy of corneal reflex
Afferent: ophthalmic division trigeminal nerve
Efferent: facial nerve to orbicularis oculi
Describe hypoglossal nerve palsy
A hypoglossal nerve (CN XII) palsy causes atrophy of the ipsilateral tongue muscles resulting in tongue deviation towards the side of the lesion
Describe sensory functions of glossopharyngeal
The glossopharyngeal nerve transmits sensory information that conveys taste from the posterior third of the tongue.
Visceral sensory fibres of CN IX also mediate the afferent limb of the gag reflex.
Describe gag reflex supply
Afferent: glossopharyngeal
Efferent: vagus
Describe 3 things to assess on inspection of pupils
Size
Shape
Symmetry
Name 3 central causes of vertigo
Central causes of vertigo include:
Posterior circulation stroke (POCS): acute onset vertigo, affects structures such as the brainstem or cerebellum
Multiple sclerosis (MS): demyelination of the brainstem and cerebellum
Space-occupying lesions: tumours in the posterior fossa cause compression of the brainstem and cerebellum
How would you assess vestibular-ocular reflex
Explain to the patient that the test will involve briskly turning their head and then gain consent to proceed
Sit facing the patient and ask them to fixate on your nose at all times during the test
Hold their head in your hands (one hand covering each ear) and rotate it rapidly to the left, at a medium amplitude
Repeat this process, but this time turn the head to the right
In the context of a vestibular lesion, the eyes will first move in the direction of the head (losing fixation), before a corrective refixation saccade occurs.
How would you assess jaw jerk
Ask the patient to open their mouth
Place your finger horizontally across the patient’s chin
Tap your finger gently with the tendon hammer
In healthy individuals, this should trigger a slight closure of the mouth.
In patients with upper motor neuron lesions, the jaw may briskly move upwards causing the mouth to close completely.
Describe features of RAPD
Normally light shone into either eye should constrict both pupils equally.
When the afferent limb in one of the optic nerves is damaged, partially or completely, both pupils will constrict less when light is shone into the affected eye compared to the healthy eye.
The pupils, therefore, appear to relatively dilate when swinging the torch from the healthy to the affected eye. This is termed a relative afferent pupillary defect (RAPD).
Describe function of hypoglossal nerve
The hypoglossal nerve (CN XII) transmits motor information to the extrinsic muscles of the tongue (except for palatoglossus which is innervated by the vagus nerve).
Describe motor component glossopharyngeal nerve
The glossopharyngeal nerve transmits motor information to the stylopharyngeus muscle which elevates the pharynx during swallowing and speech.
Name the muscle(s) supplied by the abducens nerve and describe the clinical features of abducens nerve palsy
The abducens nerve (CN VI) innervates the lateral rectus muscle.
Clinical features of abducens nerve palsy include:
Convergent squint (due to unopposed adduction)
Horizontal diplopia
Name the muscle(s) supplied by the trochlear nerve and describe the clinical features of trochlear nerve palsy
The trochlear nerve innervates the superior oblique muscle.
Clinical features of a trochlear nerve palsy include:
Vertical diplopia when looking inferiorly
Torsional diplopia
Tilting of the head forwards with the chin tucked in (compensatory)
Outline the underlying mechanism that causes a relative afferent pupillary defect (RAPD)
A relative afferent pupillary defect (RAPD) occurs when the afferent limb in one of the optic nerves is damaged (this can be either partially or completely).
When examining a patient with a relative afferent pupillary defect, both pupils will constrict less when light is shone into the affected eye. This failure of constriction means the pupils, therefore, appear to dilate when swinging the torch from the healthy to the affected eye, as less light is detected by the affected eye.
Describe function of glossopharyngeal nerve
The glossopharyngeal nerve transmits motor information to the stylopharyngeus muscle which elevates the pharynx during swallowing and speech. The glossopharyngeal nerve also transmits sensory information that conveys taste from the posterior third of the tongue. Visceral sensory fibres of CN IX also mediate the afferent limb of the gag reflex.
Name muscles innervated by oculomotor nerve
Superior rectus
Inferior rectus
Medial rectus
Inferior oblique
Levator palpebrae superioris
Sphincter pupillae
Name 3 causes of ptosis
Oculomotor nerve palsy
Horner’s syndrome
Neuromuscular pathology (e.g. myasthenia gravis)
How do you test for optic nerve
Inspect pupils (size, shape, symmetry)
Visual acuity (second number is variable)
Pupillary reflex: direct, consensual, swinging light test
Accommodation reflex
Test colour
Neglect
Fields
Blind spot
Fundoscopy
3,4,6
Inspect eyelids
Eye movements (H test)
Pupillary reflex
Trigeminal nerve testing summary
Sensory: light touch
Motor: palpate masseter and temporalis, apply resistance to opening mouth to assess pterygoids
Reflexes: Jaw jerk, corneal reflex
Facial nerve assessment
Sensory: taste: ask pt if any change to taste
Ask about hearing changes (stapedius)
Inspection
Facial movements
Vestibulocochlear nerve
Gross hearing assessment
Weber’s test
Rinne’s test
Vestibulo-ocular reflex
Glossopharyngeal and vagus nerves
-Ask pt if changes in voice/cough/swallow
-Inspect soft palate: ask to say ‘ah’
-Ask pt to cough
-Swallow assessment
-Gag reflex
How do you test accommodation reflex?
. Ask the patient to focus on a distant object (clock on the wall/light switch).
- Place your finger approximately 20-30cm in front of their eyes (alternatively, use the patient’s own thumb).
- Ask the patient to switch from looking at the distant object to the nearby finger/thumb.
- Observe the pupils, you should see constriction and convergence bilaterally.
Describe blind spot
A physiological blind spot exists in all healthy individuals as a result of the lack of photoreceptor cells in the area where the optic nerve passes through the optic disc. In day to day life, the brain does an excellent job of reducing our awareness of the blind spot by using information from other areas of the retina and the other eye to mask the defect.
How would you assess blind spot
- Sit directly opposite the patient, at a distance of around 1 metre.
- Ask the patient to cover one eye with their hand.
- If the patient covers their right eye, you should cover your left eye (mirroring the patient).
- Ask the patient to focus on part of your face (e.g. nose) and not move their head or eyes during the assessment. You should do the same and focus your gaze on the patient’s face.
- Using a red hatpin (or alternatively, a cotton bud stained with fluorescein/pen with a red base) start by identifying and assessing the patient’s blind spot in comparison to the size of your own. The red hatpin needs to be positioned at an equal distance between you and the patient for this to work.
- Ask the patient to say when the red part of the hatpin disappears, whilst continuing to focus on the same point on your face.
- With the red hatpin positioned equidistant between you and the patient, slowly move it laterally until the patient reports the disappearance of the top of the hatpin. The blind spot is normally found just temporal to central vision at eye level. The disappearance of the hatpin should occur at a similar point for you and the patient.
- After the hatpin has disappeared for the patient, continue to move it laterally and ask the patient to let you know when they can see it again. The point at which the patient reports the hatpin re-appearing should be similar to the point at which it re-appears for you (presuming the patient and you have a normal blind spot).
- You can further assess the superior and inferior borders of the blind spot using the same process.
Describe uvula deviation
Inspect the palate and uvula which should elevate symmetrically, with the uvula remaining in the midline. A vagus nerve lesion will cause asymmetrical elevation of the palate and uvula deviation away from the lesion.
Describe abnormal cough assessment
Vagus nerve lesions can result in the presence of a weak, non-explosive sounding bovine cough caused by an inability to close the glottis.
Describe abnormal swallow assessment
Ask the patient to take a small sip of water (approximately 3 teaspoons) and observe the patient swallow. The presence of a cough or a change to the quality of their voice suggests an ineffective swallow which can be caused by both glossopharyngeal (afferent) and vagus (efferent) nerve pathology.
