Examination of cranial nerves Flashcards
List the cranial nerves 1-12
- Olfactory
- Optic
- Occulomotor
- Trochlear
- Trigeminal
- Abducens
- Facial
- Vestibulococclear
- Glossopharyngeal
- Vagus
- Accessory
- Hypoglossal
What type of nerve is CNI and where does it emerge from
Olfactory nerve is a sensory nerve emerging from the cribriform plate of the ethmoid bone
How is CNI examined
- clove used to see if patient can perceive the scent
- one nostril tested at a time
What is the abnormal response to CNI examination and what could this signify
Unilateral loss could imply structural brain lesion affecting olfactory bulb/tract - could also be due to deviated septum or blocked nasal passage
Bilateral loss can occur with rhinitis or damage to cribriform plate
What type of nerve is CNII and where does it emerge from
Optic nerve is a sensory nerve which emerges from the optic foramen
How is CNII tested for visual acuity
Tests for the sharpness of image produced by optic nerve
- Snellen’s test: letter charts read
- 20/20 = normal vision
- 20/200 = legally blind
How is CNII tested for visual fields
Tests how wide you can see as a result of optic nerve
- the examiner compares patient’s visual field to their own
- wiggling finger/white pin and ask to say ‘now’
Why will a pituitary tumour affect visual field
Because the pituitary sits close to optic chasm and so a tumour will compress and damage the nasal part of the visual field
How is CNII and CNIII tested for pupillary reflex
The optic nerve detects light = afferent
The oculomotor nerve causes constriction = efferent
- observe ptosis (shows oculomotor damage)
- observe pupil size
- observe direct and consensual response to light
What happens when there is an afferent defect in the pupillary reflex test
direct and consensual reflexes are absent when light is shone in bad eye
direct and consensual reflexes present when shone in good eye
What happens when there is an efferent defect in the pupillary reflex test
direct reflex absence and consensual reflex presence when shone in bad eye
direct reflex present and consensual reflex absence when shone in good eye
What is relative afferent pupillary defect (RAPD) and what is it a common sign of
Causes asymmetric pupillary reaction to light when it is shone back and forth (swinging) and it is a common sign of asymmetric optic nerve disease/damage
Outline what response occurs in the RAPD test
When the light is shone on the stronger optic nerve there will be more constriction and when swung to the weaker side there will be slight dilation
How can accommodation be tested for
This shows how the lens adapts to distance and is related to the optic nerve; Ask the patient to look in the distance and then at the tip of their nose
- diverging when looking far
- converging when looking near
List the 6 extra ocular muscle of the eye and how they move the eye
- Superior rectus = upwards
- Lateral rectus = away from nose
- Medial rectus = towards nose
- Inferior rectus = downwards
- Superior oblique = inward downward rotation
- Inferior oblique = outward upward rotation
What are the 6 extra ocular muscles of the eye innervated by
- Superior rectus = Oculomotor nerve
- Lateral rectus = Abducens nerve
- Medial rectus = Oculomotor nerve
- Inferior rectus = Oculomotor nerve
- Superior oblique = Trochlear nerve
- Inferior oblique = Oculomotor nerve
LR6 SO4
How can the extra-ocular movements of a patient be tested
Ask the patient to follow finger in H pattern without moving head, pause at ends of each direction of gaze to observe for nystagmus (dancing eyes)
What damage does ptosis suggest
Weakness of the elevator muscle causes drooping of eyelid which occurs in myasthenia graves and CNIII palsy
What damage does strabismus cause
This is ‘lazy eye’ where they are not properly aligned and so there is a suint which can cause double vision
What damage does nystagmus suggest
This is where the eye makes abnormal repetitive uncontrolled movements thus inability to focus; there is an issue with the semi-circular canal which balances images as there is abnormal stimulation
- the eye will flip back towards to semi-circular canal
What is CNIII palsy characterised by
- Ptosis (levator palpebrae superioris)
- Large pupil (pupillary constrictor)
- Eye is down and out (due to unopposed action of LR and SO so their actions will be exaggerated)
What is CNIV palsy characterised by
- Diplopia on looking down-vertical diplopia due to weakened depression (SO)
- The bad eye will sit slightly higher than the good one
What is CNVI palsy characterised by
Horizontal diplopia (LR)
What is Horner’s syndrome characterised by
Ptosis (drooping lid)
Anhidrosis (no sweating)
Miosis (pupillary constriction)
Enophthalmos (retruded eyeball)
Result of surgery/trauma to neck, lung or breast cancer infiltration to superior cervical sympathetic ganglion
What are the branches of CNV and where does each branch emerge
Trigeminal nerve branches
- Ophthalmic = supraorbital fissure
- Maxillary = foramen ovale
- Mandibulary = foramen rotundum
What type of nerve is CNV
Trigeminal nerve is sensory and motor
- all three branches are sensory
- only mandibular branch is motor (muscles of mastication)
What are the muscles of mastication
- Temporalis
- Masseter
- Lateral pterygoid
- Medial pterygoid
How is the sensory function of CNV tested
To test sensory aspect of the trigeminal nerve, take a cotton wisp and touch it to each region and ask the patient to say now when they feel the touch
How can the motor function of CNV be tested
- palpate temporalis and masseter muscles when teeth are clenched
- ask patient to open and close mouth and watch for lateral jaw deviation (suggests one sided damage)
- ask patient to protrude jaw to either side against resistance
What are the branches of CNVII
Facial nerve
- Temporal
- Zygomatic
- Buccal
- Mandibular
- Cervical
What are the functions of CNVII
- sensory = taste to anterior 2/3 of tongue
- motor = muscles of facial expression
- autonomic = PNS to glands (lacrimal, submental, submandibular)
How can the sensory function of CNVII be tested
Protrude tongue and apply a sample of solution to one side of the anterior two thirds which is innervated by the facial nerve; with the tongue protruded ask the patient which one of the four tastes it was
How can the motor function of CNVII be tested
Observe for asymmetry; widening of the palpebral fissure of flattening of the nasolabial fold
Ask patient to wrinkle forehead by raising eyebrows and closing eyes tight
Palpate for differences of ability to resist eye opening
Ask patient to show teeth, puff cheeks and appose their lips
What causes an abnormal response when testing the motor function of CNVII
- Lower motor neurone lesion causes entire side of face weakness
- Upper motor neurone lesion of the contralateral supra nuclear pathway causes weakness in the lower muscles of facial expression
- Upper muscles of facial expression are less affected because the facial nucleus that innervates them receives partial input from the ipsilateral hemisphere
What causes CNVII palsy (LMN lesions)
- Infections; Varicella zoster (shingles), Ottitis media, Ramsey Hunt syndrome
- Bell’s palsy (viral infections)
- Injection into parotid gland
- Malignant tumour of parotid gland
- Lyme disease
What causes CNVII palsy (UMN lesions)
Cerebrovascular accidents; stroke, brain tumours, traumatic brain injuries, cerebral palsy
What causes bilateral CNVII palsy
- Guillain-Barre’s syndrome
2. Moebius syndrome
What is Guillain-Barre’s syndrome
Autoimmune condition of peripheral nervous system causing CNVII palsy
What is Moebius syndrome
Congenital bilateral facial nerve weakness/paralysis resulting from underdevelopment of the nerve causing CNVII palsy and affecting CNVI
What are the clinical presentations of Ramsay-Hunt syndrome
- vesicular rash on external ear
- LMN paralysis of facial nerve
- loss of taste sensation over anterior 2/3 tongue
What are the clinical presentations of Bell’s palsy
- inability to wrinkle brown
- drooping eyelid and inability to close eye
- inability to puff cheeks; no muscle tone
- drooping mouth; inability to smile or pucker
What is the role of CNVIII
Vestibulo-cochlear nerve
- Vestivular nerve = transmits sensory information by vestibular hair cells in semilunar canal and is for sensation of boy positioning and gaze stability
- Cochlear nerve = auditory sensory information from cochlear
How is CNVIII tested
Rinne and Weber tests;
- Rinne - air conduction is greater than bone conduction and this is tested by playing a sound at the front and behind the ear
- Weber - normally, patients will either hear it equally from both ears or respond that they are not sure when it is placed onto their forehead
Describe the abnormal responses from Rinne and Weber tests
This tests the functioning of the vestibule-cochlear nerve
- Rinne; in conductive hearing loss, bone conduction is greater than air and in sensorineural deafness air conduction is greater than bone
- Weber; the patient will lateralise it to one ear (affected ear in conductive hearing loss and sensorineural deafness)
What is the role of CNIX and where does it emerge
The glossopharyngeal nerve is involved in motor, autonomic, general and special sensory functions and it emerges from the jugular foramen
How is CNIX tested
The glossopharyngeal nerve is tested by checking for
- gag reflex
- taste sensation
- asking the patient to swallow
What is the role of CNX
The vagus nerve
1. Motor = voluntary muscle of the pharynx and most of larynx
- Autonomic = parasympathetic component of smooth muscle of viscera of thorax and abdomen
- Sensory = visceral sensory information from thorax and abdomen, chemoreceptors of aortic bodies
How are CNIX and CNX tested
Checking palatal elevation by having the patient say aahhh and assessing their gag reflex by stroking the soft palate
What is an abnormal response to CNIX and CNX tests
Unilateral palatal weakness where the palate fails to elevate on one side and the gag reflex will also be absent on this side
What is the role of CNXI
The accessory nerve is responsible for voluntary motor innervation to sternocleidomastoid and trapezius muscles
How is CNXI tested
Accessory nerve
- observe atrophy or asymmetry of muscles
- observe for quickness of shoulder shrug and ask to shrug against resistance
- ask patient to turn head with opposite side against resistance while watching and palpating sternocleidomastoid muscle
- ask the patient to flex their head forward against resistance
What is the role of CNXII and where does it emerge from
The hypoglossal nerve is responsible for motor innervation to all muscles of the tongue except the palatoglossus muscle (CNX) and emerges through foramen magnum; LMN lesion causes lateralised tongue protrusion
Which nerve is affected:
Patient presented with headache and vomitting. On examination, patient’s jaw moves to the left when opened. There is one sided reduced sensation with loss of corneal reflex
Trigeminal
Which nerve is affected:
65 year old patient was walking in the garden where he noticed drooping and weakness in the left side of his face and was unable to raise the left eyebrow
Facial
Which nerve is affected:
A patient complains of impairment of taste and smell. On formal testing, sense of smell is lost and the taste is mildly reduced
Olfactory
Which nerve is affected:
74 year old presents with headache and dizziness and instability of gait. The patients tongue deviates to the left when protruded. The patient cannot easily move the tongue from side to side
Hypoglossal
Which nerve is affected:
32 year old male with insulin deficiency diabetes mellitus (IDDM) presents with diplopia on looking to the right and is unable to abduct the right eye
Abducens
