Cranial nerves 1-6 Flashcards
What are the cranial nerves
Twelve pairs of nerves attached directly to the brain
Motor nerve
- supplies glands/muscles
Sensory
- organ which detects a signal to the brain
Types of sensory
- ) Somatic: general sensations
- ) Special sensations: taste/smell
- ) Autonomic sensations: measuring co2 in brain/eye pressure
Types of sensory
- ) Somatic: skeletal muscle
- ) Branchial: for branchial arches. (in embryos we have gill arches which fuse and branchial nerves supply these structures)
- ) Autonomic: for smooth muscle
Some Say Money Matters But My Brother Says Big Brains Matter Most
s: sensory only
b: both
m; motor
Testing olfaction
- scratch and sniff
- vials of scents e.g. vinegar
What causes problem to the olfactory nerve
- ) Olfactory groove meningioma: compresses nerve
2. ) Trauma: fine nerve fibres are damage
Optic nerve
- for vision
- runs through the optic canal
- has a complex pathway to the occipital cortex
What does the lens do
- lens inverts image
- image coming from the right side willf all onto the left side of our vision
How to test the optic nerve
- ) Visual fields
- ) Pupil reflexes
- ) Visual acuity
- ) Fundoscory
How to test the optic nerve
- ) Visual fields
- ) Pupil reflexes
- ) Visual acuity
- ) Fundoscopy
Pupillary problems
- ) Syphillis
- ) Horner’s syndrome
- ) Holmes-Adie “tonic” pupil
- ) Physiological anisocoria
Oculomotor
- has parasympathetic fibres
- supplies 4 muscles:
1. ) Superior rectus
2. ) Inferior rectus
3. ) Medial rectus
4. ) Inferior rectus - parasympathetic to pupil and to focus the lens
Anatomy of the oculomotor
- exits the midbrain near the posterior cerebral arteries
- passes alongside the cavernous sinus
- through the superior orbital fissure
- branches into two
What happens when the oculomotor nerve is damaged
- Eye is abducted (lateral rectus)
- looks down and rotates (superior oblique)
- caused by third nerve palsy
Name of 4th cranial nerve
Trochlear
Anatomy of 4th cranial nerve
- exits brain dorsally
- oases round the front near posterior cerebral arteries
- passes alongside cavernous sinus
- through the superior orbital fissure
4th cranial nerve
- supplies the superior oblique muscle
What happens when its damaged
- double vision when looking down
Name of 5th cranial nerve
Trigeminal
Function
- ) Supplies sensation to face and mouth
2. ) Muscles of mastication: temporalis/masseter/pterygoids
Anatomy
- exits from pons and passes directly into Meckle’s cave where it divides into three
- ophthalmic branch passes through the superior orbital fissure
- Maxillary branch@ foramen rotundum
- Mandibular branch: foramen ovale
The central trigeminal pathways
- Large nucleus midbrain to cervical cord
- 3 neuron pathways: sensory roots-> trigeminal sensory nuclei-> thalamus-> cortex
The 3 sensory nuceli
- ) Mesencephalic: jaw jerk
- ) Main: touch and position from face
- ) Spinal (pain and temp from face)
- 1 motor nucleus
Anatomy of cranial nerve 6
- exits brain between the pons and medulla
- passes from the posterior to middle cranial fossa
- passes alongside cavernous sinus
- through superior orbital fissure
What happens when it is damaged
Eye won’t look laterally
Name of cranial nerve 7
Facial nerve
Functions of the facial nerve
- ) Supplies sensation to muscles of facial expression and stapedius
- ) Supplies special taste: taste buds of the anterior two thirds of the tongue
- ) Visceral motor: motor control to the lacrimal gland/submandibular/sublingual salivary glands
Cortical control of facial muscles
- contralateral innervation of the lower face
- bilateral innervation of the upper face
- ‘forehead sparing’ means you can still open both your eyes
Damage to the facial nerve
- ) Bell’s palsy: facial nerve lesion
2. ) Supranuclear lesion
Examination: motor
1.) Motor: inspect face for weakness/drooping of lower eyelid
Examination: sensory
Use sugar/salt and ask the patient to identify the taste
Causes of bell’s palsy
- fractures of the petrous bone
- middle ear infections
= tumours at the CPA - inflammation of the parotid gland
- Tumours of the parotid gland
Name of cranial nerve 8
Vestibulocochlear
Functions of the vestibulocochlear nerve
- conducts auditory and vestibular-related impulses from the organ of Corti/the semi-circular canals/the utricle/the saccule
examining the cochlar
- using air induction
test by whispering a number into the patients ears by using a tuning fork
examining the vestibular
stand on one leg with eyes closed
Damage to the vestibulocochlear nerve
- skull fractures
- toxic drug effects
- ear infections
- vestibular schwannoma
Name of cranial nerve 9
Glossopharyngeal nerve
Anatomy
- emerges from the lateral sulcus of the medulla
- exits skull via the jugular foramen
Functions
- taste buds of the posterior third of the tonhue
- parotid gland
- skin of external ear
- posterior third of the tongue/pharynx/eustachian tube
Test
Testing back of the mouth with a lollipop stick
Anatomy
- emerges from the medulla
- exits skull through jugular foramen
Function
- swallowing
- cardiovascular/GI regulation
- sensations of hunger
Examination
- ask patient to say ‘ahhhh’ and observe the elevation of the palate
Name of the 11th nerve
Accessory nerve
Anatomy
- cell bodies of the nerve are situated in the ventral horn of the upper five segments of the spinal cord
- send fibres up through the formen magnim which then exit the skull with cranial nerves IX and X through the jugular foramen
Function
- supplies the sternocleidomastoid and trapezius muscles
Examination: sternocleidomastoid muscles
Inspect neck as patient turns the head against resistance
Examination: trapezius
Inspect from the back and front + ask the patient to shrug the shoulders
Name of the 12th cranial nerve
Hypoglossal
Anatomy
- Cell bodies located in the hypoglossal nucleus which lies between the dorsal motor nucleus of the vagus and the midline of the medulla
- exits the skull through the hypoglossal canal
Examination:
Ask patient to protrude tongue
- If something is wrong you get atrophy and fibrilliations (hallmarks of lower motor neuron lesion)
CBA syndrome
Syndrome due to a mass of the cerebellopontine
- Most commonly a vestibular schwannoma
Symptoms of syndrome
- tinnitus
- dizziness
- facial nerve plasy
Jugular foramen syndrome
- Due to a lesion in the jugular foramen
- Signs:
1. ) Loss of taste sensation in posterior third of tongue
2. ) Paralysis of vocal cords
