Disorders of Special Sensory Function: The Cranial Nerves Flashcards
CN 1?
olfactory N
CN 2?
optic N
CN 3?
occulomotor N
CN4?
trochlear N
CN 5?
trigeminal N
CN 6?
abducens N
CN 7?
facial N
CN 8?
vestibulocochlear N
CN 9?
glossopharyngeal N
CN 10?
vagus N?
CN 11?
accessory N
CN 12?
hypoglossal
what are 4 different functions of cranial nerves?
“Special” senses
“Ordinary” sensation
Control of muscle activity
Autonomic functions
which cranial nerves supply special senses?
Olfaction (I)
Vision (II) (seeing)
Taste (VII, IX and X)
Hearing - and balance (VIII)
which cranial nerve is in control of olfaction?
CN 1
which cranial nerve is in control of vision?
CN 2
which cranial nerves are in control of taste?
VII, IX and X
which cranial nerves are in control of hearing and balance?
VIII
which cranial nerves are in control of ordinary sensation?
Mainly the Vth (trigeminal nerve)
The ear from the VIIth (facial) and IXth (glossopharyneal) nerves
what are the eye muscles innervated by?
III (oculomotor), IV (trochlear) and VI (abducence) (LR6,SO4, rest 3)
what pneumonic is a reminder of innervation of eye muscles?
(LR6,SO4, rest 3)
what are the muscles of mastication innervated by?
V (trigeminal)
what are the muscles of facial expression innervated by?
VII (facial)
what are the muscles of larynx and pharynx innervated by?
mainly X (vagus)
what are the muscles of sternomastoid and trapezius muscle innervated by?
XI (accessory)
what is the autonomic function of occulomotor (CN III)?
Pupillary constriction
what is the autonomic function of facial (CN VII)?
Lacrimation – VII (facial)
Salivation – submandibular and sublingual glands – VII (facial)
what is the autonomic function of glossopharyngeal (CN IX)?
Salivation – parotid gland
what is the autonomic function of vagal (CN X)?
Vagal (X) input to organs in thorax and abdomen
what is tested for in affected olfactory (CN I)?
smell – unilateral or bilateral loss
use of a smell kit
what is tested for in affected optic (CN II)?
visual acuity
visual fields
pupillary reactions
fundoscopy
colour vision
what is tested for in affected III, IV and VI – oculomotor, trochlear and abducence?
any evidence of ptosis?
pupil of equal size?
pupillary reactions
eye movements – vertical and horizontal
what is tested for in affected trigeminal N?
sensation in the ophthalmic, maxillary and mandibular divisions
{light touch/pin prick}
power in the muscles of mastication (clench teeth and open mouth - feel for muscle bulk either side)
corneal reflex
jaw jerk
how do you test corneal reflex?
tiny piece cotton wool touch cornea - patient experiences blinking sensation
how do you test for jaw jerk?
light tap on jaw on finger
what is tested for in affected facial N?
Muscles of facial expression
run through cartoon, ask patient to do each one looking at symmetry and assymmetry
Corneal reflex
efferent pathway of corneal reflex
Taste
loss of sense of taste
what is tested for in affected vestibulocochlear N?
Hearing using Rinne’s and Weber’s tests
Vestibular function using Dix-Hallpike manoevre and Untenberger’s test
what is tested for in affected IX (glossopharyngeal) and X (vagal)?
movement of the palate
gag reflex quality of speech quality of cough
what is tested for in affected IX XI – Accessory nerve?
Head turning and shoulder shrugging
sternomastoid and trapezius function
what is tested for in affected XII – Hypoglossal nerve?
Appearance, movement and power of tongue
what cranial nerves are responsible for Pupillary light reaction?
afferent – II ; efferent – III
what cranial nerves are responsible for Corneal reflex?
afferent – V ; efferent – VII
what cranial nerves are responsible for jaw jerk?
afferent and efferent – V
what cranial nerves are responsible for gag reflex?
afferent – IX ; efferent - X
what is the location of III and IV (Oculomotor and Trochlear) nuclei ?
MID-BRAIN
what is the location of V, VI AND VII (Trigeminal, Abducent and Facial) nuclei?
PONS
what is the location of VIII (Vestibulocochlear) nuclei?
PONTOMEDULLARY
what is the location of IX, X XI and XII (Glossopharyngeal, Vagus, Accessory and Hypoglossal) nuclei?
MEDULLA
where would the lesion be affecting the occulomotor N?
midbrain
where would the lesion be affecting the III +IV+VI?
superior orbital fissure
where would the lesion be affecting the VI +VII?
pons
where would the lesion be affecting the CN V + VIII?
cerebellopontine angle
what would an example be of an unusual combination of CN disfunction?
chronic or malignant meningitis
what is a pure motor sign affecting neuromuscular junction (causing weakness)?
myasthenia gravis
Not all cranial nerve signs imply a cranial nerve lesion, give examples?
eye movement disorders, facial weakness, difficulty swallowing after a stroke
double vision in myasthenia or thyroid eye disease
how can cranial nerves be damaged within the brain?
ischaemia, tumour
how can cranial nerves be damaged crossing sub arachnoid space?
meningitis
how can cranial nerves be damaged outside skull?
base of skull tumours arising in nasopharynx
what is optic neuritis?
demyelination within the optic nerve
what are symptoms of optic neuritis?
monocular visual loss
pain on eye movement
reduced visual acuity
reduced colour vision
optic disc may be swollen
what condition is optic neuritis often associated with?
multiple sclerosis
what are parasympathetic pupillary responses?
constriction of the pupil
what does loss of parasympathetic input of pupil result in?
loss of parasympathetic input results in a fixed, dilated pupil
e.g. complete third nerve palsy
what does loss of sympathetic input of pupil result in
damage anywhere within the sympathetic pathway can lead to a constricted pupil
what is the sympathetic pupillary response?
pupillary dilatation
what are causes of dilated pupils?
Youth
Dim lighting
Anxiety, excitement
“Mydriatic” eye drops
Amphetamine, cocaine overdose
Third nerve palsy
Brain death
what are causes of small pupils?
Old age
Bright light
“Miotic” eye drops
Opiate overdose
Horner’s Syndrome
give examples of eye movement disorders?
Isolated third nerve palsy
Isolated fourth nerve palsy
Isolated sixth nerve palsy
Combination of the above
Supranuclear gaze palsy (not cranial nerve issue)
Nystagmus
what is microvacular third nerve palsy?
diabetes, hypertension
Painless, pupil spared
what is compressive third nerve palsy?
posterior communicating
artery aneurysm, raised ICP
Painful, pupil affected
what is Isolated sixth nerve palsy?
Numerous causes including
idiopathic
diabetes
meningitis
raised intracranial pressure
what is nystagmus?
Congenital
Serious visual impairment
Peripheral vestibular problem
Central vestibular / brainstem disease
Cerebellar disease
Toxins (medication and alcohol) (most common)
what is trigeminal neuralgia?
Paroxysmal attacks of lancinating pain
Triggers
Middle age and older
Caused by vascular loop
Compression fifth nerve in the posterior fossa
what are treatment options of trigeminal neuralgia?
Treated medically with carbamazepine (not well tolerated in older patients)
Surgical options if medication resistant
what is bells palsy?
Unilateral facial weakness
Lower motor neurone type
Often preceded by pain behind ear
Eye closure affected
Risk of corneal damage
how is bells palsy treated?
Treated with steroids
Usually good recovery
what causes upper motor neuronal facial paralysis?
stroke/tumour
what causes lower motor neuronal facial paralysis?
Bell’s Palsy, Lyme, sarcoid
what is vestibular neuronitis?
Sudden onset
Disabling vertigo
Vomiting
Gradual recovery
Cause uncertain ? viral
what is dysarthria?
disordered articulation, slurring of speech
what is dysphagia?
difficulty swallowing
what occurs in bulbar- and pseudobulbar palsy?
dysarthria and dysphagia
what causes bulbar palsy?
lower motor neurone
what causes Pseudobulbar palsy?
upper motor neurone
