Cranial Nerves Flashcards
What are the 12 cranial nerves?
Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducent, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Accessory and Hypoglossal
What does the glossopharyngeal nerve innervate?
Sensory - posterior tongue, tonsil and pharynx
Motor - pharyngeal musculature
What does the vagus nerve innervate?
Motor - heart, lungs, bronchi, GI tract
Sensory - Heart, lungs, bronchi, trachea, larynx, pharynx, GI tract and external ear
What does accessory nerve innervate?
SCM and trapezius muscle
What are the special senses of cranial nerves?
Olfactory - CNI
Vision - CNII
Taste - VII, IX, X
Hearing - VIII
What nerves cause ordinary sensation?
Mainly Vth - trigeminal
Ear - VII and IX
What nerves control muscle activity?
Eye muscles - III, IV and VI
Mastication - V
Facial expression - VII
Larynx and pharynx - mainly X
SCM and trapezius - XI
What nerve causes lacrimation?
Flow of tears - VII
What nerves cause salivation?
Submandibular and sublingual - VII
Parotid gland - IX
What nerve causes autonomic functions to organs in thorax and abdomen - parasympathetic?
Vagus - X
How do we test CN I?
Smell kit
Can be unilateral or bilateral loss
Usually presents in history
How do we test CN II?
Visual acuity, visual fields, pupillary reactions, fundoscopy and colour vision
How do we test CN III, IV and VI?
Ptosis, pupillary reflex, eye movements (H formation)
Ask for diplopia
How do we test CN V?
Sensation in ophthalmic, maxillary and mandibular divisions
Power of muscles of mastication, corneal reflex, and jaw jerk
How do we test CN VII?
Muscles of facial expression, corneal reflex for efferent pathway and sense of taste
How do we test CN VIII?
Hearing using Rinne’s and Weber’s tests
Vestibular function using Dix-Hallpike manoeuvre and Untenberger’s test
How do we test CN IX and X?
Movement of the palate, gag reflex, quality of speech and quality of cough
How do we test CN XI?
Head turning and shoulder shrugging
How do we test CN XII?
Appearance, movement and power of the tongue
What cranial nerves are involved in the pupillary light reflex?
Afferent - II
Efferent - III
What cranial nerves are involved in the corneal reflex?
Afferent - V
Efferent - VII
What cranial nerve is involved in the jaw jerk reflex?
Afferent and efferent - V
What cranial nerves are involved in the gag reflex?
Afferent - IX
Efferent - X
Where is the location of the cranial nerve nuclei?
III + IV - Midbrain
V, VI + VII - Pons
VIII - Pontomedullary junction
IX, X, XI + XII - Medulla
What combination of cranial nerves can show superior orbital fissure affected?
III, IV and VI
What combination of cranial nerves can show cerebellopontine angle affected?
V and VIII
How can cranial nerves become damaged?
Within the brain - ischemia or tumour
Crossing subarachnoid space - meningitis
Outside of skull - Base of skull tumours arising in nasopharynx
Describe optic neuritis
Inflammation of optic nerve - demyelination
Monocular visual loss, pain on eye movement, reduced visual acuity + colour vision, optic disc can be swollen
Often associated with MS
What is the parasympathetic pupillary response?
Constriction of pupil
Loss of this - results in fixed dilated pupil
Ex. complete CN III palsy
What is the sympathetic pupillary response?
Pupillary dilatation
Damage anywhere within the sympathetic pathway can lead to constricted pupil
What are come causes of dilated pupils?
Youth, dim lighting, anxiety, excitement, mydriatic eye drops, amphetamine, cocaine overdose, CN III palsy and brain death
What are some causes of constricted pupils?
Old age, bright light, miotic eye drops, opiate overdose and Horner’s syndrome
What are some eye movement disorders?
Isolated CN III palsy, VI palsy, VI palsy
Combination of above
Supranuclear gaze palsy
Nystagmus
What are the 2 causes of isolated third nerve palsy?
Microvascular - diabetes, hypertension
Compressive - posterior communicating artery aneurysm and raised ICP
What are symptoms of microvascular and compressive third nerve palsy?
Painless and pupil spared - microvascular
Painful (headache) and pupil affected - compressive
What are some cause of isolated sixth nerve palsy?
Idiopathic, diabetes, meningitis, and raised ICP
What are some causes for nystagmus?
Congenital, serious visual impairment, peripheral vestibular problem, central vestibular/ brainstem disease, cerebellar disease and toxins (alcohol and meds)
Describe trigeminal neuralgia
Paroxysmal attacks of lancinating pain in face
Triggers are chewing, speaking, cold air
Middle age and older
Caused by vascular loop which compresses CN V in posterior fossa
What is the treatment for trigeminal neuralgia?
Medically - carbamazepine and other antiepileptic medication
Surgical - if medication resistant
Describe Bell’s palsy
Idiopathic facial nerve palsy
Unilateral facial weakness, LMN type, can have pain behind ear, eye closure, risk of corneal damage
Treated with steroids
What is the difference between UMN and LMN facial paralysis?
UMN - caused by stroke or tumour. Involves forehead
LMN - caused by bell’s palsy, lyme, sarcoid. No involvement of forehead
Describe vestibular neuronitis
Sudden onset disabling vertigo
Vomiting
Gradual recovery
Cause is uncertain - viral
What is bulbar and pseudobulbar palsy?
Bulbar - LMN
Pseudobulbar - UPM
Describe pseudobulbar palsy
Bilateral UMN lesions - internal capsule, MND
Symptoms - dysarthria, dysphonia, dysphagia, spastic immobile tongue, brisk jaw jerk and gag reflex
Describe bulbar palsy
Bilateral LMN lesions affecting IX - XII - MND, polio, tumour, vascular lesion of medulla and syphilis
Symptoms - wasting, dysarthria, dysphagia, dysphonia
