Cranial nerves Flashcards
Which cranial nerves provide the special senses?
Olfaction (I)
Vision (II)
Taste (VII, IX and X)
Hearing and balance (VIII)
Which cranial nerves are general sensory?
Mainly V (Trigeminal) but some input to area around ear from the VII (Facial) and IX (glossopharyngeal)
Which cranial nerves have autonomic functions?
III (Pupillary costriction) VII (Lacrimation VII (Submandibular and sublingual) IX (Parotid) X (input to organs in thorax and abdomen)
What do you test in Olfactory (I) palsy?
Senso of smell
- Unilateral loss
- Bilaterall loss
What do you test in Optic (II) nerve palsy?
Visual acuity
Visual fields
Pupilary reactions
Fundoscopy
What do we test in Oculomotor (III), Trochlear (IV) and Abducens (VI) nerve palsy?
Any evidence of ptosis? Pupil of equal size? Pupillary reactions? Eye movements -Vertical and horizontal
What do we test in trigeminal (V) nerve palsy?
- Sensation in the ophthalmic, maxillary and mandibular divisions
- Power in the muscles of mastication
- Corneal reflex
- Jaw jerk
What do we test in facial (VII) nerve palsy?
Muscles of facial expression
Corneal reflex
(Taste)
What do we test in vestibulococlear (VIII) nerve palsy?
Hearing using Rinne’s and Weber’s tests
Vestibular function using Hallpike-Dix manoeuvre and Untenberger’s test
What do you test in Glossopharyngeal (IX) and Vagus (X) nerve palsy?
Movement of the palate
Gag reflex
(quality of speech)
(quality of cough)
What do you test in Accessory (XI) nerve palsy?
Head turning and shoulder shrugging (sternocleidomastoid and trapezius function)
What do you test for in Hypoglossal (XII) nerve palsy?
Appearance and movement of tongue
What cranial nerves are involved in the Pupillary light reaction?
Afferent = II Efferent = III
What cranial nerves are involved in the corneal reflex (blink reflex)?
Afferent = V Efferent = VII
What cranial nerve is involved in teh Jaw jerk?
Afferent and Efferent = V
What cranial nerves are involved in the Gag reflex?
Afferent = IX Efferent = X
Where do the nuclei of cranial nerves III and IV lie?
Midbrain
Where do the nuclei of cranial nerves V, VI and VII lie?
Pons
Where do the nuclei for the VIII cranial nerve lie?
Pontomedullary junction
Where do the cranial nerve nuclei for IX, X, XI and XII lie?
Medulla
Where can cranial nerves be damaged?
Within the brain (e.g. by ischaemia, tumour)
Crossing the sub-arachnoid space (e.g. by meningitis)
Outside the skull (e.g. by base of skull tumours arising in nasopharynx)
Bilateral III palsy indicates a problem where?
Midbrain
III + IV + VI palsy indicates a problem where
Superior orbital fissure
VI + VII palsy indicates a problem where?
Pons
V and VIII palsy indicates a problem where?
Cerebellopontine angle
Unusual combinations of cranial nerve palsy may indicate what?
? chronic or malignant meningitis
Pure motor signs indicates what?
?Myasthenia
What is Optic neuritis?
- Demyelination within the optic nerve
- Monocular visual loss
- Pain on eye movement
- Reduced visual acuity
- Reduced colour vision
- Optic disc may be swollen
- Often associated with MS
Describe parasympathetic input into pupillary responses
Parasympathetic input leads to constriction of the pupil:
-Loss os parasympathetic input results in a fixed, dilated pupil (e.g. complete third nerve palsy)
Describe the sympathetic input into pupillary responses
Sympathetic input leads to pupillary dilatation:
-Damage anywhere within the sympathetic pathway can lead to a constricted pupil
What are the causes of dilated pupils?
- Youth
- Dim lighting
- Anxiety, excitement
- “Mydriatic” eye drops
- Amphetamine, cocaine overdose
- Third nerve palsy
- Brain death
What are the causes of constricted pupils?
Old age Bright light "Miotic" eye drops Opiate overdose Horner's syndrome
What are the causes of isolated third nerve palsy?
Microvascular:
-Diabetes
-Hypertension
(Pailess, pupil spared)
Compressive:
-Posterior communicating artery aneurysm
-Raised ICP
(Painful, pupil affected)
What are the causes of isolated 6th nerve palsy?
Numerous causes including:
- Idiopathic
- Diabetes
- Meningitis
- Raised ICP
What are the causes of nystagmus?
- Congenital
- Secondary to serious visual impairment
- Secondary to peripheral vestibular problem
- Secondary to central vestibular/ brainstem disease
- Secondary to cerebellar disease
What is trigeminal neuralgia?
Paroxysmal attacks of lancinating pain
Triggers
Middle age and older
Usual cause is vascular loop compressing the 5th nerve in the posterior fossa
Treated medically with carbamazepine
Surgical options if severe
What is Bell’s Palsy?
Unilateral facial weakness
Lower motor neurone type
Often preceded by pain behind ear
Eye closure affected
Risk of corneal damage
Treated with steroids
Usually good recovery
Describe Vestibular Neuronitis
Sudden onset
Disabling vertigo
Vomiting
Gradual recovery
Cause uncertain
Describe Dysarthria
Disordered articulation
Slurring of speech
Describe dysphagia
Difficulty swallowing
Both occur in bulbar and pseudo bulbar palsy
Bulbar = lower motor neurone
Pseudobulbar = upper motor neurone
What is pseudobulbar palsy?
Bilateral UMN lesions (e.g. in vascular lesions of both internal capsules, MND)
- Dysarthria
- Dysphonia
- Dysphagia
- Spastic, ommobile tongue
- Brisk jaw jerk
- Brisk gag reflex
What is bulbar palsy?
Bilateral LMN lesions affecting IX-XIII
Causes include MND, polio, tumours, vascular lesions of the medulla and syphilis
- Wasted, fasciculating tongue
- Dysarthria
- Dysphonia
- Dysphagia
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