Cranial Nerves Flashcards
Name all the cranial nerves
“Over on old towering top, a fine Victorian gentleman viewed a hawk”
CN I = Olfactory
CN II = Optic
CN III = Oculomotor
CN IV = Trochlear
CN V = Trigeminal
CN VI = Abducens
CN VII = Facial
CN VIII = Vestibulocochlear
CN IX = Glossopharyngeal
CN X = Vagus
CN XI = Accessory
CN XII = Hypoglossal
State whether each nerve is sensory, motor or both
“Some say marry money but my brother says big brains matter more”
CN I = sensory
CN II = sensory
CN III = motor
CN IV = motor
CN V = both (sensory + motor)
CN VI = motor
CN VII = both (sensory + motor)
CN VIII = sensory
CN IX = both (sensory + motor)
CN X = both (sensory + motor)
CN XI = motor
CN XII = motor
What structures are innervated by the olfactory nerve?
Olfactory epithelium
What is the function of the olfactory nerve?
Olfaction
Where does the olfactory nerve enter/exit in the skull and brain?
Skull - cribriform plate
Brain - anterior perforated substance
What structures are innervated by the optic nerve?
retina
What is the function of the optic nerve?
Vision; pupillary light reflex
Where does the optic nerve enter/exit the skull?
Optic canal
What structures are innervated by the oculomotor nerve?
motor - Superior, inferior and middle rectus muscles
Inferior oblique muscle
levator palpebrae superioris muscle
What is the function of the oculomotor nerve?
motor - movement of the eyeball and elevation of the upper eyelid
Where is the entry/exit point for the oculomotor nerve in the skull?
Superior orbital fissure
What structures are innervated by the trochlear nerve?
superior oblique muscle
What is the function of the trochlear nerve?
movement of eyeball - down and out
Where does the trochlear nerve enter/exit the skull?
superior orbital fissure
Where are the central connections for the trochlear nerve?
trochlear nucleus
Where are the central connections for the olfactory nerve?
olfactory bulb
Where are the central connections for the optic nerve?
lateral geniculate nucleus
pretectal nucleus
Where are the central connections for the oculomotor nerve?
motor - oculomotor nucleus
What structures are innervated by the trigeminal nerve?
motor - muscles of mastication, tensor tympani
sensory - face, scalp, cornea, nasal and oral cavities, cranial dura mater
What is the function of the trigeminal nerve?
sensory - general sensation (pain, temperature, touch)
motor - opening and closing the mouth, chewing
Where does the trigeminal nerve enter/exit the skull?
opthalmic division = superior orbital fissure
maxillary division = foramen rotundum
mandibular division = foramen ovale
Where are the central connections for the trigeminal nerve?
sensory = trigeminal sensory nucleus
motor = trigeminal motor nucleus
What structures are innervated by the abducens nerve?
lateral rectus muscle
What is the function of the abducens nerve?
movement of the eyeball - abduct the eye (rotate gaze away from the midline)
Where is the entry/exit point for the abducens nerve in the skull?
superior orbital fissure
Where are the central connections for the abducens nerve?
abducens nucleus
What structures are innervated by the facial nerve?
sensory - anterior two thirds of the tongue
motor - muscles of facial expression
What is the function of the facial nerve?
sensory - taste
motor - facial movement
What structures are innervated by the vestibulocochlear nerve?
vestibular apparatus, cochlea
What is the function of the vestibulocochlear nerve?
vestibular sensation (position and movement of the head), hearing
Where are the central connections for the facial nerve?
sensory - nucleus solitarius
motor - facial nucleus
Where is the entry/exit point on the skull for the facial nerve?
enters via internal acoustic meatus
exits via stylomastoid foramen
Where are the central connections for the vestibulocochlear nerve?
vestibular nuclei and cochlear nuclei
Where does the vestibulocochlear nerve enter/exit the skull?
internal acoustic meatus
What structures are innervated by the glossopharyngeal nerve?
sensory - pharynx, posterior third of tongue, middle ear, carotid body, carotid sinus
motor - stylopharyngeus muscle
What is the function of the glossopharyngeal nerve?
sensory - general sensation, taste, chemoreception and baroreception
motor - swallowing
Where are the central connections for the glossopharyngeal nerve?
sensory - trigeminal sensory nucleus, nucleus solitarius
motor - nucleus ambiguus
Where does the glossopharyngeal nerve enter/exit on the skull?
jugular foramen
What structures are innervated by the vagus nerve?
sensory - pharynx, larynx, trachea, oesophagus, external ear
motor - soft palate, pharynx, larynx, upper oesophagus
What is the function of the vagus nerve?
sensory - general sensation
motor - speech, swallowing
Where are the central connections for the vagus nerve?
sensory - trigeminal sensory nucleus, nucleus solitarius
motor - nucleus ambiguus
Where is the entry/exit point for the vagus nerve on the skull?
jugular foramen
What structures are innervated by the accessory nerve?
sternomastoid and trapezius muscles
What is the function of the accessory nerve?
movement of the head and shoulder
Where are the central connections for the accessory nerve?
spinal cord
Where is the entry/exit point on the skull for the accessory nerve?
jugular foramen
What structures are innervated by the hypoglossal nerve?
intrinsic and extrinsic muscles of the tongue
What is the function of the hypoglossal nerve?
movement of the tongue
Where are the central connections for the hypoglossal nerve?
hypoglossal nucleus
Where is the entry/exit point for the hypoglossal nerve in the skull?
hypoglossal canal
Which two cranial nerves attach directly to the forebrain?
CN I and CN II
Which cranial nerves arise from the midbrain?
CN III and CN IV
Which cranial nerves arise from the pons?
CN V - CN VIII
Which cranial nerves arise from the medulla?
CN IX - CN XII
Clinical link - outline Bells palsy
Acute unilateral inflammation of the facial nerve (lower motor neuron). If caused by herpes zoster (virus that also causes shingles), a vesicular rash is present in the external auditory canal and on the oropharynx
What are the signs/symptoms of bells palsy?
Symptoms (unilateral - on one side):
- pain behind the ear
- paralysis of the facial muscles and failure to close eye on one side so the face appears to droop
Signs (unilateral - on one side):
- absent corneal reflex
- hyperacusis (certain sounds heard unpleasantly loud)
- loss of taste on the anterior two thirds of the tongue
What is hyperacusis?
Certain sounds are heard unpleasantly loud
Clinical link - outline bublar palsy (lower motor neuron palsy)
Set of conditions caused by impairment of the functions of the cranial nerves which arise from the medulla (CN IX, CN X, CN XI, CN XII)
What are the signs and symptoms of bulbar palsy?
Symptoms:
- dysphagia = difficulty swallowing
- slurring of speech
- dysphonia = difficulty forming sounds
- excess saliva (dribbling)
Signs:
- wasting and fasciculations in the tongue
- absent gag reflex
What can cause bulbar palsy?
degenerative conditions such as MND (ALS) and Guillain-Barre syndrome
brainstem strokes and tumours
What is pseudobulbar palsy?
bilateral upper motor neuron palsy - shares symptoms with bulbar palsy but this is often characterised by atypical expression of emotion (eg: outbursts of laughing or crying) - emotions usually unaffected in bulbar palsy
What causes pseudobulbar palsy?
Pseudobulbar palsy can be caused by a variety of pathological conditions including trauma, neurological disease (Parkinson’s, multiple sclerosis, etc), metabolic, vascular or tumor. Any condition which affects the corticobulbar tracts bilaterally will result in a pseudobulbar palsy.
Clinical link - outline central pontine myelinolysis
Destruction of myelin in the pons - occurs when low sodium levels (hyponatremia) are corrected too quickly
What are the symptoms of central pontine myelinolysis?
confusion
balance problems
dysphagia (difficulty swallowing)
hallucinations
reduced consciousness
slurred speech
tremor and weakness in the face or limbs
