10 - Cranial Nerves VII - XII Flashcards
What is the origin, function and course of CN VI?
ABDUCENS
How do we test CN VI and how is this nerve most likely to be injured?
- Follow finger with eyeballs, tests III, IV, VI
- Diplopia
- Microvascular complications e.g diabetes, but can resolve
- Increase ICP, e.g tumour or haemorraghe
What is the general origin and course of CN VII?
FACIAL
What are the functions of CN VII (facial)?
Which cranial nerves carry special sensory functions?
I, II, VII, VIII, IX, X
What nerves contribute to sensation and taste of the tongue?
Sensation: Lingual division of trigeminal nerve
Taste: Anterior 2/3 is facial (chorda tympani) and Posterior 1/3 is glossopharyngeal
Where is the nucleus/ganglion of the facial nerve?
- Mixed nerve so has different areas in the brain stem
- Sensory cell bodies are outside the brain in the geniculate ganglion
What are the two different roots of the facial nerve?
- Motor root
- Nervus intermedius (sensory and PS)
What are the three intracranial branches of the facial nerve and their anatomical course?
All enter the internal accoustic meatus in the petrous part of temporal bone
Greater Petrosal: Carries PS to the lacrimal and nasal glands and taste from soft pallate through the foramen lacerum
Chorda Tympani: Taste from anterior 2/3rds of tongue and motor to submandibular and sublingual salivary glands. Through petrotympanic fissure
Nerve to Stapedius: Motor to stapedius, dampens down vibrations of loud noises to protect ear
How can you test the facial nerve?
- Test muscles of facial expression and corneal reflex
- Need to take history to work out where on nerve the lesion is, e.g ask about hyperacusis, dry eyes, altered taste
What are some causes of pathology of the facial nerve?
- Parotid gland malignancy
- Middle ear pathology as in petrous bone
- Vestibulocochlear nerve pathology
What is the origin, course and function of CN VIII?
VESTIBULOCOCHLEAR
- Lateral to facial
- Only pure sensory CN in the Pons
- Special sensory: hearing and balance
How do you test CN VIII (Vestibulocochlear)?
- Crude hearing test (whisper 99 and get them to repeat)
- Enquire about balance
- Pure tone audiometry if investigating hearing loss
What can be some pathology that may lead to a hearing loss?
- Presbyacusis
- Damage to cochlea, cochlear component of vestibulocochlear or brain stem nucleus
- Acoustic neuroma
- Pathology of semicircular canals or vestibular component would not be hearing loss but would be disturbance of balance
What is an acoustic neuroma and what are some signs and symptoms?
Benign tumour of Schwann cells around the vestibular component of CN VIII. Compresses whole nerve and those close by, e.g facial nerve and trigeminal
Where do the cranial nerves in the medulla exit the skull?
- All through jugular foramen apart from hypoglossal that goes through hypoglossal canal
- All enter carotid sheath but they all leave sheath really early apart from vagus that runs whole length
What is the function of CN IX?
GLOSSOPHARYNGEAL
- Mainly sensory to oropharynx, pos 1/3 tongue and middle ear
What is the course of the glossopharyngeal nerve?
How do you test CN IX (glossopharyngeal)?
What is the origin, course and function of CNX?
VAGUS
- Predominantly motor
What are two important branches of the vagus nerve and their course?
How would you test the vagus nerve?
What is the function and course of CN XI?
SPINAL ACCESSORY
- Motor to SCM and Trapezius
- Leaves via jugular foramen and takes rootlets from cervical spine and medulla brain stem
How can you test the integrity of the spinal accessory nerve and what are some issues that could cause this nerve to be damaged?
What is the origin, course and function of CN XII?
HYPOGLOSSAL
- Purely motor to all muscles of the tongue except one
How would you assess the integrity of the hypoglossal nerve?
- Test 9, 10 and 12
- Make patient say ‘AHH’ and uvula will deviate to strong side if CN XII affected
- Tongue will move towards weak side
What nerves would need to be damaged to cause a partial and full ptosis?
Occulomotor nerve has a skeletal muscle component, levator palpebrae, and an autonomic component, superior tarsal
Partial: loss of superior tarsal
Full: loss of levator palpebrae
What nerves would have to be damaged to cause difficulty swallowing?
- Vagus X
- Glossopharyngeal IX
Label the origins of each of the cranial nerves.
Label which cranial nerves leave through which foramina.
Through which foramen do the following blood vessels pass to leave or enter the skull?
- ICA
- MMA
- IJV
- Vertebral arteries
- ICA: carotid canal
- MMA: foramen spinosum
- IJV: jugular foramen
- Vertebral: foramen magnum
What are the walls of the cavernois sinus?
What structures run through the cavernous sinus and which structures travel through it’s lateral wall meaning they are more closely associated to the artery?
What symptoms can a cavernous sinus thrombosis lead to?
- Bulging eyes due to raised ICP and oedema as the cavernous sinus blocked
- Facial nerve palsies e.g ptsosis, dilated pupils, loss of visual acuity, inability to abduct eye, facial numbness
(check session 5 blackboard for full explanation)
Draw the roots of the cranial nerves onto this brain stem.
What is a way of remembering how structures run through the cavernous sinus?
