Name the lining of the cavernous sinus:
The cavernous sinus lies in which bone?
Which artery passes through the cavernous sinus?
Internal Carotid Artery
Describe the location of the Optic Chiasm:
Directly ventral to the pituitary gland
Describe the route of CN I from the optic disc to the forebrain:
- Enters skull from the retina via the Optic canal
- Optic nerve runs from retina to optic chiasm
- Crossover occurs at optic chiasm
- Via optic tract to the Geniculate nuclei
- From geniculate nuclei to visual cortex
What part of the optic pathway may be compressed by a pituitary tumour? How may this present?
Loss of acuity +/- vision
Name some toxins which can damage the optic nerve:
- Tobacco exposure
How is the optic nerve tested?
1) Acuity via Snellen chart
2) Colour via Ishihara plates
4) Pupillary light reflexes
How is the oculomotor nerve tested?
- Inspect eyelid and pupils
- Eye movements (H)
- Pupillary light reflexes
How does an oculomotor lesion present?
- ‘down-and-out’ eye
- loss of pupil constriction
List some common ways the oculomotor nerve is damaged:
- Tumour/haemorrhage = increased intracranial pressure
- Cavernous sinus thrombosis
How is the trochlear nerve tested?
- Eye movements (H)
How does a lesion of the trochlear nerve present?
- Very subtle deviation of the eye, may compensate by tilting head
- May have diplopia, worse on downward gaze
How is the trigeminal nerve tested?
- Test muscles of mastication by asking to clench jaw
- Corneal reflex (sensation to cornea)
- Sensation to face
Which 2 cranial nerves does Shingle most commonly affect?
CN V Trigeminal
CN VII Facial
How is the abducens nerve tested?
Eye movements (H)
How does a lesion to the abducens nerve present?
Where does the facial nerve branch into 5?
Within the Parotid gland
How is the facial nerve tested?
Test muscles of facial expression:
- Close eyes against resistance
- Raise eyebrows
- Puff out cheeks
- Reveal teeth
What are the common causes of a facial palsy?
- Middle ear tumour
- Parotid tumour/infection
How is the vestibulocochlear nerve tested?
- Rinne’s test
- Weber’s test
Which cranial nerve(s) gives special sensory fibres for taste?
- Anterior 2/3rds of the tongue = Facial nerve
- Posterior 1/3rd = Glossopharyngeal nerve
- Epiglottis and root of tongue = Vagus nerve
How is the glossopharyngeal nerve tested?
- Gag reflex
Which cranial nerve gives special sensory fibres for taste to the epiglottis and root of tongue?
CN X Vagus
How is the vagus nerve tested?
- Check position of uvula
- Gag reflex
Which cranial nerves contain the efferent and afferent limbs of the gag reflex?
Efferent = vagus nerve Afferent = glossopharyngeal nerve
The accessory nerve contains roots from which segments of the c-spine?
How is the accessory nerve tested?
- Shrug shoulders against resistance
- Turn head against resistance
If a vagus nerve is damaged, will the uvula deviate towards or away from the side of the lesion?
Away from the side of the lesion
Where is the accessory nerve susceptible to injury?
Posterior triangle of neck
- Lymph node biopsy
- Stab wound etc
Which cranial nerve crosses the internal and external carotid arteries in the neck?
CN XII Hypoglossal
How is the hypoglossal nerve tested?
- Inspection of tongue
- Movement of tongue
If a hypoglossal nerve is damaged, will the tongue deviate towards or away from the side of the lesion?
Towards the side of the lesion
What is an acoustic neuroma?
A benign tumour around CN VIII
If the CN III nerve is damaged, why is the first symptom loss of pupillary constriction?
CN III autonomics ‘hitchhike’ on the outside of CN III, therefore first to be damaged.