7 - Head & Neck - Cranial Nerves 2 Flashcards
Name the lining of the cavernous sinus:
Dura mater
The cavernous sinus lies in which bone?
Sphenoid 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?
Optic chiasm
Loss of acuity +/- vision
Name some toxins which can damage the optic nerve:
- Ethambutol
- Amiodarone
- Methanol
- Tobacco exposure
How is the optic nerve tested?
1) Acuity via Snellen chart
2) Colour via Ishihara plates
3) Fields
4) Pupillary light reflexes
5) Fundoscopy
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
- diplopia
- loss of pupil constriction
List some common ways the oculomotor nerve is damaged:
- Tumour/haemorrhage = increased intracranial pressure
- Aneurysm
- Cavernous sinus thrombosis
- Diabetes
- Hypertension
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