9 - Cranial Nerves I - VI Flashcards
What do the cranial nerves supply in general?
- Part of the PNS and supply structures of the head and neck, apart from the vagus nerve which supplies structures in thorax and abdomen
- 12 pairs
Where are the majority of cranial nerve nuclei found?
BRAINSTEM - which is the area of cardiorespiratory control and consciousness
How can you remember all of the names of the cranial nerves?
Function:
Some Say Marry Money But My Brother Says Big Brains Matter More
Which of the following cranial nerves are:
- Purely sensory?
- Carry autonomics?
- Sensory (all special sensory): Vestibulocochlear (VIII), Optic (II), Olfactory (I)
- Efferent autonomics: Oculomotor (III), Facial (VII), Glossopharyngeal (IX), Vagus (X)
What is the function, path and origin of CNI?
SMELL
How would you test cranial nerve I and what would cause this nerve to be damaged?
OLFACTORY
Test: not often but sense of smell one nostril at a time
Anosmia: common cold due to swollen nasal cavity, head injury (shearing or basilar fracture), tumours as base of frontal lobe
What is the function, path and origin of CNII?
OPTIC
- After the optic chiasm the fibres from both eyes start to mix and go down the optic tract
- Travels back to occipital lobe to get to primary visual cortex to be percieved
What makes the first two cranial nerves, olfactory and optic, different from the other ten?
They are paired anterior extensions of the forebrain, not originating from the brain stem
How would you test CNII?
Why do you get photophobia in meningitis?
The optic nerve carries an extension of the meninges so this is irritated so when stimulating this nerve it causes pain
What are some ways the optic nerve can be damaged?
- Different lesions lead to different visual pathway issues, e.g one eye affected if retina or optic nerve affect
- Retinal detachment, optic neuritis, stroke
How would a pituitary tumour affect the optic nerve?
Would compress optic chiasm and cause bitemporal hemianopia
Although the optic nerve originates in the forebrain, what is it’s connection with the midbrain?
In the visual pathway
What is the function, path and origin of CNIII?
- OCULOMOTOR
- Motor and Autonomic
- Parasympathetic: sphincter and cilliary muscles
- From midbrain
How would you test CNIII and how can this nerve be injured?
How is the oculomotor nerve damaged by a raised ICP?
- Compressed between the tentorium cerebelli and uncus part of the temporal lobe as it herniates
- Compresses the outside of the nerve which contains the parasympathetic fibres so leads to a blown pupil
How can you remember which cranial nerves are to open and close the eyes?
- VII Fish Hook: closes by orbicularis oculi
- III Bars Holding Open: opens by levator palpebrae superior
Balance between the two to hold eyelid so if one goes the other wins
A patient presents with this, what is the most likely lesion?
- Ptosis and Down n Out
- Oculomotor (III) lesion
- Appears pupil sparing so if no head injury may be a microvascular complication
What is the function, path and origin of CNIV?
- TROCHLEAR
- Motor
- From DORSAL ASPECT of midbrain, one of the longest intracranial courses
How would you test CNIV and how may this nerve be injured?
What is the function, path and origin of CNV?
- TRIGEMINAL
- From the pons
- Sensory to face, teeth, sinuses
- Motor to muscles of mastication
What are the dermatomes of the face?
How would you test CNV and what are some causes of damage to this nerve?
Corneal reflex is the blink reflex when the cornea is touched
What is trigeminal neuralgia?
- Sudden, severe facial pain.
- Sharp shooting pain or like electric shock in the jaw, teeth or gums.
- Short, unpredictable attacks that can last from a few seconds to about 2 minutes. The attacks stop as suddenly as they start.
- Usually just one side of face, in lower part
- Attacks can be triggered by certain actions e.g talking, smiling, brushing teeth, kissing
- The compression of nerve is usually by nearby blood vessel, or can be due to MS or a tumour
