Cranial Nerve Problems Flashcards
The 4 groups of cranial nerve nuclei?
Cortex - 1, 2
Midbrain - 3, 4
Pons - CN 5-8
Medulla (aka bulb) - CN 9-12
UMN cranial nerve lesions:
This is a lesion of the cortex or corticobulbar tract. What cranial nerves are supplied by the corticobulbar tracts and why?
All except 3, 4 and 6.
The corticobulbar tract supplies these cranial nerves on its way to the medulla.
UMN cranial nerve lesions:
Why do you not get significant deficit?
Most CN nuclei are bilateral, though contralateral supply is often stronger.
THE EXCEPTION IS CN 7 - Facial nerve
UMN cranial nerve lesions:
Why does a cortical (central) lesion on CN 7 only cause paralysis of half of the face?
The muscles responsible for eyelid and forehead movements are innervated by fibres from both sides.
Central facial palsy: unilateral lesion between cortex and brainstem nuclei → muscles of the eyelids and forehead are still supplied by input from the other side → function is preserved
Peripheral facial palsy: unilateral lesion between nuclei and muscles → no input to the ipsilateral eyelid and forehead muscles → paralysis
The lower facial muscles are only innervated by fibers from the contralateral hemisphere (via ipsilateral nuclei and the ipsilateral peripheral nerve) → paralyzed in both central and peripheral facial palsy
https://www.amboss.com/us/knowledge/Facial_nerve_palsy
LMN cranial nerve lesions:
Where is the lesion found? - 2
What does this lead to? - ipsi/contra
What may cause lesions? - think extrinsic and intrinsic?
Lesions of the CN nuclei or nerve fibres
Ipsilateral loss of function
E - compression (tumour, aneurysm, trauma)
I - Ischaemia, inflammation
LMN cranial nerve lesions:
How would:
- CN5 - 1
- CN 8 - 2
- CN 9, 10 and 12 - What would the palsy be called? 2 signs?
- CN 10 lesions
- CN 11 lesions
- CN 12 lesions
Reduced facial sensation
Deaf and dizziness
Bulbar palsy:
- Dysarthria - difficulty articulating
- Dysphagia - difficulty swallowing
Uvula deviates to the unaffected side when saying ‘ah’
Impaired gag reflex
Decreased strength in neck and shoulders
The tongue protrudes towards lesion side
Cranial nerve 3, 4 and 6 lesions:
What extraocular muscles do the horizontal movement? - 2
What does the superior rectus do?
What does the inferior rectus do?
Lateral and medial rectus muscle
Looks up and out
Looks down and out
https://www.amboss.com/us/knowledge/Eye_and_orbit
Cranial nerve 3, 4 and 6 lesions:
What do the oblique muscle look towards do?
What muscles do they work with to look straight up or down?
What is an important fact to remember about the direction the superior and inferior obliques move the eye in?
They both look towards the nose
What looks down
Inferior/superior rectus
IT IS THE OPPOSITE OF WHAT YOU THINK:
Superior oblique = down
Inferior oblique = up
THEREFORE:
Upward gaze = SR + IO
Downward gaze = IR +SO
https://www.amboss.com/us/knowledge/Eye_and_orbit
Cranial nerve 3, 4 and 6 lesions:
What muscles do the above nerves supply?
LR6SO4
CN 3 - Oculomotor:
- Medial rectus
- Superior rectus
- Inferior rectus
- Inferior oblique
CN 4 - Trochlear - Superior oblique
CN 6 - Abducents - Lateral rectus
Cranial nerve 3, 4 and 6 lesions:
What 2 other things does CN 3 - oculomotor - control?
Pupil diameter
Levator palpebrae superioris - lifts the eyelid
Cranial nerve 3 lesions - Causes:
Intrinsic cause do to….? - 1
Extrinsic:
- What aneurysm in the brain may lead to compression? - - How does this present?
- What sinister thing could the aneurysm lead to?
- How can raised ICP cause compression of CN3?
- What 2 things can cause a cavernous sinus lesion?
Ischaemia via DM (microvascular)
Posterior communicating artery aneurysm
Headache - a sign of impending rupture
You can get uncal herniation and CN3 passes just medially to the uncus - https://medical-dictionary.thefreedictionary.com/uncal+herniation
Tumour
Aneurysm
Cranial nerve 4 lesions:
Why is this not relevant?
Isolated CN4 lesions are very rare!!!
Cranial nerve 6 lesions:
What is the main cause?
What degenerative disease can also cause lesions?
Raised ICP
MS
Other causes of eye muscle dysfunction:
What NMJ disorder may cause eye muscle dysfunction?
What is ophthalmoplegia and what endocrine condition may cause this?
Myasthenia gravis - pupils spared
Paralysis of the muscles within or surrounding the eye
Thyroid disease
Presentation of eye problems:
General presentation of eye weakness?
Diplopia Impaired movement (paralytic squint) - LOOK UP
Presentation of eye problems:
CN 3 lesion - 3 presentations?
What reflexes are reduced? - 2
What can be used to distinguish between compressive causes (e.g. parasympathetic fibres) and intrinsic causes (e.g. ischaemia)?
Down and out - SO (down) and LR (out) still working
Ptosis - weakness of upper eyelids
Dilated pupils - controls muscles of pupils
THE PUPILS
Compressive causes mydriasis (dilation of the pupils)
Intrinsic (e.g. ischaemia) - usually pupil sparing
Presentation of eye problems:
What is the likely cause if 2 adjacent nerves are affected?
What is the likely cause if > 2 CNs are affected with nystagmus?
What is the likely cause if > 2 CNs are affected WITHOUT nystagmus?
Why should you just say what you see when describing a lesion instead of saying it is a CN 6 problem for example?
Compression
CNS
Myasthenia gravis (You can check for fatigability by getting them to hold eyes in upward gaze) Myopathy
They may present with an inability to abduct on the left but it does not mean they have a CN 6 problem, it could be an NMJ problem, from the brainstem itself.
Cranial nerve 7 problems:
How do they present? - 2
What reflexes are reduced?
Weak muscles of facial expression, including the upper half
Reduced taste on the anterior tongue
Reduced corneal and blink reflexes
Cranial nerve 7 problems - Causes:
Bells palsy:
- Onset
- Treatment
- Recovery
Intrinsic cause:
- What infections may cause problems?
- What inflammatory diseases may cause problems?
Acute - hours/days
Prednisolone if in first 72 hrs
Combine with antiviral - acliclovir, valaciclovir
Weeks to months ---------- VZV - Ramsey-Hunt syndrome Otitis media Lyme disease HSV
Sarcoidosis
Guillain Barre
MS
Cranial nerve 7 problems - Causes:
Extrinsic:
Trauma is an obvious cause.
- Where may a tumour be that can compress the nerve?
- Ear tumour
- Tumour of CN 8
Parotid gland carcinoma
Cholesteatoma
Acoustic neuroma
THIS IS WHY YOU NEED TO DO OTOSCOPY FOR THOSE WITH CN 7 PROBLEMS.
Post-heRpatic neuralgia:
It can happen anywhere in the body. What CN can it also affect?
What virus causes this?
How do they describe the pain?
What happens before the pain presents?
What else could occur on the area affected?
CN 5 - trigeminal - sensory root affected
Herpes zoster virus - HZV
Burning, aching, debilitating pain
After a shingles infection
Scarring - look up - usually very severe
