Cranial nerves and ophthalmology Flashcards
What are the common pathologies which can affect a cranial nerve?
Diabetes mellitus MS Tumours Sarcoid Vasculitis SLE Syphilis
What should you look for on general inspection when performing a cranial nerve exam? (SWIFTLY)
Scars Wasting Involuntary movements Fasciculations, facial drop (asymmetry) Tremor Lids- ptosis, Horner's You- personal aids- glasses, hearing aids, walking stick
What is the medical term for a loss of sense of smell?
Anosmia
What can cause anosmia?
Ageing Traumatic brain injury Parkinson's Alzheimer's Tumour
What should you assess for in the optic nerve?
Acuity Fields Reflexes Ophthalmoscopy Special tests (colour)
Apparently F’ing Remembering OSCE Sucks
How should you assess the Pt’s acuity? What should you ensure?
Using a SNELLEN CHART
Make sure the patient wears their glasses if they normally wear glasses for reading
- position 6m away from chart
- cover one eye
- read from the lowest eye they can
- repeat with other eye
IN THE EXAM: ASK PT TO READ BOTTOM OF ID CARD
What are the causes of a loss of acuity?
REFRACTIVE ERROR (ocular media)
- cataracts
- diabetes
RETINA
- age related macular degeneration
- diabetic retinopathy
OPTIC NEUROPATHY
- MS
- ischaemia
What is conjunctivitis?
Inflammation of the conjunctiva
What are the symptoms of conjunctivitis?
Conjunctival hyperaemia Chemosis (conjunctival swelling) Crust/discharge Foreign body sensation Photophobia
What are the causes of conjunctivitis?
Bacterial
Viral
Allergic
How can you typically differentiate a bacterial conjunctivitis from viral conjunctivitis?
BACTERIAL- unilateral, thick discharge, reduced vision, ?urethritis/vaginal discharge
VIRAL- bilateral, watery discharge, normal vision, signs of viral infection
What is allergic conjunctivitis?
Type 1 hypersensitivity reaction
What are the common triggers of allergic conjunctivitis?
Pollen, dust, chemical scents
What are the clinical features of allergic conjunctivitis?
Conjunctivitis
Itching
Sneezing
Red, watery, oedematous eye
What are cataracts?
Clouding of the lens of the eye
What are the clinical features of cataracts?
Visual impairment
Glare/halos around light
Painless
Reduced red reflex
What are the risk factors for cataracts?
Old age
Congenital
Diabetes
Steroids
What is glaucoma?
Vision loss from optic nerve damage due to raised intraocular pressure
2nd leading cause of blindness
In an acute red painful eye, you need to rule out closed-angle glaucoma
What is affected in open-angle glaucoma?
Dysfunction of trabecular meshwork
What is affected in closed-angle glaucoma?
Compression of trabecular meshwork
What are the differences between open-angle and closed-angle glaucoma?
OA- 90%, bilateral, progressive vision loss, initially asymptomatic, non specific symptoms
CA- 10%, unilateral, sudden onset, severe pain, N+V, cloudy cornea, headache, dilated pupil
What are the investigations for glaucoma?
Fundoscopy
Gonioscope
Slit lamp
Tonometry
What is the uvea made up of?
Choroid
Ciliary body
Iris
What is uveitis?
Inflammation of the uvea
Can be anterior, posterior, complete, and intermediate
What are the causes of uveitis?
Systemic inflammation
Infection
What is affected in anterior uveitis?
Iris
Ciliary body
Most common
What is affected in posterior uveitis?
Vitreous body
Choroid
Retina
What are the investigations for uveitis?
Fundoscopy
slit lamp examination
What visual defect will present in a chiasmal lesion?
Bitemporal hemianopia
What visual defect will present in a pre-chiasmal lesion?
Ipsilateral monocular loss
What are the causes of a pre-chiasmal lesion?
Ischaemia- TIA (amaurosis fugax)
Inflammation- MS
What are the causes of a chiasmal lesion?
Pituitary adenoma
Chraniopharyngioma
A lesion in which part of the optic pathway can cause a contralateral homonymous hemianopia?
Optic tract lesion
A lesion in which part of the optic pathway can cause a contralateral homonymous superior quadrantanopia?
Lateral optic radiation lesion
A lesion in which part of the optic pathway can cause a contralateral homonymous inferior quadrantanopia?
Medial optic radiation lesion
A lesion in which part of the optic pathway can cause a macular sparing contralateral homonymous hemianopia?
Occipital visual cortex lesion
What is the cause of visual neglect?
Damage to the contralateral parietal lobe
What are some causes of Marcus Gunn pupil (RAPD)?
Optic neuritis
Retrobulbar optic neuritis
What is anisocoria?
Unequal size of the pupils
What does Horner’s syndrome consist of?
Ptosis
Miosis
Anhydrosis
What are some causes of Horner’s syndrome?
Loss of sympathetic innervation due to either: Carotid artery dissection Pancoast tumour SOL/stroke MS Cavernous sinus thrombosis
What is the sympathetic pathway that supplies the eye?
Hypothalamus T1 Superior cervical ganglion Carotid artery Cavernous sinus Target sites (dilator pupillae, lacrimal gland)
What are the investigations for Horner’s syndrome?
CXR (Pancoast)
CT Head (stroke)
MRI/MRA (tumour/dissection)
Refer
What signs may you see on fundoscopy?
Diabetic retinopathy
Hypertensive retinopathy
Papilloedemea
How will a Pt with a COMPLETE CN3 palsy present?
- Ptosis (levator palpebrae dysfunction)
- Affected eye deviated to a “down and out position” (unopposed lateral rectus and superior oblique)
- Diplopia- worst when looking up and out
- Fixed, dilated pupil (mydriasis) - PSNS from ciliary ganglion affected
What are the causes of a unilateral ptosis?
3rd nerve palsy
- Down and out eye + fixed dilated pupil
Horner’s syndrome
- Ptosis + anhidrosis + miosis
Myaesthenia Gravis
- Bilateral facial weakness + proximal weakness with fatiguability + weak voice
Congenital
What is the difference between a medical and surgical CN3 palsy?
MEDICAL- pupil sparing, painless
- centre of CN3 is affected
- PSNS fibres are intact until the entire nerve affected
- diabetes, atherosclerosis + vasculitis
SURGICAL- fixed, dilated pupil
- PSNS fibres located on outside of CN3 trunk- first to be affected by compression
- eg by posterior communicating artery aneurysm, SOL, coning
Causes of ptosis
First Order Neurone lesion:
- Brainstem demyelination (MS)
- Brainstem tumour
- Brainstem infarct (lateral medullary infarct) /haemorrhage
Second Order Neurone lesion:
- Apical lung tumour – classically Pancoast tumour
- Apical TB
- Cervical rib
- Brachial plexus trauma
- Dissections + aneurysms of carotid and subclavian artery
Third Order Neurone lesion:
- Herpes Zoster
- Internal carotid artery dissection
How may a Pt with a CN4 palsy present?
HEAD TILT + UPWARDS GAZE (CANT FOCUS IN + DOWN)
CN4 palsy results in PT being unable to look down and in towards nose - diplopia especially on reading
Affected eye will be slightly raised compared to the unaffected eye
To counteract the diplopia Its raise level of the affected eye by tilting their head away
What are the commonest causes of a CN4 palsy?
Idiopathic
Head trauma
Diabetes
How may a Pt with a CN6 palsy present?
Failure to abduct ipsilateral eye
What are the causes of a CN6 palsy?
Due to the long course of the 6th nerve it is easily affected: Stroke Trauma Viral illness SOL Inflammation
How does a Pt with internuclear ophthalmolegia present?
Eyes do not move together – dissociative conjugate movements
- Impaired adduction of the ipsilateral eye
- Nystagmus in the abducting contralateral eye
What are the causes of internuclear ophthalmoplegia?
If young and bilateral, MS
If old and unilateral, stroke
What are the pathways for the corneal reflex?
V1 -> VII
What are the pathways for the jaw jerk reflex?
V3 -> V
Which part of the trigeminal nerves would be affected if there was a higher central lesion?
Contralateral nerves
What are the causes of a higher central trigeminal lesion?
Stroke
Which part of the trigeminal nerves would be affected if there was a brainstem lesion?
Ipsilateral nerves
What are the causes of a brainstem trigeminal lesion?
Stroke
Raised ICP
Which part of the trigeminal nerves would be affected if there was a peripheral lesion?
Branch distribution
What are the causes of a peripheral trigeminal lesion?
Raised ICP
Trauma
What are the branches of the facial nerve?
Two Zebras Bit My (Massive) Cock
Temporal Zygomatic Buccal Marginal mandibular Cervical
What is Bell’s palsy?
Facial paralysis of the ipsilateral side
What are the causes of Bell’s palsy?
Idiopathic
Compression of the facial nerve
Inflammation (eg. viral)
-herpes simplex type 1, varicella zoster
What are the risk factors for Bell’s palsy?
Diabetes
What are the investigations for Bell’s palsy?
Serology
-Lyme, herpes, zoster