9. Neurophthalmology Flashcards
What fibres join to form the optic nerve?
1.2 million afferent fibres from retinal ganglion cells.
What are the 5 signs of Optic Nerve Dysfunction?
- Reduction in Visual Acuity
- RAPD (Relative afferent pupillary defect)
- Reduction in Light Sensitivity
- Dyschromastopsia
- Visual Field Defects
What electrophysiological examinations may be used to test optic nerve function?
Electroretinogram (ERG) = Retinal Function
Electroculogram (EOG) = Epithelium Function
Visual Evoked Potentials = CNII i.e. Cortex to Eye Function
When might electrophysiological eye tests be used?
Especially useful in unexplained visual loss, to check if CN functioning properly.
What are the Ddx for UNILateral optic disc swelling?
Optic Neuritis (Assoc with MS)
Giant Cell Arthritis
Ischaemic optic neuropathy (Assoc w/hypertension)
Compressive optic neuropathy (lymphngioma, tumour)
Orbital pathology – eg TED (thickening of tissues+structures)
Ocular pathology – posterior uveitis, scleritis
What are the Ddx for Bilateral Disc Swellings?
Papilloedema (OD swelling due to raised ICP)
Optic disc drusen (No acutally swellingCalcification of the optic disc)
What congenital condition may cause optic disc swelling?
Leber’s optic neuropathy (inherited degeneration of retinal ganglion cells)
Who is usually affected by optic neuritis?
Most common in 3rd and 4th decade
Northern Europe + Scandinavia = High Rate
W>M
What are the two types of neuritis?
Papillitis
Retrobulbar
What is the appearance of most cases of retrobulbar optic neuritis?
Optic disc looks normal cause the inflammation is behind
What is the most common type of optic neuritis?
Retrobulbar
Most caused by demyelinating disease.
Which disease has a strong association with optic neuritis?
MS
75% of definite MS patients will experience optic neuritis.
What are the signs and symptoms of optic neuritis?
Colours Become Washed-out/dull
Pain on Eye Movement
Decline in Vision
What is the key test to be performed if you suspect optic neuritis?
MRI to detect demyelination/MS
What is the usual clinical course of optic neuritis?
Most get spontaneous visual recovery in 2-3 months.
But often not full.
What is the Tx for optic neuritis?
Tx with steroids speeds up visual recovery, but does not alter final visual outcome.
3 days High Dose IV Oral follow.
(Controversial. Cochrane Review. Not much benefit in MS patients and poor evidence, but a lower threshold for IV steroids for others)
What is giant cell arthritis? What is it AKA?
Inflammatory disease of blood vessels most commonly involving large and medium arteries of the head, predominantly the branches of the external carotid artery.
Affect primarily medium and large arteries.
Systemic so affect other vessels inc aorta/cornoary vessels
Ischaemic Type Arthritis
What is the most serious complication of GCA?
Occlusion of the ophthalmic artery, a medical emergency which can cause irreversible ischema and blindness if not treated promptly.
What are the symptoms of GCA?
Symptoms can be quite vague…
Headache scalp tenderness (combing, pillow, haridressers)
Unilateral headache
Jaw lock/pain= claudication due to involvement of masseter mucles/masseter artery.
Visable temporal arteries but they are non-pulsatile
In whom is GCA more common?
Much more common in 70yo+
With what disease is GCA associated?
Assoc with polyneuropic myalgia, many have hx of system symptoms (generally unwell, fevers, specific arthritic symptoms)
What are useful tests for GCA?
Tests that help = Inflam markers ESR/CRP/IgG in men = 1/2 age, women 1/2age+10
What is NAION?
Non Arthritic Ischemic Optic Neuropathy
NAION results from the coincidence of cardiovascular risk factors in a patient with “crowded” optic discs.
In whom is NAION more common?
Affects younger people compared with AION.
40-65
What are the risk factors for AION?
DISC
Small crowded discs “disc at risk” (more likely to have circulatory compromise or sudden hyper/hypotensive event )
CARDIOVASCULAR
Sudden hypotensive event
Diabetes, HTN, atherosclerosis, Smoking etc
What is the mechanism of action during NAION?
Mechanism – probably occlusion / impaired circulation in short posterior ciliary arteries – resulting in partial or complete infarction of optic nerve head.
What are the clinical signs of NAION?
- RAPD
- Unilateral disc swelling (acute) – often sectoral, often pale nerve later (chronic)
- Second eye may become involved later
- Visual field defect – often “altitudinal” (Affects the sup part Of the disc more often)
- ESR may be raised (but to a lesser extent than AION)
What is the Tx for NAION?
Exclude GCA
Controlling Risk Factors
What might cause compressive optic neuropathy?
Optic nerve meningioma
Glioma (children, NF1)
Lymphoma
Thyroid eye disease
What are the symptoms of Compressive Optic Neuropathy?
Slow progressive visual loss
NB Slow and progressive
What is the Tx for Compressive optic neuropathy?
Look for etiology, treat the cause.
What is Leber’s hereditary opitic neuropathy?
Hereditary mitochondrial disorder
Who does Leber’s typically affect?
Young males.
Passed on by mother
Onset - young men 20/30yr
What is the clinical course of Leber’s?
Progresses from mild unilateral visual loss to severe
bilateral visual loss, to eventual blindness. End up temporal palor of the optic disc.
What is the Tx for Leber’s?
Limited treatment options (eg antioxidants?)
Gene therapy trials underway
What nutritional deficiencies/toxic substances optic neuropathies?
- B12 deficiency
- Thiamine deficiency
- Folic acid deficiency
How do alcohol, smoking cause optic neuropathy? Drugs?
They cause malnutrition.
Drugs – eg Ethambutol, isoniazid, amiodarone
Which structures in the eye are most affected by toxic /nutritional optic neuropathies? How does this impact on vision?
Particularly toxic to retinal ganglion cells of papillomacular bundle
Results in centrocaecal scotoma (field defect)
What is the Tx for toxic/nutritional optic neuropathies?
Tx = Identify definciney, address it, visual recovery is questionable, but will stop progression
What is Optic Disc Drusen?
Hyaline-like calcific material within substance of optic
nerve head.
What is the prevalence of ODD?
In 0.3% of population, often bilateral
Can run in families, not progressive, can cause certain field defect.
Is ODD progressive?
No
What is an important Ddx in ODD?
Disc swelling
And vice versa
What are the three categories of ocular motility problem causes?
Neurological
Pediatric
Other
What are the main neurological causes of ocular motility problems?
CN 3,4,6 palsies
INO
Dorsal midbrain syndrome
Nystagmus
What are the main paediatric specific causes of ocular motility problems?
Esotropia /exotropia
Syndromes
What are some other causes of ocular motility problems?
Myasthenia gravis
Thyroid eye disease
Blow out fracture
Myopathies
Describe the clinical approach to ocular motility problems?
Inspection
Examine Ocular Movements
Diplopia Y/N, Monocular/binocular?
What should be inspected in ocular motility problems?
Head posture – eg in CN IV, CN VI palsy
Ptosis – eg in CN III palsy
Eye position in primary position – any eso/exotropia?
Pupils – eg in CN III palsy
What ocular movements should be examined?
Examine ocular movements in all 9 positions of gaze
H-Test for movement.
How do you distinguish between monocular and binocular dipolopia? What does each suggest?
Monocular = Dosn’t disappear when eye covered = Optical problem
Binocular = Double vision disappears when covered on = Comes from eyes looking slightly different direction
Which muscles are supplied by the CNIII?
All extra-ocular muscles except for LR (CNVI) and SO (CNIV)
Levator Palpebrae.
FROM THE PARASYMP FIBRES ON CNIII
- Sphincter Pupillae
- Ciliary Muscles
What are the clinical signs of CN III Palsy?
- Eye looks down and out
- Partial ptosis (or full if parasymp involved…)
- ± mid-dilated pupil (if parasympathetic fibers involved)
What are some of the causes of a CNIII Palsy?
Medical v Surgical
MEDICAL (Usually pupillary-sparing)
Vascular
Diabetes
GCA
SURGICAL (pupillary involvement)
PCA aneurism (Berry Aneurysm – Post Comm Art)
Tumour (compressing nerve)
Raised ICP (e.g. uncal hernication) – Capilarry inv.
What is the important Ddx for a ‘painful CNIII palsy’? Investigation?
Painful CN III palsy is a PCA aneurism until proven
Otherwise.
– need urgent CT or MR angiogram!
What is the ocular motor sign of CNVI palsy?
CNVI supplies the lateral rectus.
Action of CNIII unopposed
Estropia (eye-turned inwards)
Can’t abduct eye
Horizontal diplopia
What are some of the causes of a CNVI Palsy?
Vascular – diabetes, hypertension, stroke (in pons) (Come on quickly in a few days, disappear over a few months)
Trauma
Tumour (eg in pons)
Cavernous sinus lesion (eg thrombosis)
Raised ICP (causes stretching of nerve)
Which muscles does the CNIV Supply? Muscles functions?
Superior oblique – primary action is DEPRESSION in ADDUCTION
eg for reading, walking downstairs), also causes incyclotorsion (rotates eye inwards
What are the signs of a CN IV palsy?
Diplopia (vertical / tilted)
Compensatory head tilt (tilts head away from affected side)
What can cause a CNIV palsy?
Vascular – diabetes, hypertension, stroke (in midbrain)
Trauma (eg closed head trauma)
Congenital
Tumour (eg in midbrain)
Cavernous sinus lesion (eg thrombosis)
What is internuclear ophthalmoplegia?
Due to a lesion in the MLF (medial longitudinal fasciculus)
MLF connects CN VI nucleus (supplies lateral rectus) to the contralateral CN III nucleus (supplies medial rectus)
It is responsible for responsible for conjugate gaze – i.e. eye movement sync
What are the clinical signs of internuclear ophthalmoplegia?
- Limitation of ADDuction on side of lesion
- ABDucting nystagmus on opposite side
So can look in the direction of the side (e.g. Right) of lesion fine. But look to the other side (left) shows a limitation of adduction on the affected side (right) resulting in a nystagmus of abducting (left) eye.
• ie – a problem with conjugate gaze
Usually normal conversion. (look toward bridge of nose).
Investigate for demylination
What disease is associated with internuclear ophthalmoplegia?
MS
What is the process for diagnosing the cause of a multiple palsy?
Work out all these apparently affect nerves?
Where do they locate in the same anatomical area?
Which nerve will be knocked out in cavernous sinus lesion (usually thrombosis)?
(III,IV, V, VI)
What pathology can affect the cavernous sinus and cause multi palsy?
Sometime fistula form venous vessel to arterial one.
Thrombosis 2ndary to inflammation spreading from Middle Ear Disease
Contains cranial nerves V, VI, VII, VIII?
Cerebellopontine angle (V, VI, VII, VIII)
– eg tumour (vestibular schwannoma), trauma (basal skull fracture)
Contains cranial nerves V, VIII, IX, X?
Lateral medullary syndrome
What other conditions might causes multiple CN palsies?
Thyroid eye disease
Myasthenia gravis
Condition associated with orbital apex inflammation?
Tolosa–Hunt syndrome
