Neuro-Ophthalmology Flashcards
Visual pathway anatomy?
Primary visual cortex
Radiations
Lateral Geniculate Nucleus
Optic Chiasm
Optic Nerve
Retina
Pupillary light reflex afferent and efferent
CNII (Optic) - Afferent
CNIII (Oculomotor) - Efferent
Pupillary light reflex pathway
Retinal ganglion cells
Optic tract
LGN
Midbrain
Ipsilateral pretectal nucleus
Contralateral Edinger Westphal nucleus
CNIII
Ciliary ganglion
Ciliary nerves
Ciliary body and sphincter pupillae.
Accommodation reflex components
Increasing lens curvature
Pupil constriction
Eye convergence
Trochlear nerve innervates
Contralateral SO (unusual for a CN in that it innervates the contralateral side)
Abducens nerve innervates
LR
Pupillary dilatation controlled by:
Sympathetic nervous system and muller muscle
Pupil dilation pathway
First-order neurons
Second order preganglionic neurons
Third order postganglionic neurons - travels around carotid artery to innervate dilator pupillae via long ciliary nerves.
What is Optic Neuropathy?
Damage of the Optic nerve - optic atrophy follows longstanding damage to the nerve
Common signs of Optic nerve dysfunction?
- Decreased visual acuity (dVA)
2.Dyschromatopsia - Visual field defects: Central scotomas, arcuate or altitudinal defects
- Diminished contrast sensitivity
- Absolute or relative afferent pupillary defect (RAPD)
Three types of Optic neuritis?
Retrobulbar neuritis
Papillitis
Neuroretinitis
Acute demyelinating Optic neuritis is most common type. What condition is it associated with?
Multiple sclerosis
MS Systemic features
● Paraesthesia.
● Muscle cramping and weakness.
● Bladder, bowel and sexual dysfunction.
● Cerebellar dysfunction: Tremor + dysarthria + ataxia (Charcot’s triad).
● Lhermitte sign: Electrical shock on neck flexion.
● Uhthoff phenomenon: Symptoms worsen when body temperature increases
(e.g. hot shower).
Ophthalmic features of MS
● Retrobulbar optic neuritis: Acute onset of unilateral retrobulbar pain
exacerbated by eye movements, dVA, central scotoma, dyschromatopsia and
RAPD. This is followed by a spontaneous resolution after a few months (3).
● Internuclear ophthalmoplegia.
● Nystagmus.
MS investigations
MRI
CSF analysis
Visual evoked potentials: delayed but preserved waveform
Mx of MS
IV Methylprednisolone 3 days
Followed by 11 days of Oral Prednisolone
What is anterior ischaemic optic neuropathy?
Anterior ischaemic optic neuropathy (AION) occurs due to damage to the optic nerve as a result of ischaemia. It can cause optic neuropathy in the elderly due to occlusion of the short posterior ciliary artery. It can be split into non-arteritic and arteritic
What is Leber hereditary optic neuropathy?
A mitochondrial inherited disease caused by ganglion cell degeneration.
Mitochondrial DNA mutation occurs at the 11,778 (most common, worst prognosis) or 14,484 (good prognosis). It mainly presents in young males aged 10–30 years. No effective treatment is available.
What are the features of Leber hereditary optic neuropathy?
● Unilateral initially with bilateral ocular involvement over weeks to months.
● Painless visual loss.
● Central or centrocaecal scotomas.
● Triad of disc ‘pseudo-oedema’, peripapillary telangiectasia and tortuosity of the medium-sized retinal arterioles
● Optic atrophy occurs in late disease.
Investigations for Leber hereditary optic neuropathy?
● Family history and genetic testing.
● Optical coherence tomography (OCT): Can show optic nerve oedema (early)
or atrophy (late).
What is papilloedema?
Bilateral optic disc swelling secondary to raised intracranial pressure (ICP).
Causes of papilloedema
- Tumours
- Haemorrhages
- Hydrocephalus
- Idiopathic intracranial hypertension
Features of raised ICP
Headache (worse in the morning) with nausea and/or vomiting.
● Pulsatile tinnitus.
● Unilateral or bilateral transient visual loss with a duration of seconds.
● Enlarged blind spot.
● Diplopia due to CNVI palsy (less common).
● Hypertension + bradycardia + bradypnea (Cushing reflex).
● Optic disc signs
● Hyperaemia and blurred margins of optic disc (early)
● Swelling and elevation of the whole optic disc with peripapillary haemorrhages (late)
What are some congenital optic disc anomalies?
Tilted discs
Morning glory anomaly
Optic disc pit
Optic disc coloboma
Optic disc drusen
Optic nerve hypoplasia
What is anisocoria
Anisocoria refers to the presence of asymmetrical pupillary size between the two eyes
Can be either pathological or physiological
20% of general population has the physiological type
What are features of Horner’s syndrome
● Ptosis: Mild eyelid drooping due to Müller muscle dysfunction.
● Miosis: Due to dysfunction of the dilator pupillae. The pupil reacts to light and near stimuli.
● Ipsilateral facial anhidrosis: Not present in third-order neuron lesions.
● The affected iris in congenital Horner syndrome has a lighter colour.
Causes of Horner’s?
First order: Lateral medullary syndrome and syringomyelia.
● Second order: Pancoast tumour and neck trauma.
● Third order: Internal carotid dissection (painful), cluster headache and cavernous sinus lesions
Also look at passmed split
Horner’s investigations
Topical aproclonidine: Causes pupillary dilation
Topical cocaine: Will dilate Horner’s pupil less than a normal pupil
Topical hydroxyamphetamine: Will dilate pupil in first and second order neuron lesions
Will fail to dilate if third order (postganglionic).
CT/MRI: If tumours or carotid dissection/aneurysm are suspected.
What is Adie’s pupil?
A unilateral condition characterized by loss of postganglionic parasympathetic
innervation to the iris sphincter and ciliary muscle.
FEATURES
● A large pupil with poor response to light but intense pupillary response
(miosis) to near stimuli with slow re-dilation (light-near dissociation: pupil
reaction to a near stimulus is greater than its reaction from a light stimulus).
● Holmes-Adie syndrome: Associated diminished deep tendon reflex of lower
limbs.
INVESTIGATIONS
● Slit lamp: Vermiform movements of pupillary borders.
● Pharmacological: 0.1% (low dose) of topical pilocarpine into both eyes causes
constriction of the affected pupil due to denervation hypersensitivity
What is Argyll-Robertson pupil
Characterized by bilateral, irregular small pupils. Both pupils do not react to light;
however, they constrict normally on accommodation (light-near dissociation).
The most common cause is diabetes; it was previously neurosyphilis
Revise visual pathway lesions
REVISE
Features of CNIII lesions
● Ptosis.
● Abduction and depression of the eye in primary position (‘down and out’)
with ophthalmoplegia (only abduction of the eye is fully normal).
● Dilated pupil and accommodation abnormalities.
Causes of CNIII lesions
Medical - Diabetes and Hypertension (usually pupil sparing)
Surgical - Posterior communicating artery aneurysm, trauma, and uncal herniation.
What is Weber syndrome?
● CNIII palsy
● Contralateral hemiparesis (damage to the cerebral peduncle)
CNIV lesions features
● Vertical diplopia: Worse on walking downstairs or looking down.
● Hypertropia: The affected eye is higher than the contralateral eye. It is made worse on tilting the head to the ipsilateral shoulder.
● Depression of the eye is limited: Most noted on adduction.
● Compensatory head posture to avoid diplopia: Patients tend to develop a contralateral head tilt and face turn.
● Bilateral CNIV palsies can present with compensatory depressed chin posture and crossed hypertropia
CN IV lesion causes
- Congenital CN IV palsy
- Closed head trauma
- Microvascular ischaemia
CN IV palsy examination
The Park-Bielschowsky three-step test can be used to identify a superior oblique
palsy. Note that the complete three steps may not always be all positive (6). The
three steps are:
- Identify hypermetropic eye in primary position.
- Eyes are examined in left and right gazes. Hypertropia increases on opposite
gaze in CNIV palsy (worse on opposite gaze [WOOG]). - With the patient fixating at a target ahead, assess hypertropia on right and
left head tilts. Hypertropia gets better on contralateral head tilt in CNIV
palsy (better on opposite tilt [BOOT]).
CN VI causes
Microvascular ischaemia
Trauma
Idiopathic
ICP
CN VI features
● Horizontal double vision: Worse on looking at distant targets.
● Esotropia in primary position.
● Abduction is limited.
What is an Internuclear ophthalmoplegia?
● Lesion to the MLF, commonly caused by demyelination or stroke.
● Defective adduction of the eye ipsilateral to the lesion and abducting
nystagmus of the contralateral eye.
● Patients may complain of horizontal diplopia
What is Parinaud syndrome?
● Lesion to the dorsal midbrain.
● Causes: Pinealoma or aqueductal stenosis in children and vascular problems
in adults.
● Supranuclear upgaze palsy.
● Lid retraction (Collier sign).
● Convergence-retraction nystagmus.
● Large pupil with light-near dissociation (not reactive to light but constrict on
accommodation)
What is one and a half syndrome?
● Lesion to the PPRF and MLF on the same side, commonly caused by a stroke.
● The only movement left is the abduction of the contralateral eye.
What is progressive supranuclear palsy?
A neurodegenerative progressive disorder characterized by vertical gaze palsy,
slowing of vertical saccades, postural instability and parkinsonism
What is Nystagmus?
Nystagmus is an involuntary rapid and repetitive oscillation of the eye which
can be physiological or pathological.
Types of Physiological Nystagmus
End-point nystagmus: Nystagmus at extreme gaze.
Optokinetic nystagmus: Nystagmus due to fast-moving repetitive objects.
Types of Pathological Nystagmus
CONGENITAL NYSTAGMUS
● The nystagmus is horizontal, pendular or jerky and disappears during sleep.
It often has a null point – a position of gaze where nystagmus is minimal.
● Common causes include sensory deprivation (e.g. bilateral cataracts), optic
nerve hypoplasia or foveal hypoplasia (e.g. albinism).
ACQUIRED NYSTAGMUS
Latent nystagmus
● Horizontal and jerky nystagmus, but only becomes present on monocular occlusion (direction is away from the covered eye).
● Most commonly associated with infantile esotropia.
Convergence-retraction nystagmus
● Co-contraction of horizontal muscles on attempted upgaze causing the globe
to retract.
● The medial rectus is the most powerful EOM. This causes eye convergence.
● Caused by dorsal midbrain lesions (e.g. Parinaud syndrome).
Upbeat nystagmus
Downward drifting of the eye followed by a fast upward corrective saccade or beat.
Caused mainly due to medulla lesions.
Downbeat nystagmus
Upward drifting of the eye followed by a fast downward corrective saccade or beat.
Caused mainly due to lesions at the craniocervical junction such as Arnold Chiari malformations.
Peripheral vestibular nystagmus
A conjugate horizontal and jerky nystagmus that occurs due to a vestibular lesion (e.g. labyrinthitis). There is a slow drifting of the eyes towards the side of the lesion followed by a fast corrective saccade in the other direction
What is Myasthenia Gravis?
An autoimmune disease affecting the post-synaptic nicotinic acetylcholine receptors (AChR) at neuromuscular junctions, leading to muscle fatigability. It typically presents in the third decade of life and has a female predominance.
It affects voluntary muscles, and smaller muscles are affected first. Ocular
involvement is commonly the presenting feature
Features of Myasthenia Gravis?
● Ptosis: Bilateral (can be unilateral initially), worse at end of the day or after prolonged upgaze.
● Cogan lid twitch: A brief upshoot of the lid elicited by making patient look downwards then upwards.
● Diplopia.
● Ophthalmoplegia.
● Fatigability and weakness of muscles of facial expression and proximal limb muscles.
● Respiratory depression.
Investigations for Myasthenia Gravis
● Ice test: Ptosis improves after applying ice for 2 minutes.
● Antibodies: Anti-AChR antibody and anti-muscle-specific kinase (MUSK)
antibody.
● Repetitive nerve stimulation (decrement of muscle action potential amplitudes).
● CT thorax: Can reveal a thymoma
Management of Myasthenia Gravis
● Acetylcholinesterase inhibitors (e.g. pyridostigmine), steroids and
immunomodulators.
● Thymectomy if thymoma is present
What is Myotonic Dystrophy?
Myotonic dystrophy is characterised by abnormal muscular relaxation and muscle
wasting. It is an AD condition due to tri-nucleotide repeats on chromosome 19.
FEATURES
● Inability of muscle relaxation.
● Early-onset cataract: Polychromatic opacities on the lens resembling a
‘Christmas tree’ cataract.
● Ptosis.
● Ophthalmoplegia
What is Miller Fisher syndrome?
A rare variant of Guillain-Barre syndrome. Anti-GQ1b antibodies may be
present. It presents with a tetrad of ataxia, areflexia, ophthalmoplegia and facial
diplegia
What is Neurofibromatosis type 1?
Neurofibromatosis type 1 (NF1) is an AD multisystem genetic disorder due to a
mutation in the Neurofibromin 1 gene on chromosome 17.
FEATURES
● Café-au-lait spots: Brownish spots most commonly found on the trunk.
● Axillary freckling.
● Ophthalmic
● Optic nerve glioma.
● Bilateral Lisch nodules (iris hamartomas)
● Plexiform neurofibromas: ‘Bag of worms’ sensation in the eyelids
● Choroidal naevi: Patients with this have a higher risk of choroidal
melanoma
What is Neurofibromatosis type 2?
Neurofibromatosis type 2 (NF2) is less common than NF1. It occurs as a result of
a mutation to the Neurofibromin 2 gene on chromosome 22.
FEATURES
● Posterior subcapsular cataracts.
● Bilateral/unilateral acoustic neuromas causing decreased sensorineural
hearing loss, tinnitus and loss of corneal reflex.
● Meningiomas
What is Tuberous Sclerosis?
● Facial angiofibroma.
● Ash-leaf spots: Hypopigmented macules on the skin.
● Seizures.
● Cognitive impairment.
● Multiple intracranial and/or retinal astrocytic hamartomas
● Glial tumours of retinal fibre layer that arise from astrocytes.
● They are commonly referred to as mulberry lesions due to their
multinodular appearance. On fundoscopy they appear as well-defined
elevated creamy white lesions.
● Associations– Tuberous sclerosis (most common association)– Neurofibromatosis– Retinitis pigmentosa (less common; lesions are non-calcified)
What is benign essential blepharospasm?
A bilateral idiopathic condition characterized by involuntary contraction of
the orbicularis oculi muscle due to basal ganglia dysfunction. Presentation is
in the sixth decade of life, with a female predominance. Blepharospasm and
oromandibular dystonia can occur together in Meige syndrome
Management of benign essential blepharospasm?
● Artificial tears for dry eyes.
● Botulinum toxin injection to orbicularis oculi. Side effects: Ptosis, dry eye,
diplopia, lagophthalmos and corneal exposure.
● Surgical myectomy if the above does not work
