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FRCS Part 1 > Ch32 Neuro-opthalmology > Flashcards

Ch32 Neuro-opthalmology Flashcards

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1
Q

What is nystagmus?

A

Involuntary rhythmic oscillation of the eyes. Described by the direction of the fast (cortical) component, which is not the abnormal component.

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2
Q

What commonly causes horizontal nystagmus?

A

Sedatives and AEDs

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3
Q

What commonly causes vertical nystagmus?

A

Posterior fossa pathologies

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4
Q

What is see-saw nystagmus?

A

Intorting eye moves up whilst the extorting eye moves down. Associated with diencephalic (thalamic) lesions. Usually accompanied by a bitemporal hemianopia due to chiasmal compression.

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5
Q

What is convergence-retraction nystagmus?

A

Associated with Parinaud’s syndrome. Nystagmus when the patient accommodate.

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6
Q

What is down-beat nystagmus indicative of?

A

Pathology at the craniocervical junction - such as Chiari malformations and syringobulbia. Classically also occurs with alcohol, phenytoin and carbamazepine intoxication.

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7
Q

What causes upbeat nystagmus?

A

Lesions in the medulla

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8
Q

What causes abducting nystagmus?

A

Internuclear opthalmoplegias (associated with MLF lesion). The abducting eye shows horizontal nystagmus.

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9
Q

What is Brun’s nystagmus?

A

Large amplitude low frequency ipsilateral and low amplitude fast frequency contralateral nystagmus. Also have upbeat torsional nystagmus. Associated with CP / pontomedullary junction lesions.

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10
Q

What is vestibular nystagmus?

A

Lesion in the pontomedullary junction or inner ear causing horizontal nystagmus with lateral gaze (worse in the left eye - called Alexander’s law)

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11
Q

What is ocular myoclonus?

A

Rapid uncontrolled eye movements. Associated with lesion in myoclonic triangle aka Mollaret’s triangle (dentato-rubro-olivary pathway)

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12
Q

What is Mollaret’s triangle?

A

Red nucleus > Sup cerebellar peduncle > Dentate nucleus > Inferior cerebllar peduncle > Inf. olivary nucleus > Central tegmental tract > Red nucleus. Lesions classically cause hypertrophic olivary degeneration and a Holme’s tremor

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13
Q

What is periodic alternating nystagmus aka pin-pong gaze?

A

During forward gaze there is alternating left and right-sided nystagmus. Associated with lesions at the foramen magnum and cerebellum

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14
Q

What are square wave jerks?

A

Inappropriate saccades that take the eye off target when fixating. Suggests a cerebellar lesion.

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15
Q

What is ocular bobbing associated with?

A

Lesion in the pontine tegmentum

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16
Q

What types of nystagmus occur with foramen magnum pathology?

A

Down-beat nystgmus (remember up-beat suggests medullary pathology)

Periodic alternating nystagmus

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17
Q

What causes papilloedema?

A

Axoplasmic stasis - usually due to raised ICP transmitted to the optic disc.

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18
Q

During fundoscopy what is the differential diagnosis of papilloedema?

A

Optic neuritis and pseudopapilloedema (Drusen)

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19
Q

How long does papilloedema take to develop after a sustained rise in ICP>

A

24-48 hours

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20
Q

What are the features of papilloedema?

A

Venous engorgement

Loss of venous pulsations

Blurring of the optic disc margins

Elevation of the optic disc

Other features include retinal haemorrhages and venous tortuosity

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21
Q

What is the grading scale for papilloedema?

A

Frisen grading: 0 - normal 1 - Minimal - normal temporal margin but blurring of the others 2 - Low degree - elevation of the nasal margin with disc swelling. 3 - Moderate degree - elevation of entire disc with obscuration of a segment of a major vessel at margin 4 - Marked degree - all vessels obscured at the margin but not disc surface 5 - Severe - all vessels obscured on disc surface and margin

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22
Q

What grade of papilloedema is this?

A

Grade 1 papilledma with blurring of the margins but sharp in the temporal region (C-shaped halo). Note the cup is still discernible.

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23
Q

What grade of papilloedema is this?

A

Grade 2 - low degree. The disc margins are blurred all the way around. Cup visible. No obscuration of the vessels at the margin

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24
Q

What grade papilloedema is this?

A

Grade 3 - moderate

Circumferential blurring and elevation of the disc

Blurring of a single vessel at the margin (arrow) but not on the disc

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25
What grade of papilloedema is this?
Grade 4 - marked papilloedema Swollen disc, loss of cupping. All vessels obscured at the disc margin but still visible on the disc
26
What grade of papilloedema is this?
Grade 5 - Severe Swollen disc, no visible cupping. Obscured vessels at the margins and on the disc.
27
What are the causes of unilateral papilloedema?
Unilateral compression (tumour) Foster-Kennedy syndrome Demyelination (MS) Local inflammatory disorder
28
What are the normal sizes of the visual fields?
35 deg nasal, 90 deg temporal, 50 deg superior and inferior.
29
Where is the optic disc?
15 deg nasal
30
What lesions result in homonymous hemianopia with macular sparing?
Optic radiation or primary visual cortex infarction
31
What is Wilbrand's knee?
Decussating fibres extend into the contralateral optic nerve before continuing along into the optic tract. Chiasmal lesions therefore result in an additional junctional scotoma (contralateral superior temporal quadrantanopia)
32
What defect does a lesion affecting Meyer's loop cause?
A homonymous contralateral superior quadrantinopia (with macular sparing)
33
What visual field defect occurs with a unilateral optic nerve injury near the chiasm?
Unilateral blindness with contralateral superior temporal quadrantinopia (junctional scotoma) due to Willbrand's knee.
34
How is pupil dilation controlled?
1st order sympathetics from the posterior lateral hypothalamus descend through the brainstem and spinal cord to the intermediolateral gray at T1-2 called the center of Budge-Waller. 2nd order sympathetics (preganglionic) exit at T1 and enter the sympathetic chain and ascend to the superior cervical ganglion. 3rd order sympathetics (post-ganglionic) run on the common carotid. Those that supply facial sweating run on the ECA. Those that continue on the ICA travel to the cavernous sinus and then run on V1 to enter the ciliary ganglion in the orbit. From the ciliary ganglion long ciliary nerves supply the pupillodilator muscles whilst other fibres travel to the lacrimal gland and Muller's muscle.
35
What is Muller's muscle?
Accessory levator muscle of the upper eyelid (works with levator palpebrae superioris)
36
How is pupil constriction controlled?
Parasympathetics from the Edinger-Westphal nucleus (preganglionic) in the midbrain run along the 3rd nerve to the ciliary ganglion in the orbit. The post-ganglionic fibres then cause pupillary constriction.
37
What are the steps in examining the pupil response?
1. Measure pupil reactions to light 2. Perform RAPD i.e. direct and consensual responses 2. Check pupil response to accommodation (should restrict with convergence).
38
What is an Argyll-Robertson pupil?
Pupillary constriction with convergence but not light Originally described in Syphilis. Pseudo-Argyll-Robertson pupil seen with Parinaud's syndrome and Adie's pupil.
39
What is a relative afferent pupillary defect?
AKA Marcus-Gunn pupil. When the consensual response is greater than the direct, suggesting pathology anterior to the chiasm i.e. retinal or optic nerve.
40
What is an Adie's pupil?
Dilated pupil due to loss of parasympathetics. Due to viral infection of the ciliary ganglion. When associated with loss of knee reflex it is called Holmes-Adie pupil, which is typically seen in women in their 20s.
41
What is the definition of anisocoria?
Unequal pupils \>1 mm
42
What is the incidence of physiological anisocoria?
20%
43
What are mydriatic drugs?
1. Sympatheticomimetics. e.g. phenylephrine, clonidine and cocaine. 2. Parasympathetic blockers e.g. tropicamide, atropine and scopolamine Both cause pupil dilation.
44
What are myotic drugs?
Drugs that cause the pupil to constrict e.g. pilocarpine and anticholinesterases e.g. pyridostigmine (used for MG)
45
What are the causes of a 3rd nerve palsy?
Medical = DM and ETOH Surgical = PCom, Basilar aneurysm, Tumour, Cavernous sinus pathology e.g. CCF and cavernous ICA aneurysm
46
How can a 3rd nerve palsy be differentiated from a pharmacologically dilated pupil?
Instill 1% pilocarpine (parasympathomimetic). A pharmocologically dilated pupil e.g. tropicamide will not constrict but a 3rd nerve palsy pupil will.
47
Why do NMJ blockers not effect the pupil response?
As these block nicotinic Ach receptor whilst the pupils have muscarinic receptors (except in very large doses where the 1st and 2nd order sympathetics can be affected)
48
How can you diagnose an Adie pupil?
Diliute pilocarpine test. Due to denervation supersensitivity the dilute 0.1% pilocarpine (parasympathomimetic) causes constriction within 30 minutes. Normal pupils needs 1% pilocarpine.
49
What are the features of a Horner's syndrome?
Miosis Ptosis Anihydrosis Enopthalmos Hyperemia of the eye
50
What causes ptosis and enopthalmos in Horner's syndrome?
Due to Muller's muscle paralysis. This is a partial ptosis as the levator palpebra superioris from CN3 is still intact with Horner's syndrome.
51
What causes damage to 1st order sympathetic neurons?
Hypothalamic or Brainstem (runs in the lateral tegmentum) damage caused by PICA infarction, syringobulbia or tumours
52
What causes damage to second order sympathetic neurones?
Pancoast tumour Chest trauma
53
What causes damage to third order sympathetic neurones?
Carotid dissection Neck trauma Skull base lesions Cavernous sinus lesion
54
How can 1st and 2nd order Horner's syndrome be distinguished from a 3rd order?
Pholedrine administration causes dilation of the miotic pupil if caused by 1st and 2nd order sympathetic injury (preganglionic) but not 3rd order (postganglionic)
55
Where is the frontal eye field?
Brodman area 8
56
What is the pathway for voluntary eye movement?
Frontal eye field \> genu of internal capsule \> paramedian pontine reticular formation \> CN 3 and 6 via MLF to coordinate eye movements
57
What is an internuclear opthalmoplegia?
Failure of the eyes to adduct bilaterally resulting in nystagmus in the abducting eye caused by a lesion in the MLF which coordinates eye movements between CN3 and 6. Convergence is not impaired.
58
Which nuclei contribute to the CN3?
Oculomotor nucleus (motor) Edinger-Westphal nucleus (parasympathetics)
59
What are the causes of a pupil sparing CN3 palsy?
DM Vasculopathy Myaesthenia gravis Due to vascular lesion occluding the vaso-nervorum causing central ischemic infarction so the peripheral parasympathetic fibres are spared.
60
Where is the trochlear nucleus?
Lateral to the cerebral aqueduct at the level of the inferior colliculus
61
What is the function of superior oblique muscle?
Downward, abduction and intortion
62
Which nerve passes through the superior orbital fissure but does not pass through the annulus of Zinn?
CN4 (also the only nerve to decussates within the brainstem)
63
What is the pupil position at rest with a CN4 palsy?
Up and in. Due to the intortion, the patient tilts their head to eliminate the diplopia.
64
What is the difference between cavernous sinus syndrome and superior orbital fissure syndrome?
V2 is spared with SOF syndrome (as it exits through F. Rotundum)
65
Which nerves are effected with orbital apex syndrome?
CN2, 3, 4, V1 and 6
66
What condition should you consider with bilateral painless ophthalmoplegia?
Myasthenia gravis!
67
What is a pseudotumour of the orbit?
Chronic granuloma - idiopathic inflammatory process confined to the orbit. Note surgery should avoided as it causes flares. Treat with steroids +/- radiotherapy
68
What is Tolosa-Hunt syndrome?
Inflammation of the superior orbital fissure associated with cavernous sinus involvement. Diagnosis of exclusion. Painful opthalmoplegia with pupil sparing. Recurrent attacks with periods of remission (months to years). Treat with steroids!
69
What is Raeder's paratrigeminal neuralgia?
1. Partial Horners (but lacks anhidrosis) 2. Trigeminal nerve distribution pain in tic-like fashion Lesion is between Meckel's cave and the cavernous sinus (remember the sympathetic fibres are on the iCA)
70
What is Gradenigo's syndrome?
Inflammation of the petrous apex causing compression of Dorello's canal. Results in CN6 palsy, retro-orbital pain and middle ear infection.
71
What is Marcus-Gunn phenomenon?
Opening the mouth opens an eye with ptosis. Caused by an abnormal connection between the pteryoid muscle sensory fibres and the CN3.
72
Where is the horizontal gaze center?
Paramedian pontine reticular formation. A lesion here causes ipsilateral lateral gaze palsy.
73
What is orbital apex syndrome?
Loss of vision associated with opthalmoplegia.
74
How do you diagnose myaesthenia gravis?
Edrophonium test (anticholinesterase inhibitor so reverses the weakness in myaesthenia gravis). Same action as pyridostigmine which is given as treatment as it lasts longer. Single fibre EMG has the greatest sensitivity. CT thorax to rule out thymoma.
75
How do you test where a lesion is that is causing Horner's syndrome?
Pathway = 1st order =hypothalamus to spinal center of Budge-Waller C8-T1 \> 2nd order = Sup. cervical ganglion \> 3rd order = eye Apraclonidine will dilate the pupil if there is loss of sympathetics due to upregulation of alpha-1 R in Horner's syndrome but not in the normal pupil Cocaine will not dilate a Horner's pupil as it blocks NorAd reuptake which is not present with loss of sympathetics at any level. It will dilate the normal pupil. Hydroxyamphetamine releases NorAd so will dilate a Horners pupil due to 1st and 2nd order neurone damage but not 3rd order damage as the neurons don't make NorAd.
76
Where is the vertical gaze center?
The rostal interstitial nucleus of the MLF
77
What causes pain when moving the eye and visual acuity deterioration?
Optic neuritis
78
What can cause a Horner's syndrome in a child?
Neuroblastoma (test for urinary catecholamines)
79
How does giant cell arteritis cause visual loss?
Anterior ischaemic optic neuropathy
80
How do you know if a Horner's syndrome is congenital?
Iris heterochromia
81
What is an Adie's tonic pupil?
Loss of parasympathetics due to inflammation of the ciliary ganglion. Adies tonic pupil does not constrict to light but does constrict with accommodation. Mid-dilated pupil will constrict with 0.1% pilocarpine but a 3rd nerve palsy will not. CN3 palsy needs 1% pilocarpine!
82
How do you differentiate Aides tonic pupil from an Argyll-Robertson pupil?
Aides responds slowly to accommodation and is mid-dilated. Argyll robertson responds briskly to accommodation and is a small pupil. Note Argyl robertson pupil with loss of deep tendon reflexes = Syphilis
83
How do you examine for a CN4 palsy?
Head tilt to the ipsilateral side will make the hypertropia (elevated eye) worse
84
What is does a cherry red spot signify?
Central retinal artery occlusion
85
What is Kearn's Sayre syndrome?
Opthalmoplegia, pigmentary retinopathy and complete heart block. Also have cerebellar ataxia, dementia, deafness, short stature and endocrinopathy.
86
What are features of PSP?
AKA Steele-Richardson-Olszweski Vertical gaze palsy, loss of Bell's phenomenon, rigidity and bulbar palsy
87
What is a Marcus Gunn pupil?
When an RAPD is present
88
What is Nothnagal syndrome?
CN3 palsy with ataxia due to superior cerebellar peduncle involvement
89
What are the brainstem syndromes affecting the: Midbrain Pons Medulla
All have contralateral hemiparesis Midbrain = Weber CN3 / Benedikt CN3+red nucleus / Nothnagal CN3+atxia Pons = Gubler-Millard CN6+7/ Fovilles CN6+7+ataxia / Raymond CN6 Medulla = Wallenberg CN5/10+vertigo+horners / Dejerine CN12
90
What is spams nutans?
Nystagmus, head nodding and tortocollis
91
What causes a homonymous horizontal sectoranopia?
A vasular lesion of the LGN characterised by posterior choroidal artery occlusion. The rest of the hemifield away from the horizontal median is unaffected as it is supplied by the anterior choroidal artery.

FRCS Part 1 (85 decks)

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