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Neurology > Pupils > Flashcards

Pupils Flashcards

1
Q

What is mydriasis?

A

Widening of the pupil

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2
Q

What is miosis?

A

Constriction of pupil

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3
Q

What is anisocoria?

A

The condition of one pupil being more dilated than the other

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4
Q

What muscle is responsible for pupillary dilatation?

A

The radial muscle

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5
Q

What nervous system controls the radial muscle?

A

SNS- activation –> pupillary dilatation (fight or flight- advantageous to see more if running away from predator etc)

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6
Q

What muscle is responsible for pupillary constriction?

A

The circular muscle

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7
Q

What nervous system controls the circular muscle?

A

PNS

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8
Q

Where is the afferent limb of the pupillarylight reflex?

A

Within CN II

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9
Q

Where is the efferent limb of the pupillary light reflex?

A

WIthin CN III

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10
Q

What nuclei are involved in the pupillary light reflex?

A

Pretectal

Edinger-Westphal

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11
Q

Describe the pathway involved in pupillary light responses

A
  • Afferent: Optic nerve –> lateral geniculate body –> pretectum (midbrain)
  • Efferent: Edinger-Westphal nucleus (midbrain) –> oculomotor nerve
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12
Q

What are the signs and symptoms of Horner’s syndrome?

A

Partial ptosis

Enophthalmos

Anhydrosis

Small pupil (miosis)

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13
Q

What is the pathology causing Horner’s syndrome?

A

Interruption of the sympathetic pathway starting at the hypothalamus

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14
Q

Will the pupillary reflexes (light and accommodation) be impaired in Horner’s syndrome?

A

No, however there is reduced or delayed dilatation of the eye due to interruption of the sympathetic pathway pupillodilator muscles.

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15
Q

What are the causes of Horner’s syndrome?

A
  • Central:
    • Demyelination e.g. MS
    • Brainstem or sc tumour or haemorrhage/infarct
  • Pre-ganglionic:
    • Pancoast’s tumour: T1 nerve root lesion
    • Trauma: Central venous catheterisation or carotid endarterectomy
    • Neck surgery (thyroid or laryngeal)
  • Post-ganglionic:
    • Cavernous sinus thrombosis: Associated with CN 3,4, 5 and 6 palsies.
    • Herpes zoster
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16
Q

How could you differentiate a post-ganglionic cause of Horner’s syndrome? (advanced q!)

A

Post ganglionic has no anhidrosis and is sensitised to 1:1000 adrenaline eye drops (cause mydriasis) unlike normal eyes or Horner’s with central or pre-ganglionic causes.

17
Q

How would you differentiate congenital Horner’s syndrome from acquired causes?

A

Congenital Horner’s- look for heterochromia of irides (iris pigmentation requires sympathetic control, which is complete after 2 years)

18
Q

What other features should you look for/examine in a patient with Horner’s syndrome?

A

Neck: Scars- central line insertion or carotid endarterectomy

Hands: Complete claw hand + intrinsic hand weakness, reduced or absent sensation in T1–> Pancoast’s tumour

19
Q

What are the cause of unliateral ptosis?

A

III nerve palsy

Myasthenia gravis

Horner’s syndrome

Congenital

20
Q

What are the causes of bilateral ptosis?

A

MG

Myotonic dystrophy

Bilateral Horner’s syndrome (e.g. syringomyelia)

Nuclear III nerve palsy

Miller Fisher syndrome

Congenital

21
Q

What signs and symptoms would you see in an oculomotor nerve palsy?

A

Complete ptosis (due to levator palpebrae superioris losing innervation)

Eye points down and out- unopposed superior oblique and lateral rectus

Dilated pupil- unless pupil spared (e.g. early medical cases). Doesn’t react.

Ophthalmoplegia and diplopia

22
Q

What is the most important thing to determine with a 3rd nerve palsy?

A

If the cause is medical or surgical

23
Q

How can you tell a medical and surgical 3rd nerve palsy apart?

A

Medical- pupil sparing

Surgical- pupil affected early (mydriatic)

24
Q

Why is the pupil spared in early medical 3rd nerve palsies?

A
  • The parasympathetic fibres are responsible for pupillary constrition
  • PNS fibres run from Edinger-Westphal nucleus on the periphery of the oculomotor nerve
  • PNS blood supply from external pial vessels (not the vasa vasorum and nervorum that are affected by medical causes)
  • The PNS fibres are therefore compressed early in surgical cases (compression by aneurysm from outside) –> permanent mydriasis of pupil only receiving SNS input
  • However they are affected late by the ischaemia associated with medical causes
25
Q

What are the medical causes of a 3rd nerve palsy?

A

Mononeuritis e.g. DM

Demyelination e.g. MS

Infarction in midbrain: Weber’s syndrome = CN3 palsy + contralateral hemiplegia

Migraine

26
Q

What are the surgical causes of a 3rd nerve palsy?

A

Raised ICP: Tentorial herniation –> uncal compression

Cavernous sinus thrombosis

Posterior communicating artery aneurysm: Painful

27
Q

What is a Holmes-Adie pupil?

A

Aka myotonic pupil.

Dilated pupil that has no response to light and a sluggish response to accommodation.

Idiopathic and benign disorder usually seen in middle-aged females.

28
Q

What is a Holmes-Adie pupil associated with?

A

Absent deep tendon reflexes- reduced or absent knee and ankle jerks

29
Q

What is an Argyll-Robertson pupil?

A

Small irregular pupils that accommodate but don’t react to light. May have an atrophied and depigmented iris.

Aka prostitute’s pupil- “they accommodate but don’t react”

30
Q

If you see a patient with an Argyll-Robertson pupil, how would you complete the exam?

A

Offer to look for ataxia- associated with tabes dorsalis (syphilis affecting the spinal cord, especially the dorsal columns)

Urine dip- glucose

31
Q

What are the causes of an Argyll-Robertson pupil?

A

Neurosyphilis (quarternary)- other causes are rare

DM

Lesions of midbrain (infarct, haemorrhage, demyelination)

Lyme disease

32
Q

What is the site of the lesion in an Argyll-Robertson pupil?

A

Exact site unknown- thought to be damage to the pretectal region of the midbrain

33
Q

What is a Marcus Gunn pupil?

A

AKA RAPD, a pupil that shows minimal constriction to direct light and dilatation on moving the light from the normal to abnormal eye during the “swinging light test”

34
Q

Why does an RAPD occur?

A
  • During the swinging torch test, when light is switched to the affected eye the direct reflex from the affected side is weaker than the consensual reflex from the unaffected eye.
  • The consensual reflex response from the opposite eye is that of pupillary dilatation, as the light source has been removed from that eye.
  • Therefore there is abnormal dilatation in the affected eye.
35
Q

What are the causes of RAPD?

A
  • Optic nerve disorders: Causes of optic neuritis
  • Retinal disorders: Central retinal vein or artery occlusion, severe ischaemic diabetic retinopathy etc.
  • Congenital: Friedrich’s ataxia, CMT
  • Toxins: Lead, B12 deficiency, ethambutol
  • Compression: Glaucoma, Paget’s, neoplasia
36
Q

What is optic neuritis?

A

An acute inflammatory process that affects the optic nerve

Neurology (29 decks)

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