Pupils

Question 1

What is mydriasis?

Answer 1

Widening of the pupil

Question 2

What is miosis?

Answer 2

Constriction of pupil

Question 3

What is anisocoria?

Answer 3

The condition of one pupil being more dilated than the other

Question 4

What muscle is responsible for pupillary dilatation?

Answer 4

The radial muscle

Question 5

What nervous system controls the radial muscle?

Answer 5

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

Question 6

What muscle is responsible for pupillary constriction?

Answer 6

The circular muscle

Question 7

What nervous system controls the circular muscle?

Answer 7

PNS

Question 8

Where is the afferent limb of the pupillarylight reflex?

Answer 8

Within CN II

Question 9

Where is the efferent limb of the pupillary light reflex?

Answer 9

WIthin CN III

Question 10

What nuclei are involved in the pupillary light reflex?

Answer 10

Pretectal

Edinger-Westphal

Question 11

Describe the pathway involved in pupillary light responses

Answer 11

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

Question 12

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

Answer 12

Partial ptosis

Enophthalmos

Anhydrosis

Small pupil (miosis)

Question 13

What is the pathology causing Horner’s syndrome?

Answer 13

Interruption of the sympathetic pathway starting at the hypothalamus

Question 14

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

Answer 14

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

Question 15

What are the causes of Horner’s syndrome?

Answer 15

• 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

Question 16

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

Answer 16

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.

Question 17

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

Answer 17

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

Question 18

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

Answer 18

Neck: Scars- central line insertion or carotid endarterectomy

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

Question 19

What are the cause of unliateral ptosis?

Answer 19

III nerve palsy

Myasthenia gravis

Horner’s syndrome

Congenital

Question 20

What are the causes of bilateral ptosis?

Answer 20

MG

Myotonic dystrophy

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

Nuclear III nerve palsy

Miller Fisher syndrome

Congenital

Question 21

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

Answer 21

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

Question 22

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

Answer 22

If the cause is medical or surgical

Question 23

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

Answer 23

Medical- pupil sparing

Surgical- pupil affected early (mydriatic)

Question 24

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

Answer 24

• 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

Question 25

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

Answer 25

**Mononeuritis** e.g. DM **Demyelination** e.g. MS **Infarction in midbrain**: Weber's syndrome = CN3 palsy + contralateral hemiplegia **Migraine**

Question 26

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

Answer 26

**Raised ICP:** Tentorial herniation --\> uncal compression **Cavernous sinus thrombosis** **Posterior communicating artery aneurysm**: Painful

Question 27

What is a Holmes-Adie pupil?

Answer 27

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.

Question 28

What is a Holmes-Adie pupil associated with?

Answer 28

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

Question 29

What is an Argyll-Robertson pupil?

Answer 29

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"

Question 30

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

Answer 30

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

Question 31

What are the causes of an Argyll-Robertson pupil?

Answer 31

Neurosyphilis (quarternary)- other causes are rare DM Lesions of midbrain (infarct, haemorrhage, demyelination) Lyme disease

Question 32

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

Answer 32

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

Question 33

What is a Marcus Gunn pupil?

Answer 33

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"

Question 34

Why does an RAPD occur?

Answer 34

* 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.

Question 35

What are the causes of RAPD?

Answer 35

* **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

Question 36

What is optic neuritis?

Answer 36

An acute inflammatory process that affects the optic nerve