Ophthalmology - Neurological Conditions

Question 1

What is mydriasis?

Answer 1

A dilated pupil

Question 2

What is miosis?

Answer 2

A constricted pupil

Question 3

Does raised intracranial pressure cause mydriasis or miosis?

Answer 3

Mydriasis (dilated)

Question 4

Does Horner’s syndrome cause mydriasis or miosis?

Answer 4

Miosis

Question 5

Do opiates cause mydriasis or miosis?

Answer 5

Miosis

Question 6

Does trauma cause mydriasis or miosis?

Answer 6

Mydriasis

Question 7

Do cluster headache cause miosis or mydriasis?

Answer 7

Miosis

Question 8

Does CN III palsy cause miosis or mydriasis?

Answer 8

Mydriasis

Question 9

What are the motor functions of CN III?

Answer 9

• Levator palpebrae superioris
• Extra-ocular muscles (except lateral rectus and superior oblique)

Question 10

What is the parasympathetic function of CN III?

Answer 10

Sphincter pupillae muscles → causes constriction

Question 11

What are the 2 types of CN III palsy?

Answer 11

1. Surgical
2. Medical

Question 12

What is a surgical CN III palsy?

Answer 12

Refers to compressive lesions e.g. posterior communicating artery aneurysm

Question 13

What is a medical CN III palsy?

Answer 13

Refer to non-compressive lesions e.g. multiple sclerosis, vascular causes such as diabetes or hypertension, vasculitis

Question 14

Describe the presentation of the eye in CN III palsy

Answer 14

• ‘Down and out pupil’
• Ptosis
• Double vision
• Pupil dilation (in surgical CN III palsy)

Question 15

Why does CN III palsy lead to a ‘down and out’ pupil?

Answer 15

Due to unopposed activation of lateral rectus and superior oblique

Question 16

Why does CN III palsy lead to ptosis?

Answer 16

Due to impaired innervation to levator palpebrae superioris

Question 17

Why does a ‘surgical’ CN III cause pupil dilation?

Answer 17

Due to parasympathetic (constrictive) fibres run on outside of nerve so external compression will impair function of these

Question 18

Does a fixed pupil dilatation indicate a ‘surgical’ or ‘medial’ CN III palsy?

Answer 18

Surgical

Question 19

What is the most common cause of a ‘surgical’ CN III palsy?

Answer 19

Posterior communicating artery aneurysm

Question 20

What are some causes of a ‘medial’ CN III palsy?

Answer 20

• Multiple sclerosis
• Vascular causes e.g. diabetes, hypertension, vasculitis

Question 21

What is the motor function of CN IV (trochlear)?

Answer 21

Superior oblique extra-ocular muscle → pulls eye down and inwards

Question 22

What is the presentation of CN IV palsy?

Answer 22

• Double vision – worse in the vertical plane
• Hypertropia (potentially) – this is a type of strabismus where either eye drifts/looks upwards
  
  • Eye points upwards and inwards
  • Patient may present with tilted head to compensate

Question 23

What are the 2 major causes of CN IV palsy

Answer 23

• Ocular trauma
• Diabetes mellitus

Question 24

What is the motor function of CN VI (abducens)?

Answer 24

Lateral rectus extra-ocular muscle → abducts eye horizontally away from midline

Question 25

In which plane is the double vision in CN VI palsy worse?

Answer 25

Horizontal plane

Question 26

In which plane is the double vision in CN IV palsy worse?

Answer 26

Vertical plane

Question 27

Presentation of CN VI palsy?

Answer 27

**Double vision** worse in **horizontal** plane

Question 28

CN VI palsy is known for being a ‘false localising sign’. What does this mean?

Answer 28

A false localising sign is a neurological sign that reflects dysfunction **distant** or **remote** from the expected anatomical locus of pathology. CN VI palsy is known for being a ‘**false localising sign’** due to path of the 6^th nerve within the brain, making it easily compromised in a state of **raised intracranial pressure**.

Question 29

What are the causes of CN VI palsy?

Answer 29

* Diabetic neuropathy * Stroke * Infection * Trauma

Question 30

What is Horner's syndrome?

Answer 30

Damage to the sympathetic nervous system supplying the face

Question 31

What are the 4 main causes of Horner's syndrome?

Answer 31

* **Pancoast** **tumour** (apices of lungs) * Stroke * Carotid artery dissection (red flag = neck pain) * Multiple sclerosis

Question 32

Clinical features of Horner's syndrome?

Answer 32

* Triad of: * 1) **Ptosis** (drooping of upper eyelid) * 2) **Miosis** (pupil constriction) * 3) **Anhidrosis** (lack of sweating) * May have enophthalmos (sunken eye)

Question 33

Are light & accommodation reflexes affected in Horner's syndrome?

Answer 33

No

Question 34

What is papilloedema?

Answer 34

Swelling of optic disc 2ary to raised intracranial pressure.

Question 35

Pathophysiology behind papilloedema?

Answer 35

The sheath around the optic nerve is connected with the subarachnoid space so CSF under high pressure can flow into the optic nerve sheath.

Question 36

What visual field defect will **pre-chiasmal** lesions result in.

Answer 36

**ipsilateral monocular visual field defect**.

Question 37

What visual field defect will **post-chiasmal** lesions result in.

Answer 37

**homonymous visual field defects of the contralateral side**.

Question 38

Describe the visual field defect in an optic nerve lesion

Answer 38

**Ipsilateral** **monocular** visual field defect

Question 39

Give some causes of an optic nerve lesion

Answer 39

* **Optic** **neuritis** * Amaurosis fugax * Optic atrophy * Trauma

Question 40

Describe the visual field defect in an optic chiasm lesion

Answer 40

**Bitemporal** **hemianopia**

Question 41

What is the main cause of an optic chiasm lesion?

Answer 41

Pituitary adenoma e.g. prolactinoma

Question 42

Describe the visual field defect in an optic tract lesion

Answer 42

Contralateral homonymous hemianopia

Question 43

What are 2 main causes of an optic tract lesion?

Answer 43

* MCA stroke * Tumour

Question 44

Describe the visual field defect in an optic radiation lesion

Answer 44

**Homonymous** **contralateral** **quadrantanopia**

Question 45

Describe the visual field defect in an optic radiation lesion affecting **Meyer's loop**

Answer 45

**Homonymous** **upper** quadrantanopia (‘pie in the sky’)

Question 46

Which lobe is Meyer's loop?

Answer 46

Temporal

Question 47

Describe the visual field defect in an optic radiation lesion affecting the parietal lobe?

Answer 47

**Homonymous** **lower quadrantanopia** (‘pie on the floor’)

Question 48

Describe the visual field defect in a lesion of the calcarine sulcus of the occipital lobe

Answer 48

**Homonymous** **hemianopia** with sparing of macula

Question 49

What are the 2 main cause of a c**alcarine sulcus of the occipital lobe lesion?**

Answer 49

* PCA stroke * Trauma

Question 50

What type of visual field defect would an MCA stroke cause?

Answer 50

Contralateral homonymous hemianopia