Session 9: Extra-ocular Eye Muscles, Action and Diplopia

Question 1

There are a total of six muscles controlling the movements of the eyeball.

Which?

Answer 1

Superior and inferior rectus
Superior and inferior oblique

Lateral and medial rectus

Question 2

What is conjugate gaze?

Answer 2

The visual axes must remain aligned and conjugate gaze shows the eyes’ ability to work together and move in unison.

Question 3

What happens if the visual axes is misaligned?

Answer 3

Diplopia

Question 4

Movements the eye can move in.

Answer 4

Elevation and depression.

Abduction and adduction

Extortion and intortion

Question 5

Explain the movement of medial rectus and lateral rectus.

Answer 5

Lateral rectus abducts the eyes

Medial rectus adducts the eyes

Question 6

Innervation of medial and lateral rectus

Answer 6

MR - Oculumotor nerve

LR - Abducens nerve

Question 7

Origin, insertion, action and innervation of Superior rectus.

Answer 7

Elevates the eyeball

Slightly adducts

Slight intorts

Arise from the apex of the orbit and inserts into superior anterolateral surface of the globe.

Innervated by the Oculumotor nerve.

Question 8

Origin, insertion, action and innervation of inferior rectus muscle.

Answer 8

Depresses the eye

Slightly adducts

Slight extorts

Originates from the apex of the orbit and inserts into the anteroinferior surface of globe.

Innervated by Oculumotor

Question 9

Origin, insertion, action and innervation of Superior oblique muscle.

Answer 9

Arise from the orbits, then passes through trochlea and inserts onto the superoposterior aspect of the eye.

Intorts the eye

Depresses the eye

Slightly abducts the eye

Innervated by the Trochlear nerve

Question 10

Origin, insertion, action and innervation of Inferior Oblique muscle.

Answer 10

Arise from the anteromedial surface of the floor of the orbit and inserts onto the inferoposterior aspect of the eye.

Extorts the eye

Elevates

Slightly abducts

Innervated by the Oculumotor nerve

Question 11

What is strabismus?

Answer 11

When the resting position of eyeball deviates and are not balanced.

Question 12

In what position is the abnormal eye held?

What muscular action on the eyeball is no longer acting on the eye?

Is there one muscle that is normally responsible for this action on the eye?

What CN innervates it?

Answer 12

Adduction

Abduction is not possible

Lateral rectus

Abducens nerve

Question 13

In what position is the abnormal eye held?

What muscular action on the eyeball is no longer acting on the eye?

Is there one muscle that is normally responsible for this action on the eye?

What CN innervates it?

Answer 13

Adducted, elevated and externally rotated

Abduction, depression and internal rotation

Superior oblique

Trochlear nerve

Question 14

Explain in simple words how a clinical examination of the eye movements is done.

Answer 14

In the form of an H.

Question 15

Why is an eye examination simply performed like a ‘+’?

Answer 15

Because elevation and depression in the midline involves two muscles each and will not isolate the muscle action as is required.

Question 16

What muscles does this involve?

Answer 16

Superior rectus

Inferior oblique

Question 17

What muscles does this involve?

Answer 17

Superior oblique

Inferior rectus

Question 18

Given that the nose will be found on the right hand side.

What muscle does each end test?

Answer 18

Question 19

Causes of cranial nerve palsies of CN III, CN IV and CN VI.

Answer 19

Raised intracranial pressure like intracranial haemorrhage or tumour.

Most commonly however due to vascular disease from e.g. diabetes or hypertension.

Question 20

In CN III lesions, how will this present upon clinical examination?

Answer 20

Ptosis

Abducted, depressed and extorted eye.

Pupil dilation

Question 21

How can you differentiate between a compressive lesion and vasculopathic lesion on CN III?

Answer 21

Vasculopathic lesion will be pupil sparing

In a compressive lesion on CN III the parasympathetics that run on the periphery of CN III will also be involved and therefore the pupil will involved and dilated.

Question 22

Causes of CN III palsy.

Answer 22

Vasculopathic (most common)

Tumour/Haemorrhage etc…

Aneurysm

Question 23

Clinical presentation of CN IV palsy.

Answer 23

Extortion, elevation and adduction of eyeball.

Patient may complain about diplopia but may tilt their head in order to correct it.

Worsening diplopia on downward vertical gaze.

The patient may report that there is worsening diplopia descending stairs or reading for example.

Question 24

Causes of CN IV palsy.

Answer 24

Vasculopathic

Tumour

Congenital trauma

Question 25

How will a CN VI palsy clinically present?

Answer 25

Inability to abduct the eye.

Diplopia made worse on horizontal gaze.

Question 26

Causes of CN VI palsy.

Answer 26

Vasculopathic

Tumour

Cranial pressure

Question 27

What is the most common cause of CN III, IV and VI palsy?

Answer 27

Vasculopathic lesion.

A lot of patients will be otherwise asymptomatic apart from the palsy of the given nerve.

The lesion will usually resolve itself within a few months.

Question 28

What signs might suggest a more concerning cause of a cranial nerve palsy?

Answer 28

Headache and/or vomiting associated with raised ICP

Recent head injury

Presence of pupil involvment in CN III lesions