Intro to paralytic strab

Question 1

What is paralytic strabismus also known as?

Answer 1

Incomitant strabismus

Question 2

On an orthoptic chart, what does the position of the muscles mean?

Answer 2

Shows were each muscle performs it’s primary action
(Not where each muscle moves the eye to)
e.g. for SR: moves up when abducted (doesn’t move up and out)

Question 3

What is a version?

Answer 3

Movement of both eyes

Question 4

What is a duction?

Answer 4

Movement of one eye

Question 5

What is the most common neurogenic palsy?

Answer 5

6th nerve (Abducens)

Question 6

What are mechanical palsies caused by?

Answer 6

Restriction of free movement in the globe, or contraction/relaxation of the muscle is interfered with.
Fibrotic muscle.

Question 7

Give some examples of mechanical palsy aetiologies.

Answer 7

Browns Syndrome
Duanes Syndrome
Blow out fracture
TED (dry phase)
Tumour

Question 8

With a mechanical palsy, in which direction of gaze is a problem noticed?

Answer 8

When looking in the opposite direction to the affected muscle.
e.g. if MR: restriction when trying to abduct

Question 9

What is the cause of a myogenic palsy?

Answer 9

Muscle weakness not caused by an innervation issue

Question 10

Give some examples of myogenic palsy aetiologies.

Answer 10

Myasthenia Gravis
Myosotis
TED (wet phase)

Question 11

What is the aim of investigations into a paralytic strabismus?

Answer 11

Work out if neuro/myo/mech
Work out which muscles are affected
Work out if congenital or acquired
Work out aetiology if acquired
Decide if referral needed
Treat sxs
Document progress and recovery

Question 12

What investigations will be done at the HES if referred for a paralytic strabismus?

Answer 12

Full history
Orthoptic assessment
Poss Hess and BSV field
Appropriate medical tests (blood tests, BP, CT/MRI)

Question 13

What urgency should acquired palsies be referred?

Answer 13

Urgent to eye casualty
If stroke suspected, straight to A&E

Question 14

What urgency should congenital palsies be referred?

Answer 14

No referral if previously investigated and no changes.
Routine if suspected congenital but not yet investigated.

Question 15

How will a 6th nerve palsy present?

Answer 15

ESOT in primary position
Full adduction
Limited abduction

Question 16

How will a 4th nerve palsy present?

Answer 16

Hyper and esotropia in primary position
Normal motility on abduction
Updrift of affected eye on adduction

Question 17

How will a 3rd nerve palsy present?

Answer 17

Ptosis
Hypo and exotropia in primary position

Question 18

Give some possible aetiologies of congenital nerve palsies.

Answer 18

Cerebral palsy
Hydrocephalus
Birth trauma
Lesions along nerve

Question 19

What is the likely cause of a 3rd or 4th nerve palsy in a child?

Answer 19

Trauma

Question 20

What are the likely causes of a 6th nerve palsy in a child?

Answer 20

Idiopathic
Benign
Raised ICP
Trauma

Question 21

What are the likely causes of a 3rd nerve palsy in an adult up to 55?

Answer 21

Aneurysm
Trauma
Lesion

Question 22

What is the likely cause of a 4th nerve palsy in an adult up to 55?

Answer 22

Trauma

Question 23

What are the likely causes of a 6th nerve palsy in an adult up to 55?

Answer 23

MS
Lesion
Trauma

Question 24

What is the likely cause of a 3rd nerve palsy in an adult over 55?

Answer 24

Microvascular event

Question 25

What are the likely causes of a 4th nerve palsy in an adult over 55?

Answer 25

Microvascular event Trauma

Question 26

What are the likely causes of a 6th nerve palsy in an adult over 55?

Answer 26

Microvascular event Lesion

Question 27

What signs can help to determine if a palsy is congenital?

Answer 27

Unacceptable cosmesis Vague onset of diplopia No sxs Amblyopia Unaware of AHP Full muscle sequelae present Extended vertical fusion range if vertical deviation Suppression

Question 28

What signs can help to determine if a palsy is acquired?

Answer 28

Sudden onset diplopia Awareness of AHP (uncomfortable) Muscle sequelae not fully developed Normal vertical fusion range (so diplopia caused)

Question 29

What signs can help to determine if a palsy is neurogenic?

Answer 29

CT: Deviation in primary position reflects extent of palsy Motility: better on ductions than versions (more innervation sent) Hess: space between inner and outer fields equal; fields displaced away from position of greatest limitation. Forced duction test: full passive movement IOP: same in all positions

Question 30

What signs can help to determine if a palsy is mechanical?

Answer 30

CT: often small deviation even when large mechanical limitation Motility: ductions = versions Hess: Outer field displaced towards inner field in position of greatest limitation Forced duction test: limited passive movements IOP: increased when looking away from position of limitation