Myogenic palsies

Question 1

What is myasthenia gravis?

Answer 1

An autoimmune disease affecting neuromuscular communication, meaning that the affected muscles are unable to contract properly, so are weakened during activity.

Question 2

When is myasthenia gravis worse?

Answer 2

During activity
End of the day

Question 3

What are the types of myasthenia gravis?

Answer 3

Congenital (not autoimmune)
Neonatal
Juvenile
Adult

Question 4

What are the subtypes of adult myasthenia gravis?

Answer 4

Mild/moderate generalised
Ocular
Severe/late generalised
Acute fulminating (lungs affected)

Question 5

What are the signs of myasthenia gravis?

Answer 5

Ptosis
Able to easily lift lid passively
Cogan’s lid twitch
EOM involvement mimicking nerve palsy

Question 6

What is Cogan’s lid twitch?

Answer 6

Overshooting of upper lid when looking up from downgaze

Question 7

What are the symptoms of myasthenia gravis?

Answer 7

Ptosis
Diplopia

Question 8

What investigations can be done to diagnose myasthenia gravis?

Answer 8

Tensilon test
Ice pack test
Blood tests
Hess chart
Field of BSV
CT and X-ray of thymus gland

Question 9

What is the ice pack test?

Answer 9

Ptosis will improve after a period of lid cooling (due to improved neuromuscular transmission)

Question 10

What is the tensilon test?

Answer 10

A short acting anticholinerase is administered. If improvement, positive test result.

Question 11

How should myasthenia gravis be managed?

Answer 11

Eye casualty referral
Occlude for sx management

Question 12

How will myasthenia gravis be managed in secondary care?

Answer 12

Referral to neurology if positive
Neurology manage systemic sxs
If stable for 12 months, surgery

Question 13

What is rhabdomyosarcoma?

Answer 13

Malignant striated muscle tumour usually developing during childhood

Question 14

What are the signs of rhabdomyosarcoma?

Answer 14

Proptosis
Strabismus

Question 15

How should rhabdomyosarcoma be managed?

Answer 15

Urgent referral

Question 16

What is chronic progressive external ophthalmoplegia?

Answer 16

Bilateral progressive loss of eye movement and ptosis

Question 17

What is a symptom of chronic progressive external ophthalmoplegia?

Answer 17

Diplopia (reduces with time)

Question 18

What are possible causes of chronic progressive external ophthalmoplegia?

Answer 18

Genetic
Mitochondrial changes to muscle fibres cause weakness

Question 19

What is orbital myositis?

Answer 19

Acute, autoimmune inflammation and swelling of EOMs which causes paretic and mechanical limitations

Question 20

What are the signs/sxs of orbital myositis?

Answer 20

Pain
Proptosis
Oedema
Possible ptosis

Question 21

How shold orbital myositis be managed?

Answer 21

Refer to eye casualty

Question 22

What is myotonic dystrophy?

Answer 22

Muscles can’t relax after contraction due to muscle fibre layer defect

Question 23

What are the signs of myotonic dystrophy?

Answer 23

Ptosis
Symmetric ophthalmoplegia

Question 24

What is myotonic dystrophy associated with?

Answer 24

Frontal baldness
Sagging jaw

Question 25

What causes thyroid eye disease?

Answer 25

Hyperthyroidism Hypothyroidism

Question 26

What are the signs of the wet phase of TED?

Answer 26

Proptosis (leads to ocular surface disease) due to EOM and orbital tissue oedema and inflammation Periorbital and conjunctival oedema Reduced VA and CV due to ON compression/stretching Epiphora

Question 27

What are the signs of the dry phase of TED?

Answer 27

Reduced VA Diplopia Grittiness Pain Mechanical restriction due to muscle fibrosis and scar tissue

Question 28

What order do the EOMs fibrose in TED?

Answer 28

IR MR SR LR

Question 29

What investigations are done to diagnose TED?

Answer 29

Hx (systemic sxs) VA CV CT Motility IOP VF Hess Check for AHP Measure exopthalmos Check cornea and fundus CT/MRI

Question 30

How should TED be managed?

Answer 30

Refer to eye casualty Manage VA and sxs during wet phase (e.g. prism if diplopia in primary position) Lubricants

Question 31

How might TED be managed in secondary care?

Answer 31

Orbital decompression surgery (if corneal exposure risk or ON compression) Squint surgery after dry phase if deviation present