Myasthenia gravis

Question 1

what are bulbar symptoms

Answer 1

dysarthria, dysphagia, fatigable chewing

Question 2

myasthenia gravis is caused by

Answer 2

auto antibodies that block acetylcholine receptors

Question 4

Generalized myasthenia gravis presentation

Answer 4

affects ocular muscles with variable involvement of bulbar symptoms (dysarthria, dysphagia, fatigable chewing)

limb respiratory muscle weakness symptoms fluctuate throughout the day and worse later in day.

Question 5

ocular myasthenia gravis presentation

Answer 5

eyelid and ocular muscle weakness

Question 7

what makes myasthenia gravis symptoms worse?

Answer 7

exercise, stress, infection and improve with rest

Question 8

how do you diagnose myasthenia gravis?

Answer 8

based on serology via the acetylcholine receptor (AchR) antibody which is present in 85% of MG pts.

Can also see muscle specific tyrosine kinase receptor antibody (MuSK) which are seen in 50% of AchR antibody negative pts

Can be done via EMG too.

Question 9

how to treat myasthenia gravis

Answer 9

treat symptomatic pts with pyridostigmine and/or immune (steriods, IVIG) therapies

in acute exacerbations or myasthenia crisis: Treat with IVIG or plasma exchange. Don’t pick steroids.

Question 10

what medical conditions is myasthenia gravis associated with?

Answer 10

thymic hyperplasia, thymoma, and autoimmune thyroid dx.

Question 11

what medical/lab tests should be done after a confirmed myasthenia gravis?

Answer 11

Need to get a TSH to evaluate for thyroiditis and CT of chest to look for mediastinal mass (thymoma)

Question 13

algorithm for myasthenia gravis evaluation

Answer 13

Question 14

what causes myasthenia crisis?

Answer 14

infection, surgery,

pregnancy or childbirth,

tapering of immunosuppressive meds,

medications (aminoglycosides and beta blockers)

Question 15

Clinical features of Myasthenia Gravis crisis (chart)

Answer 15

Question 16

Lambert Eaton myasthenic syndrome (LEMS) is

Answer 16

paraneoplastic syndrome seen with pts who have small cell lung cancer

Question 17

Lambert Eaton myasthenic syndrome is similar to

Answer 17

myasthenia gravis has _ocular symptom_s and muscle weakness DTR is decreased or absent but these improve with repetitive muscle activation.

Question 18

how to diagnose Lambert Eaton syndrome?

Answer 18

serology against voltage gated calcium channel antibodies.

Question 20

pt has fatigable diplopia and has nocturnal nasal quality of speech. what do they have?

What is most common symptom?

Answer 20

this patient has myasthenia gravis - with fluctuating and fatigable weakness. can present as ocular myasthenia (limited only to extraocular muscles and eyelids) or a generalized dx.

Most common symptom is ocular muscle weakness and can see ptosis be unilateral or bilateral or switch overtime.

Question 21

Pt has fatigue, diplopia and dysphagia for past two months. Exercises and tires easily. Has double vision at the end of the day and after a URI two weeks ago is very weak and tired. Has trouble swallowing and coughs while drinking. This is his CT scan. what does he have?

Answer 21

he has a thymoma with concurrent myasthenia gravis. See anterior mediastinal mass on CT and also 15% of myasthenia gravis pts develop thymoma

50-70% of thymoma pts have MG symptoms.

Question 22

Treatment of myasthenia gravis is

Answer 22

high dose steroids in acute crisis are second line and they are there to maintain symptom control but onset is delayed so steroids are not recommended in acute crisis.

For acute crisis need to give IVIG or plasma exchange.

Question 25

what is a myasthenic crisis?

Answer 25

severe weakness from myasthenia gravis that requires intubation.

See generalized weakness, respiratory symptoms, severe oropharyngeal weakness that results in dysphagia and aspiration.

Question 26

where to place pt in potential myasthenia gravis crisis?

what to monitor in pts and how often?

Answer 26

ICU and monitor their respiratory status

q2-4 hour vital capacity and maximal inspiratory force

Question 27

what happens to pyridostigmine with pts who have myasthenia crisis?

Answer 27

stop this while pts is on mechanical ventilation to minimize secretions and decrease aspiration risk. Can be restarted after extubation.

Question 28

Is rituximab helpful for myasthenia gravis?

Answer 28

helpful for refractory myasthenia gravis in pts who have MG muscle specific tyrosine kinase antibodies

but NOT indicated or used in management of myasthenia crisis.

Question 32

Diagnosis of Myasthenia Gravis is by

If this is negative what is done next?

Do we still diagnose based off edrophonium test?

Answer 32

serological testing: 85% of generalized MG will have positive acetylcholine receptor autoantibodies

50% of ocular MG will have positive AChR antibodies

40% of pts who are seronegative for AchR antibodies are positive for muscle-specific tyrosine kinase autoantibodies

If serology is completely negative, EMG and nerve conduction study is done with repetitive stimulation to confirm diagnosis.

We no longer do edrophonium and ice pack test due to high false positive rates.

Question 33

4T’s of anterior mediastinal masses

Answer 33

thymoma’s - most common

teratoma - and other germ cells

thyroid gland or goiter

terrible lymphoma - located in middle or posterior medastinum.

Question 34

Thymoma management

Answer 34

surgery in clinical setting with thymom and thymic carcinomas

Thymectomy is suggested for people who are <60 yrs and have generalized myasthenia gravis.

Question 35

Lambert Eaten myasthenic syndrome is

Answer 35

paraneoplastic syndrome with small cell lung cancer that presents with slowly progressive proximal muscle weakness and decreased DTR, dry mouth, and ED.

See vigorous muscle activation improves with recovery of DTR and muscle strength.

Rarely see ocular symptoms.

Question 36

back pain, paresthesias and symmetrical weakness worse in lower extremities and hyporeflexia

Answer 36

Guillain Barre syndrome or acute inflammatory demyelinated polyneuropathy

see ascending progressive symmetric weakness or paralysis after a week of URI or GI (campylobacter)

• 1/3 won’t have prior symptoms. As weakness ascends see weakness with walking, 3/5 strength of lower extremities compared to 4/5 strength of upper extremities in this pt.

See bulbar symptoms (ophthalmoplegia, facial diplegia, dysarthria, dysphagia) and respiratory compromise.

Back pain is from dx targeting the primary proximal polyneuropathy and pts having mild sensory symptoms such as paresthesias and sensory ataxia.

they can develop dysautonomia = tachycardia, diaphoresis and sluggish pupils and absent reflexes.

Question 37

if suspecting acute inflammatory demyelinated polyneuropathy then need to get

Answer 37

LP - in all suspected GBS pts to rule out infectious causes and document elevated CSF protein in normal CSF WBC. See albuminocytologic dissociation.

LP is not diagnostic for GBS because it can see abnormal symptoms a week after symptom onset.

Nerve conduction and study and EMG are needed to confirm GBS.

Question 38

Pt has fatigue, diplopia and dysphagia for past two months. Exercises and tires easily. Has double vision at the end of the day and after a URI two weeks ago is very weak and tired. Has trouble swallowing and coughs while drinking. This is his CT scan. what does he have?

Answer 38

he has a thymoma with concurrent myasthenia gravis. See anterior mediastinal mass on CT and also 15% of myasthenia gravis pts develop thymoma

50-70% of thymoma pts have MG symptoms.

Question 39

Treatment of myasthenia gravis is

Answer 39

high dose steroids in acute crisis are second line and they are there to maintain symptom control but onset is delayed so steroids are not recommended in acute crisis.

For acute crisis need to give IVIG or plasma exchange.

Question 42

First line treatment for GBS and myasthenia crisis?

Answer 42

Give IVIG or plasmapheresis. Don’t pick steroids

Myasthenia gravis crisis - steroids helps to keep things calm over time not best in acute crisis.

GBS- steroids are not helpful.