Myasthenia gravis

Question 1

What is myasthenia gravis

Answer 1

T2 Autoimmunity against nAch and MuSK receptors = poor muscle contraction (less ACh)

Question 2

What are the clinical features of Myasthenia gravis

Answer 2

Muscle weakness (worse w/exertion)
Diplopia (CN4)
Ptosis (CN3)
Myaesthenic snarl/ weak jaw(CN5)
Bulbar weakness (dysphagia, can't swallow) (CN9/10)
Fatigued speech
Better with rest

Question 3

What features might a patient present with on examination

Answer 3

Bilateral ptosis
Myasthenic snarl
Nasal speech
Dysphagia

Question 4

How will you investigate Myasthenia gravis

Answer 4

Serolgy = Anti Ach-r and Anti MUSK
Tensilon Test Positive (Power increase w/edotropium)

Question 5

How is Myasthenia gravis managed

Answer 5

ACHASE Inhibitor (Neostigmine) with steroid

Question 6

What is the Tensilon test

Answer 6

Give Edotropium and power increases

Positive = Increased muscles strength after administration

Question 7

How does Anti Ach-r cause myaesthenia gravis

Answer 7

Binds to post synaptic receptor = Comp. Inhibition of Ach
Exertion causes increased Anti-Ach-r binding
Activate complement = NMJ Destruction

Question 8

How does Anti musk cause myaesthenia gravis

Answer 8

MUSK helps synthesise Ach-r so less MuSK = less Ach-r

-Anti-musk = decrease Ach-r expression at post synaptic membrane = Complement activation = NMJ Destruction

Question 9

What is the differential of Myaesthenia gravis due to similar symptoms

Answer 9

Lamber Eaton syndrome

• Autoimmunity against PRESYNAPTIC CA2+ Channel
• Improve Sx with exertion
• Assocaited w/ SCLC
• Sx start at peripheral then head and neck
• Tx = Steroids and IV Ig

Question 10

What is thyroid asscoaition with myaesthenia gravis

Answer 10

Thymoma (Male)
Do Thymectomy

Question 11

How does the symptom progression differ between MG and Lamber Eaton

Answer 11

MG = Sx worse w/ exertion
LE = Sx better w/exertion

Question 12

How does the treatment of MG differ to its differential Lamber Eaton

Answer 12

MG = ACHASE Inhibitor( Nystigmine) w/ steroids
LE = Prednisolone w/ IV Ig

Question 13

What is Myaesthenic Crisis

Answer 13

MG Complication

• Sx worsening w/ Rapid Resp Weakness
• Tx = Plasma exchange w/ IV Ig

Question 14

Thymoma is apparent in MG, what cancer is apparent in Lamber eaton

Answer 14

Small cell lung cancer

Question 15

Where does the weakness start in Myaesthenia

Answer 15

Head to lower body

Question 16

Where does the weakness start in lamber eaton

Answer 16

Extremities to head