Myasthenia gravis Flashcards
What is myasthenia gravis
T2 Autoimmunity against nAch and MuSK receptors = poor muscle contraction (less ACh)
What are the clinical features of Myasthenia gravis
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
What features might a patient present with on examination
Bilateral ptosis
Myasthenic snarl
Nasal speech
Dysphagia
How will you investigate Myasthenia gravis
Serolgy = Anti Ach-r and Anti MUSK Tensilon Test Positive (Power increase w/edotropium)
How is Myasthenia gravis managed
ACHASE Inhibitor (Neostigmine) with steroid
What is the Tensilon test
Give Edotropium and power increases
Positive = Increased muscles strength after administration
How does Anti Ach-r cause myaesthenia gravis
Binds to post synaptic receptor = Comp. Inhibition of Ach
Exertion causes increased Anti-Ach-r binding
Activate complement = NMJ Destruction
How does Anti musk cause myaesthenia gravis
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
What is the differential of Myaesthenia gravis due to similar symptoms
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
What is thyroid asscoaition with myaesthenia gravis
Thymoma (Male)
Do Thymectomy
How does the symptom progression differ between MG and Lamber Eaton
MG = Sx worse w/ exertion LE = Sx better w/exertion
How does the treatment of MG differ to its differential Lamber Eaton
MG = ACHASE Inhibitor( Nystigmine) w/ steroids LE = Prednisolone w/ IV Ig
What is Myaesthenic Crisis
MG Complication
- Sx worsening w/ Rapid Resp Weakness
- Tx = Plasma exchange w/ IV Ig
Thymoma is apparent in MG, what cancer is apparent in Lamber eaton
Small cell lung cancer
Where does the weakness start in Myaesthenia
Head to lower body