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
Where does the weakness start in lamber eaton
Extremities to head
