Myasthenia Gravis Quick overview

Myasthenia Gravis a quick review

Myasthenia Gravis Quick overview

needs improvement

Myasthenia Gravis

Signs and Symptoms

● Fatigable muscle weakness – most common

1) ptosis and diplopia 80%.

● 2) Bulbar muscles ( dysarthria and dysphagia)

● 3) Limb weakness usually proximal and symmetric

● Worse at end of day

  • Resp muscle weakness = myasthenic crisis

Evaluation

● Bedside Icepack test

● Edrophonium test (historically)

● Anti- AChR/MuSK antibody titer – high in

  • Repetitive nerve stim shows decreasing response

Treatment

● Anti-AChE (-stigmines)

● Immunosuppressants

○ (steroids/azathioprine/cyclosporine)

● Plasmapheresis and IV-Ig

● Thymectomy?

○ Yes if thymoma present

○ Otherwise uncertain if recommended

 

– An autoimmune disease targeting post-synaptic acetylcholine receptors

Epidemiology

– 7 – 23 new cases/million people/year; 70 – 320/million people live with MG

– Bimodal age distribution: peaks in 2nd and 3rd decades (female predominance) and 6th to 8th decades (male predominance)

Patient Presentation

– Diplopia, ptosis, dysphagia which is worsened with muscle use (fatigability), and improved with rest

– Often asymmetric symptoms at presentation

– Proximal muscles sometimes involved

– Myasthenic crisis: respiratory muscle weakness leading to respiratory insufficiency and

pending respiratory failure = emergency!

Labs/Investigations

– Ice pack test (bedside), acetylcholine receptor antibodies (80% sens, 100% spec), MuSK antibodies (38% sens, unknown spec), repetitive nerve stimulation with EMG, CT chest

DDx

– Thyroid ophthalmopathy, brainstem or cranial nerve lesion, myotonic dystrophy and oculopharyngeal dystrophy, general fatigue, Lambert-Eaton, ALS, botulism

Management

– First line – pyridostigmine

– Thymectomy if thymoma present on chest CT

– If weakness affects eating/breathing, give IVIG or plasmapheresis

  • Refractory MG treated with prednisone or azathioprine

Shawn J Bird, MD. Diagnosis of myasthenia gravis. 2018.

https://www.uptodate.com/contents/diagnosis-of-myasthenia-gravis?search=myasthenia%20gravis&source=search_result &selectedTitle=2~150&usage_type=default&display_rank=2

Shawn J Bird, MD. Clinical manifestations of myasthenia gravis. 2018.

https://www.uptodate.com/contents/clinical-manifestations-of-myasthenia-gravis?search=myasthenia%20gravis&source=s earch_result&selectedTitle=4~150&usage_type=default&display_rank=4#H10

Image: ​https://goo.gl/images/kwuPjo

 

Summarized by Dr. Kazmi, Medical student : Dr. Joey Gerondale

 

This is the basic information. Needs improvement. Read up-to-date.
+1
0
+1
0
+1
0
+1
0
+1
0

1 thought on “Myasthenia Gravis Quick overview”

  1. MG : intubate: VC < 15-18cc/kg, NIF -20 cm H2O., PEF +exp force : < 40 cm H2O, TV < 5 cc/ kg, dysphagia, Tiggers fo MG: Aminoglycoside, CV: beta blockers quinidine calcium channel blocker‘s, procainamide. / Chloroquine, D penicillamine, succinylcholine and magnesium Cholinergic crisis: due to increased dose of acetylcholinestrase, inhibitors, intubate, stop offending agent, initiate or lower corticosteroid dosage, correct electrolytes, consider plasmapheresis and IVIG and corticosteroid

    Reply

Leave a Comment