AM report 10/06/16 Myasthenia Gravis

Bedside tests for Myasthenia Gravis (NOT specific enough to make the diagnosis, must check serology or electrophysiologic testing)

1)Ice-pack test: helpful if ptosis on exam. take bag/glove with ice, place on closed eyelid for 2 minutes and remove ice. Evaluate for improvement in ptosis
2)Tensilon (Erdophonium) test: Erdophonium is an acetylcholinesterase inhibitor with a rapid onset and short duration. Start with 2mg IV q60s up to 10 mg to see if response. RISK of side effects from excessive acetylcholine (caution if asthma, cardiac history)-NOT specific to make diagnosis

Serologic tests (specific enough to make diagnosis)

1)Acetylcholine receptor abx
2)Muscle specific tyrosine kinase abx (Musk-abx)-lower sensitivity for ocular MG, associated with lower frequency of thymic pathology

Electrophysiologic confirmation

1)Repetitive nerve stimulation (most common)- look for decrease in amplitude with repetitive stimulation
2)Single fiber EMG

Workup

75 % of patients have thymic abnormalities with MG (85 % Thymic hyperplasia, 15 % Thymoma) so check CT chest if new diagnosis of MG

Remember the Terrible T’s (differential for anterior mediastinal mass)

1)Thymoma
2)Terratoma/germ cell tumor
3)Terrible Lymphoma
4)Thyroid tissue

S&S

1)Ocular-ptosis/diplopia, extraocular muscle involvement, NO pupillary involvement
2)Bulbar-dysarthria, dysphagia, fatiguable chewing
3)Proximal limb weakness, neck and facial muscle weakness 
4)Respiratory muscle weakness-Myasthenia CRISIS

Treatment

1)Symptomatic treatment (anticholinesterase inhibitors): eg: Pyridostigmine (Mestinon)
2)Chronic immunomodulators (eg: steroids)
3)Rapid immunomodulators (eg: IVIG/plasmapheresis)
4)Surgical treatment (Thymectomy)

 

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