Diagnostic Considerations

Myasthenia gravis (MG) can mimic other diagnoses in elderly persons and vice versa. Examples of such pathology include diagnoses such as congestive heart failure, pulmonary embolism, and acute myocardial infarction.

Differential Diagnoses

Amyotrophic Lateral Sclerosis in Physical Medicine and Rehabilitation
Basilar Artery Thrombosis
Botulism
Brainstem Gliomas
Cavernous Sinus Syndromes
Chronic Myelogenous Leukemia (CML)
Ciguatera Toxicity
Congenital Myasthenic Syndrome
Dermatomyositis
Diphtheria
Graves Disease
Guillain-Barre Syndrome
Kearns-Sayre Syndrome
Lambert-Eaton Myasthenic Syndrome (LEMS)
Miller-Fisher Syndrome
Multiple Sclerosis
Myocardial Infarction
Neurosarcoidosis
Organophosphate Toxicity
Polymyositis
Pulmonary Embolism (PE)
Tetrodotoxin Toxicity
Thyroid Ophthalmopathy
Tick-Borne Diseases
Tolosa-Hunt Syndrome

Workup

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Media Gallery

Normal neuromuscular junction showing a presynaptic terminal with a motor nerve ending in an enlargement (bouton terminale): Synaptic cleft and postsynaptic membrane with multiple folds and embedded with several acetylcholine receptors.
Acetylcholine receptor. Note 5 subunits, each with 4 membrane-spanning domains forming a rosette with a central opening. The central opening acts as an ion channel.
CT scan of chest showing an anterior mediastinal mass (thymoma) in a patient with myasthenia gravis.
Increasing left ptosis developing upon sustained upward gaze in patient with myasthenia gravis (A through F). Note limited elevation of left eye, denoting superior rectus palsy (A). A initially, C after around 20 seconds, F after 1 minute.
Cogan sign. Patient changes gaze from downward position (A) to primary position (B). Both lids are seen to overshoot in twitch (B) before gaining their initial ptotic position (D). In this case, Cogan sign is seen more obviously on right, whereas left lid is more ptotic.
CT scan of chest and mediastinum showing thymoma in patient with myasthenia gravis.
Repetitive nerve stimulation at frequency of 2 Hz showing increasing decrement in amplitude of compound muscle action potential up to fourth response (42% amplitude loss), after which it stabilizes.
Single-fiber electromyography showing so-called jitter phenomenon (second action potential wave group).
What is myasthenia gravis? Myasthenia gravis is an autoimmune disease that's categorized as a type II hypersensitivity that involves autoantibodies binding acetylcholine receptors on skeletal muscle cells. Courtesy of Osmosis.org (https://www.osmosis.org/).
Motor end plate and innervation. Courtesy of Wikimedia Commons.

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Distribution of weakness in a large cohort of patients with myasthenia gravis (n=609)

Distribution of weakness in a large cohort of patients with myasthenia gravis (n=609)

Distribution of Weakness	Percentage of Patients
Localized ocular	17%
Ocular and generalized	50%
Ocular and bulbar	13%
Ocular and limb	20%

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Author

Abbas A Jowkar, MBBS Clinical Assistant Professor, Department of Medicine, Western Michigan University, Home Stryker, MD, School of Medicine; Neurologist, Bronson Neuroscience Center--Kalamazoo

Abbas A Jowkar, MBBS is a member of the following medical societies: American Academy of Neurology, American Academy of Physician Assistants, American Association of Neuromuscular and Electrodiagnostic Medicine

Disclosure: Nothing to disclose.

Coauthor(s)

William D Goldenberg, MD Assistant Professor, Department of Emergency Medicine, Uniformed Services University of the Health Sciences; Staff Emergency Physician, Naval Medical Center San Diego

William D Goldenberg, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, Emergency Medicine Residents' Association, Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Aashit K Shah, MD, FAAN, FANA Professor and Associate Chair of Neurology, Director, Comprehensive Epilepsy Program, Program Director, Clinical Neurophysiology Fellowship, Detroit Medical Center, Wayne State University School of Medicine

Aashit K Shah, MD, FAAN, FANA is a member of the following medical societies: American Academy of Neurology, American Clinical Neurophysiology Society, American Epilepsy Society, American Neurological Association

Disclosure: Received research grant from: Lundebck pharma.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Nicholas Lorenzo, MD, CPE, MHCM, FAAPL Co-Founder and Former Chief Publishing Officer, eMedicine and eMedicine Health, Founding Editor-in-Chief, eMedicine Neurology; Founder and Former Chairman and CEO, Pearlsreview; Founder and CEO/CMO, PHLT Consultants; Former Chief Medical Officer, MeMD Inc

Nicholas Lorenzo, MD, CPE, MHCM, FAAPL is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, American Association for Physician Leadership

Disclosure: Nothing to disclose.

Acknowledgements

Glenn Lopate, MD Associate Professor, Department of Neurology, Division of Neuromuscular Diseases, Washington University School of Medicine; Director of Neurology Clinic, St Louis ConnectCare; Consulting Staff, Department of Neurology, Barnes-Jewish Hospital

Glenn Lopate, MD is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and Phi Beta Kappa

Disclosure: Baxter Grant/research funds Other; Amgen Grant/research funds None

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment