What is the Difference Between Myasthenia Gravis and Cholinergic Crisis

The key difference between myasthenia gravis and cholinergic crisis is that myasthenia gravis is a rare chronic autoimmune disease causing abnormal muscle weakness without atrophy, while cholinergic crisis, occurring with or without myasthenia gravis, involves excessive stimulation of neuromuscular receptors at neuromuscular junctions, leading to profound muscle weakness.

Myasthenia gravis is an autoimmune disorder that causes muscles under voluntary control to feel weak and get tired very soon without atrophy. Myasthenia crisis and cholinergic crisis are two compilations that give similar feelings to the affected people. Both these crises can result in people who have myasthenia gravis disorder and trigger muscle weakness. Therefore, a cholinergic crisis can be a complication in people who have myasthenia gravis.

CONTENTS

1. Overview and Key Difference
2. What is Myasthenia Gravis  
3. What is Cholinergic Crisis
4. Similarities – Myasthenia Gravis and Cholinergic Crisis
5. Myasthenia Gravis vs. Cholinergic Crisis in Tabular Form
6. Summary – Myasthenia Gravis vs Cholinergic Crisis

What is Myasthenia Gravis?

Myasthenia gravis disorder (MG) is a chronic autoimmune disease. MG is caused by the immune system of the body destroying key segments that regulate how nerves and muscles interact. MG ultimately leads to muscle weakness. In this disorder, the immune system makes antibodies that block or destroy many of your muscles’ receptor sites for a neurotransmitter called “acetylcholine.” The risk factors for this condition include sex and age (more common in women younger than 40 and in men older than 60) and certain genetic markers like HLA-B8 and DR3.

The common symptoms of this condition include weakness of eye muscles, drooping of one or both eyelids, blurred or double vision, changes in facial expressions, shortness of breath, impaired speech, and weakness in the arms, hands, fingers, legs, and neck. Myasthenia crisis occurs as a complication of MG when muscles related to breathing become extremely weak. Moreover, 1 or 2 people out of every 10 people with myasthenia gravis disorder will usually experience myasthenia crisis. Sometimes, a cholinergic crisis can also be a complication of MG, which is caused by the overstimulation of nicotinic and muscarinic receptors at the neuromuscular junctions. Other complications of myasthenia gravis include thymus gland disorder, underactive or overactive thyroid, and other autoimmune conditions like rheumatoid arthritis or lupus.

Myasthenia gravis can be diagnosed through clinical examinations, clinical history, neurological examinations, ice pack tests, repetitive nerve stimulation tests, single fibre electromyography (EMG), imaging tests (CT scan and MRI), pulmonary function tests, and blood analysis. Furthermore, myasthenia crisis is treated through medications (cholinesterase inhibitors, corticosteroids, and immunosuppressants), intravenous therapy (plasmapheresis, intravenous immunoglobulins (IVIg), and monoclonal antibodies), and surgery (video-assisted thymectomy and robot-assisted thymectomy).

What is Cholinergic Crisis?

Cholinergic crisis can happen with and without myasthenia gravis disorder. It occurs as a result of overstimulation of nicotinic and muscarinic receptors at the neuromuscular junctions due to the overdose of acetylcholinesterase inhibitors. Cholinergic crisis can occur in patients with myasthenia gravis when they are treated with acetylcholinesterase inhibitors. However, a cholinergic crisis can also happen to people who have received general anesthesia, children and adults exposed to chemicals such as nerve gases, and people exposed to pesticides and insecticides. Moreover, the symptoms of a cholinergic crisis may include trouble breathing, blurry vision or water eyes, slower heartbeat, a frequent urge to urinate, and muscle twitches involving fine muscle fibers.

Cholinergic crisis can be diagnosed through medical history, physical examination, clinical findings related to stimulation of muscarinic receptors, clinical findings related to stimulation of nicotinic receptors, and clinical findings related to stimulation of the central nervous system. Furthermore, a cholinergic crisis can be treated with antimuscarinic drugs such as atropine or diphenhydramine.

What are the Similarities Between Myasthenia Gravis and Cholinergic Crisis?

• Cholinergic crisis can be a complication of myasthenia gravis.
• Both may show similar symptoms, such as muscle weakness, trouble breathing, etc.
• Both can be diagnosed through medical history, physical examination, and neurological examination.
• They are mainly treated through specific medications.

What is the Difference Between Myasthenia Gravis and Cholinergic Crisis?

Myasthenia gravis is a rare chronic autoimmune disease marked by the abnormal weakness of certain muscles without atrophy, while the cholinergic crisis is a complication with or without myasthenia gravis disorder that occurs as a result of overstimulation of nicotinic and muscarinic receptors at the neuromuscular junctions that is characterized by profound muscle weakness. Thus, this is the key difference between myasthenia gravis and cholinergic crisis.

Furthermore, the risk factors of myasthenia gravis include sex and age (more common in women younger than 40 and in men older than 60) and certain genetic markers such as HLA-B8 and DR3. On the other hand, the risk factors for cholinergic crisis include people who received general anesthesia, children and adults who were exposed to some chemicals such as nerve gases, people who were exposed to pesticides and insecticides, and people with myasthenia gravis who are taking very high doses of acetylcholinesterase inhibitors.

The infographic below presents the differences between myasthenia gravis and cholinergic crisis in tabular form for side by side comparison.

Summary – Myasthenia Gravis vs. Cholinergic Crisis

People with myasthenia gravis have progressive muscle weakness that typically worsens throughout the day. It is an autoimmune disease that affects the neuromuscular system. This disorder can cause complications such as myasthenia crisis, cholinergic crisis, etc. The cholinergic crisis is a less common complication that happens to someone with or without myasthenia gravis disorder. It occurs as a result of the overstimulation of nicotinic and muscarinic receptors at the neuromuscular junctions due to an overdose of acetylcholinesterase inhibitors. So, this summarizes the difference between myasthenia gravis and cholinergic crisis.

Reference:

1. “Myasthenia Gravis.” Mayo Clinic, 22 June 2023.
2. “Cholinergic Crisis.”  Statpearls – NCBI Bookshelf. 23 July 2023.

Image Courtesy:

1. “Ptosis myasthenia gravis” By Mohankumar Kurukumbi, Roger L Weir, Janaki Kalyanam, Mansoor Nasim, Annapurni Jayam-Trouth. – Rare association of thymoma, myasthenia gravis and sarcoidosis: a case report. Journal of Medical Case Reports (CC BY 2.0) via Commons Wikimedia
2. “AChe inhibitors pic” By Sbolmer – Own work (CC BY-SA 3.0) via Commons Wikimedia