Dr Ben Wild
Overview |
The 3 main muscle groups in our body are skeletal muscles, which are attached to bones, cardiac muscles (heart muscles), and smooth muscles, which are found in body cavities, blood vessels, etc. All of these muscles are stimulated by the release of neurotransmitters from their associated nerves. There are many medical conditions that can affect muscle function.
Myasthenia Gravis (MG) is an autoimmune condition where the body creates antibodies, similar to those that are created after getting the flu to help fight off the next exposure to the flu, but these antibodies attach to the receptors on skeletal muscle cells responsible for detecting the neurotransmitters that cause muscle contraction. With the antibodies stuck to these receptors, muscle cells can no longer detect neurotransmitters and therefore cannot be stimulated.
MG can be classified as systemic (full body), bulbar or ocular. It can present as early as birth or as late as 7-8th decade of life. Symptoms may worsen with certain antibiotics or beta-blocker medications. MG affects the eye muscles first in 60% of all cases with the majority of affected patients complaining of episodes of drooping eyelids and/or double vision.
On the left is a frontal view of a healthy eye and on the right, an eye showing a droopy eyelid, one of the signs of Myasthenia Gravis.
Signs and Symptoms |
Systemic | Painless fatigability, muscle weakness affecting limbs and eyes, difficulty chewing or with speech, symptoms worsen throughout the day. |
Bulbar | Difficulty swallowing, difficulty with articulation, symptoms worsen throughout the day. |
Ocular | Fatigability of eye muscles during exam, droopy lids, eye turn, double vision, symptoms worsen throughout the day. |
Causes and Risk Factors |
Causes
Autoimmune disease unknown origin.
Risk Factors
Female gender (2x more likely than men)
Prevention, Testing, and Treatment |
Prevention
There are no known preventative measures.
Tests
Droopy lids get worse after looking upwards for 60 seconds, eyelids shoot upwards after changing focus from looking down to straight ahead, droopy lids get better after 2 minutes of exposure to an ice pack, blood work, anti-cholinesterase response testing, electromyography, muscle biopsy.
Treatments
· Steroid pills.
· Pyridostigmine.
· Immunosuppressives.
· Plasmapheresis to filter the blood of these antibodies.
Prognosis |
Symptoms are usually well managed with medication. Because MG is an autoimmune condition, it cannot, at this stage, be cured. After symptoms begin, it usually takes a few months for diagnosis and treatment to begin. It is recommended to see an optometrist as they may be able to put a temporary Fresnel prism on a pair of glasses to help with the double vision, which is likely to dissipate or be resolved after starting treatment.
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