Myasthenia gravis physical examination
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Myasthenia can be a difficult diagnosis, as the symptoms can be subtle and hard to distinguish from both normal variants and other neurological disorders.[1] A thorough physical examination can reveal easy fatiguability, with the weakness improving after rest and worsening again on repeat of the exertion testing. Applying ice to weak muscle groups characteristically leads to improvement in strength of those muscles.
Physical Examination
Muscle fatigability can be tested for many muscles. A thorough examination demonstrates easy fatigability during following movements:
- Looking upward and sidewards for 30 seconds: ptosis and diplopia.
- Looking at the feet while lying on the back for 60 seconds
- Keeping the arms stretched forward for 60 seconds
- 10 deep knee bends
- Walking 30 steps on both the toes and the heels
- 5 situps, lying down and sitting up completely
It has been suggested that ice pack and edrophonium tesst are parts of neurological examination of a suspected patient.(3)
Ice pack test: Based on the fact that this test was designed by the fact that cooling can improve NMJ transmission, it can be used only in patients with ptosis since the eyelid muscle is the most accessible muscle to be cooled. We place the ice pack on closed lid for a couple of minutes and the assess the degree of ptosis in the patient. The sensitivity of this test is almost 80 percent.(3_5)
Edrophonium test: This test is used in patients with obvious ptosis or ophthalmoparesis. We begin with 2 mg of edriphonium and add another 2 mg every 60 second to the total dosage of 10 mg. this test can have serious muscarinic side effect so we begin with low dose edrophonium since so many patients will respond to drug in 4 to 6 mg dose and by this way we can reduce the side effects of the drug. The sensitivity of this test is 80 to 90 percent. A positive edrophonium test can be seen in other conditions such as motor neuron disease, brainstem tumors, and compressive cranial neuropathies.(2-3-6)