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which is improved after adequate rest. The initial be applied intramuscularly if there are any muscarinic
symptom is the ptosis either symmetrically or cholinergic receptor-mediated side effects. For children,
asymmetrically and diplopia which are observed neostigmine should be reduced to 0.02-0.03 mg/kg, while
in more than 80% of patients. In certain cases, total amount should not be more than 1.0 mg. Test should
[2]
alternative or bilaterial ptosis and nystagmus are also be performed at the muscle with significant symptoms
observed. Patients suffer also from lagophthalmos. and referred to the clinical absolute score for MG. The
However, pupil size remains normal. baseline of muscle tone should be firstly recorded, which
is repeated every 10 min for 1 h. The relative score, as the
Due to the weakness of the muscles involved in diagnostic value, should hence be pooled by the absolute
swallowing, there is dysphagia, difficulty of chewing score of the trial with most significant improvement
and velopharyngeal insufficiency. For the symptoms according to the following formula:
of vocality, patients of MG have dysarthria and
hypophonia, some of who may also have nasality. Relative score = (Baseline-absolute score of each
Weakness of facial muscle leads to hanging jaw sign, trial)/Baseline × 100%
shallow nasolabial fold, leaky cheek blowing, snarling
expression when smiling and sleepy or sad expression. There is usually less than 25% of negative diagnosis
Weakness of cervical muscle, patients could not hold while more than 60% for positive diagnosis, and 25-60%
are as suspicious positive cases. Further tests are needed
their upright easily. Although it is usually not the
primary symptoms of MG, limb movement is highly to confirm the negative diagnosis.
affected spreading from the proximal ends. In certain Electromyography
cases, the respiratory muscle is under myasthenic
crisis which leads to dyspnea. Assisted ventilation is Repetitive nerve stimulation
necessarily needed to sustain life. [3,4,5]
Repetitive nerve stimulation (RNS) is an electrical
Classification: modified Osserman scale stimulation to nerves, such as facial, accessory,
axillary and ulnar nerves, for MG diagnosis, with
Class I: ptosis and diplopia without other muscle repetitive and high-powered low frequency (2-5 Hz)
weakness elsewhere for 2 years. signal. Compound muscle action potential (CMAP)
over the testing muscles will be recorded.
Class II: generalized symptoms with more than
one set of weak muscle: (1) mild generalized form; The duration of stimulation is about 3 s. The
Weakness in limbs with or without ocular signs, decrement of CMAP of MG is measured by comparing
but without prominent bulbar signs. Patients could the CMAP value of the fourth or fifth stimuli to that
live independently; (2) moderate generalized or of the first stimulus. Diagnosis will be concluded as
faciopharyngeal form; symptoms as in II A but with positive when there is more than 10% reduction. MG
bulbar signs. Patients could live independently.
patients on acetylcholinesterase inhibitor medication
should not receive this test until 12-18 h of washing
Class III：severe acute generalized form; acute onset
and rapid development. Faciopharyngeal symptoms out. For diagnosing presynaptic lesions, frequency of
RNS should be increased to 10-20 Hz. Increment with
were observed in the first few weeks to months
followed by respiratory insufficiency with or without more than 100% should be classified as abnormal.
ocular signs. Patients could live independently. Single fiber EMG

Class IV：severe chronic generalized form; unapparent Single fiber EMG (SFEMG) is to measure the variable
signs at early stage due to the slow pathological latency of the single axon innervation to the muscle
progress. All symptoms stated in Class I, II and III are fibers, known as Jitter. The variable latency is usually
developing within 2 years.
about 15-35 s, of which more than 55 ms will be
classified as increased variability of latency. Two or
Class V: muscle atrophy form; severe development
with also muscle atrophy within 6 months. more variable latency in every 20 Jitters of a single set
of muscle will be classified as abnormal. Any block
EXAMINATION during SFEMG should also be classified as abnormal.
Despite of the significant sensitivity, SFEMG is not
Methyl sulfate neostigmine test specific for MG, which is mainly for Class I MG
and those cases without positive outcomes in RNS
Intramuscular administration of 1.0-1.5 mg methyl test. Furthermore, SFEMG is not affected by any
sulfate neostigmine for adult. Atropine (0.5 mg) could acetylcholinesterase inhibitors.

2 Neuroimmunol Neuroinfammation | Volume 3 | Issue 1 | January 20, 2016