By: Hiren K Gehloth
Myasthenia gravis means “grave muscle
weakness’ or “weakness of the voluntary or
striated muscles of the body”.
Myasthenia gravis (MG) is a relatively rare autoimmune
disorder in which antibodies form against nicotinic
acetylcholine (ACh) postsynaptic receptors at the
neuromuscular junction (NMJ) of the skeletal muscles. It
is a type-II hypersensitivity immune response.
The basic pathology is a reduction in the number of ACh
receptors (AChRs) at the postsynaptic muscle membrane
brought about by an acquired autoimmune reaction
producing anti-AChR antibodies.
The reduction in the number of AChRs results in a
characteristic pattern of progressively reduced muscle
strength with repeated use and recovery of muscle strength
after a period of rest.
The ocular and bulbar muscles are affected most
commonly and most severely, but most patients also
develop some degree of fluctuating generalized
The most important aspect of MG in emergency
situations is acute worsening of weakness leading to
neuromuscular respiratory failure. The diagnosis of
myasthenic versus cholinergic crisis and its management
is also a significant challenge in emergent settings.
“Myasthenia Gravis is a auto immune disorder affecting
the myoneural junction, characterized by varying degree
of weakness of the voluntary muscle”
CAUSES AND RISK FACTORS
MG is idiopathic in most patients. Although the main cause
behind its development remains speculative, the end result is
a derangement of immune system regulation. MG is clearly
an autoimmune disease in which the specific antibody has
been characterized completely. In as many as 90% of
generalized cases, IgG to AChR is present. Even in patients
who do not develop clinical myasthenia, anti-AChR
antibodies can sometimes be demonstrated.
Numerous findings have been associated with MG. For
example, people with certain human leukocyte antigen
(HLA) types have a genetic predisposition to autoimmune
Thymic abnormalities are
common: Of patients with
MG, 75% have thymic
disease, 85% have thymic
hyperplasia, and 10–15% have
thymoma. Extrathymic tumors
may include small cell lung
cancer and Hodgkin
disease. Hyperthyroidism is
present in 3–8% of patients
with MG and has a particular
association with ocular MG.
TYPES OF MYASTHENIA GRAVIS
→ Congenital myasthenia gravis
Congenital myasthenia gravis is defined by its cause: a
genetic defect typically inherited from both parents,
rather than an autoimmune disease in which immune
system attacks damage communication between nerves
and muscles — the cause of the other forms of this
→Ocular myasthenia Gravis
In ocular myasthenia gravis, the muscles that move the eyes and
control the eyelids are weakened and easily fatigued. Symptoms
include drooping eyelids and double vision.
While many patients with other forms of myasthenia gravis
first experience symptoms in the muscles around the eyes as
well, patients with ocular myasthenia gravis only have
symptoms in these muscles, and the weakness and fatigue do
not spread to other muscle groups.
→Generalized myasthenia gravis
In patients with generalized myasthenia
gravis, muscle weakness and fatigue
are not confined to the eye muscles
or other specific muscle groups.
It may spread to the facial
muscles as well as the limbs.
In approximately 10 percent of these patients, muscle
weakness spreads to the respiratory muscles or muscles of
the throat and jaw. This can make breathing quite difficult,
and can be extremely serious. Such episodes are called a
→Transient neonatal myasthenia gravis
Infants born to mothers with myasthenia gravis may
develop symptoms of the disease about 48 hours after birth.
Symptoms can include impaired sucking and swallowing, a
weak cry, and respiratory insufficiency. While serious, the
symptoms typically disappear within days or weeks.
→ Juvenile myasthenia gravis
In juvenile myasthenia gravis, symptoms begin before the
onset of puberty.
Juvenile myasthenia gravis in its most benign form is
confined to the eye muscles, but severe cases involving other
muscle groups are known. Symptoms can range from
clumsiness to difficulty in swallowing and tiring easily.
Young patients are less likely to test positive for the
acetylcholine receptor antibodies that characterize
generalized or ocular myasthenia gravis in adults. Juvenile
myasthenia gravis patients are also more likely to achieve
remission than adult patients, but periods of remission can
give way to relapses.
Drooping of one or both eye lids (ptosis)
Blurred or double vision
Breathing difficulty because of the chest wall muscle
Chewing swallowing difficulty, causing frequent
Difficulty in climbing stairs, lifting objects, or rising
from a seated position
Difficulty in talking(slurred speech)
Impaired speech (dysarthria)
•Facial paralysis or weakness of the
•Mask- like facial expression
•Hoarseness or changing voice
•Difficulty in maintain in steady gait
•Weakness in arm, hands, fingers, legs,
A physical and neurological examination.
A blood test.
An Edrophonium test.
This test uses injections of edrophonium chloride to briefly
relieve weakness in people with myasthenia gravis. The
drug blocks the breakdown of acetylcholine and temporarily
increases the levels of acetylcholine at the neuromuscular
junction. It is usually used to test ocular muscle weakness.
Electrodiagnostics. Diagnostic tests include repetitive
nerve stimulation, which repeatedly stimulates a person’s
nerves with small pulses of electricity to tire specific
muscles. Muscle fibers in myasthenia gravis, as well as
other neuromuscular disorders, do not respond as well to
repeated electrical stimulation compared to muscles from
normal individuals. Single fiber electromyography (EMG),
considered the most sensitive test for myasthenia gravis,
detects impaired nerve-to-muscle transmission. EMG can
be very helpful in diagnosing mild cases of myasthenia
gravis when other tests fail to demonstrate abnormalities.
Diagnostic imaging. Diagnostic imaging of the chest using
computed tomography (CT) or magnetic resonance imaging
(MRI) may identify the presence of a thymoma.
Pulmonary function testing. Measuring breathing strength
can help predict if respiration may fail and lead to a
Thymectomy- This operation to remove the thymus gland
(which often is abnormal in individuals with myasthenia
gravis) can reduce symptoms and may cure some people,
possibly by rebalancing the immune system.
A recent NINDS-funded study found that thymectomy is
beneficial both for people with thymoma and those with no
evidence of the tumors. The clinical trial followed 126
people with myasthenia gravis and no visible thymoma and
found that the surgery reduced muscle weakness and the
need for immunosuppressive drugs.
Anticholinesterase medications. Medications to treat the
disorder include anticholinesterase agents such as mestinon
or pyridostigmine, which slow the breakdown of
acetylcholine at the neuromuscular junction and thereby
improve neuromuscular transmission and increase muscle
Immunosuppressive drugs. These drugs improve muscle
strength by suppressing the production of abnormal
antibodies. They include prednisone, azathioprine,
mycophenolate mofetil, tacrolimus, and rituximab. The
drugs can cause significant side effects and must be
carefully monitored by a physician.
Plasmapheresis and intravenous immunoglobulin.
These therapies may be options in severe cases of
myasthenia gravis. Individuals can have antibodies in their
plasma (a liquid component in blood) that attack the
neuromuscular junction. These treatments remove the
destructive antibodies, although their effectiveness usually
only lasts for a few weeks to months.
Plasmapheresis is a procedure using a machine to remove
harmful antibodies in plasma and replace them with good
plasma or a plasma substitute.
Intravenous immunoglobulin is a highly concentrated
injection of antibodies pooled from many healthy donors
that temporarily changes the way the immune system
operates. It works by binding to the antibodies that
cause myasthenia gravis and removing them from
Administer cholinesterase inhibitors (Physostigmine) and
ensure proper dosing/timing
Monitor respiratory status
Provide eye care
Monitor feeding and ensure proper nutrition. Schedule meds
30-45 minutes before meals.
Maintain suction and emergency equipment.
Educate patient to identify and avoid triggers
Educate patient on s/s of cholinergic and myasthenic crisis to
report to provider.
During myasthenia crisis, the nurse should:
– Administer anti-cholinesterase medication as ordered.
– Assess and reassess respiratory status.
– Clear airway through thorough suctioning
– Administration of supplemental oxygen as advised
– Attach to ventilator assistance if necessary.
During cholinergic crisis, the nurse should:
– Hold cholinergic drugs as it could exacerbate the situation.
– Ensure airway clearance through prompt and thorough
– Administer supplemental oxygen and ventilation
assistance as needed
– Strictly monitor hypotension