Myasthenia Gravis - Causes, Symptoms, Diagnosis & Treatment

Myasthenia Gravis: A Chronic Autoimmune Neuromuscular Disease

Dr.Santosh Honavar profile Authored by Dr.Santosh Honavar on 24 Mar 2015 - 13:34.

MG-EYEMyasthenia Gravis is an auto-immune disorder characterized by muscle weakness and fatigue owing to production of anti-bodies against proteins at the neuro-muscular junction.

Myasthenia Gravis weakens the voluntary muscles such as the muscles responsible for facial expressions, chewing, swallowing, and talking. It may also weaken neck and limb muscles in some cases. Typically, the muscles around the eyes are affected first, causing the eyelids to droop. Some patients also develop double vision.

Some types of Myasthenia Gravis are:

 

Category

Severity

Class I

Any ocular muscle weakness; all other muscle strength is normal

Class II

Mild weakness affecting other than ocular muscles; may also have ocular muscle weakness of any severity

Class II a

Principally affecting limb, axial muscles, or both; may also have lesser involvement of oropharyngeal muscles

Class II b

Mainly affecting oropharyngeal, respiratory muscles, or both; may also have lesser or equal involvement of limb, axial muscles, or both

Class III

Moderate weakness affecting other than ocular muscles; may also have ocular muscle weakness of any severity

Class III a

Predominantly affecting limb, axial muscles, or both; may also have lesser involvement of oropharyngeal muscles

Class III b

Predominantly affecting oropharyngeal, respiratory muscles, or both; may also have lesser or equal involvement of limb, axial muscles, or both

Class IV

Severe weakness affecting other than ocular muscles; may also have ocular muscle weakness of any severity

Class IV a

Predominantly affecting limb, axial muscles, or both; may also have lesser involvement of oropharyngeal muscles

Class IV b

Mainly affecting oropharyngeal, respiratory muscles, or both; may also have lesser or equal involvement of limb, axial muscles, or both; use of a feeding tube without intubation

Class V

Need for intubation, with or without mechanical ventilation, except when used during routine postoperative management

 
 
 
 

 

For a better understanding of the cause, we need to know about the working muscle.

Voluntary and involuntary are the two types of muscles; the former is under our control where as involuntary muscles work on their own.

For a voluntary muscle to contract, the brain needs to send a message to the spinal cord, which is followed by a message from peripheral nerves to the muscles. The space between a nerve ending and muscle is known as neuro-muscular junction. For a message to get conducted, a neurotransmitter called acetylcholine should reach the muscle side of the junction.

In Myasthenia Gravis, antibodies are formed which act against acetylcholine and disturbs the conduction of message through the neuro-muscular junction, thereby preventing muscle contraction.

 

 

The initial symptoms of Myasthenia Gravis are specific such as:

  • Eyelid drooping and blurred/ double vision.
  • Weakness of flexion, head extension and bulbar muscles are commonly experienced.
  • Proximal limb weakness
  • Severity of weakness increases from morning to evening.
  • Weakness is escalated on exertion and relieved by rest.
  • Breathing process may also get affected in some cases.
  • Generalized weakness is seen in rare cases.

 

Physical examination in addition to diagnostic tests may confirm the disease.The following tests are used for the diagnosis:

  • The anti–acetylcholine receptor (AChR) antibody test
  • Edrophonium test
  • Electrodiagnostics
  • Ice test

Other tests such as X-ray, CT-scan, PFT and MRI may assist in the diagnosis.

The following are more prone to the disease:

  • Women between 20 and 40 years of age.
  • Men between 50 and 70 years of age.
  • New born baby from a Myasthenia Gravis patient may exhibit temporary symptoms of the disease, which gradually improves in some weeks.

Myasthenia Gravis can be treated by medications or surgery:

Acetylcholinesterase inhibitors: These are the drugs which inhibit the enzyme Acetylcholinesterase, which is responsible for degradation of Acetylcholine in the motor end plate. Therefore, the level of Acetylcholine increases causing nerve conduction and muscle contraction. Ex: Neostigmine and Pyridostigmine.

Immunosuppressive agents: these drugs are responsible for limiting the production of antibodies. Ex: Prednisone, Cyclosporine and Azathioprine.

In Myasthenic Crisis (severe condition): Intravenous Immunoglobulins can be used to bind the antibodies or Plasmapheresis can be done to remove the putative anti-bodies.

Thymectomy: Thymus gland is removed in some cases when a tumour in the thymus is found responsible for the disease.

Lifestyle modifications:

  • Eat sensibly and drink plenty of water.
  • Avoid alcohol and tobacco, as both of these agents may exacerbate the condition.
  • Extreme temperatures may weaken you, so avoid hot baths.
  • Try to eat soft food in small quantities more frequently.
  • Replace fruits and vegetables with juices if chewing is difficult.
  • Eat warm rather than hot meals.
  • Try to minimize your work and get plenty of rest to avoid fatigue.
  • Lubricate your eye when it is getting dry.
  • Some food items like lemon and tonic water may aggravate the condition, hence should be avoided.
  • Steroids used in the treatment may cause weight gain; regular exercise may help in controlling the weight.

If you have recent-onset droopy eyelids or double vision, you may have Myasthenia. See your Oculoplasty specialist soon.

 

 

 

*Disclaimer This is not medical advice. The content is for educational purposes only. Please contact your doctor for any health care issues.