Myasthenia gravis pathology | Myasthenia gravis pathogenesis

Myasthenia gravis
Myasthenia gravis is a neuromuscular disorder characterized by weakness and fatiguing of some or all muscle groups, weakness worsening on sustained exertion, or towards the end of the day, relieved by rest.

Aetiopathology

- In humans MG cause reduction of acetylcholine receptor sites in the postsynaptic folds

- Antibodies bind to the receptor sites resulting in their destruction. These antibodies are referred to as acetylcholine receptor antibodies.

- Reduced receptor synthesis and increased receptor destruction as well as well as the blocking of receptor response to acetylcholine is responsible for the disorder.

Myasthenia gravis

Clinical features:

Fatigue

Muscle wasting

Weakness of facial muscles

Ptosis

Nasal quality to speech

Weakness of jaw muscle – mouth remain open

Dysarthria

Dysphonia

Dysphagia

Weakness of neck muscle

Most commonly proximal muscle are affected

Sub division of clinical features:

 Class 1-          ocular muscle only

Class 2-           mild generalized weakness

 Class 3-          moderate generalized and mild to moderate ocular-bulbar weakness

Class 4-          severe generalized and ocular-bulbar 

                       weakness

Class 5-          Myasthenic crisis

Total: Class 1 (20%)

Class 2,3,4,5 (80%)

Management

Medical treatment:

 Anticholinesterase drugs 

 Steroids

 Immunosuppressants other than steroids

 Thymectomy 

Physiotherapy treatment

(a) Goals

- Myasthenia patient should find optimal balance between the physical activity and rest

- It’s not able to cure the weakness by active physical training, so low to medium intensity training is     recommended

- Enhance ability to function daily

- Decrease risk of falling

- Completion of functional tasks and maintenance of independence

(b)General exercise programs

- Should be done progressively

- Range of motion (flexibility) to light resistance to full resistance – Start with lower prescription : 3     sets of 5 reps

- The primary goal of therapy is to build the individual's strength to facilitate return to work and             activities of daily living

- Do not overdo resistive training to the point of fatigue

Type of exercise for strength are as follows :

Aerobic Exercises

Strength exercises 

Swimming

Postural exercise

Breathing exercise

(c)Postural exercise

-Important in assisting with breathing, speaking and swallowing

-Keeps bones and joints in the correct alignment so that muscles are being used properly

-Prevents fatigue because muscles are being used more efficiently, allowing the body to use less   energy

(d)Breathing exercise

- Help improve lung function

- Include inspiratory muscle training

- Pursed lip breathing

- Diaphragmatic breathing

- These exercises can improve respiratory endurance as many people with MG have affected                   respiratory muscles

(e) Exercise intensity

- The therapist has to look for the vitals after each sets of exercise

- During the time of exercise the symptoms should not be worsen

- Exercise peak dose is taking pyridostigmine