Myasthenia gravis is a neurological disorder in which the defect lies in the function of the neuromuscular junction (NMJ) resulting in weakness and fatigue of muscles. Timely intervention prevents the disability and dependence on the others.
It is caused by antibody-mediated destruction of acetylcholine receptors in neuromuscular junction.
Nerve ending at neuromuscular junction releases acetylcholine, which in turn binds to acetylcholine receptors located at muscle cell membrane. This binding of acetylcholine to muscle cell membrane triggers a cascade of events that causes depolarization of muscle cells and eventually muscle contracts.
The degradation of acetylcholine receptors, as in myasthenia gravis, results in impaired neurotransmission to skeletal muscle.
Myasthenia gravis is prevalent at 10 per 100000. Female to male ratio is 2:1. It is more common in second and third decades among females and in seventh and eighth decades among males.
I. Ptosis & Diplopia:
First symptom to surface is ptosis and diplopia and it remains the only symptom over a long period of time in the course of the disease.
II. Difficulty in Chewing, Swallowing and Speech:
Weakness of oropharyngeal muscles causes difficulty in chewing, swallowing and speaking.
III. Weakness of Limbs:
Weakness of limbs presents as first symptom in only 10% of the patients.
IV. Time Relationship:
Symptoms, including weakness and fatigue, are least bothering in the morning increase in severity with the course of the day and are severe by the evening.
V. Aggravating Factors:
The disease and so the symptoms get aggravated by many factors mainly diseases and medicines. These factors include, intercurrent infections, pregnancy and menses. Medicines that lead to aggravation of symptoms include beta blockers, calcium channel blockers, neuromuscular blockers, quinidine, aminoglycosides and procainamide.
VI. Course of The Disease:
Weakness remains restricted to eyes in 10% of myasthenia gravis patients. Weakness progresses in severity with time and becomes stable after 10 to 15 years of onset of disease.