neurologic disorders
Myasthenia Gravis
Symptoms and Signs of Myasthenia Gravis
The most common symptoms of myasthenia gravis are Ptosis Diplopia Muscle weakness after use of the affected muscle Weakness resolves when the affected muscles are rested but recurs when they are used again. Weakness due to myasthenia lessens in cooler temperatures. Ocular muscles are affected initially in 40% of patients and eventually in 85% and are the only muscles affected in 15%. If generalized myasthenia is going to develop after ocular symptoms, it develops in 78% of patients within 1 year and in 94% within the first 3 years. Hand grip may alternate between weak and normal (milkmaid’s grip). Neck muscles may become weak. Proximal limb weakness is common. Some patients present with bulbar symptoms (eg, altered voice, nasal regurgitation, choking, dysphagia). Sensation and deep tendon reflexes are normal. Manifestations fluctuate in intensity over minutes to hours to days. Myasthenic crisis,a severe generalized quadriparesis or life-threatening respiratory muscle weakness, occurs in about 15 to 20% of patients at least once in their life. It is often due to a supervening infection that reactivates the immune system. Once respiratory insufficiency begins, respiratory failure may occur rapidly. Cholinergic crisisis muscular weakness that can result when the dose of anticholinesterase drugs (eg,neostigmine,pyridostigmine) is too high. A mild crisis may be difficult to differentiate from worsening myasthenia. Severe cholinergic crisis can usually be differentiated because it, unlike myasthenia gravis, results in muscle fasciculations, increased lacrimation and salivation, tachycardia, and diarrhea. 