Symptoms
The disease usually begins at sites where a relatively small number of muscle fibers are supplied by a nerve at a neuromuscular junction. This is the case with muscles that are supposed to enable finely tuned movements, such as the eye muscles. The affected musculature shows a tendency towards premature fatigue when stressed, and the symptoms worsen accordingly in the course of the day and when a movement is performed several times.
This manifests itself, for example, in the increasing drooping of one or both upper eyelids (ptosis) when looking upwards (=Simpson test), and double images also appear at an early stage when looking sideways due to infestation of the eye muscles. Other muscle groups affected at an early stage are the face, throat (increasing difficulty in swallowing during a meal) and chewing muscles. Speech may appear blurred, the affected person’s face flabby and facial expressions sparse.
Clinically different classifications are made according to age at onset or severity of the symptoms. In the further course of the disease, premature fatigue and weakness on exertion also appear in the limbs, so that the patient may have difficulty climbing stairs or waddling. The affection of the respiratory muscles can also occur suddenly in a crisis (myasthenic crisis) and is a very serious complication of myasthenia gravis.
Exclusionary diseases (differential diagnoses)
The most important differential diagnosis is the Lambert-Eaton syndrome, which is particularly associated with tumor diseases. Symptomatology and disease mechanism are basically similar, but blood tests show different antibodies than for myasthenia gravis, and the picture in the electromyogram (electromyography/EMG) is also different.In addition, other diseases of the nervous system and musculature such as multiple sclerosis, muscular dystrophies or poliomyositis (“polio”), some of which have symptoms similar to those of myasthenia gravis, can theoretically be considered. In most cases, these diseases can be ruled out by a careful medical history and physical examination.
Diagnostics
The basic diagnostics include the taking of the patient’s medical history, physical examination with neurological focus and the “Tensilon Test”. The examination of the electrical activity of the muscle in the electromyogram (EMG) shows a characteristic picture (decrease in the height of the rashes during sustained stress). In the blood, antibodies against the messenger receptors at the neuromuscular end plate can be detected in 80 – 90% of the affected persons. If this is not successful, a tissue sample of the musculature must be taken for microscopic examination. In order to rule out the presence of a thymus alteration, an X-ray of the chest is taken.
