Obligatory medical device diagnostics.
- Electrophysiology – low-frequency serial stimulation (3 Hz) of the accessorius or facial nerve.
- A pathologic (pathological) result is present when the 5th amplitude is at least 10% smaller than the 1st amplitude (= decrement); from the 6th amplitude onward, a slight rebound follows (= increment)
- Is found in a maximum of 20% of patients with ocular (affecting the eyes) and about 80% of patients with generalized (affecting the entire body) myasthenia
- Electromyography (EMG; measurement of electrical muscle activity) – myopathic changes are found in prolonged courses of the disease.
- Computed tomography of the thorax/chest (thoracic CT) or magnetic resonance imaging of the thorax/chest (thoracic MRI) – to exclude/detect thymic hyperplasia (enlargement of the thymus) and a thymoma (tumor of the thymus)
- Spirometry (basic examination in the context of pulmonary function diagnostics) – to determine the vital capacity (parameter for the function of the lungs).
- Transthoracic sonography – can be informative in children already.
Optional medical device diagnostics – depending on the results of the history, physical examination, laboratory diagnostics and obligatory medical device diagnostics – for differential diagnostic clarification.
- X-ray of the chest (X-ray thorax/chest), in two planes – to exclude/detect old tuberculosis (TB); this can lead to complications during steroid therapy
- Craniocervical magnetic resonance imaging – in the case of purely ocular or oculopharyngeal symptoms, to exclude/prove a space-occupying lesion intracranially (in the skull) or in the brainstem.
Note: Single-fiber electromyography is rarely used despite its diagnostic sensitivity because it is very laborious. In addition, in the case of seronegative myasthenia gravis, no detection is possible.
