Site icon almostadoctor

Myasthenia Gravis

Introduction

Epidemiology

The prevalence of Myasthenia Gravis is about 1 in 5,000. Although anyone is susceptible to it, there are two main subgroups, young women (20-35) and older men (60-75).

Aetiology

The exact cause is unknown, however as with most autoimmune disorders, there does seem to be a genetic link.

Pathophysiology

Signs and Symptoms

Although some symptoms are more predominant than others, Myasthenia Gravis generally has a course which has periods of remission, interrupted by ‘Crises’. Some patients can predict when they are ‘due a crisis’, and others find there is no pattern whatsoever.
Due to the destruction of the synapse there is decreased conduction at the neuromuscular junctions, leading to muscle fatigue and weakness. There are four sets of muscles that are particularly affected
  1. Ocular- Ptosis and Diplobia
  2. Bulbar-Dysphagia, Dysphonia, Dysarthria and weak/droopy face
  3. Proximal muscles- Shoulders and Thighs
  4. Axial – Neck and trunk, but also muscles involved in Respiration

The fatigability of muscles can be demonstrated by getting the patient to do a repetitive movement (e.g flap their arm’s) for 30-60 seconds. They also report that their symptoms get worse as the day wears on, and that their best times are in the morning, or after a sleep.

Limb reflexes are usually normal or brisk, and there are no sensory abnormalities.

Muscle wasting is usually not present, unless there is severe disease, or the patient has had the condition for a long time.

Drooping eyelid seen in myasthenia gravis

Investigations

Management

Prognosis

Although Myasthenia Gravis (as the name suggests!) used to be a life threatening condition due to respiratory failure, with treatment a normal life expectancy can be achieved. Patients do have to be aware about the association with the development of thymomas, as this can have a large impact on both morbidity and mortality.

Flashcard

References

Read more about our sources

Related Articles

Exit mobile version