Myasthenia Gravis Flashcards
(26 cards)
Define Myasthenia Gravis?
An autoimmune disease affecting the neuromuscular junction producing weakness in skeletal muscles
What is the aetiology of Myasthenia Gravis?
Impairment of neuromuscular junction transimission
What is Myasthenia Gravis most commonly due to?
Autoantibodies against the nicotinic acetylcholine receptor
What is Lambert-Eaton Syndrome?
Pareneoplastic subtype of myasthenia gravis caused by autoantibodies against pre-synaptic calcium channels, leading to impairment of acetylcholine release
What is an example of another autoimmune condition that Myasthenia Gravis is associated with?
Pernicious Anaemia
What is the epidemiology of Myasthenia Gravis?
Prevalence: 8-9/100,000
More common in FEMALES at younger ages
Equal gender distribution in middle agee
What is the general presenting symptom of Myasthenia Gravis?
Muscle weakness that worsens with repetitive use or towards the end of the day
What happens with muscle weakness in Lambert-Eaton Syndrome?
Improves after repeated use
What are the Ocular Symptoms of Myasthenia Gravis?
Drooping eyelids
Diplopia
What is the Bulbar symptoms of Myasthenia Gravis?
Facial weakness (myasthenic snarl)
Disturbed hypernasal speech
Difficulty smiling, chewing or swallowing
What are the signs of Myasthenia Gravis?
May be generalised (affecting many muscle groups)
May be bulbar (affecting the bublar muscles)
May be ocular
What does the term bulbar mean?
Relating to the medulla oblongata (cranial nerves 9,10, 11 and 12 have their nuclei in the medulla)
What are the Eye signs of Myasthenia Gravis?
Ptosis
Complex ophthalmoplegia
Check for ocular fatigue by asking the patient to sustain and upward gaze for 1 min and watch the progressive ptosis that develops
What is the Ice on Eyes Test for Myasthenia Gravis?
Placing ice packs on closed eyelids for 2 mins can improve neuromuscular transmission and reduce ptosis
What are the Bulbar signs of Myasthenia Gravis?
Reading aloud may cause dysarthria or nasal speech
What are the signs in the limbs of Myasthenia Gravis?
Test the power of a muscle before and after repeated use of the muscle
What investigations do we do for Myasthenia Gravis?
Bloods Tensilon Test Nerve Conduction Study EMG CT Thorax/CXR
What bloods do we do for Myasthenia Gravis?
CK
Serum acetylcholine receptor antibody
TFYs
Anti-voltage gated calcium channel antibody
Why do we do CK bloods for Myasthenia Gravis?
Exclude myopathy
Why do we do Serum Acetylcholine Receptor Antibody for Myasthenia Gravis?
Positive in 80%
Why do we do TFTs for Myasthenia Gravis?
Myasthenia Gravis is associated with hyperthyroidism
Why do we do look for Anti-Voltage gated calcium channel antibodies for Myasthenia Gravis?
They are found in Lambert-Eaton Syndrome
What is the Tensilon Test?
Short-acting anti-cholinesterase (edrophonium bromide) increases ACh levels and causes a rapid and transient improvement in clinical features
Why do we normally avoid the Tensilon Test for Myasthenia Gravis?
Risk of bradycardia
