0918 - Muscle and NMJ Disorders

Question 1

How do you approach a patient presenting with weakness?

Answer 1

Constant or fluctuating - if fluctuating, could be myasthenia gravis.

If constant - lifelong or acquired (acquired - inflammatory myopathies including ALS)

If lifelong - progressive or non-progressive (non-progressive may be…….

If progressive, ocular, facial, upper or lower limb?

Question 2

What are key aspects of a muscular/NMJ history?

Answer 2

Chronicity vs acuteness

Pattern of weakness

Exacerbating factors

Associated diseases

Family history

Medications.

Question 3

What investigations would you perform for suspected muscle/NMJ diseases?

Answer 3

Blood tests - CK (non-specific muscle breakdown), Antibodies (ENAs), Thyroid Function

Genetic studies

Neurophysiology - Nerve conduction studies/EMG in affected muscle.

Muscle biopsy from affected muscle

Imaging (MRI)

Question 4

What is a myopathy?

Answer 4

Abnormality of muscle?

Question 5

What is a muscular dystrophy?

Answer 5

Genetic myopathy

Question 6

What is a myositis?

Answer 6

Inflammatory muscle disease

Question 7

What is a myotonia?

Answer 7

Abnormality of muscle contractions

Question 8

What are the more common Neuromuscular disorders?

Answer 8

Myasthenia Gravis

Lambert-Eaton Syndrome

Botulism

Congenital Myasthenic Syndromes

Drugs/Toxins

Question 9

Outline Myasthenia gravis

Answer 9

Autoimmune disorder of ABs vs ACh Receptor. Blocks binding site and can activate complement, resulting in loss of NMJ.

Young (female) or old (equal sex) onset

Prevalence 20/100,000

Question 10

Outline Lambert-Eaten Syndrome

Answer 10

Abs vs voltage-gated Ca++ channel pre-synaptically.

Small Cell Lung Cancer in 50-60%. Present with generalised weakness and depressed reflexes.

Question 11

What are the features of Myasthenia Gravis

Answer 11

Can be ocular (diplopia) or generalised (proximal limbs) - hits muscles we use a lot.

Ptosis very common

Exacerbated by intercurrent illnesses

Can lead to myasthenic crisis and respiratory failure.

Question 12

What are some common Symptoms of muscle/NMJ diseases?

Answer 12

Muscle pain not related to overuse/stress injury

Weakness (cardinal sign of muscle disease).

Unusual, non-physiological cramp (e.g. thigh/upper limb)

Muscle fatigue (e.g. ptosis)

Wasting

Family history

DON’T have sensory features/symptoms