Muscle Weakness

Question 1

What are three questions you should ask regarding muscle weakness?

Answer 1

1. Does the patient have true muscle weakness?
2. Where is the weakness?
3. What is the cause of the muscle weakness?

Question 2

How can you identify if a person has true muscle weakness?

Answer 2

They are unable to perform certain activities such as standing from a squat or moving a limb

Question 3

What types of muscle weakness are there?

Answer 3

Primary: involving the muscles themselves
Secondary: involving neuromuscular junctions, peripheral nerves, spinal nerve roots, anterior horn cells or corticospinal tracts

Question 4

What does generalised weakness indicate?

Answer 4

• Myasthenia gravis which affects the neuromuscular junction

Question 5

In non-generalised weakness, what should you find out?

Answer 5

Symmetrical/asymmetrical?

Question 6

What does asymmetric non-generalised weakness indicate?

Answer 6

usually caused by conditions that affect the CNS or PNS

Question 7

In symmetrical non-generalised weakness, what should you determine?

Answer 7

Proximal/distal?

Question 8

What does proximal/distal symmetrical non-generalised weakness indicate?

Answer 8

Proximal: usually caused by primary muscle disorders affecting axial muscle groups that is the deltoids or the muscles responsible for hip flexion
Distal: usually affects the hands of feet and may be caused y peripheral neuropathy or motor neuron disease

Question 9

What are some underlying causes of muscle weakness?

Answer 9

immunological conditions, malignancy, vascular events, drugs, metabolic disorders etc

Question 10

What are some important cardinal features to ask about regarding muscle weakness?

Answer 10

• Site
• Severity
• Time Course
• Context
• R/A Features
• Associated Features

Question 11

What are some considerations with regard to muscle weakness in terms of Site?

Answer 11

Where is the weakness? Which muscle groups? Generalised? Local? Symmetrical? Proximal? Distal?

Question 12

What are some considerations with regard to muscle weakness in terms of Severity?

Answer 12

What type of function is impaired? Can you move against gravity?
Effect on ADLs?

Question 13

What are some considerations with regard to muscle weakness in terms of Time Course?

Answer 13

Onset?
Offset?
Change over time?
Duration?

Question 14

What are some considerations with regard to muscle weakness in terms of Context?

Answer 14

Associations with movement?

Noticed anything at the onset?

Question 15

What are some considerations with regard to muscle weakness in terms of R/A Factors?

Answer 15

Relief? Triggers?

Question 16

What are some considerations with regard to muscle weakness in terms of Associated Features?

Answer 16

Any other neurological symptoms? Sensory changes?

Question 17

What are some of the differential diagnoses for muscle weakness?

Answer 17

MS - visual disturbances, sensory loss, family history Myasthenia Gravis – muscle become fatigued, family history
Stroke - family history, past history of cardiovascular problems, high cholesterol, hypertension, sensorimotor loss
Emotional – depression, lack of motivation
Sarcopaenia – Old, loss of muscle mass
Cancer – Loss of muscle mass, weight loss, fatigue, loss of appetite, family history of cancer, age, fever
Joint Pain – Pain in joint where weakness is, context
Motor neuron Disease/ Neurodegen – context, family history, distal weakness
Nerve compression – possible pain, past trauma
Myasthenia Gravis – Fatiguability, History of Autoimmune conditions, Generalised pattern of motor weakness
Metabolic Disorders – exercise intolerance, myoglobinuria, heart problems
Hypothyroidism - Weight gain, insensitivity to cold, depression, loss of hair, neck enlargement, heavy periods
Addison’s Disease – Fatigue, skin pigmentation, nausea, vomiting, diarrhoea, weight loss, low blood pressure, recurrent infections
Medications- eg statins
Muscle damage/ Muscle overuse – context, pain