Muscle strength testing is an essential component of the physical exam that can reveal information about neurologic deficits. It is used to assess weakness and can be useful in distinguishing true weakness from imbalance or poor endurance. Patterns of weakness can help localise a lesion to a certain cortical or white matter region, spinal cord level, nerve root, peripheral nerve, or muscle.
The most commonly accepted method of evaluating muscle strength is the Medical Research Council Manual Muscle Testing scale. This method involves testing key muscles from the upper and lower extremities against the examiner’s resistance and grading the patient’s strength on a 0/5 to 5/5 scale accordingly:
- 0/5: no contraction
- 1/5: muscle flicker, but no movement
- 2/5: movement possible, but not against gravity (test the joint in its horizontal plane)
- 3/5: movement possible against gravity, but not against resistance by the examiner
- 4/5: movement possible against some resistance by the examiner (sometimes this category is subdivided further into 4–/5, 4/5, and 4+/5)
- 5/5: normal strength