Weakness is another common symptom with many causes which bears careful investigation. It is important to clarify what the patient means—fatigue, apathy, drowsiness, or actual loss of strength. True motor weakness can arise from the CNS, a peripheral nerve, the neuromuscular junction, or a muscle. Time course and location are especially relevant. Is the onset sudden, gradual or subacute, or chronic, over a long period of time?

What areas of the body are involved? Is the weakness generalized, or focal to the face or a limb? Does it involve one side of the body or both sides? What movements are affected? As you listen to the patient's story, identify the patterns below:

■ Proximal—in the shoulder and/or hip girdle, for example

■ Distal—in the hands and/or feet

■ Symmetric—in the same areas on both sides of the body

■ Asymmetric—types of weakness include focal, in a portion of the face or extremity; monoparesis, in an extremity; paraparesis, in both lower extremities; and hemiparesis, in one side of the body

To identify proximal weakness, ask about difficulty with movements such as combing hair, reaching up to a shelf, getting up out of a chair, or climbing stairs. Does the weakness get worse with repetition and improve after rest (suggesting myasthenia gravis)? Are there associated sensory or other symptoms?

To identify distal weakness, ask about hand strength when opening a jar or using scissors or a screwdriver, or problems tripping when walking.

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