Weakness is reduced strength in one or more muscles.
Lack of strength; Muscle weakness
Weakness may be all over the body or in only one area. Weakness is more noticeable when it is in one area. Weakness in one area may occur:
- After a stroke
- After injury to a nerve
- During a flare-up of multiple sclerosis
You may feel weak but have no real loss of strength. This is called subjective weakness. It may be due to an infection such as mononucleosis or the flu. Or, you may have a loss of strength that can be noted on a physical exam. This is called objective weakness.
Weakness may be caused diseases or conditions affecting many different body systems. Causes may include:
Weakness may be caused by a variety of conditions, including:
BRAIN/NERVOUS SYSTEM (NEUROLOGIC)
- Amyotrophic lateral sclerosis (ALS)
- Bell's palsy
- Cerebral palsy
- Guillain-Barre syndrome
- Multiple sclerosis
- Pinched nerve (for example, caused by a slipped disk in the spine)
Follow the therapy your health care provider recommends to treat the cause of the weakness.
When to Contact a Medical Professional
Call your health care provider if you have:
- Sudden weakness, especially if it is in one area and does not occur with other symptoms, such as fever
- Sudden weakness after being ill with a virus
- Weakness that does not go away and has no cause you can explain
- Weakness in one area of the body
What to Expect at Your Office Visit
The health care provider will do a physical exam. Your provider will also ask you questions such as:
- When did the weakness begin and how long has it been going on? Did it start suddenly or come on slowly?
- Is the weakness present all the time or only at certain times (such as mornings, evenings, or after activity)?
- Have you had a vaccination or been ill with a virus?
- What parts of your body are affected?
- Is there pain or numbness along with the weakness?
- Are there things that make the problem better or worse?
- Are you having any other symptoms such as headaches, mental changes, stomach upset, or fever?
- What medicines are you taking?
The health care provider may pay close attention to your heart, lungs, and thyroid gland. The exam will focus on the nerves and muscles if the weakness is only in one area.
You may have the following tests:
Griggs RC, Jozefowicz RF, Aminoff MJ. Approach to the patient with neurologic disease. In: Goldman L, Ausiello D, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 403.
Chinnery PF. Muscle diseases. In: Goldman L, Ausiello D, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 429.
Reviewed By: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.