Smarter Decisions,
Better Care

UpToDate synthesizes the most recent medical information into evidence-based practical recommendations clinicians trust to make the right point-of-care decisions.

  • Rigorous editorial process: Evidence-based treatment recommendations
  • World-Renowned physician authors: over 5,100 physician authors and editors around the globe
  • Innovative technology: integrates into the workflow; access from EMRs

Choose from the list below to learn more about subscriptions for a:


Subscribers log in here


Approach to the patient with muscle weakness

INTRODUCTION

The evaluation of the patient presenting with a complaint of “weakness” involves three steps:

  • Distinguishing true muscle weakness from asthenia or motor impairment not due to loss of muscle power
  • Localizing, within the neuromuscular system, the site of the lesion that is producing weakness
  • Determining the cause of the lesion

This topic will review the approach to the patient with muscle weakness by addressing these three issues. The specific tests used to assess muscle weakness are discussed separately, as are the clinical manifestations and evaluation of respiratory muscle weakness. (See "Muscle examination in the evaluation of weakness" and "Respiratory muscle weakness due to neuromuscular disease: Clinical manifestations and evaluation".)

DISTINGUISHING TRUE MUSCLE WEAKNESS FROM ASTHENIA

Many patients who complain of weakness are not objectively weak when muscle strength is formally tested. A careful history and physical examination will permit the distinction between asthenia, motor impairment due to pain or joint dysfunction, and true weakness.

History — Patients with a variety of systemic disorders may interpret difficulties performing certain tasks as weakness. Included in this group are cardiopulmonary disease, joint disease, anemia, cachexia from malignancy or chronic infectious or inflammatory disease, and/or depression. Patients with any of these conditions may be functionally limited but not truly weak. Furthermore, careful questioning will reveal that the patient is limited by shortness of breath, chest pain, joint pain, fatigue, poor exercise tolerance, paresthesias, or spasticity rather than a true decrease in muscle power.

                 

Subscribers log in here

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information or to purchase a personal subscription, click below on the option that best describes you:
Literature review current through: Mar 2014. | This topic last updated: Sep 24, 2013.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2014 UpToDate, Inc.
References
Top
  1. Medical Research Council. Aids to the Examination of the Peripheral Nervous System. Memorandum no. 45. London, Her Majesty's Stationery Office, 1981.
  2. Aminoff M. Clinical electromyography. In: Electrodiagnosis in Clinical Neurology, Elsevier, Philadelphia 2005. p.233.
  3. Warren JD, Blumbergs PC, Thompson PD. Rhabdomyolysis: a review. Muscle Nerve 2002; 25:332.
  4. Miller FW. Inflammatory myopathies: Polymyositis, dermatomyositis and related conditions. In: Clinical Primer in Rheumatology, Lipincott Williams & Wilkins, Philadelphia 2003. p.182.
  5. Targoff IN. Laboratory testing in the diagnosis and management of idiopathic inflammatory myopathies. Rheum Dis Clin North Am 2002; 28:859.
  6. Bossen EH. Muscle biopsy. In: Diseases of Skeletal Muscle, Lipincott Williams & Wilkins, Philadelphia 2000. p.333.