The office evaluation of weakness.

The office evaluation of weakness can be a daunting task. Many different disorders affecting many different parts of the nervous system can manifest with "weakness," and several nonneurologic conditions may present with complaints of weakness. It is the job of the neurologist to determine whether a patient has neurologic weakness or suffers simply from fatigue. The physician then must properly localize the pathophysiologic site of weakness. The author focuses on neuromuscular causes of weakness affecting muscle, the neuromuscular junction, peripheral nerve, or the anterior horn cell. General historical and examination clues to localization will be discussed. A localization-based evaluation will be outlined, with more specific recommendations regarding the evaluation of a few specific disorders offered. Localization-specific laboratory, electrodiagnostic, imaging, and pathologic investigations will be presented.