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A 28-year-old woman presents to the urgent care clinic complaining of weakness. For the past week, she has had weakness and numbness in her right arm and bouts of dizziness. The symptoms became worse 2 days ago but have since stabilized.
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- What additional questions would you ask to learn more about her weakness?
- Can you localize her lesion to a specific anatomic site?
- How can you use the patient history to determine if the patient requires urgent intervention for weakness?
- How do the duration and evolution of symptoms help narrow the differential diagnosis?
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In approaching a patient with a complaint of weakness, the physician must first determine whether the patient has functional or motor weakness. Many patients who complain of weakness are actually suffering from functional weakness due to asthenia, the sensation of exhaustion or lethargy despite normal muscle strength, or increased fatigability, the tiring of muscles with multiple repetitions. Functional weakness may be caused by a variety of conditions including cancer, infection, metabolic derangements, inflammatory diseases, and psychiatric disorders. In these conditions, the patient has trouble completing activities of daily living because of a lack of physical or emotional energy, but has normal muscle strength. Another potential masquerader of weakness is pain that prevents a patient from completing specific activities despite retained muscle strength. Patients with neuromuscular weakness are unable to move their muscles at full strength despite maximum effort and optimization of modifiable factors.
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The first step in evaluating any patient complaining of weakness is to distinguish functional weakness from neuromuscular weakness. The history should be completed systematically with a focus on the onset, the evolution of symptoms, and location of the lesion along the motor pathway. Although all patients with weakness warrant a careful evaluation, this chapter focuses on patients whose history suggests true weakness of the muscles. For the remainder of this chapter, the term "weakness" will mean neuromuscular weakness.
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