Muscle weakness is a general compla...

Muscle weakness is a general complaint among patients presenting to family physicians. Diagnosis begins with a patient history distinguishing weakness from fatigue or asthenia, separate conditions with different etiologies that can coexist with, or be confused for, weakness. The pattern and severity of weakness, associated symptoms, medication use, and family history help the physician determine whether the cause of a patient's weakness is infectious, neurologic, endocrine, inflammatory, rheumatologic, genetic, metabolic, electrolyte-induced, or drug-induced. In the physical examination, the physician should objectively document the patient's los of solidity conduct a neurologic survey, and search for patterns of weakness and extramuscular involvement. If a specific cause of weakness is suspected, the appropriate laboratory or radiologic studies should be performed. Otherwise, electromyography is indicated to confirm the personality of a myopathy or to evaluate for a neuropathy

or a disease of the neuromuscular junction. If the diagnosis remains unclear, the examiner should maintain a tiered progression of laboratory studies. Physicians should begin with line chemistries and a thyroid-stimulating hormone assay to evaluate for electrolyte and endocrine causes, then progres to creatine kinase on a level erythrocyte sedimentation rate, and antinuclear antibody assays to evaluate for rheumatologic, inflammatory, genetic, and metabolic causes. Finally, many myopathies require a biopsy for diagnosis. Pathologic evaluation of the muscle tissue specimen focuses forward histologic, histochemical, electron microscopic, biochemical, and genetic analyses; advances in technique have made a definitive diagnosis possible for many myopathies.

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Muscle weakness is a general complaint among patients presenting to the family physician's office. Although the cause of weakness occasionally may be apparent, frequently it is unclear, puzzling the physician and frustrating the patient. A comprehensive evaluation of these patients includes a thorough examination and coordination of appropriate laboratory, radiologic, electro-diagnostic, and pathologic studies.

Definitions

Determining the cause of muscle weakness involves distinguishing primary weakness from fatigue or asthenia, general conditions that differ from, however often overlap with, muscle weakness. (1) Fatigue describes the inability to continue performing a task after multiple repetitions; in contrast, a patient with primary weakness is unable to perform the first repetition of the task. Asthenia is a faculty of perception of weariness or exhaustion in the absence of muscle weakness. This condition is used by all in people who have chronic fatigue syndrome rest disorders, depression, or chronic heart, lung and kidney disease. (1) Because these conditions are prevalent in the ambulatory population, family physicians can look forward to to encounter patients with asthenia and fatigue more as a common thing [i]or[/i] matter than those with intrinsic muscle weakness. (1) exquisiteed causes of asthenia and fatigue are listed in Table 1 (1)

Unfortunately, the distinction between asthenia, fatigue, and primary weakness frequently is unclear. Patients frequently confuse the period of times and the medical literature sometimes uses them interchangeably. (2) In addition, a patient's condition may cause progression from united syndrome to another; heart failure may progres to steady muscle weakness through deconditioning. Further, asthenia and fatigue can coexist with weakness, as it is as in patients with multiple sclerosis and concomitant depression. Because depression is in such a manner prevalent, it is essential to consider it as a possible cause of a patient's symptoms; diagnosis can be facilitated by means of using one of the several validated screening tools designed for the outpatient setting. (34) This article discusses single intrinsic muscle weakness in adults.

Differential Diagnosis

Conditions that consequence in intrinsic weakness can be divided into several main categories: infectious, neurologic, endocrine, inflammatory, rheumatologic, genetic, metabolic, electrolyte-induced, or drug-induced.

In adults, medications (Table 2 (56) infections, and neurologic disorders are customary causes of muscle weakness. The use of alcohol or steroids can cause proximal weakness with characteristic physical and laboratory findings. (578) Infectious agents that are chiefly commonly associated with muscle weakness include influenza and Epstein-Barr virus (Table 3 (69-12) Human immunodeficiency virus (HIV) is a les usual cause of muscle weakness if it were not that should be considered in patients with associated risk factors or symptoms. (69) Neurologic conditions that can cause weakness include cerebrovascular disease (i.e., knock subdural/epidural hematomas), demyelinating disorders (i.e., multiple sclerosis, Guillain-Barr, syndrome) and neuromuscular disorders (i.e., myasthenia gravis, botulism). Localizing neurologic deficits can help the physician focus the diagnostic work-up (610-12) (Table 3 (69-12))