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Weakness presenting to the ICU is either due to an acute/acquired cause or is a complication of chronic weakness, such as acute on chronic respiratory failure. This chapter will focus on the physical exam of a patient with new-onset weakness and summarize chronic neuromuscular diseases that could lead to ICU presentation.


Weakness can arise from pathology at any point along the neuroaxis from brain to muscle. It can be a single discrete lesion causing a focal deficit or a generalized process causing more disseminated signs. Physical exam is one of the key tools for localizing the lesion and narrowing the differential diagnosis. Table 45-1 describes the typical exam findings based on a lesion at each level of the neuroaxis and examples of associated disease states. Table 45-2 lists neurologic signs that are characteristic of specific lesions or disease processes.

TABLE 45-1

Physical Exam Findings and Disease Processes Based on Site of Lesion

TABLE 45-2

Physical Exam Findings with the Associated Pathologic Process


Acute weakness can be caused by ischemia/hypoperfusion, inflammation, toxin, or metabolic derangements affecting the neuroaxis. The following are summaries of pathologic conditions, starting at the spinal cord and moving distally, that could lead to ICU presentations of acute weakness. Other chapters in this handbook address brain pathology, ...

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