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Definition of the Complaint

The term decreased activity level describes a wide spectrum of existence ranging from boredom to coma. The diagnostic evaluation focuses on encouraging parents to provide a detailed account, particularly with regard to the magnitude and time course of the changes. Clearly, the differential diagnosis of subtle behavioral changes developing during a period of several months differs from that of changes occurring during several hours.

Complaint by Cause and Frequency

The causes of decreased level of activity in children vary according to age (Table 2-1), and can be placed into several broad categories (Table 2-2). Additional issues to consider include whether there is depressed sensorium indicating an underlying central nervous system (CNS) disorder, weakness indicating a muscular disorder, or endurance problems suggesting a cardiac or pulmonary issue. Systemic illness may manifest with somnolence or lethargy.

Table 2-1. Differential Diagnosis of Decreased Activity by Age.
Table 2-2. Differential Diagnosis of Decreased Activity Level by Etiology.

Clarifying Questions

The patient who presents for evaluation of decreased level of activity represents a broad differential. Several important historical questions can help classify the underlying etiology:

  • What is the time course of decreased level of activity?
    • Infectious etiologies typically present during a shorter time course than do other etiologies, such as iron deficiency anemia or certain types of CNS malignancies.
  • Is the patient febrile?
    • Fever, from an infectious etiology, can cause a decreased level of activity in children. However, hypothermia, particularly in neonates, ...

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