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PATIENT 
Mr. J is a 32-year-old man who comes to your office complaining of dizziness.
What is the differential diagnosis of dizziness? How would you frame the differential?
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CONSTRUCTING A DIFFERENTIAL DIAGNOSIS
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Dizziness may arise from diseases of the inner ear; central and peripheral nervous system; cardiovascular system; and occasionally, psychiatric conditions. This leads to an extensive differential diagnosis. Fortunately, the differential diagnosis can be narrowed with an organized approach. The first pivotal step is to recognize that most patients who complain of dizziness are actually complaining of 1 of 3 distinct symptoms: vertigo, near syncope, or dysequilibrium. (Patients who are unable to clearly describe their dizziness, are referred to as having ill-defined light-headedness.) Identifying the more specific symptom narrows the differential diagnosis and focuses the evaluation. Therefore, the first step asks the patient “What does it feel like when you are dizzy?” (Figure 14-1).
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Patients must then be given enough time, without interruptions or suggestions, to describe their dizziness as clearly as possible.
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Additionally, the event that triggers the symptom can also help classify the symptom as vertigo, near syncope, or dysequilibrium. For instance, dizziness that occurs when rolling over in bed or with head movement suggests vertigo, upon standing suggests near syncope, or when walking suggests dysequilibrium. It is also important to determine whether the symptom is constant or intermittent and to ask about other associated symptoms that may be important diagnostic clues (ie, other neurologic or cardiac symptoms). Table 14-1 summarizes chief complaints, triggers, other historical features, and differential diagnoses.
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