Kaplan USMLE Step 3: Sudden episode of confusion in a 71-year-old patient

If you’re preparing for the United States Medical Licensing Examination® (USMLE®) Step 3 exam, you might want to know which questions are most often missed by test-prep takers. Check out this example from Kaplan Medical, and read an expert explanation of the answer. Also check out all posts in this series.

A 71-year-old man is brought to the emergency department by his wife who states that he has seemed "confused" since he woke up that morning. He is now unable to provide a history, but his wife reports that he has never had such an episode in the past. He has a past medical history of a myocardial infarction 2 years ago, hypertension that is poorly controlled, and smoking.

His family history reveals that his father had hypertension and a myocardial infarction at the age of 45 and his brother also suffers from hypertension. The patient is a retired truck driver who lives with his wife, smokes 1 pack of cigarettes per day, and drinks 2-3 cans of beer per day. His temperature is 37.0ºC (98.6ºF), blood pressure is 192/105 mm Hg, pulse is 96/min and respirations are 18/min. He is in no distress.

He has normal heart and lung sounds. He is awake, alert, and attentive. He follows all commands, but he is unable to name simple objects (for example, he says "clock" when you show him a watch, and says "dog" when you show him a picture of a cat). He does not repeat phrases well. For example, he says "no its or buts" when asked to repeat "no ifs, ands, or buts."

Which of the following is the most likely diagnosis?

A. Broca's aphasia

B. Delirium

C. Dysarthria

D. Wernicke aphasia

E. Wernicke encephalopathy

The correct answer is A.

Aphasia is a disorder of language that is acquired from a lesion in the brain. Aphasia must be differentiated from delirium, dysarthria and psychosis. Expressive aphasia is caused by a lesion involving Broca's area, the posterior part of the inferior frontal gyrus. Broca's aphasia, as it is also known is characterized by intact auditory and written comprehension, but impairment of fluency, naming, repetition and writing. Patients frequently produce paraphasic speech, which is characterized by substitutions of words or sounds, such as "dog" for "cat" and "band" for "hand," respectively. This type of aphasia is frequently associated with right hemiparesis or hemisensory loss and sometimes with apraxia of the left limbs. Aphasia is frequently caused by stroke, as was the case in this clinical scenario.

The patient has many stroke risk factors (age, gender, hypertension, coronary artery disease, smoking, alcohol use, family history of early coronary artery disease) and his deficit is new, suggesting a sudden onset, which is what characterizes stroke.

Choice B. Delirium is an acute confusional state characterized by fluctuating levels of wakefulness and attention as well as psychomotor overactivity and hallucinations. Aphasia is not a component of delirium.

Choice C. Dysarthria is a disorder of speech, the articulation and phonation of sounds. This is different than aphasia, which is a disturbance of language.