Mr. B is a previously healthy 70-year-old man who underwent right upper lobectomy for localized squamous cell lung cancer 5 days ago. On morning rounds, he comments that he is in a military barracks and that he is ready to go home.
|What is the differential diagnosis of delirium and dementia? How would you frame the differential?|
Delirium and dementia are both syndromes of neurologic dysfunction. Both present as a “change in mental status.” Their similarities end here. Whereas delirium is acute, usually reversible and nearly always has an underlying, non-neurologic etiology, dementia is chronic and seldom reversible. The definitions of these syndromes, as included in the DSM-IV-TR follow:
Disturbance of consciousness with reduced ability to focus, sustain, or shift attention.
Cognitive change that is not better explained by dementia.
Symptoms develop rapidly (hours to days) and tend to vary during the day.
History, physical exam, or laboratory data suggest that a general medical condition has directly caused the condition.
Impaired memory plus at least 1 of the following:
Aphasia (inability to produce or comprehend language)
Apraxia (inability to execute purposeful movements)
Agnosia (inability to recognize objects by feel)
Impaired executive functioning (eg, abstracting and organizing)
Symptoms must also impair work, social, or personal functioning.
Because any illness can cause delirium in a susceptible patient, the differential diagnosis of delirium is long and needs to consider a broad range of illnesses, comorbidities, and medication effects. The differential diagnosis of dementia is more finite; disorders have been listed in order of their approximate prevalence as etiologic factors.
Hyperglycemia or hypoglycemia
Acidosis or alkalosis
Hypoxia or hypercarbia
Uncontrolled thyroid disease
Thiamine deficiency (Wernicke encephalopathy)
Systemic infection of any kind
Nonsteroidal antiinflammatory drugs
Dementia with Lewy bodies
Vitamin B12 deficient
|Almost any illness can cause delirium in a susceptible patient.|
Mr. B was previously healthy with only mild chronic obstructive pulmonary disease. His surgery went well but was complicated by transient hypotension and excessive blood loss. He was extubated on postoperative day 3. On postoperative day 4, his wife noted some confusion. The medical team did not detect any abnormalities when they evaluated him.
Today, postoperative day 5, he is more confused. He is oriented only to person. He is unable to answer any minimally complicated questions.
|At this point, what is the leading hypothesis, what are the active alternatives, and is there a must not miss diagnosis? Given this differential diagnosis, what tests should be ordered?|
Based on his history, Mr. B's subacute mental status change appears to fulfill the definition of delirium. The pivotal points are that his symptoms seem to vary, he is disoriented, and he is inattentive. He certainly has many potential causes of delirium. Although Mr. B does not have a history of alcohol abuse, alcohol withdrawal is always a possible diagnosis for acute mental status changes in the hospital and should not be missed. Stroke and seizure, although commonly considered in the differential diagnosis of mental status change, are rare causes of delirium. Table 10–1 lists the differential diagnosis.
On physical exam, Mr. B is lying in bed. He is irritable and somewhat hypervigilant, becoming frustrated during questioning. His vital signs are temperature, 37.0°C; BP, 146/90 mm Hg; pulse, 80 bpm; RR, 18 breaths per minute. General physical exam reveals a healing surgical scar, normal lung, heart, and abdominal exam. On neurologic exam, he scores a 3 out of 4 on the confusion assessment method. The remainder of the neurologic exam is normal.
Initial laboratory data, including basic metabolic panel, liver function tests (LFTs), and urinalysis, are normal.
|Is the clinical information sufficient to make a diagnosis? If not, what other information do you need?|
Table 10–1. Diagnostic Hypotheses for MR. B.
| Save Table
Table 10–1. Diagnostic Hypotheses for MR. B.
|Diagnostic Hypotheses||Clinical Clues||Important Tests|
|Delirium caused by postsurgical state, fluid and electrolyte abnormalities, hypoxia or hypercarbia, medications, or cardiac ischemia||Subacute onset and fluctuating course||Confusion|
|Basic metabolic panel|
|Review of medications|
|Active Alternative—Must Not Miss|
|Delirium caused by alcohol withdrawal||History of alcohol use||Clinical diagnosis|
|Predictable syndrome with systemic and neurologic symptoms|
|Delirium caused by stroke, seizure, or meningitis||Focal neurologic exam||Rarely needed (see text)|
|Fever or meningismus||CNS imaging|
Leading Hypothesis: Delirium
Delirium commonly manifests as inattention and confusion (often referred to as mental status change). It is usually seen in older patients with severe illness. Clouding of consciousness has classically been used to describe a patient's symptoms.
Almost any illness can present as delirium in a susceptible patient.
Delirium often complicates medical or surgical hospitalizations.
The most important clue to delirium is the acuity of onset and fluctuation in course.
It is most common in older persons and in patients with underlying neurologic disease.
There is always a cause of delirium. Clinicians must recognize delirium and identify the cause.
Several diseases are more likely to cause delirium than others.
Fluid and electrolyte disturbances (hyponatremia and azotemia)
Hypothermia or hyperthermia
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