What is the most likely diagnosis for an elderly patient found on the floor with a history of mild confusion the day prior, who has a normal neurological (neuro) exam and computed tomography (CT) head, and was previously active and independent?

Most Likely Diagnosis: Delirium

The most likely diagnosis is delirium, given the acute onset of mild confusion one day prior to being found on the floor, the patient's previously independent functional status, and the normal neurological examination and CT head. 1, 2

Clinical Reasoning

Why Delirium is Most Likely

• Acute temporal course: The one-day history of mild confusion followed by being found on the floor represents an acute change over hours to days, which is the hallmark timeframe for delirium rather than the insidious progression of neurocognitive disorders 1

• Previously independent baseline: The patient's prior active and independent status argues strongly against pre-existing Alzheimer's disease or vascular dementia, which would have manifested with gradual functional decline 2, 3

• Normal neurological examination: This makes acute stroke (CVA) unlikely as a primary cause, though small lacunar infarcts can occasionally present without focal deficits 1, 2

• Normal CT head: While CT has limitations, a normal scan in the acute setting makes large territorial stroke, intracranial hemorrhage, and mass lesions less likely 1

Critical Next Steps in Evaluation

Immediate bedside assessments (all require point-of-care testing):

• Fingerstick glucose to exclude hypoglycemia/hyperglycemia 2, 3
• Oxygen saturation to assess for hypoxia 2, 3
• Core temperature to identify hypothermia 2, 3
• Orthostatic vital signs to detect hypotension 3

Essential laboratory workup:

• Comprehensive metabolic panel focusing on sodium, glucose, calcium, and renal function 2, 3
• Complete blood count to assess for infection or anemia 2, 3
• Urinalysis and urine culture (urinary tract infection is the most common infectious precipitant in elderly patients) 2
• Thyroid function tests in elderly patients with new mental status changes 2, 3

Medication reconciliation is critical:

• Polypharmacy is a major contributor to delirium in the elderly 2, 3
• Specifically review anticholinergic medications (antihistamines, tricyclic antidepressants), sedatives, benzodiazepines, and narcotics 2, 3
• Consider drug or alcohol withdrawal even without obvious intoxication history 3

Why Other Diagnoses Are Less Likely

CVA (Stroke):

• While stroke can present with altered mental status alone in 70% of missed diagnoses, the completely normal neurological examination makes this less probable 1
• However, small vessel disease and lacunar infarcts may not present with obvious focal deficits, so this cannot be entirely excluded 3
• If clinical suspicion remains high despite normal CT, MRI brain without contrast has higher sensitivity for detecting acute ischemia 1

Alzheimer's Disease or Vascular Dementia:

• These are chronic, progressive conditions developing over months to years, not acute presentations over one day 2
• The patient's previously active and independent status is incompatible with established dementia 2, 3
• These diagnoses require documented cognitive decline over time, not acute confusion 4

Neurocognitive Disorder (general):

• This umbrella term encompasses chronic conditions that do not present acutely 2
• The acute timeframe and prior independence exclude this category 2, 3

Critical Pitfalls to Avoid

• Do not assume syncope without proper evaluation: While being "found on the floor" suggests a fall, the one-day history of confusion indicates a broader process. Syncope workup (ECG, cardiac evaluation) may still be warranted, but the mental status change requires delirium evaluation 1

• Do not miss non-convulsive seizures: These require EEG evaluation, not just imaging, and can present with altered mental status without obvious convulsive activity 3

• Do not overlook subdural hematoma: Even with normal initial CT, elderly patients (especially those on anticoagulation) can develop delayed subdural hematomas from unrecognized trauma during the fall 2, 3

• Mortality doubles when delirium is missed: This is a medical emergency requiring prompt identification and treatment of the underlying cause 2, 3, 5

When to Consider Advanced Imaging

MRI brain without contrast is usually appropriate as second-line imaging when 1:

• Initial CT is unrevealing but clinical suspicion for stroke remains high
• Occult pathology is suspected (small infarcts, encephalitis, subtle subarachnoid hemorrhage)
• Known malignancy raises concern for metastases
• Suspected posterior reversible encephalopathy syndrome in hypertensive patients

However, the diagnostic yield of neuroimaging is low (5-6.4%) in the absence of focal neurological deficits or signs of trauma 1