What is the most likely cause of confusion and a fall in an 80-year-old patient with a history of controlled hypertension and transient ischemic attack (TIA), with a negative computed tomography (CT) scan and no recent changes in medications or illnesses?

Most Likely Explanation: Delirium from Acute Medical Illness

The most likely explanation for confusion and a fall in this 80-year-old patient with negative CT imaging is acute delirium secondary to an undiagnosed medical condition, most commonly infection, cardiac causes (particularly congestive heart failure or arrhythmia), or metabolic derangement. 1

Diagnostic Framework

Why Delirium is Most Likely

• Acute confusion in elderly patients admitted to hospital is caused by identifiable medical conditions in 92% of cases (22 of 24 patients), with infection and congestive heart failure being the predominant causes 1
• The negative CT scan significantly reduces the probability of structural brain pathology, particularly when focal neurological signs are absent 2
• Patients without focal neurological signs who have either fever or dehydration have a 96% probability of having normal brain imaging 2
• In elderly patients with prior dementia and no focal signs, the predictive value for normal brain imaging reaches 98% 2

Critical Evaluation Steps Required

Immediate assessment should focus on:

• Orthostatic vital signs (supine and standing blood pressure/heart rate within 3 minutes) to evaluate for orthostatic hypotension, defined as systolic BP drop ≥20 mmHg or diastolic BP drop ≥10 mmHg 3
• 12-lead ECG to evaluate for arrhythmias, conduction abnormalities (particularly AV block given history of hypertension and TIA), or evidence of ischemia 3
• Laboratory workup including:
  • Complete blood count to assess for infection or anemia 3
  • Comprehensive metabolic panel for electrolyte abnormalities (hyponatremia, hypocalcemia, hypomagnesemia), renal function, and glucose 3, 4
  • Urinalysis and culture (urinary tract infection is a common precipitant) 1
  • Thyroid function (given age and risk factors) 5
  • Vitamin B12 level 5

Differential Diagnosis Priority

1. Cardiac Syncope with Post-Ictal Confusion

• Higher risk features present: advancing age, history of hypertension, prior TIA 3
• Arrhythmias or high-grade AV block can cause both syncope and transient confusion 3
• Congestive heart failure is a predominant cause of confusion in elderly admissions 1

2. Infection-Related Delirium

• Infection predominates as a cause when confusion is present on admission 1
• May present without fever in elderly patients
• Urinary tract infection, pneumonia, or occult bacteremia should be excluded

3. Metabolic Derangement

• Hypoglycemia, hyponatremia, hypocalcemia, or hypomagnesemia can cause both confusion and falls 4
• Dehydration is common and highly associated with delirium 2
• Renal dysfunction increases risk of recurrent events 3

4. Medication-Induced (Despite "No Recent Changes")

• Vestibular suppressants, benzodiazepines, and psychotropic medications are significant independent risk factors for falls and confusion 5
• Drug accumulation can occur without dose changes due to declining renal function
• Polypharmacy effects may manifest acutely 5

5. Seizure (Less Likely but Must Exclude)

• Post-stroke epileptogenic focus is the most common cause of seizures in elderly stroke patients with prior TIA 4
• However, prolonged confusion or sleepiness lasting more than a few minutes after regaining consciousness points to epilepsy rather than syncope 5
• Syncope typically has rapid recovery without postictal state 3
• Tongue biting or muscle pains lasting hours/days would support seizure 5

6. Recurrent TIA/Stroke (Lower Probability Given Negative CT)

• While CT can miss early ischemic changes, the absence of focal neurological deficits makes acute stroke less likely 2
• Patients with elevated risk (history of stroke/TIA) warrant cognitive and behavioral assessment 5
• Consider MRI if clinical suspicion remains high despite negative CT 5

Management Algorithm

Immediate Actions

1. Cardiac monitoring in a setting with resuscitation capabilities if cardiac cause suspected 3
2. Medication review to identify and potentially modify drugs contributing to hypotension or confusion 3
3. Treat identified underlying cause aggressively, as confusion resolution accompanies recovery 1

Disposition Criteria

Admission is warranted for: 3

• Evidence of cardiac cause requiring monitoring
• Inability to maintain orthostasis despite interventions
• Presence of significant comorbidities increasing risk
• Unidentified cause requiring further workup

Critical Pitfalls to Avoid

• Failing to distinguish syncope from seizure: Syncope has rapid recovery; seizure has postictal confusion 3
• Missing medication-induced orthostatic hypotension despite "no recent changes" 3
• Assuming negative CT excludes all pathology: MRI is more sensitive for subtle ischemia, encephalitis, or small hemorrhages 5
• Overlooking infection in elderly patients without fever 1
• Not obtaining collateral history from witnesses, as patients may have amnesia for loss of consciousness 5
• Attributing confusion solely to age or dementia without investigating reversible causes 5, 1