Differential Diagnosis for Altered Mental Status in a Patient Above 75 Years Old

Single Most Likely Diagnosis

• Delirium: This is the most common cause of altered mental status in elderly patients, often resulting from a combination of factors such as medication side effects, infections, metabolic disturbances, or environmental changes. Its acute onset and fluctuating course are characteristic.

Other Likely Diagnoses

• Dementia: While dementia is a chronic condition, an acute worsening can present as altered mental status. This could be due to a superimposed delirium or progression of the underlying disease.
• Infections: Elderly patients may present with altered mental status as the primary symptom of infections such as pneumonia or urinary tract infections, without the typical signs of fever or localized symptoms.
• Medication Side Effects: Polypharmacy is common in the elderly, increasing the risk of adverse drug reactions that can cause altered mental status.
• Metabolic Disturbances: Conditions like hyperglycemia, hypoglycemia, hyponatremia, or hypercalcemia can lead to altered mental status in elderly patients.

Do Not Miss Diagnoses

• Stroke or Transient Ischemic Attack (TIA): Although less common as a sole presentation of altered mental status, it is critical to rule out because timely intervention can significantly impact outcomes.
• Subdural Hematoma: Especially in patients on anticoagulation or with a history of falls, a subdural hematoma can present with altered mental status and requires urgent diagnosis and treatment.
• Sepsis: Septic patients can present with altered mental status, and early recognition and treatment are crucial for survival.
• Hypoxia: Hypoxic states, whether due to respiratory or cardiac issues, can cause altered mental status and are immediately life-threatening if not addressed.

Rare Diagnoses

• Vitamin Deficiencies: Deficiencies in vitamins such as B12 or thiamine can lead to altered mental status, although these are less common causes.
• Endocrine Disorders: Conditions like myxedema coma (severe hypothyroidism) or hyperthyroid crisis can present with altered mental status but are relatively rare.
• Autoimmune Encephalitis: A rare but potentially treatable cause of altered mental status, often associated with specific antibodies.
• Prion Diseases: Extremely rare, such as Creutzfeldt-Jakob disease, which can cause rapidly progressive dementia and altered mental status.