Differential Diagnosis for New Onset Confusion in a Patient with a Left Ischemic Infarct

Single Most Likely Diagnosis

• Post-Stroke Delirium: This is a common complication following a stroke, especially in the acute phase. The sudden change in brain function due to the infarct can lead to confusion, altered level of consciousness, and disorganized thinking.

Other Likely Diagnoses

• Medication Side Effects: Many medications used in the management of stroke and its complications, such as anticoagulants, antihypertensives, and sedatives, can cause confusion as a side effect.
• Infection: Post-stroke patients are at an increased risk of developing infections such as pneumonia or urinary tract infections, which can present with confusion.
• Metabolic Disturbances: Electrolyte imbalances, hypoglycemia, or hyperglycemia can cause confusion and are relatively common in hospitalized patients.
• Seizure Activity: Post-stroke seizures can occur and may present with confusion, especially if the seizure is complex partial or if there is post-ictal confusion.

Do Not Miss Diagnoses

• Intracranial Hemorrhage: A new hemorrhage can occur, either spontaneously or as a complication of anticoagulation therapy, leading to increased intracranial pressure and confusion.
• Stroke in a New Territory: Another ischemic or hemorrhagic stroke in a different part of the brain can cause sudden worsening of neurological symptoms, including confusion.
• Meningitis or Encephalitis: Infections of the meninges or brain tissue can present with confusion, fever, and other neurological signs.
• Hydrocephalus: Obstruction of cerebrospinal fluid pathways can lead to increased intracranial pressure and confusion.

Rare Diagnoses

• Cerebral Vasculitis: Inflammation of the blood vessels in the brain can cause stroke-like symptoms, including confusion, and is often associated with systemic diseases.
• Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like episodes (MELAS): A rare genetic disorder that can cause stroke-like episodes, including confusion, due to mitochondrial dysfunction.
• Hashimoto's Encephalopathy: A rare condition associated with autoimmune thyroiditis, characterized by confusion, altered mental status, and seizures, which is reversible with corticosteroid treatment.