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Confusion

Medicine > Endocrine & metabolic

Differential Diagnosis Schema 🧠

Infectious Causes

  • Urinary tract infection: Common in the elderly, often presents with confusion, fever, dysuria, or new incontinence
  • Pneumonia: Especially in older adults, may present atypically with confusion, fever, cough, or hypoxia
  • Sepsis: Confusion may be an early sign, often with systemic signs of infection (e.g., tachycardia, hypotension, fever)
  • Meningitis/encephalitis: Acute confusion, headache, fever, neck stiffness, photophobia, and sometimes seizures
  • Cerebral abscess: Focal neurological signs, headache, fever, and confusion in the context of a source of infection (e.g., sinusitis, otitis media)

Metabolic and Endocrine Causes

  • Hypoglycemia: Rapid onset confusion, sweating, tachycardia, often in patients with diabetes or those on insulin/oral hypoglycemics
  • Hyperglycemia (e.g., diabetic ketoacidosis or hyperosmolar hyperglycemic state): Gradual onset confusion, dehydration, polyuria, polydipsia, often with a known history of diabetes
  • Electrolyte disturbances (e.g., hyponatremia, hypercalcemia): May cause confusion, lethargy, seizures, or altered consciousness
  • Thyroid dysfunction (e.g., myxedema coma or thyrotoxicosis): Hypothyroidism leads to confusion, lethargy, and cold intolerance, while hyperthyroidism may cause agitation, tremor, and confusion
  • Liver failure (hepatic encephalopathy): Confusion, asterixis, jaundice, history of liver disease, often triggered by infection, dehydration, or GI bleeding
  • Renal failure (uremic encephalopathy): Confusion, lethargy, asterixis, history of chronic kidney disease, and elevated urea/creatinine

Neurological Causes

  • Stroke: Sudden onset of confusion, focal neurological deficits (e.g., hemiparesis, aphasia), often in the context of vascular risk factors
  • Transient ischemic attack (TIA): Brief episodes of confusion or neurological symptoms, resolves within 24 hours, a warning sign for stroke
  • Seizures and postictal state: Acute confusion, disorientation, or altered consciousness following a seizure
  • Subdural hematoma: Gradual onset confusion, headache, possible history of head trauma, particularly in the elderly or those on anticoagulants
  • Dementia: Chronic, progressive confusion with memory loss, language difficulties, and personality changes, typically in older adults
  • Delirium: Acute onset of fluctuating confusion, often with inattention, visual hallucinations, and disorganized thinking, usually triggered by an underlying medical condition

Toxic and Substance-Related Causes

  • Alcohol intoxication or withdrawal: Acute confusion, tremors, hallucinations, seizures, often with a history of heavy alcohol use
  • Drug overdose (e.g., opioids, benzodiazepines, anticholinergics): Confusion, respiratory depression, pinpoint pupils (opioids), or dry mouth, urinary retention (anticholinergics)
  • Medication side effects (e.g., sedatives, antipsychotics, polypharmacy in elderly): Confusion, drowsiness, extrapyramidal symptoms (antipsychotics)
  • Carbon monoxide poisoning: Confusion, headache, cherry-red skin (late sign), often related to exposure to faulty heating systems
  • Delirium tremens: Severe alcohol withdrawal with confusion, tremors, hallucinations, hyperthermia, and potential seizures
  • Illicit drug use (e.g., cocaine, amphetamines): Confusion, agitation, tachycardia, hypertension, often with a history of substance use

Key Points in History 🥼

Onset and Duration

  • Acute vs chronic: Acute onset suggests delirium, stroke, or metabolic disturbances, while chronic onset suggests dementia or neurodegenerative diseases
  • Fluctuating vs constant: Fluctuating confusion is characteristic of delirium, while constant confusion may indicate dementia or chronic intoxication
  • Progression: Rapid progression suggests an acute process (e.g., infection, metabolic disturbance), while slow progression suggests a chronic condition (e.g., dementia)

Associated Symptoms

  • Fever: May indicate an infectious cause such as sepsis, meningitis, or encephalitis
  • Headache: Suggests intracranial pathology (e.g., meningitis, subdural hematoma, stroke) or metabolic causes such as hypercapnia
  • Focal neurological signs: Such as hemiparesis or aphasia, suggest stroke, subdural hematoma, or space-occupying lesion
  • Visual disturbances: Blurred vision or visual field loss may indicate stroke, migraine, or hypertensive encephalopathy
  • Seizures: Suggests a neurological cause such as epilepsy, encephalitis, or metabolic disturbances (e.g., hyponatremia)
  • History of head trauma: Increases the likelihood of subdural hematoma, particularly in the elderly or those on anticoagulants
  • Alcohol or drug use: Increases suspicion of intoxication, withdrawal, or overdose
  • Polyuria/polydipsia: Suggests hyperglycemia (e.g., diabetic ketoacidosis or hyperosmolar hyperglycemic state)

Background

  • Past medical history: Previous strokes, diabetes, epilepsy, dementia, liver or kidney disease can all predispose to confusion
  • Drug history: Use of medications that can cause confusion (e.g., sedatives, anticholinergics, opioids), recent changes in medication, or polypharmacy
  • Family history: History of dementia, stroke, or psychiatric illness may suggest an inherited predisposition
  • Social history: Alcohol use, illicit drug use, smoking, and occupational exposures (e.g., to solvents or carbon monoxide) are relevant
  • Travel history: Recent travel may indicate infections like malaria or viral encephalitis
  • Lifestyle factors: Poor nutrition or dehydration, especially in the elderly, may contribute to confusion

Possible Investigations 🌡️

Bedside Tests

  • Capillary blood glucose: Essential to rule out hypoglycemia or hyperglycemia
  • Electrocardiogram (ECG): To assess for arrhythmias, ischemia, or signs of electrolyte disturbances
  • Urinalysis: To detect urinary tract infection, ketonuria (diabetic ketoacidosis), or drug intoxication
  • Cognitive assessments: Mini-Mental State Examination (MMSE) or Confusion Assessment Method (CAM) to assess the level of confusion and differentiate between delirium and dementia
  • Oxygen saturation: To assess for hypoxia, which may contribute to confusion
  • Observations: Including temperature, pulse, respiratory rate, and blood pressure to assess for infection, sepsis, or shock

Blood Tests

  • Full blood count: To assess for infection (leukocytosis), anemia, or thrombocytopenia
  • Urea and electrolytes: To identify electrolyte disturbances, renal failure, or dehydration
  • Liver function tests: To assess for hepatic encephalopathy or alcohol-related liver disease
  • C-reactive protein (CRP): Elevated in infection or inflammation
  • Thyroid function tests: To assess for hypo- or hyperthyroidism
  • Arterial blood gas: To assess for respiratory or metabolic acidosis, hypercapnia, or hypoxia
  • Toxicology screen: If drug overdose or intoxication is suspected
  • Blood cultures: If sepsis is suspected, to identify the causative organism
  • Vitamin B12 and folate levels: To assess for deficiency, which can contribute to confusion

Imaging and Special Tests

  • CT/MRI brain: To assess for stroke, subdural hematoma, space-occupying lesion, or other intracranial pathology
  • Chest X-ray: To assess for pneumonia, heart failure, or other thoracic causes of confusion (e.g., malignancy)
  • Lumbar puncture: If meningitis or encephalitis is suspected, to analyze cerebrospinal fluid (CSF)
  • EEG (electroencephalogram): To assess for seizure activity or encephalopathy, particularly in patients with unexplained confusion or altered consciousness
  • Doppler ultrasound of carotid arteries: To assess for carotid artery stenosis in patients with suspected TIA or stroke
  • Echocardiography: To assess for endocarditis, valvular disease, or cardiogenic embolism in patients with confusion and a history of cardiac conditions
  • Electrolyte monitoring and correction: Continuous monitoring if significant electrolyte disturbances are found

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Endocrine & metabolic