10.16 Delirium And Disturbance Of Consiousness

Question 1

Define acute encephalopathy

Answer 1

• Rapidly developing (< 4 weeks) pathobiological brain process
• NOT a clinical descriptor

1. Delirium
   - disturbance in attention, awareness and cognition that develops rapidly, fluctuates and is due to an underlying medical condition, substance / toxin or etiology
2. Coma (state of severely depressed responsiveness)

Question 2

Causes of acute changes in mental state

Answer 2

Acute changes in mental state(confusion,decreasedlevelofawareness etc.) may be due to:
- Primary neurological disorders, e.g. stroke, encephalitis, meningitis
- Systemic disorders (toxic-metabolic encephalopathy/TME)

Question 3

Of what is delirium a marker?

Answer 3

Of a vulnerable brain with diminished reserve capacity
- may lead to permanent cognitive decline or dementia

Question 4

Causes of delirium

Answer 4

• Usually multifactorial in elderly people
• Dependent on complex relationship between:
  ➡️Vulnerable patient with one or more predisposing factors and
  ➡️Exposure to noxious insults or precipitating factors

Question 5

Infection as common causes of toxic metabolic encephalopathy

Answer 5

• Note: refers to non-CNS infections (CNS infections discussed separately)
• Common cause of delirium in the elderly
• Mechanism multifactorial: circulating cytokines, altered BBB
  permeability, changes in neurotransmitters
• Common sources: pneumonia, UTI, skin infections

Question 6

Common endocrine disorders that cause delirium

Answer 6

Hyperglycemia
- Usually occurs with diabetic ketoacidosis or hyperglycemic hyperosmolar state
- Note: patients with one of these conditions are often systemically quite ill and may have additional precipitating factors for delirium
- Improvement more gradual, often days

Hypoglycemia
- Risk of delirium/coma directly related to speed of drop in blood glucose levels
- Typically develops when blood glucose acutely drops below 2.8 mmol/L
- Improves rapidly if promptly recognized and treated

Thyroid disorders
- Thyrotoxicosis

Question 7

Electrolyte disorders that causes delirium

Answer 7

Sodium
- Hyponatremia
• Common cause
• Development of delirium related to both degree and speed of onset
- Hypernatremia
• E.g. dehydrated patients
- NB: Rapid correction of hyponatremia may lead to osmotic demyelination
• Max1mmol/L/houror10mmol/L/day

Calcium
- Hypercalcemia
• Due to cancer or hyperparathyroidism
• Typically develops when Ca level exceeds 3.5 mmol/L, but may be lower
• Seizures uncommon
- Hypocalcemia
• More often causes seizures

Magnesium

Question 8

Organ dysfunction that causes delirium

Answer 8

Liver dysfunction / Hepatic encephalopathy
- Common cause
- Most common scenario: chronic liver disease with acute precipitant (medications, GIT bleeding, infection, surgery)
- Related to hyperammonaemia
- Delirium, N&V, (negative) myoclonus/asterixis, drowsiness, seizures
- Progresses to coma

Renal dysfunction / Uremic encephalopathy
- Acute severe or acute on chronic renal failure
- Misnomer – urea itself is not neurotoxic and does not cause the encephalopathy
- May also see asterixis, tremor, seizures

Respiratory dysfunction
- encephalopathy related predominately to degree of hypercapnia
- Hypoventilation / hypercapnia
• Usually gradual onset, sometimes acute worsening precipitated by e.g. drugs like benzodiazepines, acute respiratory infection etc.
- Hypoxemia
• Usually acute severe hypoxemia, e.g. Fat embolism syndrome; Cardiopulmonary arrest

Question 9

Posterior reversible encephalopathy syndrome (PRES) as cause of delirium

Answer 9

• A.k.a. acute hypertensive encephalopathy
• Can also be caused by eclampsia, immunosuppressive drugs (e.g.
  cyclosporin)
• Misnomer: may involve central and frontal head regions, not always reversible
• Clinical:
  • Headache
  • Seizures
  • Encephalopathy (delirium -> coma)
  • Visual disturbances (e.g. cortical blindness)

Question 10

Wernicke encephalopathy
General
Clinical manifestations

Answer 10

• Acute manifestation of thiamine deficiency
• Risk factors for thiamine deficiency
  • Alcohol abuse
  • Recurrent vomiting (e.g. hyperemesis gravidarum) or chronic diarrhoea
  • Malabsorption, e.g. GIT surgery, malignancy, HIV
• Common!

Clinical manifestations:
- Encephalopathy
- Oculomotor dysfunction
• Nystagmus commonest
• Also ophthalmoplegia or gaze palsies
- Ataxia

Question 11

Drugs and delirium

Answer 11

• Most drugs will induce delirium only in susceptible individuals, e.g. elderly, HIV infection, alcoholic
• Very common cause of delirium in the elderly
• Drugs can cause delirium directly (e.g. direct CNS effects) or indirectly (e.g. via electrolyte disturbances or dehydration)
• Both infections and antibiotic treatment (e.g.ertapenem) can cause delirium

Question 12

Structural disorders that causes coma

Answer 12

• Brain abscess
• Brain tumour
• Head trauma
• Acute hydrocephalus
• Intracranial hemorrhage
  • Intraparenchymal, e.g. hypertensive
  • Subarachnoid, e.g. ruptured berry aneurysm
• Note: stroke is unusual cause of coma, unless: (1) large with herniation or (2) large brainstem stroke

Question 13

Nonstructural disorders of coma

Answer 13

• Metabolic and endocrine disorders
• Infections
  • CNS, e.g. meningitis
  • Systemic, e.g. sepsis
• Drugs
• Other toxins
  • Carbon monoxide, cleaning substances

Question 14

Other causes of coma

Answer 14

• Seizures / status epilepticus
  • Non-convulsive status epilepticus
  • Evolves from convulsive status epilepticus
• Venous sinus thrombosis
  • Presents with seizures, headache, focal neurological involvement, confusion or coma
  • High risk group: post-partum
• Poisoning