Amnesia, total or partial

Question 1

Causes include

Answer 1

1. Psychogenic;

• conversion disorder
• fugue states
• factitious
• severe anxiety and stress
• major depression etc.

1. Wernicke–Korsakoff syndrome (alcohol)
2. post-trauma
3. transient organic states;

• CVA
• Epilepsy
• Hypoxia
• cerebral infection
• drugs, etc.

1. cerebral tumour
2. SAH
3. various drugs

• alcohol
• cannabis, antiepileptics
• digoxin
• methamphetamines, etc.

1. transient global amnesia.

Question 2

Transient global amnesia

Answer 2

Benign condition of middle-aged and elderly

Acute onset profound amnesia; also anterograde and retrograde amnesia

State of bewilderment (e.g. ‘Where am I?’); repetitive queries

Self-limited—usu. 4–8 (up to 24) h

Complete resolution

Usually single episode (20% recurrence)

May be precipitating event (e.g. stress)

No other neurological symptoms or signs

Able to perform complex motor skills (e.g. driving)

Good prognosis: complete resolution

Investigations generally unhelpful; witness of event essential for diagnosis

No active treatment recommended: reassurance and explanation

Question 3

Probability diagnosis

Answer 3

Severe anxiety/stress

Major depression esp. post ECT

Ageing/dementia

Head injury

Alcohol excess incl. Korsakoff syndrome

Iatrogenic e.g. ECT, cardiac bypass surgery

Question 4

Serious disorders not to be missed

Answer 4

Vascular:

• Cerebral haemorrhage/subarachnoid
• Cerebral infarction esp. vertebrobasilar

Infection:

• Cerebral e.g. meningitis, abscess
• Viral encephalitis e.g. Herpes Simplex
• Syphilis
• HIV/AIDS

Tumor/cancer:

• Cerebral tumour
• Paraneoplasia

Other:

• Anoxia/hypoxia
• Hypothermia
• Electrolyte disturbance esp. hyponatraemia
• Dehydration
• Post-ictal state

Question 5

Pitfalls (often missed)

Answer 5

Transient global amnesia

B1 deficiency incl. alcohol abuse

Dissociative fugue states

Depersonalisation disorder

Rarities:

• Wernicke’s encephalopathy
• Carbon monoxide poisoning

Question 6

Masquerades checklist

Answer 6

Depression esp. major

Diabetes: hypoglycaemia

Drugs: various e.g. Cannabis, amphetamines (see list)

Anaemia

Thyroid/other endocrine: hypercalcaemia/hypothyroid?

Question 7

Is the patient trying to tell me something?

Answer 7

Conversion reaction (hysterical fugue)

Psychogenic amnesia/malingering

Question 8

Key history

Answer 8

The nature of memory loss incl. onset, duration, fluctuation and associations.

Interview family members and check for possible bizarre behaviour.

PMHx;

• diabetes
• hypertension
• cerebrovascular disease
• drug esp. alcohol, smoking or illicit drugs (cannabis, amphetamines, opioids, solvent sniffing), lithium, barbiturates, benzodiazepines, anticonvulsants, digoxin, OTC drugs, etc.

Psychiatric hx, incl. severe anxiety, stress, depression, fugue features, dissociation or personality disorder.

Question 9

Key examination

Answer 9

General features: appearance of patient incl. central cyanosis, hydration status, vital signs

Psychiatric assessment and mental state examination

Neurological examination

Question 10

Key investigations

Answer 10

First line:

• urinalysis
• blood sugar
• pulse oximetry
• FBE & ESR
• LFTs (γGT)

Others according to history and findings

• blood gases
• TFTs
• syphilis serology
• CXR
• imaging: cerebral CTscan or MRI

Question 11

Diagnostic tips

Answer 11

Consider memory loss as a presenting feature of;

1. severe stress
2. anxiety or
3. depression (which can present as pseudo dementia in the elderly).

Question 12

The amnesias are?

Answer 12

Disorders involving partial or total inability to recall past experiences.