Amnesia, total or partial

Probability diagnosis

Severe anxiety/stress

Major depression esp. post ECT

Ageing/dementia

Head injury

Alcohol excess incl. Korsakoff syndrome

Iatrogenic e.g. ECT, cardiac bypass surgery

Serious disorders not to be missed

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

Pitfalls (often missed)

Transient global amnesia

B₁ deficiency incl. alcohol abuse

Dissociative fugue states

Depersonalisation disorder

Rarities:

• Wernicke’s encephalopathy

• Carbon monoxide poisoning

Masquerades checklist

Depression esp. major

Diabetes: hypoglycaemia

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

Anaemia

Thyroid/other endocrine: hypercalcaemia/hypothyroid?

Is the patient trying to tell me something?

Conversion reaction (hysterical fugue)

Psychogenic amnesia/malingering

Key history

A careful history is required recording the nature of memory loss incl. onset, duration, fluctuation and associations. Interview family members and check for possible bizarre behaviour. The key history should incl. past medical history including diabetes, hypertension, cerebrovascular disease; drug history esp. alcohol, smoking or illicit drugs (cannabis, amphetamines, opioids, solvent sniffing), lithium, barbiturates, benzodiazepines, anticonvulsants, digoxin, OTC drugs, etc.; and psychiatric history, incl. severe anxiety, stress, depression, fugue features, dissociation or personality disorder.

Key examination

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

• Psychiatric assessment and mental state examination

• Neurological examination

Key investigations

First line:

• urinalysis

• blood sugar

• pulse oximetry

• FBE & ESR

• LFTs (γGT)

• Others according to history and findings

Consider:

• blood gases

• TFTs

• syphilis serology

• CXR

• imaging: cerebral CTscan or MRI

Diagnostic tips

Consider memory loss as a presenting feature of severe stress, anxiety or depression (which can present as pseudo dementia in the elderly).