Amnesia

Differential Overview

❑ Concussion

❑ Alzheimer disease

❑ Drugs

❑ Generalized seizure

❑ Migraine

❑ Transient global amnesia

❑ Psychogenic

❑ Herpes simplex encephalitis

❑ Complex partial seizures

❑ Korsakoff syndrome

Diagnostic Approach

Amnesia is characterized by an inability to recall prior events and to learn new information, despite a normal level of consciousness. There must be injury to both temporal lobes in order for amnesia to occur.

Clinical Findings

Concussion  The injury will usually be recalled, witnessed, or at least suspected from surface contusions. Disruption of short-term memory imprinting causes transient anterograde and retrograde amnesia, with a length proportionate to the degree of injury. Transient loss of consciousness is usual.

Alzheimer disease  Amnesia with poor short-term memory may occur before generalized dementia becomes evident.

Drugs Alcohol intoxication may cause spotty amnesia for events (alcoholic blackout). Benzodiazepines produce a similar phenomenon.

Generalized seizure  The tonic-clonic motor activity is followed by a post-ictal phase of confusion and a period of time for which the patient will be amnesic.

Migraine  A migraine is classically recognized by visual aura, unilateral headache, and nausea; amnesia is an infrequent but striking symptom.

Transient global amnesia  It appears as sudden confusion and amnesia in a previously well person. The patient appears bewildered and has intact immediate recall but is unable to imprint new information. The neurological examination is otherwise normal. Symptoms last 2 to 12 hours and are often followed by a headache or nausea. The attack often follows immersion in cold or hot water, emotional stimuli, physical exertion, sexual intercourse, or automobile travel.

Psychogenic  Event-specific amnesia follows traumatic events such as witnessed homicide. Hysterical fugue is purposeful, arising from emotional conflict. The state may be prolonged, with the patient losing personal identity and past memories, yet new memories are readily imprinted.

Herpes simplex encephalitis  Early in the course, there may be a Korsakoff-like state, due to bilateral temporal lobe infection. Fever will be present.

Complex partial seizures  They may occur without any conscious awareness, with only a blank in the memory. Temporal lobe seizures are marked by auras and repetitive behaviors.

Korsakoff syndrome  The patient is unable to recall new information despite a normal level of consciousness and intact immediate recall. He compensates with fantastic confabulations. Korsakoff syndrome occurs in chronic alcoholics, especially following Wernicke encephalopathy, marked by acute confusion, and in nonalcoholic patients with thiamine deficiency.

Book Source Details

• Book Title: Field Guide to Bedside Diagnosis
• Author(s): David S. Smith
• Year of Publication: 2007
• Copyright Details: Field Guide to Bedside Diagnosis, Copyright © 2007 Lippincott Williams & Wilkins.

Other Book Chapters Related to Amnesia

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Copyright Details: Field Guide to Bedside Diagnosis, Copyright © 2008 Williams & Wilkins.

More About Causes of Amnesia

• Back to symptom: Amnesia: Introduction (review 42 causes)
• Next Book Extract About Amnesia: Alzheimer's disease (Handbook of Diseases)
• All Book Extracts: All Online Book Extracts for Amnesia

More About This Book: Title: Field Guide to Bedside Diagnosis Authors: David S. Smith Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 0-78178-165-5

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• AMNESIA (Differential Diagnosis in Primary Care)

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