Amnesia
Amnesia — a disturbance in, or loss of, memory — may be classified as partial or complete and as anterograde or retrograde. Anterograde amnesia denotes memory loss of events that occurred after the onset of the causative trauma or disease; retrograde amnesia, memory loss of events that occurred before the onset. Depending on the cause, amnesia may arise suddenly or slowly and may be temporary or permanent.
Organic (or true) amnesia results from temporal lobe dysfunction, and it characteristically spares patches of memory. A common symptom in patients with seizures or head trauma, organic amnesia can also be an early indicator of Alzheimer’s disease. Hysterical amnesia has a psychogenic origin and characteristically causes complete memory loss. Treatment-induced amnesia is usually transient.
History and physical examination
Because the patient typically isn’t aware of his amnesia, you’ll usually need help in gathering information from his family or friends. Throughout your assessment, notice the patient’s general appearance, behavior, mood, and train of thought. Ask when the amnesia first appeared and what types of things the patient is unable to remember. Can he learn new information? How long does he remember it? Does the amnesia encompass a recent or remote period?
Test the patient’s recent memory by asking him to identify and repeat three items. Retest after 3 minutes. Test his intermediate memory by asking, “Who was the president before this one?” and “What was the last type of car you bought?” Test remote memory with such questions as “How old are you?” and “Where were you born?”
Take the patient’s vital signs and assess his level of consciousness (LOC). Check his pupils: They should be equal in size and should constrict quickly when exposed to direct light. Also, assess his extraocular movements. Test motor function by having the patient move his arms and legs through their range of motion. Evaluate sensory function with pinpricks on the patient’s skin. (See Amnesia: Common causes and associated findings.)
Medical causes
❑ Alzheimer’s disease. Alzheimer’s disease usually begins with retrograde amnesia, which progresses slowly over many months or years to include anterograde amnesia, producing severe and permanent memory loss. Associated findings include agitation, inability to concentrate, disregard for personal hygiene, confusion, irritability, and emotional lability. Later signs include aphasia, dementia, incontinence, and muscle rigidity.
❑ Cerebral hypoxia. After recovery from hypoxia (brought on by such conditions as carbon monoxide poisoning or acute respiratory failure), the patient may experience total amnesia for the event, along with sensory disturbances, such as numbness and tingling.
❑ Head trauma. Depending on the trauma’s severity, amnesia may last for minutes, hours, or longer. Usually, the patient experiences brief retrograde and longer anterograde amnesia as well as persistent amnesia about the traumatic event. Severe head trauma can cause permanent amnesia or difficulty retaining recent memories. Related findings may include altered respirations and LOC; headache; dizziness; confusion; visual disturbances, such as blurred or double vision; and motor and sensory disturbances, such as hemiparesis and paresthesia, on the side of the body opposite the injury.
❑ Herpes simplex encephalitis. Recovery from herpes simplex encephalitis commonly leaves the patient with severe and possibly permanent amnesia. Associated findings include signs and symptoms of meningeal irritation, such as headache, fever, and altered LOC, along with seizures and various motor and sensory disturbances (such as paresis, numbness, and tingling).
❑ Hysteria. Hysterical amnesia, a complete and long-lasting memory loss, begins and ends abruptly and is typically accompanied by confusion.
❑ Seizures. In temporal lobe seizures, amnesia occurs suddenly and lasts for several seconds to minutes. The patient may recall an aura or nothing at all. An irritable focus on the left side of the brain primarily causes amnesia for verbal memories, whereas an irritable focus on the right side of the brain causes graphic and nonverbal amnesia. Associated signs and symptoms may include decreased LOC during the seizure, confusion, abnormal mouth movements, and visual, olfactory, and auditory hallucinations.
❑ Wernicke-Korsakoff syndrome. Retrograde and anterograde amnesia can become permanent without treatment in this syndrome. Accompanying signs and symptoms include apathy, an inability to concentrate or to put events into sequence, and confabulation to fill memory gaps. The syndrome may also cause diplopia, decreased LOC, head-ache, ataxia, and symptoms of peripheral neuropathy, such as numbness and tingling.
Other causes
❑ Drugs. Anterograde amnesia can be precipitated by general anesthetics, especially fentanyl, halothane, and isoflurane; barbiturates, most commonly pentobarbital and thiopental; and certain benzodiazepines, especially triazolam.
❑ Electroconvulsive therapy. The sudden onset of retrograde or anterograde amnesia occurs with electroconvulsive therapy. Typically, the amnesia lasts for several minutes to several hours, but severe, prolonged amnesia occurs with treatments given frequently over a prolonged period.
❑ Temporal lobe surgery. Usually performed on only one lobe, this surgery causes brief, slight amnesia. However, removal of both lobes results in permanent amnesia.
Special considerations
Prepare the patient for diagnostic tests, such as computed tomography scan, magnetic resonance imaging, EEG, or cerebral angiography.
Provide reality orientation for the patient with retrograde amnesia, and encourage his family to help by supplying familiar photos, objects, and music.
Adjust your patient-teaching techniques for the patient with anterograde amnesia because he can’t acquire new information. Include his family in teaching sessions. In addition, write down all instructions — particularly medication dosages and schedules — so the patient won’t have to rely on his memory.
If the patient has severe amnesia, consider basic needs, such as safety, elimination, and nutrition. If necessary, arrange for placement in an extended-care facility.
Pediatric pointers
A child who suffers from amnesia during seizures may be mistakenly labeled as “learning disabled.” To prevent this mislabeling, stress the importance of adhering to the prescribed drug schedule, and discuss ways that the child, his parents, and his teachers can cope with amnesia.
Pictures
Book Source Details
- Book Title: Handbook of Signs & Symptoms (Third Edition)
- Author(s): Springhouse
- Year of Publication: 2006
- Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2006 Lippincott Williams & Wilkins.
Other Book Chapters Related to Amnesia
Read excerpts from these other book chapters related to Amnesia:
Medical Books Excerpts
- AMNESIA
- "Algorithmic Diagnosis of Symptoms and Signs" (2003)
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- Amnesia
- "In a Page: Signs and Symptoms" (2004)
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- AMNESIA
- "Differential Diagnosis in Primary Care" (2007)
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- Confusion
- "Handbook of Signs & Symptoms (Third Edition)" (2006)
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- Amnesia
- "Handbook of Signs & Symptoms (Third Edition)" (2006)
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- Confusion
- "Professional Guide to Signs & Symptoms (Fifth Edition)" (2006)
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- Amnesia
- "Professional Guide to Signs & Symptoms (Fifth Edition)" (2006)
- [ read ]
- Confusion
- "The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter" (2000)
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- Amnesia
- "Field Guide to Bedside Diagnosis" (2007)
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- Confusion
- "Signs & Symptoms: A 2-in-1 Reference for Nurses" (2007)
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- Confusion
- "Nursing: Interpreting Signs and Symptoms" (2007)
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- Amnesia
- "Nursing: Interpreting Signs and Symptoms" (2007)
- [ read ]
- AMNESIA
- "Differential Diagnosis in Primary Care" (2007)
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Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2008 Williams & Wilkins.
More About Causes of Amnesia
» Next page: Alzheimer's disease (Professional Guide to Diseases (Eighth Edition))
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