Amnesia
Amnesia is an inability to remember prior events and process new information despite a normal level of consciousness. The memory center in the brain is housed in the temporal lobes; thus, the development of true amnesia requires pathology of both temporal lobes. The most common cause of transient amnesia is acute head trauma with concussion. Alzheimer's disease is the most common nontransient cause of amnesia. Anterograde amnesia is defined as an inability to remember events that follow the onset of the amnesia, whereas retrograde amnesia is an inability to remember events that occurred before the onset of the amnesia.
Differential Diagnosis
-
Head trauma (e.g., concussion, hemorrhage)
–Usually results in transient retrograde and anterograde amnesia
Alzheimer's disease
–Most common cause of chronic amnesia
Infection
–Herpes simplex encephalitis is a particularly common cause of infectious amnesia, because it has a predilection for the temporal lobes
- Seizure disorders
–Retrograde amnesia is most common after a generalized tonic-clonic seizure during the postictal period
–Some complex partial seizure foci (particularly temporal lobe epilepsy) can also produce “blank” periods of memory
-
Toxicologic insults
–Binge alcohol consumption
–Benzodiazepine use (e.g., “date rape” drug
flunitrazepam, also known as Rohypnol)
-
Psychogenic causes are relatively common, but should be a diagnosis of exclusion
-
Korsakoff's syndrome
-
Transient global amnesia
–A rare, transient, ischemic attack-like condition of proposed vascular etiology
–Causes abrupt onset of short-term memory
loss for minutes to hours
–Typically occurs in patients older than 50
–Seen in patients with migraines
Workup and Diagnosis
-
History and physical examination
–Special attention to neurologic and head examination
–Life-threatening head trauma and CNS infection should
be considered initially in patients with altered mental status and amnesia
Initial labs may include CBC, electrolytes, glucose, calcium, magnesium, phosphorus, coagulation studies, and serum and urine toxicology screens Lumbar puncture with CSF analysis should be considered early if CNS infection is suspected
–Test for opening pressure, appearance (e.g., clear, cloudy, bloody), protein, glucose, CSF-to-serum glucose ratio, Gram stain, culture
–Cryptococcal antigen and acid-fast bacilli smear and culture in patients in endemic areas or with HIV
–If there is a delay in initiating lumbar puncture due to a need for imaging (e.g., head CT to rule out increased intracranial pressure), empiric antibiotics should be administered immediately
-
Head CT without contrast may be needed to exclude bleeding in cases of head trauma, and may also identify structural lesions
-
MRI of the head with diffusion-weighted imaging is more sensitive for diagnosing stroke, tumor, and the subtle white matter changes associated with vascular disease
-
EEG to rule out seizure disorder
Treatment
-
Immediate attention to airway, breathing, and circulation
-
Prompt treatment of suspected infections and trauma
–CNS infections: Antibiotic and/or antiviral therapy
–Head trauma: Surgical intervention may be necessary to
evacuate space-occupying traumatic lesions; concussions are treated symptomatically, and patients should refrain from contact sports until symptoms resolve; control elevated intracranial pressure with head elevation, moderate hyperventilation, mannitol administration, and/or surgical drainage
-
Alzheimer's disease: Anticholinesterase medications (e.g., tacrine, donepezil) may improve cognitive function
-
Seizure disorders: Anticonvulsant agents (e.g., phenytoin, carbamazepine, valproate)
Book Source Details
- Book Title: In a Page: Signs and Symptoms
- Author(s): Scott Kahan, Ellen G. Smith
- Year of Publication: 2004
- Copyright Details: In a Page: Signs and Symptoms, Copyright © 2004 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)
- [ read ]
- Amnesia
- "In a Page: Signs and Symptoms" (2004)
- [ read ]
- AMNESIA
- "Differential Diagnosis in Primary Care" (2007)
- [ read ]
- Confusion
- "Handbook of Signs & Symptoms (Third Edition)" (2006)
- [ read ]
- Amnesia
- "Handbook of Signs & Symptoms (Third Edition)" (2006)
- [ read ]
- Confusion
- "Professional Guide to Signs & Symptoms (Fifth Edition)" (2006)
- [ read ]
- 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)
- [ read ]
- Amnesia
- "Field Guide to Bedside Diagnosis" (2007)
- [ read ]
- Confusion
- "Signs & Symptoms: A 2-in-1 Reference for Nurses" (2007)
- [ read ]
- Confusion
- "Nursing: Interpreting Signs and Symptoms" (2007)
- [ read ]
- Amnesia
- "Nursing: Interpreting Signs and Symptoms" (2007)
- [ read ]
- AMNESIA
- "Differential Diagnosis in Primary Care" (2007)
- [ read ]
Copyright Details: In a Page: Signs and Symptoms, Copyright © 2008 Williams & Wilkins.
More About Causes of Amnesia
|
|
More About This Book:
Title: In a Page: Signs and Symptoms
Authors: Scott Kahan, Ellen G. Smith
Publisher: Lippincott Williams & Wilkins
Copyright: 2004
ISBN: 1-4051-0368-X
|
|
» Next page: AMNESIA (Differential Diagnosis in Primary Care)
Rate This Website
What do you think about the features of this website?
Take our user survey and have your say:
Website User Survey
Medical Tools & Articles:
Next articles:
Tools & Services:
Medical Articles:
Forums & Message Boards
- Ask or answer a question at the Boards:
