Definition and Causes:
The
term transient global amnesia (TGA) refers to a complete memory
loss for a short duration of time (often 1-8 hrs); lasting no more
than 24 hrs. It is a well-known phenomenon whereby, individuals
experience sudden loss of memory for recent events and are unable
to retain new information.
Causes:
The
precise cause of TGA is not known, however some studies using brain
imaging techniques suggests that there may be transient disruption
in blood flow within key memory centres in the brain. Some have
observed association between TGA with:
- Physical or emotional stress
- Strenuous physical activity/exercise
There may be a small correlation between TGA and patients who
suffer from migraines.
Back to TopSymptoms:
Many
patients are anxious or agitated and may repeatedly ask questions
concerning ongoing events.
- Sudden onset of memory loss for previous events (retrograde
memory loss). The extent is variable from patient to patient. For
some the memory disturbance might be a few days, while others may
have memory loss for months or even years
- The memory loss is often describes as "confusion", as it is not
apparent to witnesses why the individual suddenly cannot recall
specific events
- Personal identity and recognition of familiar objects or people
is often retained, although the patient may not recognize recently
acquired objects or people (e.g. newborn grandchild), if their
association with the patient is within the period of retrograde
memory loss
- Asks the same questions repeatedly because she or he does not
remember the answer
- Is unable to recall the episode of memory loss once
recovered
- Usually there are no other symptoms, such as weakness, speech
or vision problems
- When the symptoms begin to clear up, the patient's memory is
usually restored completely (sometimes within minutes). They
continue to be amnestic for the event, or at best have only sketchy
memory of the event
Back to TopInvestigations and Treatment:
Physicians may enquire about:
- Unusual emotional or physical stress/strain
- Head trauma
- Prior history of seizures, migraine, stroke and dementia
- Prescribed or illicit drug use
- Psychiatric history (depression, anxiety, bipolar)
- Recent infections (cold, flu)
- Potential exposure to infectious organisms (e.g. working
environment and travel history)
Physical examination:
- Vital signs: Blood pressure, heart rate,
temperature, respirations
- Neurological examination: A brief assessment
of memory plus evaluation of speech, vision, muscle tone, strength
and reflexes, gait, posture and balance
Diagnostic criteria:
Diagnosis is largely based on
- Clinical presentation: Sudden loss of memory, in a fully
conscious individual, that is transient and recovers fully
- Not associated with recent head trauma
- No history of seizures
- No abnormality of physical examination and labs (see
below)
Labs and imaging:
Routine blood work, including electrolytes, white blood cell count,
hemoglobin (to asses for anemia) as well as some blood work such
as, a toxicology (drug) screen, and imaging of the brain by CT
scan, MRI, and electroencephalogram (EEG) to assess for seizures
may all be used to assess for or exclude other causes of memory
disturbance.
TREATMENT:
TGA
is usually a benign condition, and no specific treatment is
required. Patient's may be referred to a neurologist for an
opinion. If TGA felt to be the most likely cause then patients are
usually counselled and provided with some reassurance.
Medications
There is no medication required to treat TGA.
Back to TopRisk Factors and Prevention:
Prevention:
The
exact cause is unknown; so there is no standard prevention.
Back to TopOutcome:
Overall prognosis is usually very good. While transient ischemic
attacks (TIA) are a warning sign of an impending stroke, TGAs DO
NOT herald a stroke. Generally, TGA is solitary event; however, a
small percentage (~5%) of patients who have had TGA may experience
a recurrent event.
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