Transient global amnesia: Description, Causes and Risk Factors: Abbreviation: TGA. ICD-10: G45.4 Transient global amnesia is characterized by the sudden occurrence of amnesia while lacking other neurological symptoms. Complete remission occurs within 24 hours. The incidence is 5 per 100 000 per year. It usually affects patients between the ages of 40 and 80 years, with an average age of 62 years. It has no male or female preponderance. The underlying cause of transient global amnesia is unknown. Blood flow to specific brain areas that involve memory including the thalamus and/or mesial temporal structures appears to be disrupted transiently during transient global amnesia. There appears to be a link between transient global amnesia and a history of migraines, though the underlying factors that contribute to both conditions are not fully understood. TGA has also been reported in association with cerebral angiography, CNS infection, polycythemia, cardiac valvular disease, exposure to altitude, and heparin-induced thrombocytopenia. In many cases, an episode of transient global amnesia can be traced to a physically or emotionally stressful incident shortly before symptoms began. Among the triggering events commonly reported are: Sudden immersion in cold or hot water.

• Strenuous physical activity.
• Sexual intercourse.
• Medical procedures, such as angiography or endoscopy.
• Acute emotional distress, as might be provoked by bad news, conflict or overwork.
• Blocked arteries.
• Temporal lobe seizures.
• Migraine headaches.

Symptoms: A patient with transient global amnesia: Is acutely confused.

• Is neurologically intact except for absent memory (for example, remains alert, remembers identity, remembers past experiences).
• Asks relevant questions repeatedly because she or he does not remember the answer.
• Is unable to recall the episode once she or he has recovered.
• Usually maintains her or his semantic memory (long-term memory responsible for retaining knowledge about the world, including the meaning of words and objects) and meta memory (the awareness of what one should know).
• Anterograde amnesia must be present.

Diagnosis: In evaluating a patient with suspected transient global amnesia, one must rule out other causes of CNS dysfunction or amnesia such as head injury, epilepsy, brain tumor, CVA, migraine, meningitis, encephalitis, hypoglycemia, medications, drugs of abuse, and psychogenic fugue state. Brain and imaging tests Electroencephalogram (EEG): An EEG records the brain's electrical activity via electrodes affixed to the scalp. People with epilepsy often have changes in their brain waves, even when they are not having a seizure.

• Computerized tomography (CT) scan: Using special X-ray equipment, CT machines obtain images from many different angles and join them together to show cross-sectional images of the brain and skull. CT scans can reveal abnormalities in brain structure, including narrowed, overstretched or broken blood vessels and past strokes.
• Magnetic resonance imaging (MRI): This technique uses a magnetic field and radio waves to create detailed, cross-sectional images of the brain. The MRI machine can combine these slices to produce 3-D images that may be viewed from many different angles.

Other studies, such as CBC, electrolytes, calcium, BUN, creatinine, EKG, or liver function tests, have essentially no utility in the absence of other indications. A toxicology screen may be appropriate in certain situations. Treatment: TGA is generally a benign condition with an excellent prognosis. Overnight hospitalization has been recommended for repeated neurological examinations and observation until the episode has resolved. No specific treatment is recommended. It might be speculated that anti-migraine agents might be useful during an attack, but this is at present not supported by any data. Likewise, low-dose aspirin after the attack is probably reasonable anyway in most patients in the transient global amnesia patient's typical age range. NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.