ReviewTransient Global Amnesia
Section snippets
Basic Concepts on Memory
Memory is the brain function that allows us to encode, store, and retrieve information. It can be divided into 3 different types: immediate or working memory, short-term memory, and long-term memory.13 Immediate memory refers to the information that can be retained for a short period of time without active involvement of the memory pathways. It can be simply tested by asking the patient to repeat a 7-digit number. This type of memory can be affected by attention or language impairment or by a
Epidemiologic Profile
Transient global amnesia affects predominantly middle-aged or elderly patients. Its annual incidence has been reported to be 3.4 to 10.4 per 100,000 people.6, 14, 15, 16 If we narrow it to the population older than 50 years, the incidence increases to 23.5 per 100,000 per year.17 It is more common in individuals with migraine.18, 19
Clinical Presentation and Diagnostic Criteria
Transient global amnesia is a clinical syndrome characterized by the sudden onset of anterograde amnesia, accompanied by repetitive questioning, sometimes with a retrograde component, lasting up to 24 hours, and without compromise of other neurologic functions. Typically, TGA is encountered in patients aged 50 to 70 years who are brought to medical attention because they are noticed to have acutely lost the ability to understand their situation and grasp their surroundings. Patients repeatedly
Additional Investigations
When making a diagnosis of TGA, the question is whether to pursue additional testing. The main value of additional testing in TGA is to exclude alternative diagnoses.
Brain imaging is often considered by clinicians who suspect TGA, but findings from head computed tomography are typically normal, and evidence on the utility of brain magnetic resonance imaging (MRI) is conflicting. Case series and studies comparing patients with TGA and those with transient ischemic attack (TIA) or control cohorts
Differential Diagnosis
The differential diagnosis of TGA includes TIA or stroke in the posterior cerebral circulation, focal seizures (including TEA), postictal state, dissociative disorders or psychogenic amnesia, posttraumatic amnesia, and metabolic disorders such as hypoglycemia. The differentiating features of some of these alternative diagnoses are reviewed on Table 2. It is particularly important to remember that isolated memory loss is a very infrequent presentation of acute ischemic stroke. Meanwhile,
Pathophysiologic Mechanisms
The debate regarding the pathogenesis of TGA has focused mainly on 3 distinct mechanisms: vascular (due to venous flow disturbances or focal arterial ischemia), epileptic, and migraine related. It has also been reported that the CA1 subfield of the hippocampal cornu ammonis (which is the part of the hippocampus most affected by TGA) would have a particular vulnerability to metabolic stress caused by hypoxemia, B-amyloid–induced neurotoxicity, and ischemia; the degree of this local
Treatment
There is no specific treatment for TGA. Episodes are self-limited, and improvement is noted within 24 hours without any intervention. It seems prudent to avoid any activity that could raise intrathoracic venous pressure until the amnesia is resolved. When alternative diagnoses are suspected (eg, seizures or ischemic stroke/TIA), focused investigations should be pursued to determine whether acute treatment or secondary prevention for these disorders might be indicated.
Long-term Outcome in Patients With TGA
Transient global amnesia is generally considered a benign condition. However, there are few studies on the long-term outcome of patients who have experienced TGA regarding the risk of recurrence and the incidence of cognitive decline, stroke, and seizures over time.
Reported recurrence rates for TGA have varied considerably (between 2.9% and 23.8%) among different studies (Table 3). The reason for such a spread in the rate of recurrences found in different studies is unclear. There is no
Conclusion
Transient global amnesia is not a rare condition. It typically presents in patients aged 50 to 70 years, and it is frequently preceded by a Valsalva maneuver. Diagnosis is clinical, and its semiological hallmark is the inability to form new memories, although some retrograde amnesia can occasionally be present. Noncognitive functions are always preserved, and the presence of aphasia, hemiparesis, sensory loss, or incoordination indicates a different diagnosis and demands additional evaluation.
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