Relating hippocampal circuitry to function: recall of memory sequences by reciprocal dentate–CA3 interactions. The anatomy of memory: an interactive overview of the parahippocampal-hippocampal network. The episodic memory system: neurocircuitry and disorders. Hippocampal-anterior thalamic pathways for memory: uncovering a network of direct and indirect actions. The hippocampus and memory: insights from spatial processing. We describe results from imaging and epidemiological studies that have shed light on the functional anatomy and pathophysiological mechanisms underlying these conditions.īird, C. Here, we summarize clinically relevant aspects of transient amnesic syndromes, giving practical recommendations for diagnosis and patient management. Moreover, TEA carries a risk of persistent memory impairment that can be mistaken for dementia. ![]() Some cases of transient amnesia are attributable to focal seizure activity and are termed TEA, which has a clinical presentation similar to that of TGA, but can be distinguished from the latter by the brevity and frequency of amnesic attacks. TGA is characterized by the sudden onset of a profound anterograde and retrograde amnesia that lasts for up to 24 h, with neuroimaging after an acute TGA event showing transient perturbation of specific hippocampal circuits that are involved in memory processing. Critical clinical distinctions, such as between transient global amnesia (TGA) and transient epileptic amnesia (TEA), as well as important clues to the underlying pathophysiology, have recently been revealed. Diagnosis of such syndromes can be challenging, and their causes have been debated for over 50 years. doi:10.Transient amnesic syndromes are striking clinical phenomena that are commonly encountered by physicians in acute medical settings. Acute-Onset Amnesia: Transient Global Amnesia and Other Causes. What Does Transient Global Amnesia Really Mean? Review of the Literature and Thorough Study of 142 Cases. Quinette P, Guillery-Girard B, Dayan J et al. Transient Global Amnesia: Diffusion-Weighted Imaging Lesions and Cerebrovascular Disease. Optimal Diffusion-Weighted Imaging Protocol for Lesion Detection in Transient Global Amnesia. High-Resolution Diffusion-Weighted Imaging Increases Lesion Detectability in Patients with Transient Global Amnesia. Post-traumatic amnesia, has a history of trauma 6 Psychogenic amnesia, more-so affects semantic memory compared to episodic memory, while TGA is the opposite 6ĭrug-related amnesia, typically has features of encephalopathy 6 Transient epileptic amnesia, typically presents upon waking while TGA does not 6 hippocampal ischemic), typically exists with other neurological deficits 6 The condition rarely recurs in ~5% of patients 5,6. These changes generally appear after symptom resolution, and the highest rate of detection is approximately 2 days after symptom onset 6. These lesions can be bilateral and even multifocal 2-4. Prospective and retrospective studies based on a small number of transient global amnesia patients can detect small punctate regions of abnormally restricted diffusion on DWI/ADC sequences in the CA1 area of the hippocampus (lateral edge of the hippocampal gyrus abutting the temporal horn). Radiographic featuresĬT brain and conventional sequences of MRI brain may show no abnormalities, especially while the patient is symptomatic. epileptic phenomena, stroke, focal ischemia) have been proposed with no consensus on the exact mechanism 1,6. Most cases show complete resolution of symptoms within a few hours from onset of symptoms 6. Episodic memories are more-so affected than semantic memories 6. ![]() AssociationsĪnterograde and partial retrograde amnesia lasting less than 24 hours without any other neurological or congestive symptoms 6. Transient global amnesia is most common in the 50-70 year age range ref.
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