Pedro Neves Paiva de Castro1, Anna Luiza Bento Dutra2, Héber Samuel Colares Costa1, Caio Tasso Oliveira1, Roberto Queiroz dos Santos1, Dequitier Carvalho Machado1Patient
58 years, male
A 58-year-old female presented with sudden onset of severe anterograde amnesia, disorientation in time and space, anxiety, and agitation for 6 hours. The condition progressively worsened. However, preserved where the language, visuospatial and attention functions, and motor deficits were absent. The medical team requested imaging evaluation.
The patient underwent magnetic resonance imaging (MRI) on admission, which showed no acute abnormalities. However, MRI was repeated after 72 hours, demonstrating a T2/FLAIR-hyperintense focus, with restricted diffusion, in the lateral portion of the left hippocampus, close to the temporal horn - area CA1 (Fig. 1, 2, 3, 4, 5, 6). This hippocampal MRI abnormality is classic for diagnosing transient global amnesia (TGA) within the proper clinical context .
TGA is a neurological disorder of unknown aetiology that usually affects patients aged 50 to 70 years, characterized by acute anterograde amnesia, temporal disorientation, and iterative questioning. The clinical picture usually presents with complete resolution within 24 hours, and other neurological functions are preserved . However, the condition´s annual recurrence varies from 2.9 to 26.3%. Therefore, the diagnosis depends on the clinical picture and the exclusion of alternative diagnoses .
Imaging assessment is necessary initially to rule out other aetiologies that might be the source of the reported symptoms . In addition, other causes, such as stroke, trauma, metabolic conditions, autoimmune and infectious limbic encephalitis, transient epileptic amnesia, migraine headache, can be related to the symptoms and require correlation with MRI and laboratory for exclusion [1,2].
MRI can corroborate the diagnosis demonstrating a typical alteration characterized by restricted diffusion focus in the hippocampal lateral margin, close to the temporal horn. Lesions are usually unilateral but more rarely bilateral and multiple . Occasionally, it may present punctiform focus of hypersignal on T2 and FLAIR, as demonstrated in our case . The condition usually involves the lateral portion of the hippocampus, close to the temporal horn – area CA1 . The sensitivity of MRI progressively increases over time, with greater positivity in 48 to 72 hours and with a higher B value [4,5]. Therefore, if the first MRI is normal and clinical suspicion is high, the medical team may repeat it with thinner slices and a high B value after 48 to 72 hours to identify the abnormality.
The patient presented progressive and spontaneous improvement of the condition following hours, with complete normalization within four days.
Conclusively, MRI is an essential tool in excluding alternative diagnoses in TGA. The demonstration of characteristic findings of restricted diffusion in the hippocampal CA1 area has increased sensitivity within 48 to 72 hours and supports the diagnosis within the appropriate clinical setting. AGT is an emblematic diagnosis in emergency services, and MRI can enable the correct clinical management and accurate determination of the diagnosis.
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