Abstract
Background/Objectives Transient global amnesia (TGA), a term coined by Charles Miller Fisher and Adams in 1958, is characterised by the acute onset of anterograde (and variably retrograde) amnesia with preservation of other cognitive domains, lasting a mean duration of 6 hours and up to 24 hours. Repetitive questioning almost always occurs. MRI may reveal punctate diffusion restricting lesions either unilaterally or bilaterally in the cornu ammonis 1 (CA1) portion of the hippocampus.
However here the authors report 4 cases in which ‘typical’ imaging features of TGA appeared in patients with transient amnestic episodes due to focal seizures.
Results A review of the literature reveals only one case of focal seizures with typical imaging features of TGA. However, a recent multicentre review reported 43 patients with ‘atypical TGA’ (which included non-amnestic and asymptomatic presentations) associated with typical punctate diffusion restriction lesions in the hippocampus. In addition, transient diffusion restriction may occur after focal seizures, and although this is mostly seen after status epilepticus or a series of seizures, it was seen in 3% of patients after a single focal seizure who underwent MRI scanning within the first 24 hours after seizure onset.
Conclusions The appearance of a punctate diffusion restricting focus in the hippocampus is not specific for TGA and especially when there are atypical features, such as short duration or recurrence, a focal impaired awareness seizure should be considered.
