Transient epileptic amnesia: a retrospective cohort study of 127 cases, including CSF amyloid and tau features

Transient epileptic amnesia (TEA) is a late-onset epilepsy syndrome encompassing transient iterative amnesias and interictal cognitive impairment, two features that overlap with incipient neurodegenerative dementias. We, therefore, examined the yield of CSF amyloid and tau biomarkers in TEA.

In this retrospective study, 127 TEA patients with unremarkable imaging findings were divided into 2 groups, namely, CSF (n = 71) and no-CSF (n = 56). Both were compared for demographics; medical history; baseline neurological, cognitive, and behavioral features; baseline mesial temporal lobe atrophy; and cognitive follow-up at a median of 13 months. CSF samples were examined for amyloid β-42 peptide as well as phospho-tau and total-tau levels.

At baseline, the CSF-TEA group had significantly (p < 0.01) more frequent mild parkinsonism (42.9% vs. 20%) and cognitive concerns (31% vs. 10.7%), a more blunted sense of smell (34.3% vs. 9.4%), a lower baseline MMSE score (27 vs. 28.9), a more frequent amnestic mild cognitive impairment profile (69% vs. 42.6%), and more atrophic hippocampal changes. At follow-up, the CSF-TEA group had significantly (p < 0.01) lower MMSE scores (27.8 vs. 28.9). CSF analyses revealed amyloid and/or tau changes in 27 patients (38%), including an Alzheimer's disease (AD) profile in 17 (24%).

This study shows a good diagnostic value of CSF sampling in a specific population of TEA with characteristics suggestive of incipient degenerative diseases (i.e., red flags). It argues for TEA being the inaugurating feature in some cases of AD. More broadly, our results suggest an etiological heterogeneity in TEA.