New seizures after 55: the cognitive question is not only about the seizures

Design

prospective cross-sectional cohort with plasma biomarker, cognitive testing and 24-hour EEG sleep scoring; mediation analysis

Population

85 adults with late-onset unexplained epilepsy, onset at 55 or older, no cortical lesion on MRI; mean age 71.3, 49% female

Primary outcome

association of plasma p-tau217 with the extended Preclinical Alzheimer Cognitive Composite (PACC5)

Effect

β −0.66 per unit log p-tau217 (95% CI −1.19 to −0.13, p = 0.0017); refractory epilepsy interaction β −1.49 (−2.94 to −0.05); 24% mediated by spindle-slow oscillation coupling (3-85%)

Eighty-five patients with late-onset unexplained epilepsy — new unprovoked seizures from age 55 with no cortical lesion on MRI — were recruited prospectively for cognitive testing, plasma p-tau217 and 24-hour EEG with manually scored sleep. Mean age was 71.3 years; the average PACC5 cognitive composite was already −0.63 standard deviations.

Higher log-transformed plasma p-tau217 was associated with worse cognition (β −0.66, 95% CI −1.19 to −0.13, p = 0.0017) after adjusting for age, sex and education. Epilepsy severity modified this: patients with both raised p-tau217 and medication-refractory epilepsy did worst (interaction β −1.49, −2.94 to −0.05, p = 0.04). Higher p-tau217 also went with reduced coupling between sleep spindles and slow oscillations, and mediation analysis attributed about 24% of the p-tau217-cognition association to that coupling (95% CI 3-85%).

The practical consequence is about what you do at the first clinic visit. Late-onset epilepsy without a lesion has been treated as a seizure problem; these data support treating it as a presentation that carries a substantial chance of underlying Alzheimer pathology. That changes the counselling, the threshold for cognitive assessment, and possibly the choice of antiseizure medication — several of which have cognitive costs this population can least afford.

• Perform a cognitive assessment at baseline in new-onset epilepsy after 55 without a lesion, not only when a complaint arises
• Choose antiseizure medication with the cognitive profile in mind in this group
• Ask about sleep, and treat what is treatable — the mediation signal points at sleep architecture, not just sleep duration
• Plasma p-tau217 is a research measure here; do not order it routinely on the strength of this
• Refractory seizures plus cognitive decline is the combination that did worst — escalate rather than accept partial control

Why it matters

It reframes unexplained late-onset epilepsy as a potential first presentation of Alzheimer pathology rather than an isolated seizure disorder.

Don't overread it

Cross-sectional associations in 85 patients — this cannot show that the pathology caused the seizures, or that treating sleep would preserve cognition.

The statistics, in plain English

A mediation estimate of 24% with a confidence interval from 3% to 85% is barely distinguishable from 'somewhere between almost nothing and almost everything' — the mechanism is a hypothesis, not a measured quantity. The interaction term for refractory epilepsy has an upper bound of −0.05, meaning it only just excludes no interaction, which in a sample of 85 is what a subgroup finding usually looks like.

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