Interictal spiking in adult newly-diagnosed focal epilepsy of unknown cause: The effect of age

• Elderly subjects with recent-onset, non-symptomatic focal epilepsy show a significant propensity to express interictal epileptiform abnormalities mainly during NREM 3–4 sleep.
• Age per se seems to affect this peculiar spiking pattern.
• This observation might be useful when choosing EEG recording procedures in the presence of suspected recent-onset focal epileptic seizures.

ObjectiveTo assess the yield of interictal EEG spiking in standard and whole-night sleep EEGs in elderly subjects with recent-onset focal seizures compared to younger patients.MethodsDetection of interictal epileptiform abnormalities (IEAs) and rating of mean spike index (number of interictal discharges/minute) values for different sleep stages (NREM stages 1–2 and 3–4 and REM sleep) in standard EEG (S-EEG) and 24-h ambulatory EEG (A-EEG) at first referral in three groups of thirty consecutive outpatients [aged 20–39 (young), 40–59 (adults) and ⩾60 years (elderly)], retrospectively selected according to a subsequent diagnosis of focal epilepsy of unknown cause, no sleep disorders or drugs or comorbidities affecting sleep and EEG.ResultsElderly subjects showed a lower rate of IEAs on S-EEG (p < 0.01) but a higher propensity for spiking during deep NREM sleep, 11/30 showing IEAs exclusively during stages 3–4. Mean spike index showed a significant increase in IEAs between sleep stages 1–2 and 3–4 in the elderly subjects (p < 0.001).ConclusionsA significant association emerged between IEAs during deep sleep and age (p < 0.001).SignificanceEEG recordings covering deep NREM sleep should be recommended when IEAs detection is needed to support a diagnosis of epilepsy in elderly subjects.