This is a multicenter, randomized, double-blind, placebo-controlled trial evaluating the safety and efficacy of butylphthalide soft capsules for treating cognitive impairment in elderly patients with focal epilepsy. Study Population: 220 elderly patients (60-85 years) with focal epilepsy and mild to moderate cognitive impairment (Montreal Cognitive Assessment score 18-25). Intervention: Participants will be randomly assigned 1:1 to receive either butylphthalide soft capsules (0.2g three times daily) or matching placebo for 48 weeks, while continuing their stable anti-seizure medication regimen. Primary Outcome: Change in Montreal Cognitive Assessment (MoCA) total score from baseline to 48 weeks. Secondary Outcomes: Changes in neuropsychological tests (Trail Making Test, Digit Span, Rey Auditory Verbal Learning Test), seizure control measures, functional status (Activities of Daily Living, Quality of Life in Epilepsy), and exploratory neurobiological markers. This study addresses an important unmet medical need, as current epilepsy treatments focus primarily on seizure control but lack effective interventions for epilepsy-associated cognitive impairment. Butylphthalide, a neuroprotective agent approved for acute ischemic stroke in China, has shown promise in other cognitive disorders and may benefit this patient population through its multiple neuroprotective mechanisms.