To analyze cases of seizure exacerbation following the addition of lacosamide in epilepsy patients. Methods: Four cases with worsened seizures after lacosamide treatment were collected from the Video-EEG Monitoring Center at the Department of Neurology, Xijing Hospital affiliated to Air Force Medical University. Their clinical and electrophysiological characteristics were systematically analyzed. Results: The patients (3 males) had seizure onset ages ranging from 8 to 38 years. All exhibited focal epilepsy treated surgically: two underwent resection for frontal lobe gliomas, one received decompressive craniectomy post-traumatic brain injury, and another underwent multiple resective surgeries for drug-resistant epilepsy. When starting lacosamide therapy at ages 24～57 years postoperatively, all developed aggravated focal seizures manifesting as rightward head/eye deviation, facial twitching, aphasia, or contralateral facial paresthesia. Conclusion: Lacosamide may exacerbate preexisting focal seizures in patients with prior craniotomy histories. Further studies are needed to elucidate the mechanisms underlying its pro-seizure effects.