Epilepsy in patients with focal cortical dysplasia may be associated with autism spectrum disorder

•Patients with epilepsy secondary to FCD tended to be associated with ASD.•Focal cortical dysplasia may be the underlying pathophysiology of both epilepsy and ASD.•Autism spectrum disorder tendency was seen more in FCD I than FCD II. Introduction. Patients with epilepsy associated with focal cortical dysplasia (FCD) may be associated with autism spectrum disorder (ASD). Therefore, the purpose of this study was to compare surgically treated patients with epilepsy secondary to FCD and normal volunteers without epilepsy and to review the neuropathological findings of patients with FCD. This study involved 38 patients with medically intractable focal onset epileptic seizures who underwent epilepsy surgery (Group 1). All patients had epilepsy associated with FCD. These patients and 38 normal volunteers without epilepsy (Group 2) were administered the autism spectrum quotient (AQ) test, and the groups were compared. The 38 patients in Group 1 included 16 females and 22 males (age range 20–60, mean age, 33.0; standard deviation (SD), 11.8 years). The normal volunteers in Group 2 included 22 females and 16 males (age range 20–57, mean age, 30.6 years; SD, 8.8 years). Total AQ scores were significantly higher in Group 1 than Group 2 (p = 0.027). Patients with FCD I showed a higher AQ score than those with FCD II in the AQ test (p ≤ 0.001). Patients with epilepsy secondary to FCD were associated with higher ASD score than normal volunteers. This tendency was seen more strongly in patients with FCD I than FCD II.