Abstract
BACKGROUND: Dermoid cysts are benign ectodermal growths that commonly form at cranial sutures. Although benign, resection is often recommended to prevent intracranial extension as the cyst grows. The prognosis after resection is very good, provided a complete resection is possible. OBSERVATIONS: The authors present the case of a 10-month-old male patient with an occipital scalp dermoid cyst with intracranial extension who underwent subtotal resection and later presented with cerebellar extension. LESSONS: Scalp dermoid cysts with intradiploic extension have a significant risk of intracranial extension. Thus, care must be taken to achieve total resection in the first attempt or provide close follow-up before intracranial extension develops. https://thejns.org/doi/10.3171/CASE2548.