Cranioplasty for a Cranial Bone Defect Associated with Giant Congenital Melanocytic Nevus

Giant congenital melanocytic nevi of the scalp are rare congenital melanocytic lesions associated with cranial bone defects. Cranioplasty can be technically challenging, particularly in the absence of normal subcutaneous tissues and dissection planes. However, few surgical reports have focused on these technical difficulties. A girl (age: 6 years and 5 months) with a congenital pigmented scalp lesion, slightly to the right of the midline, underwent postnatal cranial computed tomography scanning that revealed a large cranial bone defect extending from the frontal to parietal bones. Histopathological examination of a biopsy specimen revealed a blue nevus. Considering the patient's normal neurodevelopment and the non-progression of the bone defect during follow-up, elective cranioplasty was planned before school admission. Cranioplasty using a custom-made artificial bone was performed in collaboration with plastic surgeons. Intraoperative findings revealed the absence of normal subcutaneous tissue and the subgaleal dissection plane. The dermis directly adhered to the cranial bone and dura mater, and partially to arachnoid-like tissue. Sharp dissection under careful tension was undertaken with minimal dural injury to preserve scalp viability. Postoperatively, subcutaneous fluid collection and minor scalp necrosis occurred and were successfully managed with local wound care and continuous swimming-cap compression. Congenital melanocytic scalp lesions may be associated with cranial bone defects and loss of normal tissue planes, with severe adhesions between the scalp and intracranial structures. Surgeons should consider these anatomical abnormalities when planning cranioplasty and customize surgical strategies to preserve scalp viability while minimizing intracranial complications.