The hair collar sign.

We report on two children with congenital scalp lesions which were surrounded by a ring of dark hair known as a hair collar. A review of previously reported patients with hair collars revealed that most of the scalp lesions were single and located at the vertex or parietal areas. They were most commonly composed of heterotopic neural tissue. We found a significant risk of associated skull defects, direct connections to the central nervous system (CNS), and brain and cerebrovascular anomalies in these patients. Careful clinical evaluation and MRI of the brain are indicated prior to biopsy or excision of these scalp lesions.