Neuroectodermal appendages: the human tail explained.

The human tail has been intermittently described in the literature since the early 1900s. These have typically been isolated cases presented primarily with intrigue and medical curiosity. Presented here is a series of 6 neuroectodermal appendages with a proposal for their etiological development. The material presented will support a theory of the superficial extension of a dermal sinus tract in the formation of neuroectodermal appendages. These are characterized by: a posterior localization in or near the midline, a tubular or 'tail-like' appearance, extension of the appendage into the spinal canal with attachment to neural elements, variable vertebral defects and occasionally an associated appendage which may appear as either a separate entity (probably due to breakage during development) or in connection with the posterior appendage. The appropriate evaluation and treatment of this entity will also be discussed.