Neuroectodermal Appendages: The Human Tail Explained

Abstract

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.

Human Tail with Noncontiguous Intraspinal Lipoma and Spinal Cord Tethering:Case Report and Embryologic Discussion

“…The current prevailing concept of the embryology of this malformation is that the tail structure is a form of congenital dermal sinus tract resulting from premature or incomplete dysjunction of the somatic and neuroectoderm during primary neurulation [4, 8]. This theory is consistent with the more common cases of human tail, i.e.…”

“…Human tails have been reported of various lengths (range 1–20 cm) and at various levels of the spine from the lower coccyx to the upper lumbar region [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]. They may be in the midline or off to one side, and rarely is there a history of family members born with a tail.…”

“…It differed from others because the tail tissue was not contiguous with the lipoma, and was separated from it by an intact layer of lumbosacral fascia. With one exception, all other cases reported with MR or CT myelography imaging have described a direct extension of the tail mass through the fascia and dura into the spinal cord, similar to a lipomyelomeningocele or dermal sinus tract [3, 4, 8, 9, 12, 13]. There have been several other cases published prior to the availability of MR where the authors reported no subfascial extension of the tail [5, 6, 10, 14], but only one other case has been reported with MR imaging, in 1988 by Dubrow et al [2].…”

Skin Markers of Occult Spinal Dysraphism in Children

“…By consequence, tails are often not detected before neurologic clinical manifestations. 11,[22][23][24][25]32,33 In our study, a dermal sinus was associated with OSD in 4 of 4 patients (Table 1; Figure 1B and Figure 2A). All 5 patients underwent surgical exploration because dermal sinuses carry a high risk of cerebrospinal fluid infection or intradural abscesses.…”

Teratoma in Human Tail Lipoma

“…The nonvertebrated part projects temporarily and then undergoes regression. The abnormal caudal structures in humans are classified as true tail, pseudotail and caudal appendage, which have been postulated by various authors and are unclear and confusing [1, 11,15,16,17]. However, the true tail can be explained as a failure of complete regression of the nonvertebrate part of the tail at 8 weeks of pregnancy [3, 18].…”