The human tail

A case of a tail in a 2-week-old infant is reported, and findings from a review of 33 previously reported cases of true tails and pseudotails are summarized. The true, or persistent, vestigial tail of humans arises from the most distal remnant of the embryonic tail. It contains adipose and connective tissue, central bundles of striated muscle, blood vessels, and nerves and is covered by skin. Bone, cartilage, notochord, and spinal cord are lacking. The true tail arises by retention of structures found normally in fetal development. It may be as long as 13 cm, can move and contract, and occurs twice as often in males as in females. A true tail is easily removed surgically, without residual effects. It is rarely familial. Pseudotails are varied lesions having in common a lumbosacral protrusion and a superficial resemblance to persistent vestigial tails. The most frequent cause of a pseudotail in a series of ten cases obtained from the literature was an anomalous prolongation of the coccygeal vertebrae. Additional lesions included two lipomas, and one each of teratoma, chondromegaly , glioma, and a thin, elongated parasitic fetus.

Ninety-seven children with lipomyelomeningoceles were operated on at the Hospital for Sick Children between January, 1960, and December, 1982. The most common factor that caused these patients to seek help was the cosmetic effect of the mass on their back. However, 22 patients had urinary incontinence and 15 patients had a deformed or weak leg. Sixty of the 97 patients were female and 37 were male. The patients presented for treatment between 6 days and 18 1/2 years of age with a median age of 7 1/2 months. Fifty-six patients presented before the age of 6 months and 35 of these were perfectly normal at the time of presentation. On the other hand, of the 41 patients who were brought for treatment after the age of 6 months, only 12 were normal prior to surgery. When patients were appropriately treated at an early age, with their spinal cords untethered and their dura securely closed with a dural graft, then they remained unchanged neurologically or even improved. However, when treatment was delayed or not done appropriately then they were left with significant neurological sequelae. Lipomyelomeningoceles are serious lesions which without appropriate therapy can result in gross impairment of neurological function.

Recent publications have endeavoured to differentiate between the true, or vestigial tail, and the pseudotail by clinical and pathological examination, and have indicated the benign nature of the true tail. The true tail arises from the most distal remnant of the embryonic tail, contains adipose, connective, muscle, and nerve tissue, and is covered by skin. Pseudotails represent a variety of lesions having in common a lumbosacral protrusion and a superficial resemblance to vestigial tails. A review of the case reports indicates spina bifida to be the most frequent coexisting anomaly with both. A review of occult spinal dysraphism shows it to be associated with cutaneous signs in more than 50% of instances. Three cases of spinal dysraphism with tail-like cutaneous structures are described and their radiological, operative, and pathological findings presented. The classification of each of the appendages into true tail or pseudotail remains obscure. Although the finding of these three tails was the subject of much curiosity, surgical treatment was clearly designed to adequately deal with the associated dysraphic state. The presence of a tail-like appendage in the lumbosacral region should alert the clinician to the possibility of underlying spinal dysraphism. Preoperative assessment must include a complete neurological history and examination as well as computed tomographic or magnetic resonance imaging.