Imaging Case Book

Journal of Perinatology (2008) 28, 518–519; doi:10.1038/jp.2008.39

Human tail–caudal appendage: tethered cord

T E Herman1 and M J Siegel1

1Department of Radiology, St Louis Children's Hospital, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, MO, USA

Correspondence: Dr T Herman, Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 South Kingshighway Blvd., St Louis, MO 63110, USA. E-mail: hermant@mir.wustl.edu

Received 1 February 2008; Accepted 14 February 2008.

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Case presentation

A 2490g infant girl was born at 39 weeks to a gravida 1 mother after an uncomplicated pregnancy. The child had Apgars of 7 and 8, at 1 and 5min respectively. On physical examination, the infant was found to have a left clubfoot and a 1cm tubular structure in the midline over the sacrum above the buttock. Because of the caudal appendage, a spinal sonogram and magnetic resonance imaging (MRI) (Figures 1, 2 and 3) were performed.

Figure 1.
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Transverse sonogram of dorsal sacral region. The small caudal appendage is seen between the two star markers.

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Figure 2.
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Sagittal midline spinal sonogram showing the conus (arrow) located at the L4/L5 disc space level. The filum terminale (curved arrow) is thickened and contains echogenic fat. Posterior and caudal fat (arrow head) is seen in the caudal appendage.

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Figure 3.
Figure 3 - Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, please contact help@nature.com or the author

(a) Sagittal midline T2-weighted MRI spine. The conus (arrow) is posteriorly located at the L4/L5 disc space level. (b) Sagittal midline T2-weighted MRI, limited view to lumbosacral spine. The fat within the thickened filum terminale (thin arrow) is seen. The small fatty caudal appendage is seen posteriorly (white arrow). MRI, magnetic resonance imaging.

Full figure and legend (170K)

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Denouement and discussion

The sonogram and MRI demonstrate a tethered cord with a lipoma of the filum and a fibro-fatty caudal appendage or human tail posterior. The child has been referred to a neurosurgeon for cord untethering and resection of the caudal appendage and lipoma. Human tail is an anomaly mentioned rarely but intermittently throughout history; cases have been described by both Marco Polo and Christopher Columbus.1 Caudal appendages or human tails were divided by Dao and Netsky into true tails, which contain muscle and are movable, and pseudotails, which do not move. However, this is now considered arbitrary and without clinical significance as both kinds are derived from notocordal remnants and the etiology of both is probably similar.2 Most human tails are tubular structures of mature adipose tissue and fibrous tissue containing normal blood vessels, but usually are neither muscles nor bones. These structures usually occur in the midline or just off midline in the sacro-coccygeal region. They have been reported to vary between 1 and 20cm in length.2 Their etiology is probably related to an abnormal sequence of caudal neurulation,1 and so they have also been called neuroectodermal appendages.3 As of 1997, approximately 59 cases of human tail had been described in the medical literature. Forty-nine percentage of these were associated with spinal dysraphism; 81% of those who had an MRI had a tethered cord. Symptoms related to cord tethering including ambulatory, genitourinary and bowel problems may not occur until the third decade of life in patients with human tails and spinal dysraphism.3

Caudal appendages also occur as typical or frequent manifestations of certain syndromes. Very little imaging or surgical evidence exists about the frequency of tethered cord in these syndromes, which often limits the life expectancy of the patient. These syndromes include Frank-ter Haar syndrome, an autosomal recessive condition with skeletal findings similar to Melnick–Needles syndrome but with distinctive ocular and cardiac findings, Pallister–Killian syndrome (isochromosome 12p), metatropic dysplasia, Kabuki facies syndrome and the probably genetically related Teebi–Shaltout syndrome and Malpuech syndrome (cleft palate and urogenital anomalies).4 Caudal appendages have also been described in craniosynostosis patients associated with FGFR2 (fibroblast growth factor receptor 2) gene mutations.5

Although MRI is the primary modality for spinal imaging in children and adults, spinal sonography is an excellent and useful procedure in small infants, in whom the nonossified posterior elements allow excellent visualization of the spinal cord and thecal sac.6 The conus medullaris, the tapered end of the spinal cord, from which the terminal nerve roots of the cauda equine and the fibroglial filum terminale arise, is well identified sonographically. The conus medullaris should not be located below the L2/L3 vertebral body in a neonate.7 The findings of tethered cord are low position of the conus, posterior position within the thecal sac and a thickened filum, sometimes containing a lipoma. All of these findings were present in the patient reported here. Spinal sonography provides diagnostic accuracy comparable to MRI,6 but MRI provides a much larger field of view and will be required prior to intervention, if the initial spinal sonogram demonstrates tethered cord or other abnormality requiring surgical intervention.

The most important feature of caudal appendages is the possibility of associated spinal dysraphism, which needs to be treated to prevent the development of neurologic symptoms. Therefore, caudal appendages require meticulous imaging and neurological evaluation to insure that appropriate surgery is performed to prevent progressive neurologic symptoms.

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References

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