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Intraspinal lesions associated with sacrococcygeal dimples

Clinical article

Atsuko Harada, Kenichi Nishiyama, Junichi Yoshimura, Masakazu Sano, and Yukihiko Fujii


Sacrococcygeal dimples in the gluteal fold, also known as coccygeal pits, are observed in 2%–4% of newborns. Sacrococcygeal dimples are not generally considered to be associated with a significant risk of intraspinal anomalies and therefore are not thought to require further radiographic evaluation. Accordingly, the precise incidence and nature of intraspinal lesions that may be associated with sacrococcygeal dimples is unclear. This study was conducted to determine the incidence of intraspinal lesions in patients with intergluteal dimples.


In this study, the authors used MRI to evaluate 103 children who were seen at the Niigata University Medical and Dental Hospital between 2006 and 2011 because of skin abnormalities in the lumbosacral region. Of these children, 14 were excluded as having a subcutaneous fatty mass, and 5 were excluded because the dimples were above the gluteal fold or did not end at the coccyx. The remaining 84 patients were classified according to whether the bottom of the dimple was visible (shallow) or not (deep). The authors also retrospectively examined other skin abnormalities and coexisting anomalies.


The mean age at the time of MRI evaluation was 11.7 months. Magnetic resonance imaging led to the identification of fibrolipoma of the terminal filum (FTF) in 14 cases (16.7%); 6 of these patients also had a low conus. Classified by depth, there were 58 cases with shallow and 26 with deep dimples. Fibrolipoma of the terminal filum was found in significantly more patients with deep dimples (9 [34.6%]) than in those with shallow dimples (5 [8.6%]). The frequency of other congenital anomalies was significantly higher in patients with FTF-associated dimples (6 [42.9%] of 14) than in those with dimples that were not associated with FTF (9 [12.9%] of 70).


Fibrolipoma of the terminal filum was identified by MRI in 16.7% of patients with sacrococcygeal dimples. The risk of FTF increased when the dimples were deeply excavated or were accompanied by congenital anomalies. Magnetic resonance imaging should be performed to identify intraspinal lesions when there are high risk factors for intraspinal abnormalities, or when an ultrasound screening suggests intraspinal abnormalities.