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Klippel-Feil syndrome is an uncommon alteration (1:40 000 births), mainly affecting the cervical spine.1 The classic clinical triad described by Klippel and Feil in 1912—short neck, low dorsal hairline, and restricted neck mobility—is the result of the fusion of a variable number of cervical vertebrae, sometimes reducing their number, and cervical spina bifida.2 Extraosseus changes,3 hemivertebra, vertebral body clefts, and thoracolumbar abnormalities,4 are sometimes seen.
In a prehispanic ossuary containing remains of at least 121 subjects in the island of El Hierro (Canary Islands), we noted:
- A C2-3 block, with the two vertebrae fused both by the vertebral bodies and the medial ends of the archs, well preserved right intervertebral foramina, and foramina transversaria (fig 1), and a normal medullar canal. The body of the third vertebra shows intense degenerative signs.
- A C5-6 block, consisting of two vertebrae with intense degenerative changes fused both by the vertebral bodies and the medial part of the archs. Both cervical blocks seem to belong to the same subject.
- A well preserved atlas bone, with an incomplete anterior part of the left arch, with sharp, fine proximal, and distal ends (fig 2A), supporting an underlying developmental defect rather than an acquired one.
- A left hemiatlas (fig 2B); although it is possible that the right body of the bone was partially fused with the left one (and was not recovered in the archaeological excavation), the posterior end of the arch was neither fractured nor fused to any other bony structure, thus pointing to a developmental defect.
Fusion of C2 and C3 (and C5-6), hypoplasia of the arch of the atlas,5 and complete bipartition of the atlas6 constitute distinctive features of Klippel-Feil disease. Thus the subject with the fused C2-3 and C5-6 blocks and the hemiatlas was probably affected by this disease. Possibly, the second atlas belongs to another subject with the same disease, though this possibility should be cautiously admitted. The two atlas bones show different developmental abnormalities. In the newborn, the ossification of the cartilaginous anterior and posterior archs of the atlas takes place progressively from the already ossified lateral masses. Often, especially in the anterior arch, secondary ossification centre(s) appear.7 In our case it seems that hypoplastic development of the anterior left arch took place. Because the hypoplastic part of the arch is in its middle part, probably, a second ossification centre was present, but ossification was never completed; in this sense, it is similar to the case described by Chigira et al,5 which also showed fusion of C5-6.
The “hemiatlas” perhaps is really an atlas with a midline cleft and a lost half, though the posterior arch does not reach the midline, so it never became fused with the right half of the bone. A secondary posterior ossification centre sometimes appears during the first years of life. In this case, it was absent, in contrast with the anterior secondary ossification centre which was surely present in the former case.
Perhaps familial links existed between the two subjects. Klippel- Feil syndrome is a heterogeneous disorder, showing different alterations in different families.8 The simultaneous finding of different developmental abnormalities of the atlas in our two cases—assuming that the second one truly represents a case of Klippel-Feil—may either reflect an unusually high prevalence of this entity in the prehispanic population of El Hierro, or may also indicate that even in the same family clinical expression of the Klippel-Feil syndrome is variable.
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