Ossiculum terminale—an anomaly of the odontoid process

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IT has long been recognized that atlantoaxial dislocations may result from incompetence of the odontoid process. The most common anomaly of the odontoid process is the ossiculum terminale.1 It is characterized by failure of fusion of the apical segment of the dens to its base, which is joined to the body of the second cervical vertebra. The size of the base may be quite small, or it may appear almost normal; the apical segment may also vary in size. The term ossiculum terminale has been erroneously used to describe many varieties of anomalies of the odontoid process, but it should be used only to describe a failure of fusion of the apical segment and the base with the body of the axis, a condition that is extremely rare.2

Bizarre clinical syndromes are caused by atlantoaxial dislocations secondary to incompetence of the odontoid process.3–5 Upper cervical cord compression may result in neurologic changes that are often progressive. Associated symptoms are pain and stiffness in the neck, headache, transitory quadriparesis, and progressive hemiparesis. Our report is concerned with an anomaly of the odontoid process together with atlantoaxial dislocation and cervical cord compression.

Report of a case

On April 17, 1967, a 10-year-old boy was examined at the Cleveland Clinic because of the chief symptom of a “catch” in the neck. In June 1965, his parents noted the onset of frequent episodes of his slumping to the ground in great pain after throwing a ball. He was examined by a chiropractor, and subsequently . . .



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