Atlanto-axial subluxation in Down's syndrome.

Atlanto-axial subluxation, which was causing symptoms in eight patients with Down's syndrome, was treated by operation. In every case various congenital bony anomalies were found. Marked myelopathy was present in four cases of ossiculum terminale, and mild myelopathy in one with anteroposterior spondyloschisis. Successful posterior arthrodesis was performed from C1 to C2 in six cases, and from the occiput to C2 in the other two patients with anteroposterior spondyloschisis. Excellent bony union and an overall improvement in symptoms was achieved. The follow-up period was from one year to five years and six months. Early surgical stabilization is the treatment of choice in those cases of symptomatic atlanto-axial subluxation in Down's syndrome where there are congenital osseous anomalies and generalised ligamentous laxity, and where the spinal cord is at risk.