Asymptomatic occipito-atlantal instability in Down syndrome (trisomy 21). Report of two cases in children.

Atlanto-Occipital and Atlanto-Axial Instability in Children with Down Syndrome

“…Atlanto-occipital subluxation was first reported in association with Down syndrome in 1981 18 and, in contrast with that seen in trauma, is almost always posterior. Other groups of patients have been described by El-Khoury, 19 Brooke, 5 Tredwell, 7 Stein 4 and most recently by Parfenchuck. 6 In 1991, Stein presented five new patients and reviewed nine others previously presented in the literature.…”

“…There is negligible horizontal translation or rotation. 5 15 assessed the atlanto-occipital relationship by constructing a line tangential to the cranial surface of the clivus which, when extended, barely touched the posterior aspect of the odontoid tip, the relationship remaining stable in flexion and extension. With posterior AOI, the line moves posterior to the odontoid.…”

Exploration for reliable radiographic assessment method for hinge-like hypermobility at atlanto-occipital joint

“…O-C1 instability can be also associated with rheumatoid arthritis (RA) [16,20] ankylosing spondylitis (AS) [8,22], Down syndrome [3,11,23] or infectious diseases [26], as mentioned. Future study using the radiographic method we proposed in the current study may also contribute to clarify the underlying mechanism of these diseases.…”

“…Non-traumatic O-C1 instability [3,8,14,16,20,22,23,26], which is less common, is usually associated with rheumatoid arthritis (RA) [16,20] or ankylosing spondylitis (AS) [8,22]. It can also be associated with Down syndrome [3,11,23] or infectious diseases [26].…”

C2/3 Instability in a Child with Down’s Syndrome

“…Few cases of symptomatic AAI have been reported [11,12]. In light of the low incidence of these lesions becoming symptomatic, many authors are hesitant to consider surgical stabilization [9,[13][14][15][16]. Unfortunately, neurological injury that may have been prevented with aggressive stabilization has occasionally resulted [13].…”