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Source publication
Atlantoaxial instability (AAI) occurs as a result of trauma, congenital conditions such as os odontoideum, neoplasm, infection and degenerative connective tissue disorders such as rheumatoid arthritis, genetic conditions such as HOX-D3 and Down syndrome, and heritable connective tissue disorders, emblematic of which are the Ehlers Danlos syndromes...
Context in source publication
Context 1
... the hypermobility disorders, there may be abnormal facet overlap on full neck rotation<20% [30,31] (Figure 3); lateral translation of the facet joints: translation in aggregate >7 mm on coronal imaging as seen on open mouth odontoid views. Open mouth odontoid views are very effective in identifying AAI [32] (Figure 4). ...
Citations
... The authors have adopted an angular displacement of 41 as the pathological threshold. 35,36,41,42,78 In this population, AAI is often undiagnosed for several reasons. 36 Rotary subluxation (Fielding Type 1) requires full neck rotation (80 e90 ) to demonstrate alar ligament incompetence. ...
... Translational displacement greater than 3.5 mm is considered pathological. [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][67][68][69][70][71][72][73][74][75][76][77][78][79] Limitations This study was a retrospective examination of a relatively small cohort of 20 surgical subjects. Three subjects (of 23 total subjects to whom questionnaires were sent) did not return questionnaires; we cannot exclude the possibility that they had less positive outcomes. ...
Background
The proclivity to atlanto-axial instability (AAI) has been widely reported for conditions such as rheumatoid arthritis and Down syndrome. Similarly, we have found a higher-than-expected incidence of AAI in the hereditary connective tissue disorders. We demonstrate a strong association of AAI with manifestations of dysautonomia, in particular syncope and lightheadedness, and make preliminary observations as to the salutary effect of surgical stabilization of the atlanto-axial motion segment.
Methods
In an IRB-approved retrospective study, twenty subjects (16 women, 4 men) with hereditary connective tissue disorders had AAI diagnosed by CT. Subjects underwent realignment (reduction), stabilization and fusion of C1-C2 motion segment. All subjects completed pre-operative and postoperative questionnaires in which they were asked about performance, function and autonomic symptoms, including lightheadedness, pre-syncope, and syncope.
Results
All patients with AAI reported lightheadedness, and 15 had refractory syncope or pre-syncope despite maximal medical management and physical therapy. Postoperatively, subjects reported statistically significant improvement in lightheadedness (p=.003), pre-syncope (p=.006), and syncope (p=.03), and in the frequency (p < 0.05) of other symptoms related to autonomic function, such as nausea, exercise intolerance, palpitations, tremors, heat intolerance, gastroesophageal reflux, and sleep apnea.
Conclusions
This study draws attention to the potential for AAI to present with syncope or pre-syncope that is refractory to medical management, and for surgical stabilization of AAI to lead to improvement of these and other autonomic symptoms.
Atlanto-axial instability (AAI) is common in the connective tissue disorders, such as rheumatoid arthritis, and increasingly recognized in the heritable disorders of Stickler, Loeys-Dietz, Marfan, Morquio, and Ehlers-Danlos (EDS) syndromes, where it typically presents as a rotary subluxation due to incompetence of the alar ligament. This retrospective, IRB-approved study examines 20 subjects with Fielding type 1 rotary subluxation, characterized by anterior subluxation of the facet on one side, with a normal atlanto-dental interval. Subjects diagnosed with a heritable connective tissue disorder, and AAI had failed non-operative treatment and presented with severe headache, neck pain, and characteristic neurological findings. Subjects underwent a modified Goel-Harms posterior C1-C2 screw fixation and fusion without complication. At 15 months, two subjects underwent reoperation following a fall (one) and occipito-atlantal instability (one). Patients reported improvement in the frequency or severity of neck pain (P < 0.001), numbness in the hands and lower extremities (P = 0.001), headaches, pre-syncope, and lightheadedness (all P < 0.01), vertigo and arm weakness (both P = 0.01), and syncope, nausea, joint pain, and exercise tolerance (all P < 0.05). The diagnosis of Fielding type 1 AAI requires directed investigation with dynamic imaging. Alignment and stabilization is associated with improvement of pain, syncopal and near-syncopal episodes, sensorimotor function, and exercise tolerance.
