Atlanto-occipital dislocation: a modern case series refining management paradigms through integration of CT and MR imaging.

backgroundAtlanto-occipital dislocation (AOD) is a rare but devastating craniocervical injury typically seen in victims of high-energy trauma. Improvements in pre-hospital care have increased the number of patients presenting with AOD, thus early diagnosis and management are critical for survival. Despite this, there are no established diagnostic pathways, and the role of MRI is not well-characterized. This case series aims to highlight CT, MR, and clinical features of patients with AOD with the goal of evaluating and refining current paradigms on the pathology.

methodsA retrospective review was performed of 12 cases of AOD treated at our institution between September 2018 and April 2023. All patients had a history of trauma with MRI evidence of atlanto-occipital ligamentous injury - those without MRI were excluded. Patient demographics, mechanism of injury, clinical presentation, CT and MRI findings, management, neurological outcomes, complications, and mortality were recorded and analyzed.

resultsA total of 12 patients (mean age 51.4 years; 5 females, 7 males) with MR evidence of ligamentous injury were treated at our institution. Average Glasgow Coma Scale (GCS) on presentation was 14. 8 (75%) patients were neuro intact. 5 (42%) of patients had associated TBI, 1 (8.3%) had severe TBI (GCS ≤ 8). 11 (92%) patients had concomitant spinal injuries with 9 (75%) cervical and 3 (27%) thoracic spine fractures. 3 (25%) patients had occipital condyle fractures, 3 (25%) patients had concurrent atlanto-axial dislocation (AAD), 6 (50%) patients had additional C1-C2 injuries, and 2 (17%) patients had sub-axial cervical spine injuries. 5 patients (42%) had increased condyle-C1 interval (CCI) and 3 patients (25%) had increased basion-dental interval (BDI) on CT. No patient had Power's ratio > 1. The most frequently injured structures on MRI were the cruciate and apical ligament complex (83%), anterior atlanto-occipital membrane (AOM) (75%), and the tectorial membrane (58%). 7 (58%) patients underwent non-operative management with a cervical collar, 4 (25%) underwent occipitocervical fusion, and 1 (8.3%) was managed with halo orthosis. Overall survival was 92% and 10/11 (91%) survivors had equivocal or improving neurological exam at last follow-up (average 13.8 months, range 0.9-77.2).

conclusionThis case series on CT and MR evaluation of AOD re-demonstrates the importance of CT criterion in guiding diagnosis of AOD, particularly CCI, in line with existing paradigms. It challenges the current scheme of AOD management by demonstrating the successful non-operative treatment of patients with injury to the tectorial, apical, and cruciate ligaments. This suggests that patients with injury to these ligaments without clear CT findings may exist as a "Grade 1.5" AOD, where decision to treat non-operatively or fuse should be carefully considered based on neurological exam, concomitant injuries, and patient overall health.