Our retrospective analysis of 25 cases from two Level 1 Trauma Centers presents the largest case series to date of odontoid fractures with concurrent cardiac arrest and ROSC after CPR. Despite successful pre-hospital resuscitation, the mortality rate was 92% after mean of 2.0 ± 1.4) days.

The global incidence of out-of-hospital cardiac arrest is estimated at 55 cases per 100,000 person-years, with survival rates varying widely due to differences in emergency medical response and public health infrastructure. Typically, shorter downtimes, such as the median of 5 min in our cohort, result in much higher survival rates of up to 60% when the downtime is 0–10 min, and still in the double digits even when exceeding 20 min, as shown by larger series [33, 34].

Odontoid fractures significantly elevate mortality risks due to various factors, including neurological damage leading to respiratory arrest and complications from immobilization, such as cardiovascular, respiratory, and septic issues, resulting in nearly 15% mortality within 30 days [35, 36]. Our findings reveal that despite rapid intervention and advanced care, the prognosis for patients suffering from odontoid fractures with concurrent cardiac arrest remains grim: with survival and consciousness recovery rates below 10%, our study echoes observations from earlier case reports that similarly document minimal survival in such scenarios, with only two cases reporting survival [29, 30]. This underscores the severe impact of the combined scenario of cardiac arrest with odontoid fracture and spinal cord injury, indicating a compounded risk that significantly lowers survival prospects. Conversely, another study analyzing out-of-hospital cardiac arrests found that the optimal cut-off for favorable neurological outcomes is 12 min of CPR, which is shorter than the mean duration reported in our cohort [37]. This suggests that considerable damage has already occurred by the time ROSC is achieved.

As highlighted in earlier reports, initial cardiac arrests can obscure severe spinal injuries [27]. Odontoid injuries are primarily of two types: one involves potentially fatal complete atlanto-axial (C1-C2) displacement, and the other features slight displacement with complete rupture of the capsular structure, leading to significant instability [28]. Recognizing the latter is crucial for initiating immobilization to prevent further neurological damage.

The atlanto-axial vertebrae region has a notably wide margin of safety within the spinal canal, allowing substantial fracture displacement without immediate contact between the odontoid fragment or the posterior ring of the first cervical vertebra and the spinal cord [38]. Acute and severe neurological impairments, such as tetraplegia accompanied by cardiac arrest, often indicate high-energy trauma involving at least temporary high-grade dislocation. However, even low-velocity accidents, like falls from standing height with whiplash mechanisms, can lead to odontoid fractures with neurological impairment and cardiac arrest [39]. In our series, one patient (4%) and two out of seven cases (29%) in our systematic review experienced such trauma [10, 30]. We support the hypothesis that in these low-energy scenarios, particularly among elderly patients with reduced cervical spine flexibility, the odontoid process can endure high localized forces. This can result in transient dislocation and spinal cord damage despite the low-energy nature of the incident [35, 40]. It is crucial to consider this mechanism in cases of cardiac arrests following falls, even in seemingly low-energy accidents, to initiate further diagnostics and spinal immobilization promptly.

Pathophysiologically, neurogenic shock induced by autonomic dysfunction from high cervical spinal cord injuries typically leads to catastrophic outcomes [41]. This condition primarily disrupts preganglionic sympathetic interneurons that originate in the hypothalamus and exit the spinal cord between T1 and T6. The resultant shift towards parasympathetic dominance triggers severe bradyarrhythmias and atrioventricular blocks [10]. Our case series, which exclusively involved patients with cardiac arrest after odontoid fractures, appears to corroborate this pathophysiology. It is further supported by MRI findings showing severe signs of myelopathy in all patients, consistent with other reported cases [10, 30, 42]. Typically, neurological symptoms develop with 7–9 mm of lateral fracture displacement instability [35]. However, in our series, the mean displacement at the time of imaging was less, suggesting that severe dislocation may have occurred during the accident, evidenced by the high rates of myelopathy. Caregivers should consider the connection between odontoid fractures and cardiac arrest, even when trauma CT shows low dislocation.

Early suspicion of odontoid fractures, particularly in the elderly, is critical due to their nonspecific presentation and rapid deterioration, as demonstrated by a case where cardiac arrest occurred in the hospital [31]. These findings underscore the necessity of immediate and controlled spinal immobilization in unconscious patients, regardless of the trauma mechanism. Additionally, they highlight the importance of prompt CT imaging and the early involvement of neurosurgery, orthopedics, and critical care specialists to effectively coordinate care in suspected spinal trauma cases.

The use of MRI in previous case series has been inconsistent, with no clear guidelines on when to perform it. At our centers, the consensus is to conduct an MRI when spinal trauma is indicated on CT and the patient’s neurological status cannot be assessed, typically due to deep sedation, as was the case for all 25 patients in this series. This MRI is scheduled at an appropriate time when more critical issues have been stabilized. This approach is consistent with recommendations from other authors [43]. Additionally, an MRI is considered particularly prudent if neurological injury or ligamentous damage is suspected based on imaging findings or clinical history. The validity of this protocol is underscored by the 100% presence of myelopathy in our cases, indicating a high pretest probability that further supports the utility of this approach.

In treating odontoid fractures, the decision between surgical and conservative approaches depends on specific clinical criteria and patient characteristics: Surgical options, including anterior and posterior approaches, provide high rates of fracture stability and fracture union; notably, posterior instrumented fusion of C1-C2 also minimize complications such as dysphagia associated with anterior methods [4]. Conservative approaches are recommended for patients with less severe injuries or significant surgical risks [44]. In our series, two patients underwent successful screw fixation for a type II Anderson d’Alonzo fracture with 3 mm displacement and a type III fracture with 4 mm displacement, both without dislocation, but high risk of instability and non-union. Both had shown neurological improvement prior to surgery. This was a prerequisite for the chosen treatment.

Our findings have important clinical implications for managing patients with odontoid fractures associated with cardiac arrest, which can be summarized as follows:

First, in cases of trauma-associated cardiac arrest, clinicians should maintain a high index of suspicion for potential high cervical spinal cord injuries. Immediate spinal immobilization and prompt imaging with CT and MRI are essential to prevent further injury and to assess the extent of damage.

Regarding surgical intervention, there are two main pathways:

1.

No Persistent Spinal Cord Compression: If imaging confirms an odontoid fracture with myelopathy but without ongoing spinal cord compression, immediate surgical decompression or stabilization may not be necessary. The primary focus should remain on effective cardiopulmonary resuscitation and stabilization of vital functions. For patients who achieve cardiopulmonary stabilization and show neurological improvement, timely surgical stabilization can be considered during hospitalization to prevent future instability or deformity.

2.

Persistent Spinal Cord Compression: Conversely, if initial imaging reveals myelopathy with persistent spinal cord compression, immediate surgical intervention with spinal decompression and stabilization should be contemplated to offer the patient a chance for neurological recovery.

This patient-specific decision-making approach emphasizes the importance of prioritizing life-saving measures while tailoring surgical interventions based on individual neurological and physiological status.

Beyond focusing solely on odontoid fractures associated with cardiac arrest, comparing our findings with studies on cardiac arrest following severe neurological injuries like traumatic brain injury (TBI) offers further context. These cohorts consistently report low but notable survival rates and emphasize the critical importance of prompt resuscitation and continuous neurological evaluation to guide treatment decisions [45,46,47]. In TBI cases, interventions may include intracranial pressure monitoring or surgical craniectomy for decompression [47]. Similarly, for odontoid fractures with cardiac arrest, the initial focus should be on resuscitation and stabilization, with immediate surgical interventions, such as decompression and stabilization, reserved for rare instances of persistent myelocompression. Subsequent management should be tailored based on neurological assessments, considering surgical stabilization when there is potential for general and neurological improvement. Our findings align with this broader understanding, reinforcing that while survival rates are low, they are not zero. A systematic, patient-centered approach that prioritizes immediate life-saving measures and carefully evaluates the potential benefits of surgical interventions is essential in managing these complex cases.

The limitations of this study stem primarily from its design; it is retrospective in nature and includes a relatively small sample size coupled with a brief follow-up period. These factors significantly restrict the generalizability of our findings. However, it is worth noting that despite these limitations, this study represents the largest series to date addressing this rare and severe scenario as per our systematic literature review. The small sample size also prevented the execution of robust statistical analyses, highlighting the need for larger trials. Future research should aim to employ larger sample sizes to facilitate detailed statistical evaluations, such as linear regression, to identify factors associated with the outcomes studied.