Case 254: Posttraumatic Migrating Fat Embolus Causing Fat Emboli Syndrome

Do you know the diagnostic importance of susceptibility-weighted imaging on MRI for patients with cerebral fat embolism?

Key Clinical Message

If you suspect cerebral fat embolism (CFE) of the diagnosis for the patients who present with impaired consciousness and hypoxia following a fracture, susceptibility-weighted imaging should be included of head MRI imaging.

Abstract

We report a case of cerebral fat embolism (CFE) that could be identified only by susceptibility-weighted imaging (SWI). Collection and analysis of previous case reports of CFE revealed utilization of SWI in less than one third of suspected cases, despite its known diagnostic ability for CFE.

Multisystemic involvement of post-traumatic fat embolism at a Pediatric Trauma Center: a clinical series and literature review

Post-traumatic fat embolism syndrome (FES) is a severe complication consequent to bone fractures. The authors describe its clinical features and management in a population of teenagers by detailing demographics, organ involvement, laboratory, and imaging findings, as well as outcome. Moreover, a systematic review of pediatric published case reports of post-traumatic FES is provided. First, a series of eight episodes of post-traumatic FES that occurred in seven patients (median age 16.0 years, IQR 16.0-17.5) admitted to a pediatric intensive care unit (PICU) in an 8-year period was analyzed through a retrospective chart review. Secondly, a systematic research was performed on PUBMED database. Trauma patients ≤ 18 years without comorbidities in a 20-year period (2002-2022) were included in the review. Neurological impairment was present in five out of seven patients, and a patent foramen ovale was found in four cases. Hemodynamic instability requiring vasoactive drugs was recorded in four patients. A severe form of acute respiratory distress syndrome (ARDS) occurred in five cases, with the evidence of hemorrhagic alveolitis in three of them. In the literature review, eighteen cases were examined. Most cases refer to adolescents (median age 17.0 years). More than half of patients experienced two or more long bone fractures (median: 2 fractures). Both respiratory and neurological impairment were common (77.8% and 83.3%, respectively). 88.9% of patients underwent invasive mechanical ventilation and 33.3% of them required vasoactive drugs support. Neurological sequelae were reported in 22.2% of patients.

CONCLUSION

Post-traumatic FES is an uncommon multi-faceted condition even in pediatric trauma patients, requiring a high level of suspicion. Prognosis of patients who receive prompt support in an intensive care setting is generally favorable.

WHAT IS KNOWN

•Post-traumatic fat embolism syndrome is a severe condition complicating long bone or pelvic fractures. •Little is known about clinical features and management in pediatric age.

WHAT IS NEW

•Post-traumatic fat embolism syndrome can cause multiple organ failure, often requiring an intensive care management. •Prompt supportive care contributes to a favorable prognosis.

Single-case metanalysis of fat embolism syndrome

BACKGROUND

Only one large series has been reported on fat embolism syndrome (FES), a condition caused by fat globules release into the circulation, primarily as consequence of bone fracture. Thus, more data on clinical features, therapies, and prognosis are needed.

METHODS AND RESULTS

The study screened 1090 manuscripts in PubMed and Web of Science on cases of FES published from June 2010 to June 2020. The authors identified 124 studies and included in the pooled-analysis 135 patients (>14 years), plus one additional unpublished case managed in Tongji hospital. All had confirmed diagnosis of FES with complete clinical data. The median age at presentation was 39 years, and 82 (61.8%) were men. FES was predominantly associated with bone fractures (78, 57.4%), particularly femur fracture (59, 43.4%). The most common clinical finding at the onset was respiratory abnormalities in 34.6% of all clinical presentations. Therapies included respiratory supportive care in 127 (93.4%) patients, application of corticosteroids in 22 (16.2%) and anticoagulant in 5 (3.7%) cases. Overall mortality was 30.2% (N = 41), and logistic regression analysis showed that corticosteroid therapy was significantly associated with reduced mortality with an OR of 0.143 (95%CI 0.029-0.711), while age ≥ 65 years and non-orthopedic conditions were significantly associated with increased mortality with an OR of 4.816 (95%CI 1.638-14.160) and 4.785 (95%CI 1.019-22.474).

CONCLUSIONS

FES has been associated with a larger mortality rate than previously observed, although publication bias can have led to overestimation of mortality. Finally, a potential protective effect of corticosteroid therapy has been suggested by the current analysis.

Adolescent Fat Embolism Syndrome after Closed Tibial Shaft Fracture: Treatment with Emergent External Fixation

Case

An adolescent male developed fat embolism syndrome 24 hours after sustaining a closed right tibial shaft fracture in a football game. The patient was treated with emergent external fixator application due to declining respiratory and mental status and experienced swift recovery after stabilization. He was treated with an intramedullary nail within 1 week of injury.

Conclusion

Pediatric fat embolism syndrome is uncommon, and a high index of suspicion is required to facilitate appropriate orthopaedic involvement. External fixation can be performed emergently with minimal fracture manipulation. Rapid provisional fixation appears to have facilitated recovery in this example.

Microbleeds show a characteristic distribution in cerebral fat embolism

This systematic review aims to test the hypothesis that microbleeds detected by MRI are common and show a characteristic pattern in cerebral fat embolism (CFE). Eighty-four papers involving 140 CFE patients were eligible for this review based on a systematic literature search up to 31 January 2020. An additional case was added from hospital records. Patient data were individually scrutinised to extract epidemiological, clinical and imaging variables. Characteristic CFE microbleed pattern resembling a "walnut kernel" was defined as punctuate hypointensities of monotonous size, diffusely located in the subcortical white matter, the internal capsule and the corpus callosum, with mostly spared corona radiata and non-subcortical centrum semiovale, detected by susceptibility- or T2* weighted imaging. The presence rate of this pattern and other, previously described MRI markers of CFE such as the starfield pattern and further diffusion abnormalities were recorded and statistically compared. The presence rate of microbleeds of any pattern, the "walnut kernel microbleed pattern", diffusion abnormality of any pattern, the starfield pattern, and cytotoxic edema in the corpus callosum was found to be 98.11%, 89.74%, 97.64%, 68.5%, and 77.27% respectively. The presence rate between the walnut kernel and the starfield pattern was significantly (p < 0.05) different. Microbleeds are common and mostly occur in a characteristic pattern resembling a "walnut kernel" in the CFE MRI literature. Microbleeds of this pattern in SWI or T2* MRI, along with the starfield pattern in diffusion imaging appear to be the most important imaging markers of CFE and may aid the diagnosis in clinically equivocal cases.

A Rare Case of Complex Pelvic Injury and Associated Intrathecal Fat Embolism due to Spinopelvic Dislocation with Sacral Burst Fracture

Introduction

Pelvic and lumbar spine injuries are very common especially in multiple trauma patients. The usual mechanism in young patients leading to pelvic fractures is a high-energy trauma such as traffic accidents. In elderly patients, low energy traumas are causal for such injuries. Compared to the high number of patients with pelvic or lumbar spine injuries, cerebral fat embolism is a quite rare finding but it needs to be considered to not misinterpret the radiological findings.

Case

We present the case of a 41-year-old patient, who got hit and trapped in the lumbar region by a hydraulic arm in a car repair shop. The patient was primarily admitted to a level II trauma center. The radiological and clinical examinations revealed an open pelvic type C injury in terms of a spinopelvic dissociation, dislocation of the left hip joint, rupture of the mesentery of the rectum and colon sigmoideum, and a complex injury to the left ureter. Additionally, CT scan showed fluid with higher density than cerebro spinal fluid (CSF) in the lateral ventricles indicating an intracranial bleeding. After an immediate surgery to stabilize the patient, he was admitted to a level I trauma center. The reanalysis of the existing CT datasets combined with a new head CT leads to the conclusion that the high density fluid in the lateral ventricles is not a intracranial bleeding but rather fat deriving from the complex pelvic and lumbar spine fracture into the CSF system. Therefore, an immediate operation was performed to stabilize the spinopelvic dissociation and to close the injured dural sheath. Additionally, a ventricle drainage has been placed, which confirmed the diagnosis of intrathecal fat embolism. Afterwards, complex plastic surgery was necessary to restore the soft tissue damage.

Conclusions

Intrathecal fat embolism in muliple trauma patients is a rare condition, which should be considered in patients with complex spine or pelvic injuries. It is important to distinguish this rare condition from intracranial bleedings, which are much more common because the consequent therapeutic strategy is quite different. In case of intrathecal fat embolism, a ventricle drainage system should be placed immediately, and the underlying spine or pelvic injuries need to be stabilized combined with closure of the dural sheath to prevent continuous fat embolism and meningeal infection.

Fat embolism in the popliteal vein detected on CT: Case report and review of the literature

Fat emboli are a common phenomenon, but are rarely detected or reported on extremity CT imaging. We present a case of fat embolus in the popliteal vein in the setting of a femoral fracture. This is the most distal fat embolus described in the literature. There are no guidelines regarding intervention if a fat embolus is detected in a peripheral vein on CT. A review of all the previous cases of peripheral fat emboli is presented for reference.