Fracture of the tibia and fibula in a car accident with cerebral fat embolism syndrome (FES): A case report

Fat embolism syndrome (FES) is defined as the occurrence of dysfunction damage to one or more organs, suggesting a complication or atypical evolution of fat embolism [1]. It has a predominant epidemiology in young patients, with an average age of 30 years, associated with polytrauma with bone fractures (usually long bones of the lower limbs) [1],[2]. It has rarely been described as part of a sickle cell crisis with bone marrow fat necrosis and subsequent embolism. Brain manifestations of fat embolism syndrome can be highly variable and non-specific. Symptom spectra include: headache, lethargy, irritability, delirium, stupor, convulsions, or coma [2]. The diagnosis is clinical, with the changes found and classified (Gurd and Wilson) into major and minor criteria, making the sign of fat embolism syndrome when it does not present at least one major criterion and four minor criteria. The major criteria include: (a) respiratory failure (PaO <60 mmHg); (b) neurological signs disproportionate to hypoxia; (c) axillary or conjunctival petechiae, and (d) pulmonary edema. The minor criteria are: (a) fever (>38 °C), (b) tachycardia (>110 bpm), (c) retinal changes, (d) renal changes, (e) anemone, and (f) thrombocytopenia (<100,000) [3],[4].

We report a case of a 28-year-old male patient, victim of medium impact collision, presenting long bone fracture (tibia and fibula). He was admitted to the emergency room with a lucid, oriented and Glasgow 15. The patient was admitted and taken to the operating room. After 12 hours, he developed decreased level of consciousness (Glasgow 9). On physical examination: isochoric and photoreactive pupils, global hypotonia, global rot 3, and bilateral Babinski were found. His heart rate was: 88 bpm and temperature was: 37.8 °C. Laboratory report showed: HB: 11.9 g/dL, platelets: 171,000 mm³, creatinine: 2.02 mg/dL. High field magnetic resonance imaging was requested, which showed: small multifocal and non-confluent lesions presenting hypersignal in the fluid-attenuated inversion recovery (FLAIR)-weighted sequences (Figure 1) and signs of diffusion restriction (Figure 2) compromising the white matter of the frontal and parietal lobes, as well as the core-capsular regions and the thalamus. Bilaterally, characterizing the “star field” pattern (field/starry sky), therefore being a pattern of cerebral fat embolism. The patient continued to be monitored in the intensive care unit (ICU) and, however, progressed with brain deterioration and, eventually, death.

Fat embolism syndrome is clinically diagnosed, with no laboratory and neuroimaging tests that alone provide the diagnosis. In this sense, it is essential to investigate the different differential diagnoses: (a) Traumatic brain injury (TBI), (b) Pulmonary thromboembolism (PTE), and (c) Sepses [5],[6]. The anatomopathology of FES has important characteristics such as: petechiae in white matter with enhancement of fat globules in the capillary lumen. This is because the white substance is five times more vascularized than the gray one. Capillaries are more sparse, rectilinear, and with bilious anastomoses [7]. If a capillary is obstructed by a fatty plunger, the microterritorial local circulation is interrupted and, therefore, endothelial necrosis will occur, allowing a punctiform leakage of blood (petechiae) [7].

Fat embolism syndrome (FES) consists of the presence of fat globules in the bloodstream, generally resulting from the exposure of the yellow bone marrow in fractures of the long bones, such as the femur, tibia, and pelvis bones, polytrauma and orthopedic surgery, such as arthroplasty, knee, and hip, which can cause occlusion of small vessels [3],[8]. The presence of fatty emboli is common, being observed in 67–95% of patients who have suffered long bone fractures or major trauma [8]. Few, however, are patients with emboli capable of causing clinical manifestations and complications. FES does not install itself immediately after the trauma. There is a lucid, or latent, period of 12 to 14 hours, which was exactly witnessed according to the patient’s evolution after admission to the emergency unit [9],[10],[11],[12].

The pathogenesis of fat embolism is unknown. There are two theories: the mechanical theory in which fat emboli may be the result of fat globules entering the bloodstream through tissue (usually bone marrow or adipose tissue) that has been ruptured by trauma, and the biochemical theory in which inflammation results from the production of toxic substances intermediary with circulating fat (for example, chylomicrons, infused lipids, or fat derived from bone marrow). It is possible that both mechanisms are involved in action in many cases. Fat embolism syndrome is more commonly associated with long bones (especially the femur) and pelvic fractures and less commonly with fractures of other bones containing marrow (for example, ribs). In this case, the polytrauma patient evolved with FES receiving a supportive measure and rapid action by the neurosurgery team, but the patient died. The description of this case allows the scientific community to manifest an emergency and efficiently operate it in a medical service that must be prepared for a fat embolism syndrome. Take away message: Fat embolism syndrome has a predominant epidemiology in young patients. It is usually associated with polytrauma and rarely been described as part of a sickle cell crisis. Medical services must be prepared for a FES.