Assessment of cerebral fat embolism by magnetic resonance imaging in the acute stage

Spinal cord infarction as a rare complication of fat embolism syndrome following bilateral intramedullary nailing of femur fractures

Fat embolism syndrome (FES) is a rare and potentially fatal complication occurring most often after long bone or pelvic fractures and orthopaedic procedures. It can consist of pulmonary, central nervous system and cutaneous manifestations. The exact pathophysiology of emboli reaching the arterial circulation is poorly understood.1 It is suggested that this may occur by either 'paradoxical' embolism or microembolism.2 3 Its true incidence is unknown but increases in the presence of multiple closed fractures. It can be a diagnostic dilemma for clinicians and if suspected diffusion-weighted MRI is the modality of choice for the investigation of the central nervous system.4 We present the case of a 22-year-old man who developed multifocal cerebral infarcts, a right-sided cerebellar infarct and an infarct in the anterior cord bilaterally at the level of C5-C6 as a result of FES.

Fat Embolism: A Central Nervous System Problem

Microvascular fat in the systemic circulation is a common postmortem finding in patients dying after trauma or cardiopulmonary bypass. The causative relationship between the microvascular fat and tissue inflammation, ischemia, and injury is unclear. Characteristic clinical lesions on magnetic resonance imaging and evidence in animal models suggest that focal cerebral edema may be associated with fat microemboli. This fat occludes cerebral vessels 5-15 microns in diameter, after passing through either the lung or filters in cardiopulmonary bypass circuits. Microvascular fat may directly cause the injury or may be a ‘second hit’ phenomenon, thus aggravating a pre-existing inflammatory reaction to injury, indirectly causing cerebral injury and adverse neurocognitive outcomes after cardiac surgery and trauma.

Magnetic Resonance Diffusion W Imaging in Cerebral Fat Embolism

The use of diffusion weighted imaging with apparent diffusion coefficient mapping in the diagnosis of cerebral fat embolism is shown here to demonstrate infarcts secondary to fat emboli more intensely than T2 weighted sequences 24 hours after the onset of symptoms. Embolic foci are hypointense on apparent diffusion coefficient mapping consistent with cytotoxic edema associated with cell death and restricted water diffusion. This technique increases the sensitivity for detecting cerebral fat embolism and offers a potentially important tool in its diagnosis.

Massive cerebral involvement in fat embolism syndrome and intracranial pressure management

Fat embolism syndrome (FES) is a common clinical entity that can occasionally have significant neurological sequelae. The authors report a case of cerebral fat embolism and FES that required surgical management of intracranial pressure (ICP). They also discuss the literature as well as the potential need for neurosurgical management of this disease entity in select patients. A 58-year-old woman presented with a seizure episode and altered mental status after suffering a right femur fracture. Head CT studies demonstrated hypointense areas consistent with fat globules at the gray-white matter junction predominantly in the right hemisphere. This CT finding is unique in the literature, as other reports have not included imaging performed early enough to capture this finding. Brain MR images obtained 3 days later revealed T2-hyperintense areas with restricted diffusion within the same hemisphere, along with midline shift and subfalcine herniation. These findings steered the patient to the operating room for decompressive hemicraniectomy. A review of the literature from 1980 to 2012 disclosed 54 cases in 38 reports concerning cerebral fat embolism and FES. Analysis of all the cases revealed that 98% of the patients presented with mental status changes, whereas only 22% had focal signs and/or seizures. A good outcome was seen in 57.6% of patients with coma and/or abnormal posturing on presentation and in 90.5% of patients presenting with mild mental status changes, focal deficits, or seizure. In the majority of cases ICP was managed conservatively with no surgical intervention. One case featured the use of an ICP monitor, while none featured the use of hemicraniectomy.

Alveolar hemorrhage in a case of fat embolism syndrome: A case report with short systemic review

Fat embolism and fat embolism syndrome (FES) are well-known complications of long bone fracture and surgery involving manipulation of skeletal elements. Many non-traumatic causes of FES have been suggested but they constitute only a small portion. FES presents with classical symptoms of petechiae, hypoxemia, central nervous system symptoms along with other features such as tachycardia and pyrexia. Diagnosis of FES relies on clinical judgment rather than objective findings such as emboli present in the retinal vessels on fundoscopy, fat globules present in urine and sputum, a sudden inexplicable drop in hematocrit or platelet values, increasing erythrocyte sedimentation rate.

Cerebral Fat Embolism: A diagnostic challenge

Fat embolism syndrome (FES) is a rare but a serious clinical catastrophe occurring after traumatic injury to long bones. Cerebral involvement in the absence of pulmonary or dermatological manifestation on initial presentation may delay the diagnosis of cerebral fat embolism (CFE). We discuss a case series of CFE which posed a challenge in diagnosis. The clinical presentations of these patients did not satisfy the commonly used clinical criteria for aiding the diagnosis of FES. Early MRI brain (DWI and T2 weighted sequences) in patients with neurological symptoms after trauma even in the absence of pulmonary and dermatological findings should be the goal.

Analyzing fat embolism syndrome in trauma patients at AIIMS Apex Trauma Center, New Delhi, India

BACKGROUND

Fat embolism syndrome (FES) is a constellation of symptoms and signs subsequent to orthopedic trauma.

MATERIALS AND METHODS

The clinical profile of FES in the trauma population was studied over 2 years and 8 months.

RESULTS

The incidence of FES among all patients with long bone and pelvic fractures was 0.7% (12). The mean injury severity score was 10.37 (SD 1.69) (range 9-14). The diagnosis of FES was made by clinical and laboratory criteria. Hypoxia was the commonest presentation (92%). The average days of onset of symptoms were 3.5 (SD1.29) days. Management included ventilator support in 75%, average ventilator days being 7.8 (SD 4.08) days. The average ICU stay and hospital stay were 9.1 days and 29.7 days, respectively. A mortality of 8.3% (1) was observed.

CONCLUSION

Fat embolism remains a diagnosis of exclusion and is a clinical dilemma. Clinically apparent FES is unusual and needs high index of suspicion, especially in long bone and pelvic fractures.

Pulmonary and cerebral lipiodol embolism after transcatheter arterial hemoembolization in hepatocellular carcinoma

Pulmonary and cerebral lipiodol embolism after transcatheter arterial chemoembolization (TACE) of hepatocellular carcinoma is rare. To our knowledge, only 7 cases have been reported in the literature. We present a case of pulmonary and cerebral lipiodol embolism, and analyzed retrospectively the imaging and clinical data of the patient and conclude the most probable mechanism of pulmonary and cerebral lipiodol embolism, which is different from that of the cases reported previously.

Cerebral lipiodol embolism after transcatheter arterial chemoembolization of hepatocellular carcinoma

A case of cerebral lipiodol embolism after transcatheter arterial chemoembolization (TACE) of hepatocellular carcinoma is presented. A 76-year-old man underwent TACE for advanced hepatocellular carcinoma. Immediately after chemoembolization, his level of consciousness deteriorated. Computed tomography revealed deposition of iodized oil in the cerebral cortex, basal ganglia, and thalami. Magnetic resonance imaging showed restricted diffusion within the thalami and basal ganglia. The patient's level of consciousness gradually improved, and all neurologic symptoms disappeared over 6 weeks.

Magnetic resonance imaging and histologic findings of experimental cerebral fat embolism

RATIONALE AND OBJECTIVES

The purpose of this study was to determine whether cerebral fat embolism demonstrated reversible or irreversible findings in magnetic resonance (MR) imaging over time and to compare the features in MR images with histologic findings in a cat model.

MATERIALS AND METHODS

MR images were obtained serially at 2 hours, 1 and 4 days, and 1, 2, and 3 weeks after embolization with 0.05 mL of triolein into the internal carotid artery in 19 cats. Any abnormal signal intensity and change in the signal intensity were evaluated on T2-weighted images, T1-weighted images, diffusion-weighted images (DWIs; including apparent diffusion coefficient [ADC] maps), and gadolinium-enhanced T1-weighted images (Gd-T1WI) over time. After MR imaging at 3 weeks, brain tissue was obtained and evaluated for light microscopic (LM) examination using hematoxylin-eosin and Luxol fast blue staining. For electron microscopic examination, the specimens were obtained at the cortex. The histologic and MR findings were compared.

RESULTS

The embolization lesions showed hyperintensity on T2-weighted images, hyperintensity, or isointensity on DWIs, hypointensity, or isointensity on ADC maps and contrast enhancement on Gd-T1WIs at 2 hours. The T2-weighted hyperintensity extended to the white matter at day 1 and decreased thereafter. Contrast enhancement decreased continuously from day 1, and hyperintensity on DWI decreased after day 4. Hypointensity on ADC maps became less prominent after day 4. By week 3, most lesions had reverted to a normal appearance on MR images and were correlated with LM findings. However, small focal lesions remained in the gray matter of 8 cats and in the white matter of 3 cats on MR images, and this correlated with the cystic changes on LM findings. Electron microscopic examination of the cortical lesions that reverted to normal at week 3 in MR images showed that most of these lesions appeared normal but showed sporadic intracapillary fat vacuoles and disruption of the endothelial walls.

CONCLUSIONS

The embolized lesions of the hyperacute stage were of 2 types: type 1 lesions, showing hyperintensity on DWIs and hypointensity on ADC maps, have irreversible sequelae, such as cystic changes; whereas type 2 lesions, showing isointensity or mild hyperintensity on DWIs and ADC maps, reverted to a normal appearance in the subacute stage.

Early Diagnosis of Cerebral Fat Embolism Syndrome by Diffusion-Weighted MRI (Starfield Pattern)

Background — Cerebral fat embolism syndrome is a rare, but potentially lethal, complication of long bone fractures. Neurological symptoms are variable, and the clinical diagnosis is difficult. The purpose of this case study is to demonstrate the value of diffusion-weighted MRI of the brain for early diagnosis of fat embolism syndrome.

Case Description — A non-head-injured 18-year-old woman suffered acute mental status changes 21 hours after an uncomplicated fracture of the left tibia. MRI of the brain was performed 48 hours after injury. T2-weighted images showed multiple nonconfluent areas of high signal intensity, which, on the diffusion-weighted scans, were revealed as bright spots on a dark background (“starfield” pattern). We suggest that this indicates areas of restricted diffusion that are due to cytotoxic edema, resulting from multiple microemboli.

Conclusions — High-intensity lesions in the brain on diffusion-weighted images may serve as an early-appearing and more sensitive indicator of the diagnosis of fat embolism in the clinical context of long bone injury without head trauma.

[Febrile coma and multiple organ failure: suspected hemoglobinopathy SC]

We report the case of febrile fatal coma in a 51-year-old man from Burkina Faso. Magnetic resonance imaging (MRI) shows cerebral fat embolism. Haemoglobin electrophoresis shows probably haemoglobinopathy SC. A short review of the literature demonstrate the need to consider this complication in patients with neurological or respiratory disorders, in areas where this disease is highly prevalent, irrespective of age. It also emphasizes the diagnostic contribution of MRI and discusses the mechanism, the diagnosis as well as the difficulty of choosing the appropriate therapeutic course.

Cerebral embolization presenting as delayed, severe obtundation in the postanesthesia care unit after total hip arthroplasty

Catastrophic neurologic events occur rarely postoperatively and must be diagnosed quickly. A 63-year-old woman who had undergone uneventful total hip arthroplasty experienced obtundation after admission to the postanesthesia care unit. Cranial magnetic resonance imaging revealed multiple lesions consistent with ischemia or infarction, and fat cerebral embolism was diagnosed. We describe the numerous complications that may occur in patients in the postanesthesia care unit and review the differential diagnosis of altered mental status in such patients. Paradoxical cerebral fat embolization must be considered in the differential diagnosis of altered mental status after pelvic or long bone fracture or lower extremity major joint replacement, and this condition may occur despite normal pulmonary function and no patent foramen ovale or right-to-left intracardiac shunt. Magnetic resonance imaging with T2-weighted sequences is the cranial imaging study of choice for early evaluation of patients with sudden multifocal neurologic deficits and suspected fat embolism syndrome.

Pulmonary fat embolism syndrome: CT findings in six patients

PURPOSE

Our purpose is to describe the CT findings in pulmonary fat embolism syndrome (FES).

METHOD

Chest radiographs and CT scans of six patients with pulmonary FES were reviewed. Initial and follow-up CT findings were noted, and the extent of CT abnormalities was correlated with partial pressure of arterial oxygen (PaO2).

RESULTS

Focal areas of consolidation or ground-glass opacity and nodules were seen in all patients, predominantly in the upper lobes of the lungs. Association between these opacities and pulmonary vessels was indicated in three patients. In the lower lobes of all patients, gravity-dependent opacities predominated. Diffuse ground-glass opacity was noted in five patients. Follow-up CT scans showed rapid improvement in three patients, but the gravity-dependent opacity progressed. The extent of CT abnormalities correlated positively with PaO2 (r = 0.8, p < 0.05).

CONCLUSION

CT findings reflect the pathophysiology of this syndrome, which differs from that of simple capillary permeability pulmonary edema.

[Cerebral fat embolism after closed leg injury]

A 21-year-old man sustained a closed fracture of the leg from an industrial accident, without associated head trauma. The orthopaedic treatment consisted of immediate immobilization by setting leg in plaster. Two hours after admission, the Glasgow coma scale score was 10. Four hours after admission he developed a coma (Glasgow coma scale score = 7) with repetitive seizures. No lesion was visible on cerebral CT scan. Chest X-ray was unremarkable. Petechiae on the anterior chest wall and abdomen with bilateral mydriasis occurred. Thrombocytopenia with prothrombine time increase were observed. Magnetic resonance imaging, 27 hours after admission, showed high-intensity areas on T2 weighted views due to fat embolism. Retinal haemorrhages were observed. The bronchoalveolar lavage showing fat staining of tracheal aspirates confirmed the diagnosis of fat embolism. This case report emphasizes the possibility of predominant neurologic manifestations of a fat embolism and the diagnostic help of cerebral magnetic resonance imaging.

[From fat emboli to fat embolism syndrome]

The occurrence of a fat embolism syndrome (FES) can be explained by two hypothetic mechanisms. In the mechanical hypothesis, bone marrow enters into the cardiovascular system during an intramedullary peak pressure. This peak could occur during either long bone fracture and/or intramedullary nailing or cemented or noncemented arthroplasty. According to the biochemical hypothesis, the FES could occur in nontraumatic conditions such as lipid emulsion infusion or sickle cell disease. The C-reactive protein is a possible factor for destabilizing plasma fat (chylomicrons or Intralipid liposomes). Treatment with heparin has been reported to interfere with lipid metabolism through a "creaming" phenomenon. Plasma fatty acids increase lipid peroxidation, with potential severe oxidative stress of lung. Vascular lung injury is increased by granulocytes and the clotting cascade is activated by neutral fat. After a symptom-free period, the full clinical picture is characterized by pulmonary insufficiency with hypoxaemia, neurological impairment, pyrexia and petechial haemorrhages. The accurate incidence cannot be assessed as many subclinical forms remain unrecognized. Transoesophageal echocardiography with color-flow Doppler allows considerable insight into the sequence of embolic events and patent foramen ovale (PFO). A PFO induces an increase in right-to-left shunt in case of an elevated intrapulmonary pressure. PFO might elicit systemic manifestations of the FES, particularly with neurological impairment. Carotid ultrasonography helps to visualize embolism. Magnetic resonance imaging of cerebral fat emboli is a better diagnostic tool for detecting brain embolism than computerized tomography. Quantification of cells containing fat droplets in bronchoalveolar lavage material could also be helpful. Pulmonary microvascular cytology analysis of capillary blood samples obtained through a pulmonary artery catheter in combination with blood gas changes are of value for earlier stage FES. Prophylactic and therapeutic measures are aimed to counteract the various mechanisms leading to FES. The decrease in time delay of fracture management is probably the most effective prophylactic means. A reaming procedure can be noxious, particularly in a patient with a severe thoracic trauma. The insertion without reaming of a small diameter nail, plating or external fixation have several advantages. Albumin infusion is recommended for restoration of blood volume and binding of fatty acids. Among pharmacologic measures, only corticosteroids have a proven benefit, not only for prophylaxis but also for therapy. Aprotinin and heparin are beneficial in counteracting blood cell aggregation. A prophylactic use of vena cava filters has been advocated. Prevention or early treatment of hypovolaemia and hypoxaemia are essential.