Early development of vasogenic edema in experimental cerebral fat embolism in cats: correlation with MRI and electron microscopic findings

Saturated Fatty Acid Emulsions Open the Blood-Brain Barrier and Promote Drug Delivery in Rat Brains

We performed this study to evaluate whether saturated fatty acid (SFA) emulsions affect the BBB and determine the duration of BBB opening, thereby promoting drug delivery to the brain. Butyric, valeric, caproic, enanthic, and caprylic acid emulsions were infused into the carotid artery of the rat model. We evaluated the BBB opening and drug delivery over time. The trypan blue and doxorubicin delivery studies were repeated from 30 min to 6 h. In the 1 h rats in each group, transmission electron microscopy (TEM) was performed to morphologically evaluate tight junctions, and the delivery of temozolomide was assessed by desorption electrospray ionization mass spectrometry. The ipsilateral hemisphere was positive for trypan blue staining in all the five SFA emulsion groups. In the valeric, enanthic, and caprylic acid emulsion groups, RGB ratios were significantly higher at 30 min and decreased thereafter. Doxorubicin delivery increased in all emulsion groups at all time points. Tight junctions were observed to be open in all groups. TMZ delivery was significantly higher in the ipsilateral hemisphere. In conclusion, intra-arterially infused SFA emulsions opened the BBB and promoted drug delivery within 30 min, which decreased thereafter. Therefore, SFA emulsions may aid BBB research and promote drug delivery to the brain.

A Case of Fat Embolism Syndrome with Cerebral Involvement in Sickle Cell Anemia

Fat embolism syndrome (FES) is a rare condition that can occur as a complication of sickle cell disease. We describe a case of a patient with sickle cell disease (homozygous Hb S or HBB: c.20A>T) presenting with initial signs and symptoms consistent with a vaso-occlusive crisis (VOC). Within 24 hours, the patient developed evidence of coagulopathy, multi organ failure and a reduced level of consciousness (LOC) prompting intubation. A diagnosis of FES was made on the basis of the patient's clinical presentation, in conjunction with magnetic resonance imaging (MRI) of the brain revealing innumerable tiny foci of restricted diffusion, intracytoplasmic microvesicular fat on Sudan Red staining of bronchoalveolar lavage samples and evidence of a pulmonary shunt on echocardiogram bubble study. Red blood cell (RBC) exchange transfusion was initiated 3 days following initial presentation and no further exchange transfusions were needed on the basis of subsequent Hb S (HBB: c.20A>T) levels. The LOC gradually improved and the patient was extubated 12 days following presentation. Neurological improvement was slow, with mild cognitive impairment initially evident at 3 months and no cognitive or neurological deficits remaining within 6 months of admission. This case highlights the importance of understanding the pathophysiology and clinical presentation of FES, as early exchange transfusion may improve survival in patients with sickle cell disease and FES.

Triolein emulsion enhances temozolomide brain delivery: an experimental study in rats

Purpose

To evaluate the enhancement of temozolomide (TMZ) delivery in the rat brain using a triolein emulsion.

Materials and Methods

Rats were divided into the five groups as following: group 1 (negative control), group 2 (treated with triolein emulsion and TMZ 20 mg/kg), and group 3 (TMZ 20 mg/kg treatment without triolein), group 4 (treated with triolein emulsion and TMZ 10 mg/kg), and group 5 (TMZ 10 mg/kg treatment without triolein). Triolein emulsion was infused into the right common carotid artery. One hour later, the TMZ concentration was evaluated quantitatively and qualitatively using high-performance liquid chromatography (HPLC-MS) and desorption electrospray ionization mass spectrometry (DESI-MS) imaging, respectively. The concentration ratios of the ipsilateral to contralateral hemisphere in each group were determined and the statistical analysis was conducted using an unpaired t-test.

Results

Quantitatively, the TMZ concentration ratio of the ipsilateral to the control hemisphere was 2.41 and 1.13 in groups 2 and 3, and were 2.49 and 1.14 in groups 4 and 5, respectively. Thus, the TMZ signal intensities of TMZ in group 2 and 4 were statistically high in the ipsilateral hemispheres. Qualitatively, the signal intensity of TMZ was remarkably high in the ipsilateral hemisphere in group 2 and 4.

Conclusions

The triolein emulsion efficiently opened the blood-brain barrier and could provide a potential new strategy to enhance the therapeutic effect of TMZ. HPLC-MS and DESI-MS imaging were shown to be suitable for analyses of enhancement of brain TMZ concentrations.

Triolein emulsion infusion into the hepatic artery increases vascular permeability to doxorubicin in rabbit liver

BACKGROUND

The infusion of triolein emulsion (TE) induced increased vascular permeability and a negligible and temporary decrease in liver function without specific histopathological damage.

AIM

To assess changes in doxorubicin concentration according to the percentage of TE infused via a hepatic artery to study the vascular permeability in the rabbit liver.

METHODS

Thirty-nine healthy rabbits were divided into five groups according to the concentration of emulsified triolein infused into the hepatic arteries: Group 0, saline infusion (control group, n = 5); group 1, 0.3% TE (n = 13); group 2, 0.6% TE (n = 6); group 3, 0.9% TE (n = 8); and group 4, 1.5% TE (n = 6). Doxorubicin (2.4 mg/kg) was infused immediately after TE injection via the hepatic arteries. After 2 h, the livers were harvested, and doxorubicin concentrations were calculated fluorometrically. The doxorubicin concentrations were compared between TE groups and the control group, and the optimal concentrations within the TE groups were calculated. Statistical analysis was performed using the nonparametric Mann-Whitney U test and Kruskal–Wallis test. P < 0.05 were considered statistically significant.

RESULTS

In the liver, doxorubicin concentrations were 2.06, 2.07, 2.16 and 1.66 times higher in groups 1 through 4, respectively, and significantly higher in the TE groups than in the control group (all P < 0.05). However, there were no significant differences in the mean doxorubicin concentrations between the four TE groups (P = 0.642). In the lungs, the mean doxorubicin concentrations were not significantly different between the control and TE groups (P > 0.05).

CONCLUSION

TE infusion into the hepatic arteries significantly increased the doxorubicin concentration approximately twofold but was not different between the TE groups. These findings suggest that TE infusion might be a useful adjuvant treatment of liver cancers.

Doxorubicin concentration in brain remains high for one day after triolein emulsion infusion induced BBB opening

Aim: The purpose of this study was to assess changes in doxorubicin concentration in rabbit brain with respect to time after BBB opening induced by triolein emulsion infusion via a carotid artery and the mechanism of BBB opening.Materials and Methods: Doxorubicin (2.4 mg/kg) was infused immediately after triolein emulsion (1%) into rabbit carotid arteries. Bilateral hemispheres were harvested 2, 4, 6 12 and 24 h later and doxorubicin concentrations were measured fluorometrically. Doxorubicin concentration ratios of ipsilateral versus contralateral hemispheres were calculated, and a TEM study was performed to investigate the mechanism responsible for the increased vascular permeability induced by triolein.Results: Doxorubicin concentrations were higher in ipsilateral hemispheres at all time points, and peaked at 2 h after treatment. Doxorubicin was still detected in ipsilateral hemispheres at 24 h after treatment. TEM showed tight junction opening by triolein emulsion with lanthanum tracer spillage into neural interstitium and transcytotic vesicles.Conclusion: Doxorubicin was delivered into neural interstitium because of the increased vascular permeability of the BBB induced by triolein emulsion. Doxorubicin concentrations in brain peaked within 2 h of triolein and doxorubicin administration and remained high for 24 h. The study shows increased vascular permeability induced by triolein emulsion may involve paracellular and transcellular pathways.

From the diagnosis to the therapeutic management: cerebral fat embolism, a clinical challenge

Cerebral fat embolism (CFE) is an uncommon incomplete type of fat embolism syndrome (FES), characterized by purely cerebral involvement. It usually occurs 12-72 hours after the initial trigger, mainly represented by closed, long-bone multiple fractures of the lower extremities. Neurological manifestations are mainly characterized by headache, confusion, seizures, focal deficit, and alteration of the consciousness state up to coma onset. It represents a diagnostic challenge, above all when secondary to uncommon nontraumatic causes, because neurological signs and symptoms are variable and nonspecific, not satisfying the Gurd and Wilson's criteria, the diagnostic features most widely used today for FES diagnosis. Neuroimaging (mainly MRI, but in some cases, brain computed tomography too) can hasten the diagnosis, avoiding other unnecessary investigations and treatment. Usually self-limiting, CFE may sometimes be fatal. Treatment is to date mainly supportive and prophylactic strategies are considered an important tool to decrease the development of fat embolism and, consequently, the rate of CFE.

Case 254: Posttraumatic Migrating Fat Embolus Causing Fat Emboli Syndrome

History An otherwise healthy 18-year-old man was admitted to the emergency department with a closed displaced fracture of the left femoral shaft ( Fig 1 ) after a high-velocity motorbike accident. At admission, other physical examination findings were unremarkable. Initial unenhanced and contrast material-enhanced (120 mL of Iomeron 400; Bracco Imaging, Milan, Italy) computed tomography (CT) was performed in the arterial and venous phases from the head to the knees. No abnormalities were noted in the brain or chest at initial CT. [Figure: see text] Within a few hours, the patient developed sudden mental confusion and severe hypoxemia, with rapidly worsening tachypnea and perturbed arterial blood gas with low partial pressure of oxygen (61 mmHg [8.1 kPa]; normal range, 75-100 mmHg [10.0-13.3 kPa]) and low partial pressure of carbon dioxide (32 mmHg [4.3 kPa]; normal range, 38-42 mmHg [5.1-5.6 kPa]). A second contrast-enhanced chest CT examination and initial brain magnetic resonance (MR) imaging were performed. Femoral fracture was stabilized with external fixation, and the patient was admitted to the intensive care unit, with progressive neurologic recovery at day 3 and respiratory improvement at day 4. Treatment included intubation with mechanical ventilation and intravenous administration of steroids and noradrenaline. Afterward, the femoral fracture was stabilized with an intramedullary nail. The patient made a full neurologic recovery 1 month after the accident.

Morphologic mechanisms of increased vascular permeability of triolein emulsion to the blood-brain barrier

Triolein emulsion has been known to increase vascular permeability in the brain when it is infused into the carotid artery. The purpose of this study was to identify the morphologic mechanism of increased vascular permeability in brain induced by infusion of emulsified triolein into the carotid artery by transmission electron microscopy (TEM). Triolein emulsion was infused into the carotid artery of rats. TEM using lanthanum tracer was used to evaluate morphologic changes in endothelium with a focus on transcytotic vesicles and tight junction opening. The treat group showed multiple transcytotic vesicles containing lanthanum tracer within endothelium on TEM. TEM also revealed that lanthanum tracer entered neural interstitium through tight junctions between capillary endothelial cells infrequently in the treat group. No evidence of transcytotic vesicles containing lanthanum tracer or lanthanum leakage through tight junctions was observed in the control group. Transcytosis and the opening of tight junctions appears the pathway for vascular permeability enhancement by triolein. This result could be utilized in studies on the blood-brain barrier and by those searching for chemotherapeutic methods that deliver anti-tumor agents to normally drug inaccessible organs.

Cerebral Fat Embolism: Clinical Presentation, Diagnostic Steps and Long-Term Follow-Up

OBJECTIVE

Symptomatic cerebral fat embolism (CFE) is a rare complication that occurs after a traumatic injury or orthopaedic surgery and is diagnostically challenging. No data is currently available concerning long-term follow-up.

METHODS

We identified from medical records 9 patients with CFE and revised the clinical signs and the diagnostic process. We then analysed long-term follow-up data, targeting clinical course after discharge, neurological impairment, and current quality of life, using the Barthel index and the modified Rankin Scale.

RESULTS

All 9 patients initially showed severe neurological deficits, including disturbance of consciousness ranging from somnolence to coma. During the follow-up period for 3-58 months after the insult 2 patients had died. The 7 patients who remained alive had either recovered completely or showed only minor neurological deficits after rehabilitation. They were nearly independent in daily life and needed only minimal assistance. We performed the first brain biopsy in a patient with CFE.

CONCLUSION

Most patients had a good outcome after long-term follow-up. In patients with an unexplained altered state of consciousness after a traumatic injury or an orthopaedic surgery, an MRI with diffusion-weighted imaging must be performed to uncover the characteristic pattern of disseminated hyperintense lesions in the white matter that are associated with CFE.

Triolein Emulsion Infusion Into the Carotid Artery Increases Brain Permeability to Anticancer Agents

BACKGROUND

Triolein emulsion infusion into the carotid artery has been reported to induce temporary and reversible opening of the blood-brain barrier by increasing vascular permeability.

OBJECTIVE

To evaluate the effect of triolein emulsion infusion on brain permeance by anticancer agents.

METHODS

In the doxorubicin study. 2.4 mg/kg doxorubicin was injected immediately after triolein emulsion (1%, 1.5%, and 2%) infusion into rabbit carotid arteries. Two hours later, bilateral hemispheres and eyeballs were harvested, and doxorubicin concentrations were measured fluorometrically. Doxorubicin ratios of ipsilateral/contralateral hemispheres were compared with those of doxorubicin controls by use of the Kruskal-Wallis test followed by the Dunn test. In the cisplatin study, 10 mg/kg cisplatin was injected immediately after 2% triolein emulsion infusion into rat carotid arteries. Ipsilateral hemispheres were harvested 2, 6, 12, 24, and 36 hours after treatment. Time-dependent cisplatin concentrations were determined by liquid chromatography/electrospray ionization-tandem mass spectrometry/mass spectrometry.

RESULTS

Doxorubicin concentrations were significantly higher in ipsilateral hemispheres and eyeballs in all 3 triolein treatment groups than in doxorubicin controls. In the cisplatin study, cisplatin concentrations in the ipsilateral hemispheres peaked at 6 hours after infusion of cisplatin.

CONCLUSION

Brain permeance to anticancer agents was increased by triolein emulsion infusion, which suggests that triolein infusion might be a useful adjuvant treatment for brain tumors.

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.

Prominent hypointense veins on susceptibility weighted image in the cat brain with acute infarction: DWI, SWI, and PWI

BACKGROUND

The multiple prominent hypointense veins on susceptibility-weighted imaging (SWI) have been found in the ischemic territory of patients with acute ischemic stroke. Venous side is the unknown area in the hemodynamics of brain infarction.

PURPOSE

To evaluate the venous aspect in acute brain infarction through an animal study.

MATERIAL AND METHODS

The acute infarction in cat brains was induced with a bolus infusion of 0.25 mL of triolein through one side of the common carotid artery. The magnetic resonance (MR) images, including diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC) map, SW, and perfusion-weighted (PWI) images, were obtained serially at 2 h (n = 17), 1 day (n = 11), and 4 days (n = 4) after triolein infusion. The obtained MR images were evaluated qualitatively and quantitatively. For qualitative assessment, the signal intensity of the serial MR images was evaluated. The presence or absence and the location with serial changes of infarction were identified on DWI and ADC map images. The presence or absence of prominent hypointense veins and the serial changes of cortical veins were also evaluated on SWI. Quantitative assessment was performed by comparing the relative cerebral blood volume (rCBV), cerebral blood flow (rCBF), and mean transit times (MTT) of the lesions with those of the contralateral normal side calculated on PWI. The serial changes of rCBV, rCBF, and MTT ratio were also evaluated.

RESULTS

Acute infarction in the first and second medial gyrus of lesion hemisphere was found by qualitative evaluation of DWI and ADC map images. On the serial evaluation of SWI, the cortical veins of cat brain with infarction were obscured at 2 h and then re-appeared at 1 day. The hemorrhage transformation and prominent hypointense veins were seen at 4 days on SWI. The quantitative evaluation revealed increased MTT ratios and decreased rCBV and rCBF ratios on PWIs in the acute infarction of cat brain.

CONCLUSION

The prominent hypointense veins on SWI were seen in the half of the acute infarction at 4 days. The prominent hypointense veins on SWI may have good agreement with the increased MTT ratio.

The minimum percentage of triolein emulsion for studying cerebral vascular permeability with least brain edema

Background:

Triolein emulsion infusion into the brain produces transiently increased vascular permeability.

Objectives:

The purpose of this study was to find the minimum percentage of triolein emulsion required for studying vascular permeability with minimal brain edema.

Materials and Methods:

Sixty healthy cats were divided into six groups according to the concentration of emulsified triolein infused into the carotid artery: group 1, 0.125% (n = 10); group 2, 0.25% (n = 10); group 3, 0.5% (n = 10); group 4, 1% (n = 10); group 5, 2% (n = 10); and group 6, saline infusion (control group, n = 10). T2-, T1- and contrast enhanced T1-weighted MR images were obtained 2 hours after infusing triolein emulsion. Contrast enhancement ratios (CERs) and signal intensity ratios (SIRs) versus contralateral hemispheres were calculated. Statistical analysis was performed by analysis of variance followed by Tukey’s test. P values of ≤ 0.05 were considered significant.

Results:

The lesion hemispheres showed mild hyperintensity due to edema on T2-weighted images, and contrast enhancement on post-contrast T1-weighted images in cats of group 1-5. CERs showed statistically significant differences between the control group and group 3 (P = 0.006), group 4 (P = 0.003), and group 5 (P < 0.001). However, SIRs were significantly different between the control group and group 5 only (P < 0.001).

Conclusion:

The minimum concentration of triolein emulsion required to increase vascular permeability adequately with minimal brain edema in a cat model was 0.5%.

Hemorrhage in cerebral fat embolisms in a cat model using triolein dependent on the physical properties of triolein

PURPOSE

Hemorrhage is a finding of clinical fat embolism syndrome. The purpose of the present study was to evaluate the occurrence of hemorrhage in the cat brain by SW MR imaging after infusion of triolein as a bolus or as an emulsion into the carotid artery.

MATERIALS AND METHODS

Twenty-two cats were divided into two groups according to the type of triolein infused: group 1 (n = 11) was infused with a 0.1 ml triolein bolus, group 2 (n = 11) with triolein emulsion containing 0.1 ml triolein in 20 ml saline. SW imaging was performed before and after triolein infusion (at 2 h, 1 and 4 days). After MR imaging on day 4, cats were sacrificed and brains were immediately excised. Hemorrhage was evaluated using H&E staining.

RESULTS

Hemorrhage was observed in eight cats in group 1, in no cats in group 2. Hemorrhage on SW images was found to correspond with light microscopy.

CONCLUSIONS

SW images revealed hemorrhage in lesion hemispheres infused with triolein bolus. However, there was no evidence of hemorrhage infused with emulsified triolein. Thus, the occurrence of hemorrhage in cerebral fat embolism may depend on fat status.

Dynamic MR imaging patterns of cerebral fat embolism: a systematic review with illustrative cases

Different MR imaging patterns of cerebral fat embolism have been reported in the literature without a systematic review. Our goal was to describe the patterns, explore the relationship between disease course and the imaging patterns, and discuss the underlying mechanism. We reveal 5 distinctive MR imaging patterns: 1) scattered embolic ischemia occurring dominantly at the acute stage; 2) confluent symmetric cytotoxic edema located at the cerebral white matter, which mainly occurs at the subacute stage; 3) vasogenic edematous lesions also occurring at the subacute stage; 4) petechial hemorrhage, which persists from the acute to the chronic stage; and 5) chronic sequelae, occurring at late stage, including cerebral atrophy, demyelinating change, and sequelae of infarction or necrosis. Underlying mechanisms of these imaging patterns are further discussed. Recognition of the 5 evolving MR imaging patterns of cerebral fat embolism may result in adjustment of the appropriate management and improve the outcome.

Blood-brain barrier experiments with clinical magnetic resonance imaging and an immunohistochemical study

OBJECTIVE

The purpose of study was to evaluate the feasibility of brain magnetic resonance (MR) images of the rat obtained using a 1.5T MR machine in several blood-brain barrier (BBB) experiments.

METHODS

Male Sprague-Dawley rats were used. MR images were obtained using a clinical 1.5T MR machine. A microcatheter was introduced via the femoral artery to the carotid artery. Normal saline (group 1, n = 4), clotted autologous blood (group 2, n = 4), triolein emulsion (group 3, n = 4), and oleic acid emulsion (group 4, n = 4) were infused into the carotid artery through a microcatheter. Conventional and diffusion-weighted images, the apparent coefficient map, perfusion-weighted images, and contrast-enhanced MR images were obtained. Brain tissue was obtained and triphenyltetrazolium chloride (TTC) staining was performed in group 2. Fluorescein isothiocyanate (FITC)-labeled dextran images and endothelial barrier antigen (EBA) studies were performed in group 4.

RESULTS

The MR images in group 1 were of good quality. The MR images in group 2 revealed typical findings of acute cerebral infarction. Perfusion defects were noted on the perfusion-weighted images. The MR images in group 3 showed vasogenic edema and contrast enhancement, representing vascular damage. The rats in group 4 had vasogenic edema on the MR images and leakage of dextran on the FITC-labeled dextran image, representing increased vascular permeability. The immune reaction was decreased on the EBA study.

CONCLUSION

Clinical 1.5T MR images using a rat depicted many informative results in the present study. These results can be used in further researches of the BBB using combined clinical MR machines and immunohistochemical examinations.

Intra-arterial delivery of triolein emulsion increases vascular permeability in skeletal muscles of rabbits

Background

To test the hypothesis that triolein emulsion will increase vascular permeability of skeletal muscle.

Methods

Triolein emulsion was infused into the superficial femoral artery in rabbits (triolein group, n = 12). As a control, saline was infused (saline group, n = 18). Pre- and post-contrast T1-weighted MR images were obtained two hours after infusion. The MR images were qualitatively and quantitatively evaluated by assessing the contrast enhancement of the ipsilateral muscles. Histologic examination was performed in all rabbits.

Results

The ipsilateral muscles of the rabbits in the triolein group showed contrast enhancement, as opposed to in the ipsilateral muscles of the rabbits in the saline group. The contrast enhancement of the lesions was statistically significant (p < 0.001). Histologic findings showed that most examination areas of the triolein and saline groups had a normal appearance.

Conclusion

Rabbit thigh muscle revealed significantly increased vascular permeability with triolein emulsion; this was clearly demonstrated on the postcontrast MR images.

The steroid effect on the blood-ocular barrier change induced by triolein emulsion as seen on contrast-enhanced MR images

Objective

The purpose of this study is to evaluate the effect of dexamethasone on the damaged blood-ocular barrier caused by triolein emulsion, using contrast-enhanced MR imaging.

Materials and Methods

An emulsion of 0.1-mL triolein in 20 mL of saline was infused into the carotid arteries of 32 cats, 12 cats were placed in the treatment group and 18 cats were placed in the Control group. Thirty minutes after the infusion of triolein emulsion, a set of orbital pre- and post-contrast T1-weighted MR images (T1WIs) were obtained. Infusion of 10 mg/kg dexamethasone into the ipsilateral carotid artery of each of the cats in the treatment group cats and 20 mL saline in each of the cats in the control group was given. A second set of pre- and post-contrast orbital T1WIs were obtained three hours following triolein emulsion infusion. Qualitative analysis was performed for the the anterior chamber (AC), the posterior chamber (PC), and in the vitreous humor of the ipsilateral and contralateral eyes. The signal intensity ratios of the ipsilateral eye over the contralateral eye were quantitatively evaluated in the three ocular chambers on the first and second set of T1WIs, and were then statistically compared.

Results

Qualitatively, the AC, the PC or the vitreous did not show immediate contrast enhancement on the first and the second set of post-contrast T1WIs. However, the AC and the PC showed delayed contrast enhancement for both groups of cats on the second pre-contrast T1WIs. No enhancement or minimally delayed enhancement was seen for the vitreous humor. Quantitatively, the signal intensity ratios in the PC of the treatment group of cats were statistically lower than the ratios of the control group of cats for the second set of T1WIs (p = 0.037). The AC and vitreous showed no statistically significant difference between the feline treatment group and control group (p > 0.05).

Conclusion

Contrast-enhanced MR images revealed increased vascular permeability in the PC of the eye after infusion of triolein emulsion. Dexamethasone seems to decrease the breakdown of the blood-aqueous barrier in the PC.

Cerebral fat embolism: diffusion-weighted magnetic resonance imaging findings

PURPOSE

To demonstrate the diffusion-weighted (DWI) magnetic resonance imaging (MRI) findings, and the follow-up MRI findings, of cerebral fat embolism in the acute stage.

MATERIAL AND METHODS

The initial DWI and clinical findings of six patients with cerebral fat embolism were retrospectively evaluated. The finding of DWI with a b-value of 1000 s/mm2 (b=1000) was compared with that of DWI with a b-value of 0 s/mm2 (b=0). In three patients who underwent follow-up MRI, the interval change of the lesion on T2-weighted images was investigated.

RESULTS

The characteristic DWI finding of cerebral fat embolism in the acute stage was multiple, hyperintense, dot-like lesions disseminated in the brain. These lesions were distributed dominantly in the bilateral border-zone areas. Some lesions had an ancillary location including the cortex, deep white matter, basal ganglia, and cerebellum. The lesions were more intense and numerous in DWI (b=1000) than in DWI (b=0). The findings on the follow-up T2-weighted images were multiple confluent hyperintense lesions in the white matter with progression since the initial MRI.

CONCLUSION

DWI could be a sensitive tool for detecting cerebral fat embolism in the acute phase. It is recommended that DWI be included in the initial evaluation of cerebral fat embolism with MRI.

A Model for Research on the Blood–Brain Barrier Disruption Induced by Unsaturated Fatty Acid Emulsion

PURPOSE

The authors investigated whether fatty acid emulsion affects the blood-brain barrier (BBB), whether disrupted BBB is reversible, and whether the fatty acid emulsion technique may be a model for BBB research.

MATERIALS AND METHODS

The fat emulsion was made with 0.05 mL of oleic acid or linoleic acid and 20 mL of normal saline. The internal carotid artery in 14 cats was infused with oleic acid emulsion (group 1) and with linoleic acid emulsion in 12 cats (group 2). Gd-enhanced T1-weighted (Gd-T1WI), diffusion-weighted (DWI), and additional apparent diffusion coefficient (ADC) map magnetic resonance imaging (MRI) was obtained at 1 hour, 1 and 4 days, and 1 week after infusion. MRI findings were evaluated qualitatively. Quantitatively, the signal intensity ratio (SIR) of the lesion to the contralateral hemisphere was measured on Gd-T1WIs. The SIRs were statistically analyzed using the student t test. The brain tissue was removed immediately for light and electron microscopy examination if the lesion showed no contrast enhancement and was isointense on DWIs and the ADC maps.

RESULTS

The lesions appeared at 1 hour in both groups as contrast enhancement on Gd-T1WIs, as isointensity or mild hyperintensity on DWIs, and as isointensity on the ADC maps. On day 1, these MRI findings were decreased in group 1 and were not seen in group 2. At 1 hour, the SIRs of group 1 were significantly higher than those of group 2 (P = 0.016). On day 1, the SIRs of both groups approximated 1.0. Light microscopy findings revealed minor necrosis and demyelination in one cat from group 1 and in 3 cats from group 2. Electron microscopy examinations showed minimal findings in the cortical lesions in groups 1 and 2.

CONCLUSIONS

Infusion of unsaturated fatty acid emulsion into the carotid artery of cats revealed vasogenic edema of the brain and reversible changes as depicted on MRI. This unsaturated fat emulsion technique may be used as a model for research on BBB disruption.

Cerebral fat embolism: usefulness of magnetic resonance spectroscopy

We report a case of cerebral fat embolism which occurred in a 33-year-old man after a diaphyseal femoral fracture without cranial traumatism. The initial examination showed an incomplete picture of coma with tetrapyramidal syndrome and cutaneomucous purpura. There was no respiratory damage. We present a magnetic resonance spectroscopy analysis of the cerebral lesions observed in the initial phase of the embolism, as well as follow-up, which has strengthened the clinical and imaging features for the diagnosis.

Effect of triolein emulsion on the blood-testis barrier in cats

PURPOSE

Although the blood-testis barrier (BTB) is beneficial physiologically, it acts as an obstacle to chemotherapy. We wished to determine whether a triolein emulsion could alter the permeability of the BTB in cats.

MATERIALS AND METHODS

An emulsion of 0.05-mL triolein in 20 mL of saline was infused into the abdominal aorta just proximal to the branching of the renal arteries of each of 15 cats (embolic group). As controls, 12 cats were each similarly infused with 20 mL of normal saline (control group). Pre and postcontrast MR images were obtained 30 minutes and 2 hours after embolization. The images were analyzed for the presence and degree of contrast enhancement (qualitative analysis), and the contrast enhancement ratios (CER) derived from one testis of each animal were compared and statistically analyzed by the mixed linear model (quantitative analysis).

RESULTS

Contrast enhancement of the testis was observed in both groups at both time points, but it was more prominent in the embolic group. The CERs in the embolic group (0.63 at 30 minutes, 0.42 at 2 hours) were significantly higher than in the control group (0.36 at 30 minutes, 0.28 at 2 hours; P = 0.0001). In each group, the CERs at 2 hours were significantly lower than those at 30 minutes (P = 0.006).

CONCLUSION

Intra-arterial infusion of triolein emulsion increased the permeability of the BTB. This result may be useful in future studies of BTB disruptions caused by fat emulsions.

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.