Gray-white matter contrast reversal on T1-weighted spin-echo in postmortem brain.

PURPOSE: The image contrast of postmortem magnetic resonance imaging (MRI) may differ from that of antemortem MRI because of circulator arrest, changes in postmortem tissue, and low-body-temperature scanning conditions. In fact, we have found that the signal intensity of white matter (WM) on T1-weighted spin-echo (T1WSE) images of the postmortem brain was lower than that of gray matter (GM), which resulted in image contrast reversal between GM and WM relative to the living brain. However, the reason for this phenomenon is unclear. Therefore, the aim of this study is to clarify the reason why image contrast reversal occurs between GM and WM of the postmortem brain. MATERIALS AND METHODS: Twenty-three corpses were included in the study (mean age, 60.6 years; range: 19-60 years; mean rectal temperature at scan, 6.9℃; range: 4-11℃). On a 1.5 T MRI system, postmortem T1W-SE MRI of the brain was conducted in the 23 corpses prior to medico-legal autopsy. Next, T1 and T2 of the GM and WM at the level of the basal ganglia were determined in the same participants using inversion recovery and multiple SE sequences, respectively. The proton density (PD) was also calculated from the T1 and T2 images (in the same slice). RESULTS: T1W-SE image contrast between the GM and WM of all postmortem brains was inverted relative to the living brain. T1 (579 ms in GM and 307 ms in WM) and PD (64 in GM and 44 in WM) of the postmortem brain decreased compared with the living brain. While T1 of WM/GM remained below 1 even postmortem, the PD of WM/GM decreased. T2 (110 ms in GM and 98 ms in WM) of the postmortem brain did not differ from the living brain. CONCLUSION: The decrease in PD of WM/GM in the postmortem brain may be the major driver of contrast reversal between the GM and WM relative to the living brain.

Two medicolegal autopsy cases of multinodular and vacuolating neuronal tumor revealed by postmortem MRI.

The multinodular and vacuolating neuronal tumor (MVNT) is a recently recognized brain lesion. MVNT has a characteristic appearance in MRI images and is potentially epileptogenic. To the best of our knowledge, no report has yet described this pathological entity in the forensic medicine literature. We present two medicolegal autopsy cases where postmortem MRI (PMMR) was useful to detect this lesion. Case 1: a man in his 30s, with about a 7-year history of intractable epilepsy and known MVNT died suddenly. Although MVNT was not detected in the initial morphological evaluation during autopsy, PMMR of the formalin-fixed brain revealed the lesion in the left frontal lobe. Histopathology confirmed it as a MVNT. Case 2: a man in his 20s hanged himself to death. PMMR prior to autopsy revealed MVNT in his brain, and the diagnosis was confirmed by a detailed histopathological evaluation. In both cases, postmortem CT was not useful for evaluation. The cases suggested that MVNT can cause sudden, unexpected epileptic death, and pre- or post-autopsy PMMR may be useful to detect it.

Significance of systolic-phase imaging on full-phase ECG-gated CT angiography to detect intimal tears in aortic dissection.

PURPOSE: For patients with aortic dissection (AD) and intramural hematoma (IMH), the optimal cardiac phase to detect intimal tears (IT) and ulcer-like projections (ULP) on retrospective electrocardiogram (ECG)-gated computed tomography angiography (CTA) remains unclear. The purpose of this study was to compare the accuracy of retrospective ECG-gated CTA for detecting IT in AD and ULP in IMH between each cardiac phase. MATERIALS AND METHODS: A total of 75 consecutive patients with AD and IMH of the thoracic aorta were enrolled in this single-center retrospective study. The diagnostic performance to detect IT and ULP in the thoracic aortic regions (including the ascending aorta, aortic arch, and proximal and distal descending aorta) was compared in each cardiac phase on retrospective ECG-gated CTA. RESULTS: In the systolic phase (20%), the accuracy, sensitivity, and specificity to detect IT in AD was 64% (95% confidence interval [CI] 56-72%), 69% (95%CI 60-78%), and 25% (95%CI 3.3-45%), respectively. In the diastolic phase (70%), the accuracy, sensitivity, and specificity to detect IT in AD was 52% (95%CI 43-60%), 52% (95%CI 42-61%), and 50% (95%CI 25-75%), respectively. The accuracy to detect IT in AD on ECG-gated CTA was significantly higher in the systolic phase than that in the diastolic phase (P = 0.025). However, there were no differences in the accuracy (83%; 95%CI 78-89%), sensitivity (71%; 95%CI 62-80%), or specificity (100%; 95%CI 100%) to detect ULP in IMH between the cardiac cycle phases. CONCLUSION: Although it is currently recommended for routine diagnosis of AD and IMH, single-diastolic-phase ECG-gated CTA has risk to miss some IT in AD that are detectable in the systolic phase on full-phase ECG-gated CTA. This information is critical for determining the optimal treatment strategy for AD.

Postmortem magnetic resonance imaging revealed bilateral globi pallidi lesions in a death associated with prolonged carbon monoxide poisoning: a case report.

A man and a woman were found dead in the same car with a burned coal briquette. The cause of death of the woman was assigned to acute carbon monoxide (CO) poisoning without difficulty based on typical findings associated with this condition, including elevation of carboxyhaemoglobin (COHb). However, the man had an unremarkable elevation of COHb and a higher rectal temperature compared to that of the woman. Postmortem computed tomography (PMCT) revealed ambiguous low-density areas in the bilateral globi pallidi. Further analysis by postmortem magnetic resonance (PMMR) imaging showed these lesions more clearly; the lesions appeared as marked high signal intensity areas on both the T2-weighted images and the fluid-attenuated inversion recovery sequences. A subsequent autopsy revealed signs of pneumonia, dehydration, starvation, and hypothermia, suggesting that the man died from prolonged CO poisoning. Both globi pallidi contained grossly ambiguous lesions, and a detailed neuropathologic investigation revealed these lesions to be coagulative necrotic areas; this finding was compatible with a diagnosis of prolonged CO poisoning. This case report shows that postmortem imaging, especially PMMR, is useful for detecting necrotic lesions associated with prolonged CO poisoning. This report further exemplifies the utility of PMMR for detecting brain lesions, which may be difficult to detect by macroscopic analysis.

Detection of the intimal tear in aortic dissection and ulcer-like projection in intramural hematoma: usefulness of full-phase retrospective ECG-gated CT angiography.

PURPOSE: To compare the accuracy of non-electrocardiogram (ECG)-gated CT angiography (CTA), single-diastolic-phase ECG-gated CTA, and full-phase ECG-gated CTA in detecting the intimal tear (IT) in aortic dissection (AD) and ulcer-like projection (ULP) in intramural hematoma (IMH). MATERIALS AND METHODS: A total of 81 consecutive patients with AD and IMH of the thoracic aorta were included in this single-center retrospective study. Non-ECG-gated CTA, single-diastolic-phase ECG-gated CTA, and full-phase ECG-gated CTA were used to detect the presence of the IT and ULP in thoracic aortic regions including the ascending aorta, aortic arch, and proximal and distal descending aorta. RESULTS: The accuracy of detecting the IT and ULP was significantly greater using full-phase ECG-gated CTA (88% [95% CI: 100%, 75%]) than non-ECG-gated CTA (72% [95% CI: 90%, 54%], P = 0.001) and single-diastolic-phase ECG-gated CTA (76% [95% CI: 93%, 60%], P = 0.008). CONCLUSION: Full-phase ECG-gated CTA is more accurate in detecting the IT in AD and ULP in IMH, than non-ECG-gated CTA and single-diastolic-phase ECG-gated CTA.

Postmortem CT and MRI findings of massive fat embolism.

OBJECTIVE: To elucidate postmortem computed tomography (PMCT) and postmortem magnetic resonance (PMMR) imaging findings suggesting massive fat embolism. MATERIALS AND METHODS: Consecutive forensic cases with PMCT and PMMR scans of subjects prior to autopsy were assessed. For PMCT, 16- or 64-row multidetector CT scans were used; for PMMR, a 1.5 T system was used. MRI sequences of the chest area included T2- and T1-weighted fast spin-echo imaging, T2*-weighted imaging, T1-weighted 3-dimensional gradient-echo imaging with or without a fat-suppression pulse, short tau inversion recovery, and in-phase/opposed-phase imaging. At autopsy, forensic pathologists checked for pulmonary fat embolism with fat staining; Falzi's grading system was used for classification. RESULTS: Of 31 subjects, four were excluded because fat staining for histopathological examination of the lung tissue could not be performed. In three of the remaining 27 subjects, histology revealed massive fat embolism (Falzi grade III) and the cause of death was considered to be associated with fat embolism. CT detected a "fat-fluid level" in the right heart or intraluminal fat in the pulmonary arterial branches in two subjects. MRI detected these findings more clearly in both subjects. In one subject, CT and MRI were both negative. There were no positive findings in the 24 subjects that were fat embolism-negative by histology. DISCUSSION AND CONCLUSION: In some subjects, a massive fat embolism can be suggested by postmortem imaging with a "fat-fluid level" in the right heart or intraluminal fat in the pulmonary arterial branches. PMMR potentially suggests fat embolism more clearly than PMCT.

Traumatic axonal injury revealed by postmortem magnetic resonance imaging: A case report.

In forensic investigations, it is important to detect traumatic axonal injuries (TAIs) to reveal head trauma that might otherwise remain occult. These lesions are subtle and frequently ambiguous on macroscopic evaluations. We present a case of TAI revealed by pre-autopsy postmortem magnetic resonance imaging (PMMR). A man in his sixties was rendered unconscious in a motor vehicle accident. CT scans revealed traumatic mild subarachnoid hemorrhage. Two weeks after the accident he regained consciousness, but displayed an altered mental state. Seven weeks after the accident, he suddenly died in hospital. Postmortem computed tomography (PMCT) and PMMR were followed by a forensic autopsy. PMMR showed low-intensity lesions in parasagittal white matter, deep white matter, and corpus callosum on three-dimensional gradient-echo T1-weighted imaging (3D-GRE T1WI). In some of these lesions, T2∗-weighted imaging also showed low-intensity foci suggesting hemorrhagic axonal injury. The lesions were difficult to find on PMCT and macroscopic evaluation, but were visible on antemortem MRI and confirmed as TAIs on histopathology. From this case, it can be said that PMMR can detect subtle TAIs missed by PMCT and macroscopic evaluation. Hence, pre-autopsy PMMR scanning could be useful for identifying TAIs during forensic investigations.

Reduced Field-of-View Diffusion Tensor Imaging of the Spinal Cord Shows Motor Dysfunction of the Lower Extremities in Patients With Cervical Compression Myelopathy.

STUDY DESIGN: A cross-sectional study. OBJECTIVE: The aim of this study was to quantify spinal cord dysfunction at the tract level in patients with cervical compressive myelopathy (CCM) using reduced field-of-view (rFOV) diffusion tensor imaging (DTI). SUMMARY OF BACKGROUND DATA: Although magnetic resonance imaging (MRI) is the standard used for radiological evaluation of CCM, information acquired by MRI does not necessarily reflect the severity of spinal cord disorder. There is a growing interest in developing imaging methods to quantify spinal cord dysfunction. To acquire high-resolution DTI, a new scheme using rFOV has been proposed. METHODS: We enrolled 10 healthy volunteers and 20 patients with CCM in this study. The participants were studied using a 3.0-T MRI system. For DTI acquisitions, diffusion-weighted spin-echo rFOV single-shot echo-planar imaging was used. Regions-of-interest (ROI) for the lateral column (LC) and posterior column (PC) tracts were determined on the basis of a map of fractional anisotropy (FA) of the spinal cord and FA values were measured. The FA of patients with CCM was compared with that of healthy controls and correlated with Japanese Orthopaedic Association (JOA) score. RESULTS: In LC and PC tracts, FA values in patients with CCM were significantly lower than in healthy volunteers. Total JOA scores correlated moderately with FA in LC and PC tracts. JOA subscores for motor dysfunction of the lower extremities correlated strongly with FA in LC and PC tracts. CONCLUSION: It is feasible to evaluate the cervical spinal cord at the tract level using rFOV DTI. Although FA values at the maximum compression level were not well correlated with total JOA scores, they were strongly correlated with JOA subscores for motor dysfunction of the lower extremities. Our findings suggest that FA reflects white matter dysfunction below the maximum compression level and FA can be used as an imaging biomarker of spinal cord dysfunction. LEVEL OF EVIDENCE: 4.

Diffusion tensor imaging can predict surgical outcomes of patients with cervical compression myelopathy.

PURPOSE: The aim of this study was to assess the potential role of diffusion tensor imaging (DTI) as a predictor of surgical outcomes in patients with cervical compressive myelopathy (CCM). Surgical decompression is often recommended for symptomatic CCM. It is important to know the prognosis of surgical outcomes and to recommend appropriate timing for surgery. METHODS: We enrolled 26 patients with CCM who underwent surgery. The Japanese Orthopaedic Association (JOA) score for cervical myelopathy was evaluated before and 6 months after surgery. Surgical outcomes were regarded as good if there was a change in JOA score of three points or more, or the recovery rate of JOA score was 50% or more. The patients were examined using a 3.0 T magnetic resonance system before surgery. Measured diffusion parameters were fractional anisotropy (FA) and mean diffusivity (MD). The correlations between DTI parameters and surgical outcomes were analyzed. RESULTS: Both change and recovery rate of JOA score moderately correlated with FA. Furthermore, the area under the receiver-operator characteristic curve based on FA for prognostic precision of surgical outcomes indicates that FA is a good predictive factor. The cut-off values of FA for predicting good surgical outcomes evaluated by change and recovery rate of JOA score were 0.65 and 0.57, respectively. Neither change nor recovery rate of JOA score correlated with MD. CONCLUSIONS: FA in spinal cord DTI can moderately predict surgical outcomes. DTI can serve as a supplementary tool for decision-making to guide surgical intervention in patients with CCM.

Tract-Specific Diffusion Tensor Imaging Reveals Laterality of Neurological Symptoms in Patients with Cervical Compression Myelopathy.

BACKGROUND: Patients with cervical compression myelopathy (CCM) generally present bilateral neurological symptoms in their extremities. However, a substantial portion of patients with CCM exhibit laterality of neurological symptoms. The aim of this study was to assess the correlation between intrinsic structural damage and laterality of symptoms using spinal cord diffusion tensor imaging (DTI) of the corticospinal tract. METHODS: We enrolled 10 healthy volunteers and 40 patients with CCM in this study. We evaluated motor function using the American Spinal Injury Association (ASIA) motor score for left and right extremities. For DTI acquisitions, a 3.0-T magnetic resonance imaging system with diffusion-weighted spin-echo sequence was used. Regions-of-interest in the lateral column tracts were determined. We determined the correlations between fractional anisotropy (FA) and ASIA motor scores. An FA asymmetry index was calculated using left and right regions-of-interest. RESULTS: Four patients exhibited laterality of symptoms in their extremities, for which left and right ASIA scores correlated moderately with FA in the left and right lateral columns, respectively (left: ρ = 0.64, P < 0.001; right: ρ = 0.67, P < 0.001). The area under the receiver-operator characteristic curve showed that the FA asymmetry index indicated laterality of symptoms. CONCLUSIONS: Using tract-specific DTI, we demonstrated that microstructural damages in the left and right corticospinal tracts correlated with corresponding neurological symptoms in the ipsilateral side and the FA asymmetry index could indicate laterality in neurological symptoms of patients with CCM.

Diffusion tensor imaging of lumbar spinal nerve in subjects with degenerative lumbar disorders.

Recently several authors have reported that diffusion tensor imaging (DTI) might provide a new understanding of sciatica. The purpose of this study was to investigate the clinical feasibility of DTI for the evaluation of lumbar spinal nerve of patients with sciatica associated with lumbar degenerative disorders. Thirty-four patients (25men, mean age63. 3years) with degenerated lumbar disease, 14 patients with lumbar spinal stenosis with foraminal stenosis, 12 with lumbar spinal stenosis without foraminal stenosis, five with lumbar disc herniation, two with discogenic low back pain, and one with spondylolysis who underwent 3.0T magnetic resonance (MR) imaging and surgical treatment were included in the present study. Fractional anisotropy (FA) was calculated from an FA map, and tractography was investigated. In asymptomatic nerves, tractography showed all L3-S1 spinal nerve roots clearly. Abnormalities of tractography were classified into three types by shape; "Disrupted", "Narrowing", and "Tapering". More abnormalities of tractography were found in patients with lumbar spinal stenosis, and especially in patients with foraminal stenosis. The disrupted type was the most common. The mean FA of entrapped symptomatic nerves was less than seen on the intact side. This study demonstrates that tractography shows abnormal findings for nerve roots in lumbar spinal degeneration and that FA decreases in symptomatic roots. DTI may offer not only morphological evaluation, but also quantitative evaluation. We believe that DTI can be used as a tool for the diagnosis of lumbar spinal degenerative disease.