Macroscopic and histological examination of human bridging veins.

In infantile abusive head injury (AHT), subdural haemorrhage (SDH) is commonly held to result from traumatic damage to bridging veins traversing from the surface of the brain to the dura and dural venous sinuses. However, there are limited published radiological or autopsy demonstrations of ruptured bridging veins and several authors also assert that bridging veins are too large to rupture due to the forces associated with AHT. There have been several studies on the size, locations and numbers of adult bridging veins and there is one small study of infant bridging veins. However, there are no microscopic studies of infant bridging veins and only a select few ultrastructural investigations of adult bridging veins. Hitherto, it has been assumed that bridging veins from infants and younger children will display the same anatomical characteristics as those in adulthood. At 19 neonatal, infant and young child post-mortem examinations, we macroscopically examined and sampled bridging veins for microscopy. We compared the histology of those samples with bridging veins from an older child and two adults. We demonstrate that adult bridging veins are usually surrounded by supportive meningeal tissue that appears to be lacking or minimally present around the bridging veins of younger children. Neonatal, infant and young children's veins had a free 'bridging' section. Neonatal and infant bridging veins had smaller diameter ranges and thinner walls (some only 5-7 µm) than those seen in older children and adults. Bridging vein walls contained both fine strands of elastic fibers and a more pronounced elastic lamina. The presence of an elastic lamina occurred more frequently in the older age groups These anatomical differences between the veins of adults and young children may help to explain apparent increased vulnerability of neonatal/infant bridging veins to the forces associated with a shaking-type traumatic event.

A systematic autopsy survey of human infant bridging veins.

In the first years of life, subdural haemorrhage (SDH) within the cranial cavity can occur through accidental and non-accidental mechanisms as well as from birth-related injury. This type of bleeding is the most common finding in victims of abusive head trauma (AHT). Historically, the most frequent cause of SDHs in infancy is suggested to be traumatic damage to bridging veins traversing from the brain to the dural membrane. However, several alternative hypotheses have been suggested for the cause and origin of subdural bleeding. It has also been suggested by some that bridging veins are too large to rupture through the forces associated with AHT. To date, there have been no systematic anatomical studies on infant bridging veins. During 43 neonatal, infant and young child post-mortem examinations, we have mapped the locations and numbers of bridging veins onto a 3D model of the surface of a representative infant brain. We have also recorded the in situ diameter of 79 bridging veins from two neonatal, one infant and two young children at post-mortem examination. Large numbers of veins, both distant from and directly entering the dural venous sinuses, were discovered travelling between the brain and dural membrane, with the mean number of veins per brain being 54.1 and the largest number recorded as 94. The mean diameter of the bridging veins was 0.93 mm, with measurements ranging from 0.05 to 3.07 mm. These data demonstrate that some veins are extremely small and subjectively, and they appear to be delicate. Characterisation of infant bridging veins will contribute to the current understanding of potential vascular sources of subdural bleeding and could also be used to further develop computational models of infant head injury.

Could post-mortem computed tomography angiography inform cardiopulmonary resuscitation research?

AIM: Firstly, to develop an optimised chest compression post mortem computed tomography angiography protocol in the adult human during closed chest compression to investigate cardiopulmonary resuscitation blood flow, and secondly to provide preliminary observations of post-mortem anatomical cardiac chamber movement using a novel radiolucent static chest compression device. METHODS: Variable volumes of radiological contrast agent were injected intravenously into a series of consented human cadavers. Each cadaver had chest compressions delivered with a LUCAS™2 mechanical chest compressor. Following each cycle of chest compressions, each cadaver was imaged with a Toshiba Aquilion CXL 128 slice computed tomography (CT) scanner to investigate the extent of contrast distribution. A chest compression simulator was then designed and built to allow static CT imaging of 1cm incremental cadaver chest compressions to a depth of 5cm. RESULTS: Mechanical compressions: Ten cases were recruited for the CT angiography component of the study. Two were subsequently excluded from the study at the time of the initial, non-contrast PMCT scan. A further case was recruited in Emergency Department (ED). CT demonstrable antegrade arterial contrast distribution was achieved in 2 cases. The other 7 cases, including that undertaken in ED shortly after death, showed venous retrograde flow. Incremental compressions: Five new cases underwent incremental chest compression imaging. All cases demonstrated compression of the sternum, ribs, atria and great vessels. The right and left ventricles were not compressed, but moved laterally and inferiorly, further into the left chest cavity. The left hemi-diaphragm, stomach and liver moved inferiorly. The sternum, ventricles, hemi-diaphragm, stomach and liver all moved back to their original position on incremental release. CONCLUSION: The study suggests that with further protocol modification and access to human cadavers as near to death as possible, chest compression post mortem computed angiography (CCPMCTA) could be used as a model for the study of human vascular flow and heart movement during CPR.

Diagnostic accuracy of post-mortem CT with targeted coronary angiography versus autopsy for coroner-requested post-mortem investigations: a prospective, masked, comparison study.

BACKGROUND: England and Wales have one of the highest frequencies of autopsy in the world. Implementation of post-mortem CT (PMCT), enhanced with targeted coronary angiography (PMCTA), in adults to avoid invasive autopsy would have cultural, religious, and potential economic benefits. We aimed to assess the diagnostic accuracy of PMCTA as a first-line technique in post-mortem investigations. METHODS: In this single-centre (Leicester, UK), prospective, controlled study, we selected cases of natural and non-suspicious unnatural death referred to Her Majesty's (HM) Coroners. We excluded cases younger than 18 years, known to have had a transmittable disease, or who weighed more than 125 kg. Each case was assessed by PMCTA, followed by autopsy. Pathologists were masked to the PMCTA findings, unless a potential risk was shown. The primary endpoint was the accuracy of the cause of death diagnosis from PMCTA against a gold standard of autopsy findings, modified by PMCTA findings only if additional substantially incontrovertible findings were identified. FINDINGS: Between Jan 20, 2010, and Sept 13, 2012, we selected 241 cases, for which PMCTA was successful in 204 (85%). Seven cases were excluded from the analysis because of procedural unmasking or no autopsy data, as were 24 cases with a clear diagnosis of traumatic death before investigation; 210 cases were included. In 40 (19%) cases, predictable toxicology or histology testing accessible by PMCT informed the result. PMCTA provided a cause of death in 193 (92%) cases. A major discrepancy with the gold standard was noted in 12 (6%) cases identified by PMCTA, and in nine (5%) cases identified by autopsy (because of specific findings on PMCTA). The frequency of autopsy and PMCTA discrepancies were not significantly different (p=0·65 for major discrepancies and p=0·21 for minor discrepancies). Cause of death given by PMCTA did not overlook clinically significant trauma, occupational lung disease, or reportable disease, and did not significantly affect the overall population data for cause of death (p≥0·31). PMCTA was better at identifying trauma and haemorrhage (p=0·008), whereas autopsy was better at identifying pulmonary thromboembolism (p=0·004). INTERPRETATION: For most sudden natural adult deaths investigated by HM Coroners, PMCTA could be used to avoid invasive autopsy. The gold standard of post-mortem investigations should include both PMCT and invasive autopsy. FUNDING: National Institute for Health Research.

Post-mortem computed tomography coaxial cutting needle biopsy to facilitate the detection of bacterioplankton using PCR probes as a diagnostic indicator for drowning.

We report for the first time the use of coaxial cutting needle biopsy, guided by post-mortem computed tomography (PMCT), to sample internal body tissues for bacterioplankton PCR analysis to investigate drowning. This technical report describes the biopsy technique, the comparison of the needle biopsy and the invasive autopsy sampling results, as well as the PMCT and autopsy findings. By using this new biopsy sampling approach for bacterioplankton PCR, we have developed on previous papers describing the minimally invasive PMCT approach for the diagnosis of drowning. When such a system is used, the operator must take all precautions to avoid contamination of the core biopsy samples due to the sensitivity of PCR-based analytic systems.

Ventilated post-mortem computed tomography through the use of a definitive airway.

Ventilated post-mortem computed tomography (VPMCT) has been shown to achieve lung expansion in cadavers and has been proposed to enhance the diagnosis of lung pathology. Two key problems of the method of ventilation have been identified: firstly, the presence of head and neck rigor making airway insertion challenging and, secondly, air leak, if there is not a good seal around the airway, which diminishes lung expansion and causes inflation of the stomach. Simple procedures to insert a 'definitive' cuffed airway, which has a balloon inflated within the trachea, are therefore desirable. This study aims to test different procedures for inserting cuffed airways in cadavers and compare their ventilation efficacy and to propose a decision algorithm to select the most appropriate method. We prospectively tested variations on two ways of inserting a cuffed airway into the trachea: firstly, using an endotracheal tube (ET) approach, either blind or by direct visualisation, and, secondly, using a tracheostomy incision, either using a standard tracheostomy tube or shortened ET tube. We compare these approaches with a retrospective analysis of a previously reported series using supraglottic airways. All techniques, except 'blind' insertion of ET tubes, were possible with adequate placement of the airway in most cases. However, achieving both adequate insertion and a complete tracheal seal was better for definitive airways with 56 successful cases from 59 (95 %), compared with 9 cases from 18 (50 %) using supraglottic airways (p < 0.0001). Good lung expansion was achieved using all techniques if the airway was adequately positioned and achieved a good seal, and there was no significant chest pathology. We prefer inserting a shortened ET tube via a tracheostomy incision, as we find this the easiest technique to perform and train. Based on our experience, we have developed a decision algorithm to select the most appropriate method for VPMCT.

The effect on cadaver blood DNA identification by the use of targeted and whole body post-mortem computed tomography angiography.

Post-mortem computed tomography angiography (PMCTA) involves the injection of contrast agents. This could have both a dilution effect on biological fluid samples and could affect subsequent post-contrast analytical laboratory processes. We undertook a small sample study of 10 targeted and 10 whole body PMCTA cases to consider whether or not these two methods of PMCTA could affect post-PMCTA cadaver blood based DNA identification. We used standard methodology to examine DNA from blood samples obtained before and after the PMCTA procedure. We illustrate that neither of these PMCTA methods had an effect on the alleles called following short tandem repeat based DNA profiling, and therefore the ability to undertake post-PMCTA blood based DNA identification.

Pump injector system applied to targeted post-mortem coronary artery angiography.

Targeted post-mortem computed tomography angiography (PMCTA) is one of several methods described that can be used to investigate the coronary arteries after death. Previously, this particular method has involved the manual injection of contrast media. However, manual systems do not mimic physiological conditions (arterial pressure) and may not provide optimal contrast, as iodinated contrast medium dissipates rapidly from the intra- to the extra-vascular space. To try and overcome these problems, we now report the use of a clinical automatic pump injector for targeted PMCTA. We present our final protocol for this pump system developed from experience of 74 cases, showing how these clinical pumps can be translated from clinical into autopsy practice for the injection of air and positive contrast media to visualise the coronary arteries of cadavers.

Consent of the recently bereaved to post-mortem targeted angiography research: 207 adult cases.

AIMS: To present our experience of prospective telephone consenting for post-mortem CT angiography (PMCT-A) research using HM coroners' cases. METHODS: Local ethics committee, research and development office, and local HM coroners gave their permission for the families of the deceased, in cases where a 'routine' coroner's autopsy had been authorised, to be approached for their consent to PMCT-A research before the autopsy examination. A forensic pathologist or trial consenter telephoned the next of kin, discussed the nature of the study and obtained verbal informed consent for post-mortem imaging, angiography, case-dependent histological and toxicology sampling and for the use of the images for teaching and training. Thematic analyses of the reasons for giving or refusing consent are provided. RESULTS: Of the 207 cases approached, seven relatives refused to enter their next of kin into the study (96.6% consent rate). CONCLUSIONS: This study shows that prospective consenting for HM coroners' cases to be used for autopsy research is feasible in adults, and can be done ethically, and in the limited time available, by obtaining the consent of the next of kin by telephone before autopsy.