The cadaveric perfusion and angiography as a teaching tool: imaging the intracranial vasculature in cadavers

Biostasis: A Roadmap for Research in Preservation and Potential Revival of Humans

Human biostasis, the preservation of a human when all other contemporary options for extension of quality life are exhausted, offers the speculative potential for survival via continuation of life in the future. While provably reversible preservation, also known as suspended animation, is not yet possible for humans, the primary justification for contemporary biostasis is the preservation of the brain, which is broadly considered the seat of memories, personality, and identity. By preserving the information contained within the brain's structures, it may be possible to resuscitate a healthy whole individual using advanced future technologies. There are numerous challenges in biostasis, including inadequacies in current preservation techniques, methods to evaluate the quality of preservation, and potential future revival technologies. In this report, we describe a roadmap that attempts to delineate research directions that could improve the field of biostasis, focusing on optimizing preservation protocols and establishing metrics for querying preservation quality, as well as pre- and post-cardiac arrest factors, stabilization strategies, and methods for long-term preservation. We acknowledge the highly theoretical nature of future revival technologies and the importance of achieving high-fidelity brain preservation to maximize the potential of future repair technologies. We plan to update the research roadmap biennially. Our goal is to encourage multidisciplinary communication and collaboration in this field.

Exploring arterial anatomy of the internal capsule: an analysis of the deep vascular structures and related white matter pathways

BACKGROUND AND OBJECTIVES

The internal capsule is supplied by perforators originating from the internal carotid artery, middle cerebral artery, anterior choroidal artery and anterior cerebral artery. The aim of this study is to examine the vascular anatomy of the internal capsule, along with its related white matter anatomy, in order to prevent potential risks and complications during surgical interventions.

METHODS

Twenty injected hemispheres prepared according to the Klingler method were dissected. Dissections were photographed at each stage. The findings obtained from the dissections were illustrated to make them more understandable. Additionally, the origins of the arteries involved in the vascularization of the internal capsule, their distances to bifurcations, and variations in supplying territories have been thoroughly examined.

RESULTS

The insular cortex and the branches of the middle cerebral artery on the insula and operculum were observed. Following decortication of the insular cortex, the extreme capsule, claustrum, external capsule, putamen and globus pallidus structures were exposed. The internal capsule is shown together with the lenticulostriate arteries running on the anterior, genu and posterior limbs. Perforators supplying the internal capsule originated from the middle cerebral artery, anterior cerebral artery, internal carotid artery and anterior choroidal artery. The internal capsule's vascular supply varied, with the medial lenticulostriate arteries (MLA) and lateral lenticulostriate arteries (LLA) being the primary arteries. The anterior limb was most often supplied by the MLA, while the LLA and anterior choroidal artery dominated the genu and posterior limb. The recurrent artery of Heubner originated mostly from the A2 segment. The distance from the ICA bifurcation to the origin of the first LLA on M1 is 9.55 ± 2.32 mm, and to the first MLA on A1 is 5.35 ± 1.84 mm. MLA branching from A1 and proximal A2 ranged from 5 to 9, while LLA originating from the MCA ranged from 7 to 12.

CONCLUSION

This study provides comprehensive understanding of the arterial supply to the internal capsule by combining white matter dissection. The insights gained from this study can help surgeons plan and execute procedures including oncological, psychosurgical, and vascular more accurately and safely. The illustrations derived from the dissections serve as valuable educational material for young neurosurgeons and other medical professionals.

Simple modified silicone rubber injection technique in fresh cadaveric pelvis and extremities

The silicone rubber injection technique was first described in 1999 and has been used in the vascular study of neurology and head and neck dissection. Silicone rubber is durable, flexible, and inexpensive. However, the original silicone rubber injection formula perfuses poorly into the pelvis and extremities. We present a simple modification to the silicone rubber injection technique, showcasing its effectiveness in studying the vascular structures in the pelvis and extremities. We used an ordinary mold-making silicone rubber. The new formula involves mixing the silicone rubber with silicone thinner, acetone, catalyst, and resin color. The mixture is then injected into the artery until the color becomes visible under the skin. The specimen is left at room temperature for 0.5-1 h for the silicone rubber to harden. With our technique, the silicone rubber substance perfuses adequately into small arterial perforators and can penetrate into the subdermal plexus. The smallest subdermal arteries identified under a light microscope measured 6 μm. The modified silicone rubber injection technique has proven to be a valuable tool in anatomical education and surgical training.

Combined cone-beam CT imaging and microsurgical dissection of cadaver specimens to study cerebral venous anatomy: a technical note

PURPOSE

Cadaver dissections and X-ray based 3D angiography are considered gold standards for studying neurovascular anatomy. We sought to develop a model that utilize the combination of both these techniques to improve current tools for anatomical research, teaching and preoperative surgical planning, particularly addressing the venous system of the brain.

MATERIALS AND METHODS

Seven ethanol-fixed human cadaveric heads and one arm were injected with a latex-barium mixture into the internal jugular veins and the brachial artery. After the ethanol-based fixation, specimens were scanned by high-resolution cone-beam CT and images were post-processed on a 3D-workstation. Subsequent, microsurgical dissections were performed by an experienced neurosurgeon and venous anatomy was compared with relevant 3D venograms.

RESULTS

Latex-barium mixtures resulted in a homogenous cast with filling of the cerebral venous structures down to 150 μm in diameter. The ethanol-based preparation of the cadaveric brains allowed for near-realistic microsurgical maneuverability during dissection. The model improves assessment of the venous system for anatomical education and hands-on surgical training.

CONCLUSION

To our knowledge we describe the first preparation method which combines near-realistic microsurgical dissection of human heads with high-resolution 3D imaging of the cerebral venous system in the same specimens.

Brain Vasculature Color-Labeling Using the Triple-Injection Method in Cadaveric Heads: A Technical Note for Improved Teaching and Research in Neurovascular Anatomy

BACKGROUND

Color-labeling injections of cadaveric heads have revolutionized education and teaching of neurovascular anatomy. Silicone-based and latex-based coloring techniques are currently used, but limitations exist because of the viscosity of solutions used.

OBJECTIVE

To describe a novel "triple-injection method" for cadaveric cranial vasculature and perform qualitative and semiquantitative evaluations of colored solution penetration into the vasculature.

METHODS

After catheter preparation, vessel cannulation, and water irrigation of embalmed cadaveric heads, food coloring, gelatin, and silicone solutions were injected in sequential order into bilateral internal carotid and vertebral arteries (red-colored) and internal jugular veins (blue-colored). In total, 6 triple-injected embalmed cadaveric heads and 4 silicone-based "control" embalmed cadaveric heads were prepared. A qualitative analysis was performed to compare the vessel coloring of 6 triple-injected heads with that of 4 "control" heads. A semiquantitative evaluation was completed to appraise sizes of the smallest color-filled vessels.

RESULTS

Naked-eye and microscope evaluations of embalmed experimental and control cadaveric heads revealed higher intensity and more distal color-labeling following the "triple-injection method" compared with the silicone-based method in both the intracranial and extracranial vasculature. Microscope assessment of 1-mm-thick coronal slices of triple-injected brains demonstrated color-filling of distal vessels with minimum diameters of 119 μm for triple-injected heads and 773 μm for silicone-based injected heads.

CONCLUSION

Our "triple-injection method" showed superior color-filling of small-sized vessels as compared with the silicone-based injection method, resulting in more distal penetration of smaller caliber vessels.

Antigenicity is preserved with fixative solutions used in human gross anatomy: A mice brain immunohistochemistry study

Background

Histology remains the gold-standard to assess human brain biology, so ex vivo studies using tissue from brain banks are standard practice in neuroscientific research. However, a larger number of specimens could be obtained from gross anatomy laboratories. These specimens are fixed with solutions appropriate for dissections, but whether they also preserve brain tissue antigenicity is unclear. Therefore, we perfused mice brains with solutions used for human body preservation to assess and compare the tissue quality and antigenicity of the main cell populations.

Materials and methods

Twenty-eight C57BL/6J mice were perfused with 4% formaldehyde (FAS, N = 9), salt-saturated solution (SSS, N = 9), and alcohol solution (AS, N = 10). The brains were cut into 40 μm sections for antigenicity analysis and were assessed by immunohistochemistry of four antigens: neuronal nuclei (NeuN), glial fibrillary acidic protein (GFAP astrocytes), ionized calcium-binding adaptor molecule 1 (Iba1-microglia), and myelin proteolipid protein (PLP). We compared the fixatives according to multiple variables: perfusion quality, ease of manipulation, tissue quality, immunohistochemistry quality, and antigenicity preservation.

Results

The perfusion quality was better using FAS and worse using AS. The manipulation was very poor in SSS brains. FAS- and AS-fixed brains showed higher tissue and immunohistochemistry quality than the SSS brains. All antigens were readily observed in every specimen, regardless of the fixative solution.

Conclusion

Solutions designed to preserve specimens for human gross anatomy dissections also preserve tissue antigenicity in different brain cells. This offers opportunities for the use of human brains fixed in gross anatomy laboratories to assess normal or pathological conditions.

Sternocleidomastoid flap for pedicled reconstruction in head & neck surgery- revisiting the anatomy and technique

Background

Previous studies on sternocleidomastoid flaps, have defined the importance of preserving sternocleidomastoid (SCM) branch of superior thyroid artery (STA). This theory drew criticism, as this muscle is known to be a type II muscle, i.e., the muscle has one dominant pedicle (branches from the occipital artery at the superior pole) and smaller vascular pedicles entering the belly of muscle (branches from STA and thyrocervical trunk) at the middle and lower pole respectively. It was unlikely for the SCM branch of STA to supply the upper and lower thirds of the muscle. We undertook a cadaveric angiographic study to investigate distribution of STA supply to SCM muscle.

Methods

It is a cross-sectional descriptive study on 10 cadaveric SCM muscles along with ipsilateral STA which were evaluated with angiography using diatrizoate (urograffin) dye. Radiographic films were interpreted looking at the opacification of the muscle. Results were analyzed using frequency distribution and percentage.

Results

Out of ten specimens, near complete opacification was observed in eight SCM muscle specimens. While one showed poor uptake in the lower third of the muscle, the other showed poor uptake in the upper third segment of muscle.

Conclusion

Based on the above findings we suggest to further investigate sternocleidomastoid muscle as a type III flap, as the STA branch also supplies the whole muscle along with previously described pedicle from occipital artery. However, this needs to be further corroborated intra-operatively using scanning laser doppler. This also explains better survival rates of superior thyroid artery based sternomastoid flaps.

A novel ex vivo, in situ method to study the human brain through MRI and histology

BACKGROUND

MRI-histology correlation studies of the ex vivo brain mostly employ fresh, extracted (ex situ) specimens, aldehyde fixed by immersion, which has several disadvantages for MRI scanning (e.g. deformation of the organ). A minority of studies are done ex vivo-in situ (unfixed brain), requiring an MRI scanner readily available within a few hours of the time of death.

NEW METHOD

We propose a new technique, exploited by anatomists, for scanning the ex vivo brain: fixation by whole body perfusion, which implies fixation of the brain in situ. This allows scanning the brain surrounded by fluids, meninges, and skull, preserving the structural relationships of the brain in vivo. To evaluate the proposed method, five heads perfused-fixed with a saturated sodium chloride solution were employed. Three sequences were acquired on a 1.5 T MRI scanner: T1weighted, T2weighted-FLAIR, and Gradient-echo. Histology analysis included immunofluorescence for myelin basic protein and neuronal nuclei.

RESULTS

All MRIs were successfully processed through a validated pipeline used with in vivo MRIs. All cases exhibited positive antigenicity for myelin and neuronal nuclei.

COMPARISON WITH EXISTING METHODS

All scans registered to a standard neuroanatomical template in pseudo-Talairach space more accurately than an ex vivo-ex situ scan. The time interval to scan the ex vivo brain in situ was increased to at least 10 months.

CONCLUSIONS

MRI and histology study of the ex vivo-in situ brain fixed by perfusion is an alternative approach that has important procedural and practical advantages over the two standard methods to study the ex vivo brain.

Perfusion fixation in brain banking: a systematic review

Background

Perfusing fixatives through the cerebrovascular system is the gold standard approach in animals to prepare brain tissue for spatial biomolecular profiling, circuit tracing, and ultrastructural studies such as connectomics. Translating these discoveries to humans requires examination of postmortem autopsy brain tissue. Yet banked brain tissue is routinely prepared using immersion fixation, which is a significant barrier to optimal preservation of tissue architecture. The challenges involved in adopting perfusion fixation in brain banks and the extent to which it improves histology quality are not well defined.

Methodology

We searched four databases to identify studies that have performed perfusion fixation in human brain tissue and screened the references of the eligible studies to identify further studies. From the included studies, we extracted data about the methods that they used, as well as any data comparing perfusion fixation to immersion fixation. The protocol was preregistered at the Open Science Framework: https://osf.io/cv3ys/.

Results

We screened 4489 abstracts, 214 full-text publications, and identified 35 studies that met our inclusion criteria, which collectively reported on the perfusion fixation of 558 human brains. We identified a wide variety of approaches to perfusion fixation, including perfusion fixation of the brain in situ and ex situ, perfusion fixation through different sets of blood vessels, and perfusion fixation with different washout solutions, fixatives, perfusion pressures, and postfixation tissue processing methods. Through a qualitative synthesis of data comparing the outcomes of perfusion and immersion fixation, we found moderate confidence evidence showing that perfusion fixation results in equal or greater subjective histology quality compared to immersion fixation of relatively large volumes of brain tissue, in an equal or shorter amount of time.

Conclusions

This manuscript serves as a resource for investigators interested in building upon the methods and results of previous research in designing their own perfusion fixation studies in human brains or other large animal brains. We also suggest several future research directions, such as comparing the in situ and ex situ approaches to perfusion fixation, studying the efficacy of different washout solutions, and elucidating the types of brain donors in which perfusion fixation is likely to result in higher fixation quality than immersion fixation.

Electronic supplementary material

The online version of this article (10.1186/s40478-019-0799-y) contains supplementary material, which is available to authorized users.

A novel micro-CT-based method to monitor the morphology of blood vessels in the rabbit endplate

PURPOSE

The aim of this study was to develop a novel method for observing the morphology of the blood vessels in the rabbit endplate.

METHODS

Twenty 6-month-old rabbits were used in this study. The blood vessels in the L5 endplate in Group A were injected with iohexol and Group B with barium sulfate. Group C was the control group with saline. To optimize the study, Group B was divided into two subgroups: Group B-1 was injected with 100% (w/v) barium sulfate and Group B-2 with 50% (w/v). After injection, the L4-L5 vertebral body was excised and the cranial endplate of L5 was scanned using a micro-CT scanner. Models of the vertebral endplate and vessels were reconstructed using the 3D reconstruction software (Mimics 16.0) by calculating a bone threshold value, and then merged these two models to create a superimposed model.

RESULTS

The 3D vessel models could not be created in Groups A and C, but they were clearly visualized in Group B. In the 3D model, the blood vessels extended from the subchondral bone to the endplate, and the density of the blood vessels in the area of the nucleus pulposus (NP) was higher than in the annulus fibrosus.

CONCLUSIONS

The results of this study suggest that the blood vessels in the rabbit endplate can be clearly observed by the method described using barium sulfate [the 50% (w/v) gave better results compared with the 100% (w/v)]. The information from the 3D vessel structure could provide essential data to help us understand the nutrient pathways within the vertebral endplate.