Technique for Latex Injection and Reuse of Human Heads Preserved in Formaldehyde

Toward an optimal cadaveric brain model for neurosurgical education: assessment of preservation, parenchyma, vascular injection, and imaging

OBJECTIVE

We assessed types of cadaveric head and brain tissue specimen preparations that are used in a high throughput neurosurgical research laboratory to determine optimal preparation methods for neurosurgical anatomical research, education, and training.

METHODS

Cadaveric specimens (N = 112) prepared using different preservation and vascular injection methods were imaged, dissected, and graded by 11 neurosurgeons using a 21-point scale. We assessed the quality of tissue and preservation in both the anterior and posterior circulations. Tissue quality was evaluated using a 9-point magnetic resonance imaging (MRI) scale.

RESULTS

Formalin-fixed specimens yielded the highest scores for assessment (mean ± SD [17.0 ± 2.8]) vs. formalin-flushed (17.0 ± 3.6) and MRI (6.9 ± 2.0). Cadaver assessment and MRI scores were positively correlated (P < 0.001, R2 0.60). Analysis showed significant associations between cadaver assessment scores and specific variables: nonformalin fixation (β = -3.3), preservation within ≤72 h of death (β = 1.8), and MRI quality score (β = 0.7). Formalin-fixed specimens exhibited greater hardness than formalin-flushed and nonformalin-fixed specimens (P ≤ 0.006). Neurosurgeons preferred formalin-flushed specimens injected with colored latex.

CONCLUSION

For better-quality specimens for neurosurgical education and training, formalin preservation within ≤72 h of death was preferable, as was injection with colored latex. Formalin-flushed specimens more closely resembled live brain parenchyma. Assessment scores were lower for preparation techniques performed > 72 h postmortem and for nonformalin preservation solutions. The positive correlation between cadaver assessment scores and our novel MRI score indicates that donation organizations and institutional buyers should incorporate MRI as a screening tool for the selection of high-quality specimens.

Latex vascular injection as method for enhanced neurosurgical training and skills

Background

Tridimensional medical knowledge of human anatomy is a key step in the undergraduate and postgraduate medical education, especially in surgical fields. Training simulation before real surgical procedures is necessary to develop clinical competences and to minimize surgical complications.

Methods

Latex injection of vascular system in brain and in head-neck segment is made after washing out of the vascular system and fixation of the specimen before and after latex injection.

Results

Using this latex injection technique, the vascular system of 90% of brains and 80% of head-neck segments are well-perfused. Latex-injected vessels maintain real appearance compared to silicone, and more flexible vessels compared to resins. Besides, latex makes possible a better perfusion of small vessels.

Conclusions

Latex vascular injection technique of the brain and head-neck segment is a simulation model for neurosurgical training based on real experiencing to improve surgical skills and surgical results.

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.

Fascial layers encountered in the lateral skull base region: A cadaveric and radiological analysis

BACKGROUND

In our experience, the anterior carotid sheath forms an important plane of dissection when excising temporal bone region cancers. However, its anatomical composition, relationships, and radiological appearance remains unclear.

METHODS

Eight sides of cadaveric heads were dissected. Anatomical findings were correlated with a high-resolution baseline T1 MRI.

RESULTS

The anterior carotid sheath was formed by the tensor-vascular-styloid fascia, stylopharyngeal fascia, buccopharyngeal fascia (BPF), and longus capitis fascia (LCF), and appeared as a hypointense line on MRI. Not previously described, the glossopharyngeal nerve pierced the sheath 9.0 mm (SD 2.1 mm) below the skull base and traveled through its LCF and BPF layers to exit near the pharynx.

CONCLUSION

Multiple fascial layers formed the anterior carotid sheath at the skull base, and this was radiologically identifiable. Further studies are required to validate findings and investigate the role this fascial plane has in forming an effective barrier to spread of malignancy.

Latex-injected, non-decapitated, saturated salt method-embalmed cadaver technique development and application as a head and neck surgery training model

Published cerebrovascular injection techniques have mostly used decapitated, fresh cadavers or heads embalmed with 10% formaldehyde. There have been no reports using vascular-injected cadavers for head and neck surgical training models or using vascular injections in saturated salt method-embalmed cadavers. Thus, we performed vascular labeling of five saturated salt method-embalmed cadavers without decapitation. Latex mixed with red ink was injected into the common carotid artery via a 3D-printed vascular adapter. The injection force was provided by a peristaltic pump. Thyroidectomy, submandibular gland excision, neck dissection, parotidectomy, and mandibulotomy were performed on both sides of each cadaver (n = 10). The consistency of the cadavers was softer than fresh ones. Subcutaneous tissues were well preserved, and muscles were moist and elastic. Five physicians graded the resemblance of the heads and necks of the latex-injected, saturated salt method-embalmed, non-decapitated of five cadavers compared to living humans using a Likert scale from 0 (no resemblance) to 5 (maximum resemblance). Fifty-two percent of the head and neck region resemblance scale ratings were four or five. Although the cadavers were practical for head and neck surgical simulations, the brain parenchyma was only partially preserved and unsuitable for use. The most distal arterial branches reached by the injected latex were measured. The external caliber of the smallest vessels reached were lacrimal arteries (mean caliber ± SD, 0.04 ± 0.04 mm; 95% CI [0, 0.09]). There were no significant differences in the mean caliber of the smallest vessels reached between the left- and right-sided arterial branches (all p < 0.05).

Development of an Experimental Model for Studying the Nasosinusal and Skull Base Arterial and Venous Systems Using Iodinated Contrast and Latex in Cadavers

BACKGROUND

Cadaver dissection remains one of the most reliable and safest ways to study anatomy, whereas computed tomography angiography (CTA) is an essential technology for enabling students to become familiar with human anatomy and surgical planning. Thus, the convergence of both radiologic and anatomic information is important for surgical success, especially in regions of complex anatomy such as the nasosinusal and skull base regions. Here we propose an experimental model in formalinized cadaver heads consisting of intravascular injection of colored latex and iodinated contrast mixture, followed by CTA scans of the nasosinusal and skull base arterial and venous systems before dissection.

METHODS

Six cadaver heads that had been preserved for >5 years in 10% formaldehyde were immersed for 72 hours in a solution containing a dimethyldiethanol mono/dialkyloyl ester quaternary ammonium salt. In 5 of these heads, a mixture composed of latex, tissue ink, and iodinated contrast (Ultravist 300) was injected into the vascular system. CTA scans were performed sequentially after the injection, followed by endonasal and macroscopic dissections.

RESULTS

There was good radiologic and macroscopic vessel uptake in 4 specimens, allowing a detailed anatomic study.

CONCLUSIONS

An experimental model was made feasible by injecting iodinated contrast and colored latex into formalinized cadavers for CTA evaluation of the nasosinusal and skull base arterial and venous systems before performing dissections.