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

A standalone minimally invasive presigmoid retrolabyrinthine suprameatal approach: A cadaveric morphometric study

Background

Presigmoid approaches provide access to several structures anterior to the sigmoid sinus (SS) and may be intended for the treatment of lesions located in the middle and posterior fossa. We conducted a morphometric cadaveric study investigating the infratentorial presigmoid retrolabyrinthine suprameatal approach (PRSA) as a unique operative corridor. The typical anatomic-radiological characteristics and variations were evaluated and analyzed to predict surgical accessibility.

Methods

A total of 10 surgical dissections were performed on both sides of five adults, injected, and cadaveric heads. Fifteen morphometric parameters were measured, analyzed, and categorized into pre-procedural, intra-procedural, and additional parameters.

Results

Preoperative anatomic-radiological parameters provide valuable information to select patients with favorable anatomy that may offer appropriate surgical accessibility to the medial part of cerebellopontine angle cistern, lateral pons, and prepontine cistern through a PRSA corridor. An obtuse petroclival angle of ≥144° with a more horizontally oriented petrous bone, a posterior SS position, and a large mastoid cavity provided the greatest surgical accessibility through the PRSA corridor. The superior petrosal sinus drainage and the degree of petrous apex pneumatization were important factors affecting surgical fluency and speed. However, they were not determinant factors for selecting the most appropriate patients eligible for the PRSA.

Conclusion

The PRSA represents a minimally invasive modification of the trans-labyrinthine approach that may be offered in patients with lesions medial to the internal auditory canal or anterior/lateral to the brainstem, with the goal of preserving vestibulocochlear functions. Preoperative anatomic-radiological parameters are mandatory for a patient-tailored selection of the most effective surgical approach.

Minimally invasive presigmoid retrolabyrinthine suprameatal approach (PRSA): A cadaveric study for accessing premeatal anterior inferior cerebellar artery (AICA) aneurysms

Background

The surgical management of aneurysms involving the proximal third of the anterior inferior cerebellar artery (AICA) usually necessitates complex and invasive approaches, thus posing major challenges. We aimed to investigate the infratentorial presigmoid retrolabyrinthine suprameatal approach (PRSA) as a surgical corridor for premeatal AICA aneurysms.

Methods

We performed 10 PRSA dissections in five cadaveric heads. Twelve morphometric parameters were measured, analyzed, and categorized into pre-procedural, intra-procedural, and additional parameters. The typical anatomic-radiological characteristics and variations were evaluated, and the related anatomical and radiological parameters were analyzed to predict surgical accessibility.

Results

Preoperative anatomic-radiological parameters provide valuable information to select patients with favorable anatomy that may offer appropriate surgical accessibility to the premeatal AICA through a PRSA corridor. The position of the basilar artery from the midline determines the degree of accessibility to the origin of AICA through the infratentorial PRSA. The PRSA for targeting proximal AICA aneurysms was also compared to other surgical approaches based on the available current literature.

Conclusion

Premeatal AICA aneurysms can be accessed and clipped through the infratentorial PRSA corridor. This would allow surgeons to avoid the sacrifice of hearing and balance as compared to other available invasive alternative approaches. The selection of the appropriate patients should be based on the individualized preoperative radiological characteristics for both the vascular and bony anatomy.

Indications, operative techniques, and outcomes of occipital artery-vertebral artery bypass: an institutional series

PURPOSE

Posterior circulation cerebral bypasses often show higher risks and lower patency. Only few reports discussed occipital artery (OA)-vertebral artery (VA) bypasses. We present our illustrative cases to address current gaps in the literature on OA-VA bypass.

METHODS

A single-center retrospective review was conducted to include all institutional cases of OA-VA bypass, discussing the technique and outcomes.

RESULTS

Four institutional cases undergoing a total of 5 bypasses were evaluated, including 3 males and 1 female, with median age of 65 years (range, 62-73). All patients had vertebrobasilar insufficiency (VBI) with recurrent strokes/TIAs due to intracranial atherosclerosis, leading to unilateral VA stenosis with contralateral occlusion (1, 25%), bilateral VA stenosis (1, 25%) or occlusion (1, 25%). Medical management included aspirin for all cases (100%), with clopidogrel in 3 (75%). Surgery was performed through a far lateral approach, connecting the OA to the VA-3 segment, with no inter-positional graft. One patient underwent contralateral OA-VA bypass 6 months after the prior surgery due to worsening of the contralateral VA stenosis. Bypass patency was confirmed in all cases with post-operative angiography. All patients had clinical improvement, with one case of wound dehiscence managed conservatively. All patients were alive at last follow-up (median 7.0 months; range: 1.5-18).

CONCLUSION

OA-VA bypass is a challenging yet effective strategy in selected patients with VBI. Current literature lacks unique definitions of surgical indications and techniques, which we addressed in our series. Surgical education should focus on expanding the microsurgery anatomy knowledge.

Anatomical Study of the Supratentorial Extension for the Retrolabyrinthine Presigmoid Approaches

BACKGROUND

Supratentorial craniotomy represents the upper part of the combined trans-tentorial or the supra-infratentorial presigmoid approach. In this study, we provide qualitative and quantitative analyses for the supratentorial extension of the presigmoid retrolabyrinthine suprameatal approach (PRSA).

METHODS

The infratentorial PRSA followed by the supratentorial extension craniotomy with dividing and removal of the tentorial strip were performed on both sides of 5 injected human cadaver heads (n = 10 sides). Quantitative analysis was performed for the surface area gained (surgical accessibility) by adding the supratentorial craniotomy. Qualitative analysis was performed for the parts of the brainstem, cranial nerves, and vascular structures that became accessible by adding the supratentorial craniotomy. The anatomical obstacles encountered in the added operative corridor were analyzed.

RESULTS

The supratentorial extension of PRSA provides an increase in surgical accessibility of 102.65% as compared to the PRSA standalone. The mean surface area of the exposed brainstem is 197.98 (standard deviation: 76.222) and 401.209 (standard deviation: 123.96) for the infratentorial and the combined supra-infratentorial presigmoid approach, respectively. Exposure for parts of III, IV, and V cranial nerves is added after the extension, and the surface area of the outer craniotomy defect has increased by 60.32%. Parts of the basilar, anterior inferior cerebellar, and superior cerebellar arteries are accessible after the supratentorial extension.

CONCLUSIONS

The supratentorial extension of PRSA allows access to the supra-trigeminal area of the pons and the lower part of the midbrain. Considering this surgical accessibility and exposure significantly assists in planning such complex approaches while targeting central skull base lesions.

The Vertebrobasilar Trunk and Its Anatomical Variants: A Microsurgical Anatomical Study

BACKGROUND

The trunk of the basilar artery has not been included in microanatomy studies. Anatomical variants of the perforant branches of the vertebrobasilar trunk and their relationship with neural structures are very important in surgical approaches. Surgical dissection for the treatment of vascular lesions requires a perfect knowledge of the microsurgical anatomy.

METHODS

We conducted a descriptive analysis of 50 brains, which were fixed with formalin at 10% for 2 weeks, and the arterial system was injected with colored latex. After microsurgical dissection, it was divided into three segments: the lower portion went from the anterior spinal artery to the anteroinferior cerebellar artery, the middle segment was raised from the upper limit of the lower portion to the origin of the superior cerebellar artery, and the upper segment ranged from the previous portion until the origin of the posterior cerebral artery.

RESULTS

The basilar artery had an average length of 30 mm. The average diameter at its junction with the vertebral arteries was 4.05 mm. The average middle segment was 3.4 mm in diameter and 15.2 mm in length. The diameter of the upper segment was 4.2 mm, and its average length was 3.6 mm. The average number of bulbar arteries was three, and their average diameter was 0. 66 mm. The number of caudal perforator arteries were five on average, with a diameter of 0.32 mm. We found three rare cases of anatomical variants in the vertebra-basilar junction.

CONCLUSIONS

The basilar artery emits penetrating branches in its lower, middle, and upper portions. The origin of penetrating branches was single or divided after forming a trunk. However, we observed long branches from perforant arteries.

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.

Peritrigeminal Safe Entry Zone Access to Anterolateral Pons Using the Presigmoid Retrolabyrinthine Suprameatal Approach: A Cadaveric Morphometric Study

BACKGROUND AND OBJECTIVES

Access to the anterolateral pontine lesions can be achieved through the peritrigeminal and supratrigeminal safe entry zones using Kawase, retrosigmoid, or translabyrinthine approaches. However, these approaches entail shallow extensive dissection, tangential access, and compromise vestibulocochlear function. We aimed to investigate infratentorial presigmoid retrolabyrinthine approach to access pontine lesions through the peritrigeminal zone.

METHODS

We performed 10 presigmoid retrolabyrinthine suprameatal approach dissections in 5 cadaveric heads. Anatomic-radiological characteristics and variations were evaluated. Six morphometric parameters were measured and analyzed to predict surgical accessibility.

RESULTS

The pontine infratrigeminal area was accessible in all patients. The mean exposed area of the anterolateral pontine surface was 98.95 cm 2 (±38.11 cm 2 ). The mean length of the exposed trigeminal nerve was 7.9 cm (±2.9 cm). Preoperative anatomic-radiological parameters may allow to select patients with favorable anatomy that offers appropriate surgical accessibility to the anterior pontine cavernoma through a presigmoid retrolabyrinthine corridor.

CONCLUSION

Anterolateral pontine lesions can be accessed through a minimally invasive infratentorial presigmoid retrolabyrinthine approach by targeting the infratrigeminal safe entry zone. Further clinical studies should be conducted to evaluate the viability of this technique for treating these complex pathologies in real clinical settings.