Purely Endoscopic Supracerebellar Infratentorial Approach to the Pineal Region in Pediatric Population

Pineal lesions represent less than 1% of all brain tumors (Villani et al., Clin Neurol Neurosurg 109:1-6, 2007). The abysmal location and critical neurovascular structures remain a surgical challenge, despite the advent of microneurosurgery. The classical wide surgical suboccipital craniotomy with the supracerebellar infratentorial approach, described by Sir Victor Horsley (Victor, Proc R Soc Med 3:77-78, 1910), is infamous for its considerable surgical morbidity and mortality. This was later upgraded microneurosurgically by Stein to improve surgical outcomes (Stein, J Neurosurg 35:197-202, 1971).Ruge et al. reported the first purely endoscopic fenestration of quadrigeminal arachnoid cysts via this corridor (Ruge et al., Neurosurgery 38:830-7, 1996). A cadaver-based anatomical study by Cardia et al. demonstrated the viability for endoscope-assisted techniques (Cardia et al., J Neurosurg 2006;104(6 Suppl):409-14). However, the first purely endoscopic supracerebellar infratentorial (eSCIT) approach to a pineal cyst was performed in 2008 by Gore et al. (Gore PA et al., Neurosurgery 62:108-9, 2008).Unlike transventricular endoscopy, eSCIT approach poses no mechanical risk to the fornices and can be utilized irrespective of ventricular size. More vascular control and resultant reduction in uncontrolled hemorrhage improve the feasibility of attaining complete resection, especially around corners (Zaidi et al,, World Neurosurg 84, 2015). Gravity-dependent positioning and cerebrospinal fluid (CSF) diversion aid cerebellar relaxation, creating the ideal anatomical pathway. Also, angle of the straight sinus, tentorium, and tectal adherence can often influence the choice of approach; thus direct endoscopic visualization not only counteracts access to the engorged Galenic complex but also encourages sharp dissection of the arachnoid (Cardia et al., J Neurosurg 104:409-14, 2006). These tactics help provide excellent illumination with magnification, making it less fatiguing for the surgeon (Broggi et al., Neurosurgery 67:159-65, 2010).The purely endoscopic approach thwarts the dreaded risk of air embolisms, via simple copious irrigation from a small burr hole (Shahinian and Ra, J Neurol Surg B Skull Base 74:114-7, 2013). The tiny opening and closure are rapid to create, and the smaller wound decreases postoperative pain and morbidity. Recent literature supports its numerous advantages and favorable outcomes, making it a tough contender to traditional open methods.

Dynamic Lateral Semisitting Position for Supracerebellar Approaches: Technical Note and Case Series

BACKGROUND

It has always been a matter of debate which position is ideal for the supracerebellar approach. The risk of venous air embolism (VAE) is the major deterrent for surgeons and anesthesiologists, despite the fact that sitting and semisitting positions are commonly used in these operations.

OBJECTIVE

To demonstrate a reduction on the risk of VAE and tension pneumocephalus throughout the operation period while taking advantages of the semisitting position.

METHODS

In this study, 11 patients with various diagnoses were operated in our department using the supracerebellar approach in the dynamic lateral semisitting position. We used end-tidal carbon dioxide and arterial blood pressure monitoring to detect venous air embolism.

RESULTS

None of the patients had clinically significant VAE in this study. No tension pneumocephalus or major complications were observed. All the patients were extubated safely after surgery.

CONCLUSION

The ideal position, with which to apply the supracerebellar approach, is still a challenge. In our study, we presented an alternative position that has advantages of the sitting and semisitting positions with a lower risk of venous air embolism.

Comparison Between the Supracerebellar Infratentorial and Precuneal Interhemispheric, Transtentorial Approaches to the Cerebellomesencephalic Fissure: An Anatomoradiological Study and Illustrative Cases

BACKGROUND

The dorsal brainstem and cerebellomesencephalic fissure are challenging surgical targets. To afford a preferentially craniocaudal trajectory to this region, the precuneal interhemispheric transtentorial approach (PCIT) has been proposed.

OBJECTIVE

To didactically describe and compare exposures and anatomic indications of the supracerebellar infratentorial approach (SCIT) and PCIT to the cerebellomesencephalic fissure.

METHODS

Nine formalin-fixed, latex-injected cadaveric head specimens were used to perform a midline SCIT and bilateral PCITs and measure the distance of each approach. Twenty-four formalin-fixed specimens were used to measure the distance from the most posterior cortical bridging vein entering the superior sagittal sinus to the calcarine sulcus and the torcula. Fifty-one magnetic resonance images were reviewed to calculate the angle of each approach. Three illustrative surgical cases were described.

RESULTS

Mean distances from the brain or cerebellar surface to the operative target of the PCIT and SCIT were 7.1 cm (range: 5-7.7 cm) and 5.5 cm (range: 3.8-6.2 cm), respectively. The SCIT provided direct access to structures of the quadrigeminal cistern bilaterally. The PCIT provided access from the ipsilateral inferior colliculus to the ipsilateral infratrochlear zone. The PCIT's benefit was the direct access it provided to the cerebellomesencephalic fissure because of its superior to inferior trajectory.

CONCLUSION

The PCIT is indicated for unilateral lesions of the cerebellomesencephalic fissure and dorsal brainstem that harbor a craniocaudal long axis and do not have a superior extension beyond the superior colliculi. The SCIT is beneficial for lesions that extend bilaterally, have an anteroposterior long axis, or involve the Galenic complex.

Occipito-transtentorial approach for falcotentorial meningiomas: how I do it

BACKGROUND

Falcotentorial meningiomas are rare tumors that arise at the junction of the dural folds of the tentorium and falx cerebri, at the junction of the vein of Galen with the straight sinus with possible extensions along the course of the straight sinus. Surgery of falcotentorial meningiomas remains challenging due to the intimate neurovascular relationships in the posterior incisural space.

METHODS

We describe the key steps of the occipito-transtentorial approach for falcotentorial meningiomas with a video illustration. The surgical anatomy is described along with the advantages and limitations of this approach.

CONCLUSION

The occipito-transtentorial approach offers good surgical exposure and outcomes in carefully selected patients harboring falcotentorial meningiomas. Precise understanding of the relationship between the tumor and the internal cerebral veins, basal veins, and vein of Galen should be thoroughly analyzed as these structures may be infiltrated or displaced.

Extreme Lateral Supracerebellar Infratentorial Approach: Surgical Anatomy and Review of the Literature

OBJECTIVE

The extreme lateral supracerebellar infratentorial (ELSI) approach has the potential to access several distinct anatomical regions that are otherwise difficult to reach. We have illustrated the surgical anatomy through cadaveric dissections and provided an extensive review of the literature to highlight the versatility of this approach, its limits, and comparisons with alternative approaches.

METHODS

The surgical anatomy of the ELSI has been described using 1 adult-injected cadaveric head. Formalized noninjected brain specimens were also dissected to describe the brain parenchymal anatomy of the region. An extensive review of the literature was performed according to each targeted anatomical region. Illustrative cases are also presented.

RESULTS

The ELSI approach allows for wide exposure of the middle and posterolateral incisural spaces with direct access to centrally located intra-axial structures such as the splenium, pulvinar, brainstem, and mesial temporal lobe. In addition, for skull base extra-axial tumors such as petroclival meningiomas, the ELSI approach represents a rapid and adequate method of access without the use of extensive skull base approaches.

CONCLUSIONS

The ELSI approach represents one of the most versatile approaches with respect to its ability to address several anatomical regions centered at the posterior and middle incisural spaces. For intra-axial pathologies, the approach allows for access to the central core of the brain with several advantages compared with alternate approaches that frequently involve significant brain retraction and cortical incisions. In specific cases of skull base lesions, the ELSI approach is an elegant alternative to traditionally used skull base approaches, thereby avoiding approach-related morbidity.

Venous corridors in gravity-assisted retractor-less occipito-transtentorial approach - Our experience of an avenue through the tentacles of pod

Background:

Occipital transtentorial approach for selected posterior third ventricular or retrosplenium region tumors provides an ergonomic and safe access. Over centuries, the opponents of this approach highlight the problem of postoperative visual field defect, related to the retraction of occipital lobe. The aim was to describe the surgical nuances of gravity-assisted retractor-less occipital-transtentorial approach (GAROTA) as a modification of originally described GAROTA to minimize the complications with a similar ease of surgery.

Methods:

In this study, we have retrospectively analyzed our prospectively maintained surgical databases of patients operated by occipito-transtentorial from 2015 to 2019. Demographic variables, preoperative and postoperative neurological deficits (especially visual field defect) were analyzed. Radiological data included relation of veins with tumor, presence of hydrocephalus, size, and extent of lesion.

Results:

Fifteen patients underwent GAROTA (right-sided extension, n = 7; left-sided extension, n = 4; and midline lesions, n = 4). Headaches (73.3%) and diplopia (40%) were the most common symptoms. No patient had any postoperative visual deficits in both short-term and long-term follow-up.

Conclusion:

A thorough anatomical knowledge of posterior third interhemispheric region in the semi-prone position is required for GAROTA. Meticulous arachnoid dissection around the deep venous complex and release of cerebrospinal fluid through the cisterns is required. Postoperative cortical vision loss may be prevented by following the key surgical principles in GAROTA.

Quantitative analysis of ipsilateral and contralateral supracerebellar infratentorial and occipital transtentorial approaches to the cisternal pulvinar: laboratory anatomical investigation

OBJECTIVE

The cisternal pulvinar is a challenging location for neurosurgery. Four approaches for reaching the pulvinar without cortical transgression are the ipsilateral supracerebellar infratentorial (iSCIT), contralateral supracerebellar infratentorial (cSCIT), ipsilateral occipital transtentorial (iOCTT), and contralateral occipital transtentorial/falcine (cOCTF) approaches. This study quantitatively compared these approaches in terms of surgical exposure and maneuverability.

METHODS

Each of the 4 approaches was performed in 4 cadaveric heads (8 specimens in total). A 6-sided anatomical polygonal region was configured over the cisternal pulvinar, defined by 6 reachable anatomical points in different vectors. Multiple polygons were subsequently formed to calculate the areas of exposure. The surgical freedom of each approach was calculated as the maximum allowable working area at the proximal end of a probe, with the distal end fixed at the posterior pole of the pulvinar. Areas of exposure, surgical freedom, and the working distance (surgical depth) of all approaches were compared.

RESULTS

No significant difference was found among the 4 different approaches with regard to the surgical depth, surgical freedom, or medial exposure area of the pulvinar. In the pairwise comparison, the cSCIT approach provided a significantly larger lateral exposure (39 ± 9.8 mm2) than iSCIT (19 ± 10.3 mm2, p < 0.01), iOCTT (19 ± 8.2 mm2, p < 0.01), and cOCTF (28 ± 7.3 mm2, p = 0.02) approaches. The total exposure area with a cSCIT approach (75 ± 23.1 mm2) was significantly larger than with iOCTT (43 ± 16.4 mm2, p < 0.01) and iSCIT (40 ± 20.2 mm2, p = 0.01) approaches (pairwise, p ≤ 0.01).

CONCLUSIONS

The cSCIT approach is preferable among the 4 compared approaches, demonstrating better exposure to the cisternal pulvinar than ipsilateral approaches and a larger lateral exposure than the cOCTF approach. Both contralateral approaches described (cSCIT and cOCTF) provided enhanced lateral exposure to the pulvinar, while the cOCTF provided a larger exposure to the lateral portion of the pulvinar than the iOCTT. Medial exposure and maneuverability did not differ among the approaches. A short tentorium may negatively impact an ipsilateral approach because the cingulate isthmus and parahippocampal gyrus tend to protrude, in which case they can obstruct access to the cisternal pulvinar ipsilaterally.

Parietal interhemispheric transfalcine transtentorial approach for posterior incisural space lesions: from the lab to the operative room

The operative approach to the posterior incisural space is challenging because of its deep location, the surrounding eloquent areas, and the intimate relationship with the deep veins. Several approaches have been proposed to manage the lesions in this region: supratentorial, infratentorial and a combination of them. Brain retraction, injury to the occipital lobe and corpus callosum, and venous bleeding are the principle drawbacks of these routes. We performed anatomical dissection study using 10 embalmed human cadaver specimens injected with colored latex exploring a different route, parietal interhemispheric transfalcine transtentorial (PITT). Then we used a PITT approach on two patients with posterior incisural space (PIS) lesions. The PITT approach led to successful and safe complete removal of PIS lesions in our cases. No complications were reported. The present approach could be a valuable option in case of PIS lesions, especially those associated with downward displacement of the deep venous complex; thanks to the gravity it reduce the complications related to the occipital lobe retraction and manipulation. Moreover, cutting the superior-anterior edge of the tentorium, the sub-tentorial space could be reached.

Tumor retractor: a simple and novel instrument for brain tumor surgery

Background

It is important to secure a surgical space during brain tumor surgery. One of the commonly used methods is to retract the brain. We hypothesized that the tumor can be retracted and that the normal brain tissue retraction can be minimized during surgery, and thus, the degree of collateral damage caused by brain retraction would be reduced.

Methods

The tumor retractor had a 90°, hard, and sharp tip for fixation of the tumor. The distal part of the retractor has a malleable and thin blade structure. By adjusting the angle of the distal malleable part of the tumor retractor, the operator can make the retracting angle additionally. Retractors with thin blade can be used in a conventional self-retraction system. To pull and hold the tumor constantly, the tumor retractor is held by a self-retraction system. The surgical technique using a tumor retractor is as follows: The first step is to fix the retractor to the tumor. The second step is to pull the retractor in the operator’s desired direction by applying force. After the tumor is pulled by adjusting the degree of force and angle, the surgical arm should be held in place to maintain the tumor retracted state.

Results

The tumor retractor was used to minimize the brain retraction, pulling the tumor in the opposite direction from the surrounding brain tissue. In clinical cases, we can apply the tumor retractor with good surgical outcomes.

Conclusions

A tumor retractor can be used to pull a tumor and minimize the brain retraction.

Midline and Paramedian Supracerebellar Infratentorial Approach to The Pineal Region: A Comparative Clinical Study in 112 Patients

OBJECTIVE

The midline supracerebellar infratentorial (SCIT) approach and its paramedian development are commonly used for dealing with pineal lesions. Comparative clinical studies are lacking, however. We aim to establish the better performance of the paramedian SCIT approach in terms of clinical safety in surgically treated pineal cysts and pineal region tumors. Procedural functionality and effectiveness have been also analyzed.

METHODS

A comparative analysis of clinical, radiologic, pathologic, and surgical features, and outcome was performed between 55 midline and 57 paramedian SCIT approaches that were exclusively performed in 112 patients (57 pineal cysts and 55 tumors of the pineal region) operated in sitting position by a single surgeon. Information was retrieved from hospital records and microsurgical videos.

RESULTS

The paramedian SCIT approach linked with fewer postoperative complications (odds ratio [OR]: 0.40) and fewer approach-related complications (OR: 0.28) than the midline SCIT approach. The SCIT paramedian approach was achieved in a shorter time, by a smaller bone flap, and with fewer complex procedural steps than the midline approach. The SCIT paramedian approach did not require the opening of the falx cerebelli, midline cerebellar retraction, section of the midline cerebellar draining veins, nor wide opening of the dura. Gross total resection, size of the lesion, microsurgical time for removal, histopathological diagnosis and postoperative outcome were statistically similar in both groups.

CONCLUSIONS

The SCIT approach represents a safer and more functional approach for the removal of cysts and tumors of the pineal region than the classic midline approach, while maintaining the same effectiveness.