Planning ETV and Biopsy in Posterior Third Ventricle Lesions

Tumors within the posterior third ventricle and pineal region frequently obstruct the aqueduct of Sylvius. Consequently, affected patients present with acute obstructive hydrocephalus and severe intracranial hypertension. Neurosurgeons must promptly relieve elevated intracranial pressure while obtaining diagnostic tissue samples for definitive histopathological confirmation. Performing combined ETV and biopsy addresses both critical therapeutic goals within a single surgical session. However, choosing between a single burr hole trajectory and a dual burr hole approach remains controversial in neurosurgery. A single burr hole minimizes brain parenchymal disruption and shortens operative exposure. Nevertheless, rigid endoscopes passed through a solitary entry can exert mechanical traction on delicate periventricular structures. In particular, the column of the fornix and subependymal veins face shear injury during acute instrument angulation. Therefore, surgical teams must carefully evaluate preoperative anatomical relationships before making a final choice. A recent retrospective investigation evaluated twenty-six consecutive patients treated with these neuroendoscopic techniques. Every patient presented with symptomatic hydrocephalus from posterior third ventricular lesions. By analyzing procedural success, complication profiles, and trajectory angles, this study provides actionable guidance for operative teams managing complex ventricular tumors.

Evaluating Single Versus Dual Burr Hole Strategies

Historically, neurosurgeons have deployed either single-port or dual-port endoscopic trajectories to manage posterior third ventricular lesions. In a single burr hole procedure, the surgeon introduces a rigid endoscope through a single pre-coronal entry site. Consequently, the instrument accesses both the anterior third ventricle floor and the posterior tumor through one corridor. However, reaching both targets through a solitary entry necessitates significant endoscope tilting across the foramen of Monro. This sharp trajectory change can place considerable mechanical stretch on the ipsilateral fornix. Furthermore, forceful manipulation within the narrow ventricle risks tearing subependymal veins or injuring the choroid plexus. To circumvent these anatomical constraints, many surgeons advocate placing two independent burr holes. The primary burr hole occupies the classic coronal point to facilitate an ergonomic ventriculostomy. Meanwhile, the secondary burr hole sits further anteriorly, providing an aligned, direct trajectory toward the posterior tumor. Therefore, a dual burr hole strategy avoids acute angular strain on the foramen of Monro. Nonetheless, making two cranial openings requires creating two separate parenchymal trajectories through the cerebral cortex. As a result, neurosurgeons must balance cortical parenchymal disruption against the risk of intraventricular tractive injury.

Surgical Outcomes and Cerebrospinal Fluid Diversion

Clinical data demonstrate that both endoscopic techniques achieve excellent operative success and high procedural safety. Specifically, the surgical teams successfully accomplished both ventriculostomy and tumor biopsy or resection across all twenty-six analyzed cases. Notably, no operative procedure required premature abandonment due to anatomical failure or technical difficulty. Furthermore, postoperative follow-up confirmed long-term therapeutic efficacy and persistent control of intracranial pressure. Overall, endoscopic third ventriculostomy achieved an impressive 88.5 percent success rate, representing twenty-three out of twenty-six patients remaining free from shunt dependence. Only three patients eventually developed persistent hydrocephalus necessitating the secondary placement of a ventriculoperitoneal shunt. Thus, endoscopic diversion proved highly durable as a standalone intervention for obstructive hydrocephalus. In addition, the retrospective analysis recorded zero operative mortality and documented no permanent neurological deficits. In tertiary neurosurgical centers, avoiding foreign-body shunt implantation offers tremendous clinical value for patients with pineal tumors. Cerebrospinal fluid shunts carry lifelong risks of infection, mechanical obstruction, and overdrainage. Consequently, achieving definitive internal drainage through endoscopic third ventriculostomy dramatically improves patient independence and minimizes long-term morbidity.

Complication Rates and Forniceal Protection

Detailed intraoperative video reviews and postoperative radiological analyses highlighted important procedural safety metrics. Overall, intraoperative forniceal contusion or stretching was noted in eight of the twenty-six patients, yielding an incidence of 31 percent. Fortunately, these minor mechanical impacts presented primarily as asymptomatic, superficial petechiae without causing transient or persistent memory deficits. Furthermore, intraoperative microvascular bleeding occurred in 81 percent of the surgical cohort. The majority of these hemorrhages represented minor capillary oozing that resolved promptly following continuous warm-saline irrigation. In five patients, persistent bleeding required prolonged irrigation times to clear the endoscopic optical field completely. However, neither cohort required conversion to an open craniotomy, nor did any patient require dry-field microdissection. Neurosurgeons must remember that pineal region tumors contain extremely delicate vascular networks. Therefore, maintaining meticulous hemostatic technique and low-pressure continuous irrigation is essential for surgical safety. Additionally, surgeons must refrain from excessive torque when sampling deep pineal lesions. While single burr hole access carries higher fulcrum stress, gentle micro-forceps handling helps preserve anatomical integrity. Consequently, neurosurgeons can achieve safe biopsy samples without compromising neurocognitive function.

Trajectory Angles and Practical Decision-Making

A crucial insight emerging from this comparative study involves the objective measurement of the two-dimensional intertrajectory angle. Using preoperative magnetic resonance imaging, clinicians evaluated the angle formed between the ventriculostomy line and the posterior biopsy trajectory. Notably, the mean intertrajectory angle measured significantly smaller in the single-burr-hole group than in the double-burr-hole group. Specifically, single-hole cases exhibited a mean angle of 41.8 degrees, whereas double-hole cases demonstrated a mean angle of 48.7 degrees. Statistical testing confirmed this difference was highly significant, yielding a p-value of 0.001. Therefore, anatomical geometry served as the primary clinical driver for trajectory selection. The authors established that an intertrajectory angle of approximately 45 degrees acts as a valuable post-hoc threshold. When the trajectory angle remains below 45 degrees, a single burr hole provides adequate visualization without excessive forniceal displacement. Conversely, when the trajectory angle surpasses 45 degrees, rigid instruments require substantial angulation, significantly increasing traction on the foramen of Monro. In such anatomies, utilizing two burr holes provides direct, collinear access that protects vulnerable periventricular tracts. Although this 45-degree cutoff requires external multicenter validation, it provides neurosurgeons with a practical framework for operative planning.

When should neurosurgeons choose a two-burr-hole approach for ETV and biopsy?

Surgeons should favor a two-burr-hole approach when the preoperative intertrajectory angle between the third ventricle floor and the posterior tumor exceeds approximately 45 degrees. This dual-access configuration prevents excessive endoscope tilting at the foramen of Monro, significantly reducing mechanical stretch on the fornix while providing direct, uncompromised visualization.

What is the expected success rate of endoscopic third ventriculostomy in these cases?

Endoscopic third ventriculostomy achieves durable hydrocephalus resolution in approximately 80 to 90 percent of patients with posterior third ventricle tumors. In this comparative cohort, 88.5 percent achieved complete shunt independence. Only three patients required subsequent ventriculoperitoneal shunt placement during follow-up, confirming neuroendoscopy as an effective definitive treatment.

How should neurosurgeons manage intraoperative bleeding during endoscopic ventricular biopsy?

Surgeons manage intraoperative hemorrhage by selecting relatively avascular biopsy sites, taking gentle tissue bites, and employing warm lactated Ringer\'s irrigation for optical clearance. Maintaining continuous fluid exchange effectively controls minor ependymal oozing, ensuring that procedures rarely require conversion to open craniotomy or formal dry-field microsurgical techniques.

Disclaimer: This content is for informational and educational purposes only and should not be taken as professional medical advice. Always consult a qualified healthcare provider for diagnosis and treatment of medical conditions. Refer to the latest local and national guidelines for clinical practice.

References

1. Lepshokov M et al. Obstructive hydrocephalus due to posterior third ventricle pathology: One or two burr hole approaches for ETV and biopsy. Neurosurg Rev. 2026 Nov 06. doi: 10.1007/s10143-026-04564-8. PMID: 42988954.


2. Ahmed R, et al. One- vs Two-Burr-Hole Technique for Combined Endoscopic Third Ventriculostomy and Pineal Region Biopsy: Volumetric Analysis of Brain at Risk. Oper Neurosurg (Hagerstown). 2020;20(1):E18-E25.


3. Attri G, Gosal JS, Khatri D, Das KK, et al. Endoscopic Third Ventriculostomy and Simultaneous Tumor Biopsy in Pineal Region Tumors using the "Single Burr Hole" Technique: An Analysis of 34 Cases. Asian J Neurosurg. 2020;15(4):976-982.