Single-stage microscopic and endoscopic resection of spatially separate meningiomas through a single craniotomy

Abstract

Background:

Multiple meningiomas are frequently encountered; however, determining the optimal surgical strategy for single-stage resection can be challenging. Conventional approaches include performing multiple craniotomies or a single large craniotomy encompassing both lesions, which may be overly invasive depending on patient factors and tumor characteristics. Endoscopic approaches have increasingly been used to reduce the invasiveness of meningioma surgery, but their application to multiple lesions remains limited.

Case Description:

An 85-year-old man with incidentally discovered meningiomas located in the left parasagittal region (primary lesion) and the right convexity (separate lesion) underwent single-stage resection of both lesions. Based on meticulous preoperative simulation, both lesions were removed through a small craniotomy (3.5 × 2.5 cm) placed directly over the primary lesion. The parasagittal tumor was removed microscopically, while the separate convexity lesion was resected endoscopically. Endoscopic visualization enabled access to and resection of the separate lesion without additional bone removal.

Conclusion:

For selected patients deemed feasible and safe based on preoperative simulation, endoscopic resection of an additional convexity lesion located beyond the craniotomy site may provide a less invasive alternative to multiple or extended craniotomies. This approach may be beneficial for older adults, for whom minimizing surgical invasiveness is essential.

INTRODUCTION

Meningiomas involving multiple intracranial sites are not uncommon. The standard surgical management of multiple meningiomas includes performing separate craniotomies for each lesion or creating a single large craniotomy encompassing all tumors. However, these approaches may be overly invasive, depending on patients’ clinical condition and tumor characteristics. A less invasive approach is preferred for older patients. Nevertheless, no standardized approach has been established for such cases.

In recent years, minimally invasive endoscopic techniques have been increasingly applied to the surgical treatment of meningiomas. Compared with conventional microsurgical approaches, endoscopic resection has been associated with smaller craniotomies and skin incisions, reduced intraoperative blood loss, and shorter surgical duration and hospital stays.[13] In addition, endoscopic visualization may reduce brain injury associated with retraction.[7] Epidemiological studies indicate that approximately half of patients with meningioma are older,[1] and neurosurgeons are often required to treat these tumors in older individuals. Conventional craniotomy can impose considerable surgical stress on this population and may lead to delayed recovery from anesthesia, postoperative cognitive decline, and progression of disuse syndrome.[7] Preservation of quality of life is a key consideration for older patients, favoring surgical strategies that limit invasiveness and complications. With appropriate patient selection, minimally invasive techniques, including endoscopic approaches, may reduce complication rates and hospital stay while maintaining satisfactory tumor control.[12]

Reports describing the use of endoscopy for meningiomas at multiple intracranial sites remain limited. Endoscopic resection for multiple falcine and parasagittal meningiomas has been reported, suggesting that endoscopic approaches may also apply to multiple lesions.[15] However, reports of endoscopic removal for multiple lesions remain limited. With regard to tumor location, endoscopic surgery for meningiomas has more commonly been applied to deep-seated lesions, including those of the skull base.[5,11] posterior fossa,[8,9] and ventricular system.[14,16] In contrast, its use for meningiomas arising in the superficial convexity has been infrequently reported. This may be because convexity meningiomas are usually accessible through conventional microscopic approaches due to their superficial location, often allowing complete resection without the need for endoscopic assistance. Reports describing endoscopic resection of convexity meningiomas are limited.[4,6] In one report, endoscopy was used to treat a recurrent convexity meningioma after a prior wound infection had required free flap reconstruction; the endoscopic approach allowed access to the tumor while avoiding the reconstructed flap. In another case, endoscopy combined with a relatively small craniotomy was employed for minimally invasive removal of en plaque-type meningioma in an older patient. These reports suggest that endoscopy for convexity meningiomas may facilitate access to distant areas beyond the craniotomy site and potentially reduce surgical invasiveness. While no standardized surgical strategy has been established for multiple tumors in superficial regions such as the convexity, endoscopic techniques may be reasonable alternatives for carefully selected cases.

We report a case of an older patient with multiple meningiomas for whom endoscopic removal of an additional lesion located beyond the craniotomy site was successfully performed. We microscopically resected the primary parasagittal lesion, followed by endoscopic resection of the contralateral convexity lesion through the same craniotomy. The technical details of this approach are presented.

CASE DESCRIPTION

An 85-year-old man with no significant medical or family history was incidentally found to have meningiomas in the left parasagittal region and right convexity on magnetic resonance imaging. Both lesions gradually enlarged during follow-up. Over the preceding 18 months, the left parasagittal lesion had increased in size by approximately 6 mm. At the time of surgery, the maximum tumor diameter was 36 mm for the parasagittal lesion [Figure 1A and B] and 19 mm for the convexity lesion [Figure 1C and D]. Preoperative evaluation also demonstrated occlusion of the superior sagittal sinus caused by the primary lesion. Although the patient was asymptomatic, his left parasagittal tumor indicated surgery due to its progressive growth and the presence of peritumoral edema. The convexity lesion was small and could have been managed with continued observation, but surgical intervention was considered likely in the future due to its tendency to enlarge. Therefore, simultaneous resection was considered if technically feasible. Preoperative imaging and cerebral angiography suggested that the convexity tumor was relatively hypovascular and exhibited minimal adhesion to the cortical surface, indicating that resection would likely be straightforward. However, a large craniotomy encompassing both lesions and two separate craniotomies would have been highly invasive. Further, removal of the convexity lesion was not mandatory at that time, and we planned to attempt endoscopic resection of this tumor through the craniotomy created for the parasagittal lesion, if feasible.

Figure 1:

Preoperative imaging findings. Preoperative contrast-enhanced magnetic resonance imaging demonstrating the left parasagittal meningioma on (A) axial and (B) coronal views and the right convexity meningioma on (C) axial and (D) coronal views.

Preoperative simulation and craniotomy planning were performed using Synapse Vincent (Fujifilm Corporation, Tokyo, Japan). A single craniotomy was designed directly over the primary lesion in the left parasagittal region. The surgical plan consisted of microscopic resection of the parasagittal tumor followed by endoscopic resection of the separate convexity lesion through the same craniotomy. Given the advanced age of the patient, the size of the craniotomy was carefully optimized to provide sufficient yet limited exposure for safe microscopic removal of the primary lesion. The craniotomy was centered over the parasagittal tumor and extended slightly across the midline to the contralateral side [Figure 2A and B]. Adequate space was secured on the right side to allow dural opening, and the absence of bridging veins at the planned incision site was confirmed. The longitudinal axis of the craniotomy was oriented toward the convexity lesion, and our preoperative simulation had already confirmed access to this tumor [Figure 2C]. Based on these considerations, the craniotomy was designed as shown, measuring 3.5 × 2.5 cm.

Figure 2:

Preoperative simulation and surgical planning. (A) Spatial relationship between the tumor (orange) and veins (blue). (B) Planned craniotomy centered over the primary lesion in the left parasagittal region. The yellow arrow indicates the endoscopic trajectory to the secondary lesion. The blue dotted circle indicates the location of the secondary lesion. (C) Preoperative simulation demonstrating access to the right convexity lesion. A magnified view is shown in the lower right corner. The viewing axis was aligned with the endoscope insertion axis. PL: Primary lesion, SL: Secondary Lesion.

The skin incision was planned along the posterior margin of the craniotomy [Figures 3A and B]. The skin incision was designed to allow extension toward the separate lesion, enabling a craniotomy directly over the lesion if required.

Figure 3:

The operative setting and skin incision. (A and B) Skin incision placed along the posterior margin of the craniotomy. Extension of the skin incision allows craniotomy directly over the secondary lesion in the right convexity.

Preoperative embolization of the middle meningeal artery feeding the left parasagittal lesion was performed. The right convexity lesion was relatively hypovascular and was not embolized.

Surgical procedure

Under general anesthesia, the patient was placed supine with slight elevation of the upper body. The head was fixed in the midline position with the vertex elevated using a three-pin fixation device. Neuronavigation was registered and used throughout the procedure. A gently curved skin incision of approximately 7 cm was made along the posterior margin of the planned craniotomy. The craniotomy was performed as designed preoperatively. The primary lesion in the left parasagittal region was resected microscopically, achieving Simpson Grade II removal.

Subsequently, a small dural incision measuring approximately 0.5 × 1 cm was created on the contralateral side, and endoscopic resection of the right frontal convexity lesion was initiated [Figure 4A]. Following removal of the parasagittal tumor, the brain became slack, providing sufficient working space within the right frontal subdural space for endoscopic manipulation [Figure 4B]. Adhesions between the tumor and the arachnoid membrane were carefully dissected using malleable instruments [Figure 4C]. Internal tumor debulking was performed using a clarity ultrasonic surgical aspirator (Integra LifeSciences, Princeton, NJ, USA) [Figure 4D], after which the remaining tumor was dissected from its dural attachment. The dural attachment was coagulated with a suction-coagulation device, achieving Simpson’s Grade II resection. The operative field was irrigated to confirm complete hemostasis [Figure 4E]. Tumor resection was performed using a two-hand technique with the endoscope in one hand and a single instrument in the other [Figure 4F]. The endoscope and instrument were advanced in parallel, and the direction of the tip was controlled by rotating the instrument along its longitudinal axis [Figure 5]. The dura was reconstructed with an artificial dural substitute, the bone flap was fixed with titanium plates, and the wound was closed in layers. The total surgical time was 4 h and 45 min, including 58 min for resection of the convexity tumor.

Figure 4:

Intraoperative endoscopic views. (A) Two dural openings were created: one directly over the primary lesion in the parasagittal region (DO1) and another to allow endoscopic access to the secondary lesion in the right convexity region (DO2). (B-D) Endoscopic resection of the right convexity lesion. The arrows in panel B indicate the arachnoid membrane under tension due to the weight of the brain, which should be dissected from the tumor. (E) Underwater view of the operative field confirming hemostasis. (F) A two-hand technique with the endoscope in one hand and a single instrument in the other. A: Arachnoid, B: Brain, C: CUSA, D: Dura mater, DA: Dural attachment, DO1: Dural opening over the primary lesion in the left parasagittal region, DO2: Dural opening performed for endoscopic access to the right convexity lesion, E: Endoscope, S: Superior sagittal sinus, T: Tumor.

Figure 5:

Technical maneuvers for endoscopic manipulation in a confined surgical field. (A) Coordinated advancement and lateral movement of the endoscope and working instrument as a single unit. (B) Rotation of the working instrument along its longitudinal axis, translating rotational motion into precise tip control. The red arrows indicate the rotational movement of the instrument shaft and the lateral movement of the instrument tip.

The patient could ambulate independently on postoperative day 1. The postoperative course was uneventful with no complications, and the patient was discharged on postoperative day 9. Postoperative magnetic resonance imaging confirmed complete resection of both lesions [Figure 6].

Figure 6:

Preoperative contrast-enhanced MRI demonstrating the left parasagittal meningioma on (A) axial and (B) coronal views and the right convexity meningioma on (C) axial and (D) coronal views. Both tumors were completely resected.

DISCUSSION

We have reported a case of an older patient with multiple meningiomas for whom endoscopic removal of an additional lesion located beyond the craniotomy site was successfully performed. This case highlights the potential role of endoscopic techniques in the management of multiple lesions and resecting convexity meningiomas located outside the primary microscopic field. It also emphasizes the importance of meticulous preoperative simulation in planning such approaches. With appropriate endoscopic handling and instrument control, tumor resection may be achievable through a limited craniotomy. This strategy may be especially beneficial for older patients for whom minimizing surgical invasiveness is a major concern.

Using an endoscope, the separate convexity lesion was successfully resected through the craniotomy created for the primary parasagittal tumor. Conventional surgical management of meningiomas located at multiple sites often requires a large craniotomy, multiple craniotomies, or staged procedures. In contrast, the endoscopic approach used in this case limited bone removal and avoided additional craniotomies or separate surgeries, thereby reducing overall surgical invasiveness. For older patients for whom less invasive treatment is particularly desirable, endoscopic resection of small, accessible lesions may represent a reasonable option. In the present case, the patient was able to ambulate independently on postoperative day 1, experienced no postoperative complications, and was discharged on postoperative day 9. These favorable postoperative outcomes suggest that this less invasive approach may be clinically beneficial, particularly in elderly patients. The total duration of surgery was 4 h and 45 min, including 58 min for resection of the convexity lesion. This duration was not shorter than expected for large or multiple craniotomies, but further technical refinement of endoscopic manipulation will improve surgical efficiency in the future.

Careful case selection is essential, as an endoscopic approach is most suitable for convexity meningiomas for which safe dissection is anticipated. The working angle from the craniotomy to a distant convexity lesion becomes steep, potentially complicating endoscopic procedures. For this case, three factors facilitated the successful endoscopic resection of the convexity tumor. First, removal of the primary lesion resulted in brain relaxation, expanding the subdural space over the convexity and providing additional working space for endoscopic manipulation. Second, the gravitational shift of the brain created natural tension between the tumor and the surrounding brain tissue, allowing effective dissection with limited retraction. Third, the advanced age of the patient and associated cerebral atrophy contributed to a relatively wide subdural space compared with that of younger patients. This facilitated better instrument handling. Multiple meningiomas are reported to occur in approximately 1–10% of patients,[3] with recent studies suggesting rates as high as 18%.[10] The most frequent locations are the convexity, skull base, and ventricles, in that order.[2] Therefore, cases involving convexity lesions are not uncommon among patients with multiple meningiomas. An endoscopic approach for multiple lesions, including convexity tumors, may be clinically useful for selected patients – particularly older individuals with cerebral atrophy and an anticipated wider subdural space – when the lesion is expected to be easily dissectible, and the risk of bleeding is low.

When performing endoscopic manipulation through a small craniotomy, as in the present case, only the endoscope and a single working instrument are introduced into the operative field, requiring coordinated bimanual control. With appropriate technical modifications, tumor removal was accomplished without difficulty. Two technical points were important for reducing interference between the endoscope and the instrument. First, the endoscope and instrument were advanced, withdrawn, and moved laterally together [Figure 5A]. Second, the instrument was rotated along its longitudinal axis to control the tip’s direction, enabling controlled lateral movements within the limited working space [Figure 5B].

When accessing convexity lesions beyond the craniotomy, a flatter surgical trajectory is preferred over that used for deeper lesions; however, the thick scalp flap and the skull may obstruct the instrument trajectory. As in the present case, the scalp flap should be reflected in a direction that does not obstruct the instrument trajectory, and the craniotomy should be oriented with its long axis along the intended access direction. A craniotomy diameter of at least 3 cm is recommended to provide sufficient working space.

For effective endoscopic surgical techniques like the one discussed here, rigorous preoperative simulation is vital to address two critical concerns: Technical feasibility and procedural safety. If there is a possibility of significant intraoperative bleeding, dense adhesions to nearby structures, or if the lesion is too large for safe management with a two-hand endoscopic approach, a conventional craniotomy – or an expanded craniotomy for endoscopic access – should be seriously considered to ensure patient safety.

In addition, it is crucial to confirm that no vital structures are located along the planned endoscopic trajectory that could impede the procedure or be susceptible to injury. In this case, a thorough preoperative evaluation confirmed the absence of bridging veins along the intended insertion pathway. Thus, a meticulous analysis of tumor characteristics – including potential bleeding, adhesion severity, and size – alongside a careful assessment of the proposed endoscopic route is essential for a successful outcome.

We have reported a case of an older patient who, despite having multiple meningiomas, benefited from the successful endoscopic removal of an additional tumor beyond the craniotomy. While the applicability of this technique may be limited by specific tumor features and the feasibility of the endoscopic approach, it offers a promising alternative for carefully selected patients – especially older adults – where reducing surgical invasiveness is critical.

CONCLUSION

We successfully performed endoscopic removal of an additional meningioma beyond the craniotomy in an older patient with multiple meningiomas. This approach may reduce the invasiveness of surgery while enabling the treatment of additional lesions through a limited craniotomy. Although its applicability depends on tumor characteristics and the feasibility of the endoscopic trajectory, preoperative simulation to assess the surgical corridor and careful patient selection may allow this technique to serve as an effective surgical option, particularly for older patients in whom minimizing surgical invasiveness is important.

Ethical approval:

The Institutional Review Board approval is not required.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given consent for their images and other clinical information to be reported in the journal. The patient understands that the patient’s names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript, and no images were manipulated using AI.

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