Neurosurg Focus 61(3):E7, 2026
The surgical challenge of a parasagittal meningioma extends beyond determining whether the superior sagittal sinus is invaded. Safe exposure and resection also depend on residual venous flow, collateral drainage, bridging-vein anatomy and extension across the falx or adjacent convexity dura. Li and colleagues propose an imaging-based framework that brings these relationships into preoperative planning. Their study is most useful as an anatomical guide to the operative strategy, rather than as evidence that a particular sinus-directed maneuver improves outcomes.
Objective
To evaluate the Superior Sagittal Sinus Involvement Grading system (SSIG) in relation to established invasion grading, operative complexity and resection strategy.
Methods
This retrospective, single-center series included 62 consecutive resections performed by one surgeon. Fifty-five tumors were primary and seven recurrent. SSIG was assigned by consensus among three senior neurosurgeons using contrast-enhanced coronal MRI. CT or MR venography was available in 49 patients to assess sinus patency and collateral drainage.
The framework distinguishes convexity-adjacent disease with an intact sinus wall (grade 1), falcine involvement with deeper wall invasion (grade 2), predominantly intraluminal tumor (grade 3), continuous convexity-sinus-falx involvement with residual flow (grade 4a), more extensive invasion with severe stenosis or functional near occlusion (grade 4b), and complete sinus occlusion (grade 5).
For comparisons, grades 1, 2 and 4a formed a low-involvement group of 44 patients; grades 3, 4b and 5 formed a high-involvement group of 18. This grouping reflects anticipated sinus management rather than a simple numerical progression.
Main results
SSIG correlated with Sindou grade (Spearman r = 0.790) and venography-based involvement in the 49 evaluable patients (r = 0.742). Operative time and blood loss differed across the six SSIG categories. However, in the binary low-versus-high comparison, blood loss remained significantly different whereas operative time did not.
Simpson grade I resection was recorded in 38 of 44 low-involvement cases and six of 18 high-involvement cases. Simpson grades II-III were correspondingly more frequent with high involvement: 66.7% versus 13.6%. In this study, that category represented gross tumor removal with preservation of the invaded sinus wall or segment, rather than necessarily indicating a visible residual mass.
Neurological adverse events occurred in 10 patients (16.1%), including seven with new or worsened limb numbness or weakness. The authors also reported systemic morbidity, including lower-extremity venous thrombosis in 22 patients and one pulmonary embolism. Surgery-related complication rates did not differ significantly between the two involvement groups, but the small sample does not establish equivalent safety. No radiographic recurrence or progression was observed during a mean follow-up of 13.3 months.
Interpretation – operative relevance
The first practical contribution concerns exposure. In the authors’ practice, grade 1-2 lesions generally required an ipsilateral parasagittal craniotomy reaching the midline. When intraluminal work or contralateral exposure was anticipated, the bone flap crossed the midline to permit visualization and control of the relevant sinus segment. Thus, falcine and convexity extension help determine the operative corridor in addition to the depth of sinus invasion.
The second concerns venous dissection. The described principles include internal tumor decompression, dissection along the arachnoid interface, sharp separation of adherent veins and particular protection of bridging-vein entry zones. Early treatment of the dural or falcine attachment is integrated with preservation of the functioning venous pathways.
The distinction between grades 4a and 4b is especially useful. Both may involve the convexity, sinus and falx, but residual effective flow favors conservative handling of the sinus wall. Severe narrowing or near occlusion requires a more detailed assessment of compensatory drainage before contemplating sinus-directed resection. An imaging label alone cannot demonstrate that a venous segment is expendable.
For completely occluded grade 5 lesions, the authors describe selected resections without sinus reconstruction after assessment of collateral compensation and protection of the venous drainage at the segment boundaries. This is their reported strategy, not a general recommendation to sacrifice an occluded sinus. The series does not compare reconstruction with nonreconstruction or validate a universal threshold for safe ligation.
Limitations
The study is retrospective and restricted to one surgeon. Subgroups were uneven, with only one grade 3 lesion, and venography was unavailable in 13 patients. Although grading was assigned by consensus, interobserver reproducibility was not formally established. Exploratory comparisons were not adjusted for multiple testing, and the small number of events limits complication analysis. Short follow-up without progression cannot establish long-term tumor control or the superiority of a resection strategy.
Clinical takeaway
Plan the exposure and resection boundary around functional venous anatomy, not sinus invasion alone. SSIG offers a useful structure for reviewing convexity and falcine extension, residual flow and collateral pathways; its principal value is to organize surgical judgment while keeping preservation of effective venous drainage central to the operation.