CHAPTER 26 Management of Superior Sagittal Sinus Invasion in Parasagittal Meningiomas
Resection Versus Irradiation
INTRODUCTION
Treatment of meningiomas that invade vital vascular structures is still a significant challenge in neurosurgery.1 Invasion of the superior sagittal sinus (SSS) is commonly observed in parasagittal meningiomas; it increases the risk of recurrence, and, in certain cases, the management of the venous sinus invasion becomes a greater problem than the resection of the tumor.1,2 Current treatment options vary according to the involved segment and to the extent of invasion; however, many unresolved problems remain.
PARASAGITTAL MENINGIOMAS AND THE SUPERIOR SAGITTAL SINUS
Parasagittal meningiomas comprise 21% to 31% of intracranial meningiomas.3–5 The distribution of the meningiomas along the SSS ranged from 14.8% to 33.9% in the anterior third, from 44.8% to 70.4% in the middle third, and from 9.2% to 29.6% in the posterior third of the sinus.6 As shown by several studies the recurrence rate of meningiomas depends on the completeness of resection.3,7–9 Therefore, the aim of surgery in parasagittal meningiomas is complete surgical resection of the tumor along with the involved dura and bone with minimal morbidity and possibly supplement this with adjuvant therapies to decrease the chance of recurrence. This is a major challenge if the tumor has invaded the SSS, because damage to the venous drainage of the brain can result in permanent neurologic damage.
The extent of venous involvement by the meningioma can range from invasion of the outer surface of the venous wall to complete invasion and obliteration of the sinus. Several authors have devised classification schemes for surgical decision making.1,10,11 The first detailed classification scheme of Krause was later modified by Merrem,11 then Bonnal and Brotchi.10 The latest, simplified version by Sindou1 describes 6 types of parasagittal meningiomas according to the degree of sinus invasion:1
The reported incidences of these types are 31%, 8%, 11%, 13%, 5%, and 32%, respectively.2
The superior sagittal sinus drains the superficial veins of both cerebral hemispheres. The sinus increases in size from anterior to posterior and is divided into anterior, middle, and posterior thirds.1 The clinical consequences differ from one region to the other. It is widely cited that the sacrifice of the anterior third is well tolerated. However, even when its rarely encountered, general slowing of the thought process and activity or even akinetic mutism may complicate such a resection.1 The middle third receives the central group of cortical veins and its sacrifice carries the risk of hemiplegia and akinesia.1 The posterior third is the largest portion, which receives the straight sinus. Acute occlusion or surgical sacrifice of the posterior third carries a significant risk of fatal brain edema and increase in intracranial pressure (ICP).
MANAGEMENT STRATEGIES
Parasagittal meningiomas located in the middle third portion of the superior sagittal sinus are the most difficult to treat. This is caused by the abundance of afferent veins, the significant morbidity associated with this location, and the high risk of recurrence. For meningiomas that totally obstruct the SSS, total excision of the tumor and the obstructed part of the sinus is traditionally considered to be the treatment of choice. However, there are reports that challenge this belief. Some studies indicated that replacement or bypass of the sagittal sinus by using a vein graft may be useful and result in reduced morbidity and mortality, as compared with radical excision including the occluded sinus without venous reconstruction.2 Sindou and colleagues reported their results in 15 patients who had complete occlusion of the SSS by the tumor and who were treated with global resection of both the tumor and the invaded sinus: 3 (20%) of the patients died and 6 (40%) had permanent neurological morbidity. In contrast, only 1 (7.7%) of the 13 patients who had a venous reconstruction after global resection of both the tumor and the invaded sinus suffered permanent neurologic morbidity. The authors explained this unexpected finding with the possibility that veins running in the capsule or inside the tumor might provide some degree of continual flow between the proximal and distal aspects of the occluded sinus.2
The significant challenge lies in the management of patients with patent SSS. In such cases surgical resection of the meningioma along with the infiltrated but patent SSS carries a significant risk of mortality and morbidity.12–15 Certainly, at least the bulk of the tumor should be removed whenever possible when the patient is progressively symptomatic; however, there is no clear consensus on how aggressive the surgeon should manage the part that invades the sinus. Two surgical strategies exist for the management of an infiltrated but patent SSS: (1) maximal safe tumor resection outside the involved sinus and (2) aggressive surgical resection of the involved portion with subsequent venous reconstruction.
Colli and colleagues6 reviewed their 53 patients with parasagittal meningiomas. In 7 cases, the tumor involved and partially obstructed the SSS. They removed the tumor subtotally and did not attempt sinus resection or reconstruction. They found that the recurrence-free survival rate was not related to extent of resection. Caroli and colleagues16 reported surgical results for 328 cases of parasagittal meningiomas. Their strategy involved resection of the SSS if it was obliterated by the tumor and to preserve if it was not obliterated. This study included 221 patients with meningiomas involving the middle or posterior third of the SSS. The recurrence rate was 3% in Simpson grade 1 resections, 35% in Simpson grade 2 resections with sinus completely resected cases, and 8% in Simpson grade 3 with sinus marginally resected cases.
Recurrence in limited resections and the risk of serious morbidity and mortality after sacrificing a patent sinus prompted surgeons to develop techniques for reconstructing the sinus at the time of resection.1,10,14,16–19 Such a venous reconstruction is a formidable surgical challenge and the literature contains only few large case series of SSS reconstruction. In 1978, Bonnal and Brotchi10 reported their results for SSS repair in 34 cases of parasagittal meningioma. Their aim was to preserve SSS patency and they used venous autografts when necessary. In 9 cases, the surgeons were able to preserve the patency of the sinus without using a graft. In the other 25 cases, they removed 1 or more walls of the SSS and then rebuilt the structure using a dural or venous graft. In 1 case, it was necessary to remove the entire SSS and then create a new sinus structure using a total vein graft. Immediate postoperative control angiography demonstrated patent SSS in 87% of the 34 patients. In 2003, Brotchi’s research group documented the long-term results for these cases.10 Of the 25 individuals who underwent partial or total SSS removal and sinus reconstruction, 15 cases were total tumor excisions and these patients had been followed for more than 10 years. Five (33%) of these 15 individuals had developed focal meningioma recurrence. The remaining 10 of the 25 patients underwent subtotal tumor excision, and 8 of them had been followed for more than 10 years. Five (63%) of these 8 patients had developed local recurrence. Based on these outcomes, the authors questioned the efficacy of their approach to these tumors. They concluded that the optimal strategy for meningiomas involving the SSS is gross tumor removal followed by monitoring, and radiosurgery if regrowth occurs.
Hakuba and colleagues20 reported his results with 23 cases of parasagittal meningiomas. In 6 cases he removed the tumor and the sinus totally. In 17 cases, there was a sinus involvement and after total tumor excision he repaired the sinus wall or reconstructed the sinus with a vein graft. In this group, there was 29% of postoperative paresis. Postoperative angiogram demonstrated the patency of SSS in 66% of cases. This means that in one third of the cases the reconstruction of the SSS did not work.
