Neurosurgery and the intracranial venous system.

1) Numerous of the so-called "unpredictable" post-operative complications are likely to be related to the lack of prevention or non-recognition of venous problems, especially damages to the dangerous venous structures, namely: the major dural sinuses, the deep cerebral veins and some of the dominant superficial veins like the vein of Labbé. 2) Tumors invading the major dural sinuses (superior sagittal sinus, torcular, transverse sinus)--especially meningiomas--leave the surgeon confronted with a dilemma: leave the fragment invading the sinus and have a higher risk of recurrence, or attempt at total removal with or without venous reconstruction and expose the patient to a potentially greater operative danger. Such situations have been encountered in 106 patients over the last 25 years. For decision-making, meningiomas were classified into six types according to the degree of sinus invasion. Type 1: meningioma attached to outer surface of the sinus wall; Type II: one lateral recess invaded; Type III: one lateral wall invaded; Type IV: one lateral wall and the roof of the sinus both invaded; Types V and VI: sinus totally occluded, one wall being free of tumor in type V. In brief, our surgical policy was the following: Type I: excision of outer layer and coagulation of dural attachment; Type II: removal of intraluminal fragment through the recess, then repair of the dural defect by resuturing recess. Type III: resection of sinus wall and repair with patch (fascia temporalis). Type IV: resection of both invaded walls and reconstruction of the two resected walls with patch. Type V: this type can be recognized from type VI only by direct surgical exploration of the sinus lumen. Opposite wall to the tumor side is free of tumor, it is possible to reconstruct the two resected walls with patch. Type VI: removal of involved portion of sinus and restoration with venous bypass. 3) As 20% of the patients presenting with manifestations of intracranial hypertension due to occlusion of posterior third of the superior sagittal sinus, torcular, predominant lateral sinus or internal jugular vein(s) develop severe intracranial hypertension, venous revascularisation by sino-jugular bypass--implanted proximally to the occlusion and directed to the jugular venous system (external or internal jugular vein)--can be a solution.