Dural Venous Sinus Injury
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Several neurosurgical approaches expose or manipulate the dural venous sinuses. The skilled surgeon should master the venous anatomy through a detailed study of the preoperative images, expect intraoperative difficulty and prepare appropriately. Compared to the cerebral arteries, the veins and dural sinuses do not get the attention they deserve.
Despite the use of meticulous microsurgical techniques, dural venous sinus injury and bleeding is encountered by virtually all neurosurgeons. Dural sinus injury and occlusion can lead to devastating venous infarction and irreversible neurologic deficits, if not handled judiciously. Therefore, it is imperative to anticipate, be prepared, remain calm, and be determined to manage dural sinus bleeding wisely.
Some measures are worth special emphasis. As a preventive measure, unnecessary exposure of the venous sinuses should be avoided and craniotomies should be no closer than 1.5 cm to midline. When the craniotomy is in close proximity to these sinuses, the wall of the sinus should be generously separated from the inner skull bone before the footplate of the drill is used. The difficulty of this dissection is anticipated in elderly patients, repeat operations, and patients with thick skull.
Aggressive retraction along the dura near the dural venous sinuses may lead to sinus occlusion and thrombosis. Venous sinus compromise can cause intraoperative brain swelling and spontaneous intracerebral hemorrhage. Therefore, if intraoperative cerebral tension is encountered, one should rule out inadvertent occlusion of the neighboring venous sinuses. Microdoppler ultrasonography can confirm the patency of and flow within of the sinuses during temporary retraction.
When bleeding from a nonvital venous sinus, such as the occipital sinus, is encountered, the sinus may be ligated using silk sutures or Weck clips. This can occur during Y-shape dural opening during posterior fossa operations.
To protect the sinus during dural opening, I incise the dura based over the sinus. The extensions of the venous sinuses and venous lakes often reach beyond the margins of the sinuses; therefore, the dural opening must be conducted judiciously along the paramedian regions.
After exposing the area of the injury, the next step involves reaching hemostasis and/or clearing the operative field to select the maneuvers necessary to repair the sinus. The operator should remain composed in the face of torrential bleeding and warn the anesthesiologist about imminent massive blood loss and the need for immediate volume replacement.
Gentle tamponade using cotton patties readily controls the low-pressurized venous bleeding. The operator should not indiscriminately pack hemostatic agents (such as Gelfoam, or Surgicel) into the lumen of the sinus because this maneuver would lead to sinus occlusion and potentially cerebral swelling.
Assessment of collateral venous drainage is important before determining the appropriate reconstruction techniques. Proximal and distal vascular control over the sinus is preferred. Subject to the extent of the tear and ease of this maneuver, long aneurysm clips or vascular bulldogs may be used to temporarily halt bleeding. In the event of venous sinus transection, if the proximal and distal control is not feasible because the sinus is covered by bone along the craniotomy edges, cotton balls may be used to seal the sinus lumen temporarily.
Bipolar coagulation is contraindicated in partial sinus tears as this maneuver will enlarge the tear/opening by shrinking the dural edges and compounding the problem. Gentle elevation of the patient’s head (15 degrees) will reduce venous pressure within the sinus. However, this tactic dramatically increases the risk of air embolism and a high index of suspicion for air emboli must be pursued. The patient’s head may be elevated to reduce bleeding, but should not be raised to stop an anterograde venous hemorrhage because this leads to retrograde air siphoning.
Repair of the Dural Venous Sinus Injury
A variety of techniques may be employed to repair large lacerations within the dural sinuses. The fundamental principle is preservation of the sinus while controlling blood loss. To avoid hemodynamic instability, the operator may pause to obtain complete hemostasis and work intermittently in face of some bleeding from the lumen to make sure the anesthesiologist has a chance to replace the blood volume.
Injury to the Anterior One-Third of the Superior Sagittal Sinus
The anterior one-third segment of the superior sagittal sinus (anterior to the coronal suture) may be occluded with little or no risk to the patient as long as there is paucity of parasagittal veins around this segment. There are exceptions to this rule, and I have therefore attempted to save the venous sinus along its entire length when possible.
Injury to the Posterior Two-Thirds of the Superior Sagittal Sinus
This segment of the sinus is vital for drainage of the hemispheres, and its patent lumen must be preserved to avoid devastating venous infarction. The mode of injury plays an important role regarding the recommended methods to repair the defects in the wall.
Injury to the Torcula
Repair of the Transverse Sinus Injury
Dealing with injury of the transverse sinuses can be challenging because these sinuses are critical for drainage of supratentorial and infratentorial contents. It is critically important to determine the dominance of the transverse sinuses preoperatively; the right transverse sinus is most often dominant.
Right-sided transverse sinus bleeding can be catastrophic when it is the predominant drainage outlet for the superior sagittal sinus. The torcula must be preserved at all cost. The principles of transverse sinus reconstruction are the same as those discussed above in the case of the posterior superior sagittal sinus.
Pearls and Pitfalls
- A meticulous study of the preoperative images is crucial for understanding variations in venous anatomy and the precautions that are necessary during surgery to avoid venous injuries.
- Venous bleeding may be easily controlled using gentle tamponade. The lumen of the sinus should not be occluded with hemostatic packing materials.
- Most dural sinus injuries can be repaired after proximal and distal control are secured.
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