45.1 Introduction

The risks of hearing loss and facial nerve injury associated with microsurgical resection of vestibular schwannomas (VSs) have been extensively studied; yet, neurovascular complications that can arise and lead to devastating consequences have received little attention by comparison. Intracranial vascular injury remains an uncommon, yet gravely feared complication of VS surgery. Vascular complications including arterial or venous stroke, intraoperative hemorrhage, hematoma formation, and venous thrombosis can result in significant perioperative morbidity and mortality.

Vascular complications associated with microsurgical resection of VS are uncommon and have been reported in up to 7 to 10.1% of patients.s. Literatur ^,​ s. Literatur Mahboubi et al reviewed 6,553 VS resections, reporting a 2.1% risk for requiring a blood transfusion, 0.8% risk of stroke, 0.7% risk of cerebral edema, and 0.6% risk of intracranial hemorrhage.s. Literatur Betka et al reported hemorrhages occurred in 5% of 317 consecutive patients undergoing microsurgery—with cerebellopontine angle (CPA) hematomas reported in 8 (2.5%) patients and intracerebellar hematomas in 4 (1.3%) patients, all of which were managed with immediate reoperation.s. Literatur In 2001, Slattery et al reported that 0.9% (15/1,687) of patients developed intracranial hemorrhage postoperatively, with 6 occurring within 24 hours of surgery.s. Literatur Interestingly, at the time of revision surgery, the origin of bleeding was not identified in most cases. In 1994, Briggs et al reviewed 167 VSs greater than 4 cm that underwent translabyrinthine (TL) resection and reported a vascular complication rate of 4.8%; four patients demonstrated brainstem or cerebellar infarcts, three required exploration for evacuation of intracranial hematoma, and one had a cerebellar hematoma.s. Literatur

To date, studies have not demonstrated differences in vascular complication rates when comparing surgical approaches. Sade et al compared the incidence of vascular complications in a total of 413 retrosigmoid and TL approaches for VS resection, noting that vascular complications occurred in 2.7% of patients, regardless of the approach.s. Literatur Similarly, Ansari et al performed a systematic review, noting no significant differences in developing a major neurological complication, including stroke, seizure, and persistent cerebellar dysfunction, between the three most common microsurgical approaches to the CPA.s. Literatur

45.2 Hemorrhage/Hematoma

Intraoperative and postoperative hemorrhage with hematoma formation is a rare, albeit potentially devastating, complication of VS microsurgery (Fig. 45‑1 ). The reported incidence of hemorrhage ranges from 0.8 to 2.4%,s. Literatur ^,​ s. Literatur ^,​ s. Literatur with rates of 0.8% for both subdural and extradural hematomas.s. Literatur Barker et al, utilizing data from the Nationwide Inpatient Sample hospital discharge database, representing about 20% of all inpatient admissions to nonfederal hospitals, noted that hematomas occurred in 1.1% of VS cases, while postoperative neurological complications, attributed to either infarction or hemorrhage, developed in 10.1% of all patients.s. Literatur Springborg et al reviewed 1,244 patients within the Denmark centralized clinical database who underwent TL VS resection and reported a mortality rate of 0.96%.s. Literatur Within this series, eight (0.64%) deaths were the result of postoperative hematomas, which prompted the authors to routinely obtain postoperative head CT scans to hopefully identify these complications early in the course of development.s. Literatur In a review of approximately 1,600 VS cases from a single institution, Slattery et al described one patient who developed bleeding under the temporalis muscle following a middle fossa approach, medializing the bone flap and requiring surgical evacuation, and two other patients who developed postoperative bleeding 10 and 14 days following surgery. In the latter two cases, both were monitored and treated with steroids, with resolution in symptoms prior to discharge.s. Literatur

To evaluate for any bleeding at the end of the procedure, Sanna et al performed at least 10 minutes of continuous suction irrigation, including a Valsalva maneuver, to identify occult bleeding and to help achieve hemostasis. In addition, they stress the importance of immediate extubation at the conclusion of the procedure when possible, since deterioration in mental status is one of the most reliable early clinical indicators of intracranial hematoma.s. Literatur Several other publications have reported that postoperative intracranial hemorrhage is noted within the first 24 hours in only 33 to 40% of cases, requiring intervention in about half of all cases.s. Literatur ^,​ s. Literatur ^,​ s. Literatur As for the presenting symptoms, Sade et al noted that all patients with hemorrhage presented with progressive signs of cerebellar dysfunction, cranial nerve deficits, headache, vomiting, and deterioration in their level of consciousness within 72 hours.s. Literatur

In most cases, the likely explanation for early hematoma development is poor intraoperative hemostasis, where an arterial or more likely venous bleeding source was not adequately recognized or managed. If the source was arterial, rapid blood accumulation would most likely produce immediate clinical effects identifiable in the recovery room. Furthermore, arterial bleeding almost always requires surgical intervention, while venous bleeding will generally tamponade when the hematoma becomes large enough. Elevated blood pressure (BP) and increased intracranial pressure from coughing, emesis, or constipation is not uncommon after VS surgery and therefore meticulous hemostasis is mandatory. Less commonly, bleeding diathesis, pharmacologic anticoagulation, or antiplatelet therapy may contribute to perioperative hemorrhage.

While we are unaware of any studies evaluating the risk of venous thromboembolism (VTE) prophylaxis and hemorrhage in patients undergoing VS surgery, several studies have evaluated VTE prophylaxis in intracranial meningioma patients undergoing excision. Eisenring et al compared two regimens between 724 meningioma patients: cohort A included 5,000 international units (IUs) of low-molecular-weight heparin (LMWH) every 24 hours on the first postoperative day, while cohort B included intraoperative leg elevation to facilitate venous backflow, as well as unfractionated heparin on the day of surgery, replaced with 5,000 IU of LMWH on the first postoperative day.s. Literatur While there were significantly more pulmonary embolisms in cohort A (8 vs. 2.5%), there were no significant differences in deep venous thrombosis, hemorrhage, or death.s. Literatur Additional studies with meningioma patients have looked at the initiation of preoperative pharmacologic prophylaxis, as well as the addition of intraoperative hemodilution and the initiation of LMWH 12 hours postoperatively with mixed results.s. Literatur ^,​ s. Literatur

In regards to hypertension, defined as sustained BPs greater than or equal to 160/90, Basali et al reviewed 11,214 patients who underwent craniotomies at one institution, and noted that patients who had either intraoperative or postoperative hypertension within the first 12 hours were significantly more likely to develop an intracranial hemorrhage.s. Literatur While rare, features intrinsic to the tumor itself may risk postoperative hemorrhage when subtotal resection is performed, including increased tumor vascularity, dilation and thinning of intratumoral vessels, or cystic tumors, with two known case reports of intratumoral hemorrhage following subtotal VS resections, which may have been the result of intrinsic tumor factors or inadequate hemostasis.s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur Lastly, one should always be aware of the risk with excessive cerebrospinal fluid (CSF) removal with lumbar drain placement in older patients with tenuous bridging subdural vessels. In such cases, a subdural bleed may occur even outside the surgical field of view and may carry grave consequences.

45.3 Petrosal Vein and Superior Petrosal Sinus Injuries

The transverse pontine vein and veins of the cerebellopontine fissure and middle cerebellar peduncle all join to form a superior petrosal vein, also known as Dandy’s vein, which drains into the superior petrosal sinus, usually lateral to the trigeminal nerve.s. Literatur There are a variety of reports on the number of petrosal veins present, ranging from 40 to 69.1% for a single vein, 27.3 to 60% for two or more veins, with some even reporting the absence of a petrosal vein.s. Literatur ^,​ s. Literatur With significant debate within the literature regarding the consequences of sacrificing the petrosal vein, Ebner et al conducted a cadaveric study after injection of the petrosal vein, finding that following petrosal vein occlusion, compensatory venous blood drainage is directed toward anastomotic supratentorial deep vein pathways.s. Literatur Nonetheless, Sampath and colleagues routinely sacrifice the rostral bridging petrosal vein in larger size VS in order to reduce the risk of bleeding during surgery, and to allow easier retraction of the superior cerebellar hemisphere to aid in exposure of the tumor.s. Literatur

While we are not aware of any VS articles discussing outcomes following petrosal vein sacrifice, other pathologies have several reported complications associated with petrosal vein occlusion, including hearing loss, cerebellar venous infarction, peduncular hallucinosis, cerebellar and brainstem edema, brainstem and cerebellar hemorrhage, hydrocephalus, and transient organic psychosyndrome (comparable to presenile dementia with a reduction in memory and intellect), and death.s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur Assessing the sectioning of the petrosal vein in petrous apex meningiomas, Koerbel et al retrospectively assessed cerebellar edema, ventriculomegaly, and/or cerebellar infarction following petrosal vein obliteration via video recordings in 57 cases, noting that in 30 cases, at least one vein was not preserved, with nine of those patients developing venous-related complications.s. Literatur Interestingly, when compared to those patients in whom the petrosal vein complex was preserved, there were no significant differences in complications associated with venous congestion.s. Literatur However, they found that those patients who developed complications following superior petrosal vein sectioning tended to have petrosal veins larger than 1.2 mm as compared to those patients whose veins were sectioned but did not develop complications.s. Literatur Nonetheless, while some reports suggest complication rates as high as 30% in CPA surgery when the superior petrous vein is sacrificed, many surgeons, especially in VS resections, experience much lower complication rates.

Several groups have looked at the relationship between superior petrosal vein injury and hearing loss with conflicting results. Strauss et al noted postoperative hearing loss following injury to the superior petrosal vein during a microvascular decompression.s. Literatur ^,​ s. Literatur However, Gharabaghi et al found no differences in hearing preservation and hearing loss with petrosal vein sacrifice during petroclival meningioma resections, further reporting that the size of the vein had no significant impact.s. Literatur They concluded that superior petrosal vein occlusion is not related to postoperative hearing loss, but its preservation should be attempted since other significant complications, such as venous congestion and hemorrhage, have been reported.s. Literatur

It is routine in our institution to preserve the petrosal vein in CPA surgery when feasible, while avoiding any stretching that may lead to inadvertent tearing, avulsion, or thrombosis. The risk of inadvertent injury is greatest while using a cerebellar retractor, delivering the superior pole of the tumor, or drilling intracranially. Drilling should be avoided at all costs while pledgets or other loose hemostatic agents are present within the surgical field due to the significant damage that can occur if the drill was to capture the substrate while rotating at approximately 60,000 RPM. Small tears of the vein may be spot-welded on a low bipolar setting or effectively managed with Gelfoam or Floseal (Baxter, Hayward, CA), while larger tears may require vein sacrifice.

45.4 Dural Sinus Thrombosis and Vein of Labbé

Another venous complication associated with lateral skull base surgery is the development of dural or lateral sinus thrombosis, with a reported incidence rate between 0.1 and 4.7% (Fig. 45‑2 and Fig. 45‑3 ).s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur ^,​ s. Literatur While lateral sinus thrombosis may develop without clinical signs or subjective complaints, dural venous thrombosis may cause increased intracranial pressure, retinal hemorrhage, papilledema, headache, visual loss, dizziness, brain edema, and mental status changes, particularly when involving a dominant venous outflow system.s. Literatur ^,​ s. Literatur ^,​ s. Literatur

De Bruijn et al prospectively studied prognostic factors in patients with cerebral venous sinus thrombosis, noting that patient age older than 33 years, involvement of the straight sinus, papilledema, diagnostic delay greater than 10 days, impaired consciousness, coma, and intracerebral hemorrhage were all associated with poor outcomes, while a negative or empty delta sign on CT, where contrast outlines a triangular filling defect of the superior sagittal sinus, and isolated intracranial hypertension, were associated with good outcomes.s. Literatur

Ohata et al reviewed 174 presigmoidal-transpetrosal approaches, identifying five cases of sigmoid sinus occlusion.s. Literatur They documented that the sinus was injured in seven cases, five of which developed occlusions postoperatively.s. Literatur However, it must be noted that the superior petrosal sinus was transected in all cases, followed by division of the tentorium.s. Literatur In one patient, a large hemorrhage developed in the ipsilateral temporal lobe 4 hours following the procedure, which required immediate drainage, with the patient subsequently developing a large intracerebral hematoma in the contralateral frontoparietal region 1 week later.s. Literatur Given the risks regarding dural sinus thrombosis, many authors have attempted to classify venous configurations of the torcular herophili,s. Literatur transverse sinus,s. Literatur sigmoid sinus,s. Literatur as well as documenting if one transverse sinus is dominant as compared to the other.s. Literatur Ohata et al commented that occlusion of the ipsilateral sigmoid sinus in cases of hypoplastic or atretic transverse sinuses can lead to vein of Labbé congestion.s. Literatur The vein of Labbé, also known as the inferior anastomotic vein, arises from the midpoint of the Sylvian fissure and travels posteroinferiorly to enter the transverse sinus at least 7 mm posterior to the superior petrosal sinus, draining the lateral temporal lobe.s. Literatur Injury or occlusion to the vein can lead to disturbances in memory, speech, and contralateral motor deficits.s. Literatur It is most frequently at risk with prolonged temporal lobe retraction and during combined middle and posterior fossa approaches, with the tentoriotomy placing the vein at risk. Multiple methods have been described to avoid injury to the vein of Labbé, including working above and below the tentorium with two operative fields, transecting the sigmoid sinus and ligating the transverse sinus distally to the vein of Labbé, cutting the tentorium in a posteroanterior direction, among other techniques.s. Literatur

To avoid sinus thromboses, various authors have suggested maintaining adequate hydration during and after surgery, limiting the bony exposure to what is necessary to prevent desiccation, minimizing retraction against venous structures, and maintaining the integrity of a dominant sinus.s. Literatur ^,​ s. Literatur Preoperative sinus anatomy should be examined to determine the best approach. In some cases, for example, a very high jugular bulb or anterior sigmoid sinus may indicate that a retrosigmoid approach would be advantageous over a TL approach (Fig. 45‑4 ). If the sigmoid sinus is injured, bipolar cautery with irrigation may be used to spot-weld a small tear, or extraluminal collagen, gelatin sponge, or oxidized cellulose packing may be used to control bleeding from a small- or medium-sized venotomy without immediate occlusion.s. Literatur ^,​ s. Literatur In rare cases, a large sinus laceration may be amenable to suture repair, with or without a patch graft. Intraluminal packing or ligation should only be used as a last resort. Collagen and gelatin sponges work by providing mild mechanical compression via absorption of blood and fluids leading to swelling of the sponge, while oxidized cellulose reacts with blood to precipitate an artificial coagulum, covering the venous injury to provide hemostasis.

Though there are studies investigating a possible association between hemostatic agents and an increased risk of deep venous thromboses and pulmonary emboli in patients undergoing meningioma resections,s. Literatur other large studies have reported no complications associated with gelatin-thrombin materials.s. Literatur Thrombin, which is used in Floseal, and in association with collagen or gelatin sponges, assists with the clotting cascade by converting fibrinogen to fibrin, activating factor XIII which stabilizes clots, and inhibiting fibrinolysis. While rare, acquired factor V antibodies can develop, which can lead to life-threatening bleeding.s. Literatur In our experience, sigmoid sinus injuries can almost always be controlled with a large piece of absorbable gelatin sponge covered by a cottonoid pledget with mild compression. The gelatin sponge should always be large enough to prevent inadvertent entry into the lumen of the vein and vascular system. Direct suturing is rarely needed, and extraluminal packing with ligation of the jugular vein in the neck is essentially never required.s. Literatur

Further postoperative management options include steroids, anticoagulation, volume repletion, carbonic anhydrase inhibitors, direct endovascular thrombolysis, and surgical thrombectomy depending on patient condition and risk of clot propagation.s. Literatur Other predisposing factors such as smoking, pregnancy, contraceptive use, or underlying coagulopathies (e.g., antiphospholipid syndrome, proteins C and S deficiency, lupus anticoagulant, or factor V Leiden mutation) should be investigated.