EC-IC bypass for cerebral revascularization following skull base tumor resection: Current practices and innovations

Complex skull base tumors can involve critical vessels of the head and neck. To achieve a gross total resection, vessel sacrifice may be necessary. In cases where vessel sacrifice will cause symptomatic cerebral ischemia, surgical revascularization is required. The purpose of this paper is to review cerebral revascularization for skull base tumors, the indications for these procedures, outcomes, advances, and future directions.

Monitoring of balloon test occlusion of the internal carotid artery by parametric color coding and perfusion imaging within the angio suite: first results

BACKGROUND

Temporary balloon test occlusion (BTO) might be performed prior to procedures in which occlusion of the internal carotid artery (ICA) might be necessary. We tested the hypothesis that parametric color coding (PCC) of angiographic series (digital subtraction angiography (DSA)) along with the assessment of cerebral blood volume (CBV) in the angiography suite would simplify and enhance the identification of candidates who are most likely to tolerate occlusion.

MATERIALS AND METHODS

Fifteen patients underwent angiographic series (DSA) and perfusion imaging before and during BTO. Pre- and postocclusion DSA acquisitions were evaluated for venous delay by conventional methods ("eye balling") and by PCC measurements. Comparison of CBV values between the left and right hemisphere in 6 defined regions was performed.

RESULTS

Values of venous delay by eye balling and PCC showed a high correlation (r = 0.87, p < 0.01). Bland-Altman plot indicated slightly lower values (-0.05 s) by the PCC method. One of the 15 patients developed an asymmetrical CBV map with an increase in CBV of more than one standard deviation in 3 of the 6 regions of interest (ROIs). Acquisition of angiographic series and perfusion imaging did not prolong the test occlusion time.

CONCLUSION

PCC and CBV mapping are feasible during BTO. The use of PCC seems to simplify the ability to measure changes in venous filling delay. Perfusion imaging may show an increase in CBV in patients reaching the limits of cerebral autoregulation. These patients may be at risk for delayed infarction, even though they seem to tolerate temporary occlusion, and could be unsuitable candidates for permanent ICA occlusion.

KIS, Zhang Y, Zhou Z, Sun Y. Bypass of the maxillary to proximal middle cerebral artery or proximal posterior cerebral artery with radial artery graft

The authors report three cases of radial artery (RA) graft bypass from the maxillary artery (MA) to either the middle cerebral artery (MCA) or the posterior cerebral artery (PCA). The first two cases presented with the features of basal ganglion ischemia, and magnetic resonance imaging (MRI) revealed left and right basal ganglion ischemia respectively, whereas angiogram showed MCA occlusion. Computed tomography angiography (CTA) of the third case, who presented with headache and dysphasia, showed a giant basilar artery aneurysm with an absence of the left posterior communicating artery (PComA). The first two cases underwent MA-MCA graft bypass and the third case underwent MA-posterior cerebral artery (PCA) RA graft bypass, followed by clipping of the left dominance vertebral artery and a sub-occipital decompressive craniotomy. Postoperative angiogram disclosed patent RA graft and refilling of the ischemic segment. Follow-up at 7-9 months showed marked clinical improvement in all cases. To our knowledge, MA bypass has not been performed clinically till the date and this method may be a safe, effective and new surgical technique for the extracranial-intracranial (EC-IC) bypass surgery.

Management of Complications in Neurotology

Neurotologic and skull base surgery involves working around important neurovascular and neurotologic structures and can incur unwarranted complications. Knowledge of surgical anatomy, good preoperative planning, intraoperative monitoring, and excellent microsurgical technique contribute to minimizing and avoiding complications. In the event of a complication, however, the neurotologic surgeon should be prepared to manage it. In this article, the authors focus on the management of complications encountered in neurotologic skull base surgery, including hemorrhage, stroke, cerebrospinal fluid leak, extraocular motility deficits, facial paralysis, hearing loss, dizziness, lower cranial nerve palsies, and postoperative headache.

A modified technique for bypass of the external carotid artery to the proximal posterior cerebral artery: an anatomical and technical study

CONCLUSIONS

Our results support the proposition that bypass between the external carotid artery (ECA) and proximal posterior cerebral artery (PCA) can be achieved by using a short saphenous venous graft. The diameters of the ECA and vein graft may provide an increased blood flow with a straighter course. This technique may be helpful for management of patients with vertebrobasilar insufficiency or those requiring a high volume blood flow to the posterior circulation.

OBJECTIVES

We aimed to describe a modified technique using a short saphenous vein graft for bypass between the ECA and the PCA in order to use a small length of graft material and increase the patency of the anastomosis.

MATERIALS AND METHODS

Ten sides of five cadavers were dissected bilaterally. After a frontotemporal craniotomy and zygomatic arch osteotomy, the middle cranial fossa was exposed. A hole located approximately 2-3 cm posterolateral to the foramen rotunda was created extradurally. The sylvian fissure and the interpeduncular and ambient cisterns were opened. The proximal P2 segment of the PCA was identified. The ECA was found through a cervical incision. A short interposition saphenous vein graft was conducted to pass just behind the ramus mandible to the infratemporal fossa. The bypass between the ECA and P2 segment of the PCA was performed by using a short saphenous vein graft. The diameters of the ECA, P2 segment of PCA and both ends of the saphenous vein graft and its length were measured using an electronic micrometer.

RESULTS

The mean cross-clamping time of the PCA was 10.4+/-1.8 min. The mean diameters of the P2 segment of the PCA and ECA were 2.2+/-0.15 mm and 3.83+/-0.28 mm, respectively. The mean length of the saphenous vein graft was 88.8+/-3.8 mm.

Superficial temporal artery graft for bypass of the maxillary to proximal middle cerebral artery using a transantral approach: an anatomical and technical study

CONCLUSION

Using a transantral approach, we examined a new bypass of the maxillary artery (MA) to proximal middle cerebral artery (MCA). The caliber of the MA was suitable to provide sufficient blood flow. The length of the graft was shorter and it had a straighter course in the new technique than in previously described techniques.

OBJECTIVE

To examine a new bypass of the MA to proximal MCA using a transantral approach as an alternative to other forms of anterior circulation bypass surgery.

MATERIAL AND METHODS

The method was applied to five adult cadavers bilaterally. The MA and its branches were easily found after removal of the posterior sinus wall using a transantral approach. Then, a hole was created in the sphenoid bone 5-6 mm lateral to the posteroinferior edge of the superior orbital fissure extradurally. After the carotid and sylvian cisternae had been opened, the M2 segment of the MCA was exposed. The MA was transected just before the origin of the descending palatine artery branch. After opening the dura over the hole, the MA was passed through the hole to reach the intracranial cavity. The proximal side of the superficial temporal artery graft was anastomosed end-to-end with the MA and the distal side was anastomosed end-to-side with the M2 segment of the MCA.

RESULTS

The mean caliber of the MA was 2.4+/-0.3 mm before the origin of the descending palatine artery branch. The mean caliber of the largest trunk of the M2 segment of the MCA was 2.3+/-0.3 mm. The average length of the graft was 24+/-3 mm.

Saphenous vein graft for bypass of the external carotid artery to supraclinoid internal carotid artery using a modified technique: an anatomical and technical study

OBJECTIVE

To investigate the use of a saphenous vein graft for bypass of the external carotid artery (ECA) to supraclinoid internal carotid artery (ICA) when the proximal middle cerebral artery (MCA) is not suitable for a bypass procedure.

MATERIAL AND METHODS

Five adult cadaver sides were used. Dissection required a frontotemporal craniotomy and a zygomatic arch osteotomy, with a hole being opened 2-3 mm lateral to the foramen rotundum extradurally. The ECA was found easily via a second incision in the cervical region. The ophthalmic segment of the ICA was exposed by removal of the anterior clinoid process intradurally. After the dura over the hole was opened, the 7-8-cm long bypass graft was passed just behind the mandibula and through the hole inside the dura to reach the ICA. The ECA was then transected proximal to the occipital artery (OA) branch and the distal side of the vein graft was anastomosed end-to-end with the ECA and end-to-side with the supraclinoid ICA.

RESULTS

The mean diameter of the ECA proximal to the OA was 3.75+/-0.4 mm (range 3.35-4.15 mm) and that of the supraclinoid ICA was 3.4+/-0.5 mm (range 2.9-3.9 mm). The mean length of the venous graft was 7.5+/-0.5 cm (range 7-8 cm).

CONCLUSION

When high blood flow is needed and the proximal MCA is not suitable for a bypass, the bypass described herein may be an alternative to a superficial temporal to MCA bypass as well as to extracranial carotid artery to MCA or ICA bypasses, which both need long vein grafts.

Radial artery graft for bypass of the maxillary to proximal posterior cerebral artery: an anatomical and technical study

OBJECTIVE

To examine the use of a radial artery graft for bypass of the maxillary artery (MA) to proximal posterior cerebral artery (PCA) as an alternative to the external carotid artery (ECA) to PCA anastomosis used in posterior circulation bypass surgery.

MATERIALS AND METHODS

The method was applied to five adult cadaver sides bilaterally. The MA was easily found 1-2 cm beneath the infratemporal crest after a frontotemporal craniotomy and a zygomatic arch osteotomy. Extradurally, 2-3 cm posterolateral to the foramen rotundum, a hole was drilled in the sphenoid bone with a 4-mm tipped drill. After sylvian fissure, the interpedincular and ambient cisternae were opened and the P2 segment of the PCA appeared. The graft was passed through the hole and dura to reach the P2 segment. Proximal to the infraorbital artery branch, the MA was freed from the surrounding tissue and transected. The proximal side of the radial artery graft was anastomosed end-to-end with the MA and the distal side was anastomosed end-to-side with the P2 segment of the PCA.

RESULTS

The average diameter of the MA proximal to the infraorbital artery branch was 2.6+/-0.3 mm. The average diameter of the P2 was 2.2+/-0.2 mm. The average length of the graft was 47+/-5.2 mm.

CONCLUSION

As MA to proximal PCA bypass uses a short radial graft and as the calibers of the MA and PCA are >2 mm such a bypass may provide sufficient blood flow and represents a reasonable alternative to "ECA to PCA" bypass.

Carotid Perfusion CT with Balloon Occlusion and Acetazolamide Challenge Test: Feasibility

Carotid balloon test occlusion (BTO) is used to assess the collateral circulation and cerebrovascular reserve in patients in whom carotid artery occlusion is contemplated. Eight patients in whom the test was successful were evaluated with perfusion computed tomography (CT) in the resting state and after acetazolamide challenge. Three of the patients showed symmetric blood flow and normal response to acetazolamide. One of them underwent permanent carotid occlusion and did not develop any delayed ischemic stroke. The remaining five patients showed asymmetric blood flow. One of them had markedly low blood flow and abnormal response to acetazolamide. The patient developed ipsilateral hemispheric stroke following permanent carotid occlusion after the superficial temporal artery to middle cerebral artery bypass graft occluded. In the other four patients, the steal phenomenon was seen in ipsilateral and contralateral hemispheres. Although definitive quantitative values for perfusion CT are not yet standardized, it may be feasible to predict that the patients with symmetric blood flow and normal acetazolamide-enhanced challenge test results will do well after permanent carotid occlusion. Patients with asymmetric blood flow and abnormal response to the acetazolamide challenge test may require a revascularization procedure to protect them from delayed ischemic stroke.

Cerebral perfusion CT: technique and clinical applications

Perfusion computed tomography (CT) is a relatively new technique that allows rapid qualitative and quantitative evaluation of cerebral perfusion by generating maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). The technique is based on the central volume principle (CBF = CBV/MTT) and requires the use of commercially available software employing complex deconvolution algorithms to produce the perfusion maps. Some controversies exist regarding this technique, including which artery to use as input vessel, the accuracy of quantitative results, and the reproducibility of results. Despite these controversies, perfusion CT has been found to be useful for noninvasive diagnosis of cerebral ischemia and infarction and for evaluation of vasospasm after subarachnoid hemorrhage. Perfusion CT has also been used for assessment of cerebrovascular reserve by using acetazolamide challenge in patients with intracranial vascular stenoses who are potential candidates for bypass surgery or neuroendovascular treatment, for the evaluation of patients undergoing temporary balloon occlusion to assess collateral flow and cerebrovascular reserve, and for the assessment of microvascular permeability in patients with intracranial neoplasms. This article is a review of the technique, clinical applications, and controversies surrounding perfusion CT.

Bypass combined with embolization via a venous graft in a patient with a giant aneurysm in the posterior communicating artery and bilateral idiopathic occlusion of the internal carotid artery in the neck

The authors describe the case of a patient with a symptomatic giant aneurysm of the posterior communicating artery (PCoA) associated with bilateral idiopathic occlusion of the internal carotid artery (ICA). The presence of severe tortuosity of the vertebral arteries (VAs), both at their origin from the subclavian artery and at the level of the third segment, impeded navigation of the catheter for embolization of the aneurysm with Guglielmi detachable coils (GDCs). A direct surgical approach was considered to be a high-risk procedure because of the bilateral occlusion of the ICAs and the size of the aneurysm. The following therapeutic strategy was therefore adopted: 1) balloon occlusion test of the left VA; 2) vertebro-vertebral bypass with saphenous vein graft to provide a pathway for subsequent embolization; 3) ICA-left middle cerebral artery bypass to ensure blood flow in the event that embolization resulted in closure of the PCoA; and 4) GDC embolization of the aneurysm via the posterior circulation graft to ensure complete exclusion of the lesion from the arterial circulation and preservation of the PCoA. At 3-month follow-up review the patient did not present with any neurological deficits; at 1-year control examination, magnetic resonance (MR) imaging and MR angiography both confirmed complete exclusion of the aneurysm and patency of the two bypasses.

Glomus tympanicum and glomus jugulare tumors

The ideal management of most paragangliomas is complete surgical excision. Because of technical advances, issues of resectability have given way to issues of functional outcome and postsurgical quality of life. This article reviews the surgical strategy for craniocervical paragangliomas. Intracranial extension, defect reconstruction, and cranial nerve rehabilitation are addressed.

Saphenous vein graft for bypass of the maxillary to supraclinoid internal carotid artery: an anatomical short study

The use of a saphenous vein graft for bypass of the maxillary artery (MA) to the supraclinoid internal carotid artery (ICA) in internal carotid occlusions is investigated. Five adult cadaver sides were used. Dissection required zygomatic arch osteotomy and a pterional craniotomy with extensive removal of the floor of the middle cranial fossa. The MA was found easily medial to infratemporal crest. The clinoidal segment of the ICA was exposed with the removal of the anterior clinoid process intradurally. The bypass graft was 4 to 5 cm long and was sutured end-to-end to the MA and end-to-side to the supraclinoid ICA. When high blood flow is needed in cases with ICA occlusion, such a bypass may be an alternative to superficial temporal (STA)-to-middle cerebral artery (MCA) bypass as well as to common carotid-to-MCA or-ICA bypass, which needs a long vein graft. This type of bypass will provide the opportunity to clip the ICA proximal to the origin of ophthalmic artery, which may inhibit distal embolization.

Management of the carotid artery at the skull base

PURPOSE

To determine appropriate management of benign lesions with significant involvement of the carotid artery at the skull base and present an algorithm for safe treatment of these patients.

MATERIALS AND METHODS

From 1982 to 1999, 115 patients with significant parapharyngeal space masses were treated at our institution. Of these patients, 43 had lesions involving the carotid artery at the skull base and served as the basis for this study. All patients underwent preoperative computed tomography or magnetic resonance imaging scans to determine carotid involvement, and all had preoperative 4-vessel arteriograms and carotid occlusion tests with continuous electroencephalography or neurologic examination monitoring to predict safety of carotid sacrifice.

RESULTS

Of 43 patients, 41 passed carotid occlusion testing and were treated surgically. Of these patients, 33 (81%) underwent resection of their lesions with preservation of the internal carotid artery, 5 (12%) had resection with bypass or reconstruction of the artery, and 3 (7%) had en bloc resections without artery reconstruction. There were no transient or permanent neurologic sequelae in any patient.

CONCLUSIONS

When carotid artery encasement occurs in the setting of benign lesions at the skull base, safe resection with vascular preservation is possible in most cases. If carotid artery resection is necessary, vascular bypass or reconstruction is recommended to minimize neurologic morbidity.

Invasion of the internal carotid artery by cavernous sinus meningiomas

BACKGROUND

Meningiomas are the most common tumor involving the cavernous sinus. Although these tumors have been known to invade adjacent structures such as bone, soft tissue, and brain, invasion of the internal carotid artery (ICA) by meningiomas has only been recognized recently. The authors evaluate the extent of carotid wall involvement in nine patients with cavernous sinus meningiomas encasing the ICA who underwent en bloc resection of the cavernous sinus.

METHODS

The en bloc tumor-ICA specimens were fixed in formalin, embedded in paraffin, and sectioned on a rotary microtome. Hematoxylin and eosin, EVG, and HVG stains were performed and evaluated by light microscopy.

RESULTS

There were four males and five females with a mean age of 47 years. Eight patients had not undergone previous surgery, whereas one patient had been operated on before. In this latter case, however, the cavernous sinus was not entered during the first operation. In all patients, stenosis of the ICA was confirmed by preoperative angiography and/or magnetic resonance imaging (MRI). In seven cases, the tumors were excised en bloc along with the stenotic ICA segment. A petrous-to-supraclinoid ICA bypass was performed in these seven patients. In two cases, the tumor was excised with the stenotic artery, but no bypass was performed. The final pathological diagnosis was meningothelial meningioma. In all cases tumor cells were found in the adventitia of the cavernous carotid with stenosis of the arterial lumen. Compression and/or obliteration of the vasa vasorum within the adventia was noted in all specimens. In four cases, the tumor was found to have invaded the external elastic lamina. In two instances the external elastic lamina was disrupted and the tumor focally extended into the media.

CONCLUSIONS

These findings suggest that in the case of cavernous sinus meningiomas with encasement and stenosis of the intracavernous ICA, invasion of the vessel wall has occurred. The effect of these findings on the management of cavernous sinus meningiomas and the involved ICA is discussed.

Venous and arterial bypass grafts for difficult tumors, aneurysms, and occlusive vascular lesions: evolution of surgical treatment and improved graft results

OBJECTIVE: In the treatment of patients with cranial base tumors, unclippable aneurysms, or medically intractable ischemia, it may be necessary to use high-flow bypass grafts. The indications, surgical techniques and complications are discussed. METHODS: During a 10-year period, 99 saphenous vein grafts and 3 radial artery grafts were performed for 101 patients, i.e., 72 with neoplasms, 23 with aneurysms, and 6 with ischemia. Clinical follow-up monitoring of the patients was by direct examination or telephone interview, with a mean follow-up period of 41.2 months (range, 5-147 mo). Radiological follow-up monitoring was by magnetic resonance imaging, magnetic resonance angiography, or three-dimensional computed tomographic angiography, with a mean follow-up period of 32 months (range, 1-120 mo). During the follow-up period, there was one late graft occlusion and one graft stenosis. RESULTS: The use of intraoperative angiography improved the patency rate from 90 to 98% and reduced the incidence of perioperative stroke from 13 to 9.5%. Ninety-two percent of the patients were in excellent or good neurological condition at the time of discharge from the hospital, compared with 95% before surgery. The perioperative mortality rate was 2%. Other complications included three intracranial hematomas, rupture of a vein graft in a patient with Marfan's syndrome, and five tumor resection-related problems. The long-term survival rates for patients who received grafts were excellent for patients with benign tumors, fair to poor for patients with malignant tumors, good for patients with aneurysms, and excellent for patients with ischemia. CONCLUSION: The results of saphenous vein and radial artery grafting have been greatly improved by the use of intraoperative angiography, improvements in surgical techniques, and improved perioperative treatment.

Results of surgical management of internal carotid artery aneurysm by the cervical approach

From 1981 to 1995 a total of 14 patients with a mean age of 52 years (range: 23-71) underwent surgery for 15 aneurysms of the extracranial internal carotid artery. Fusiform aneurysms of the carotid bifurcation were not included in this study. Aneurysm led to brain ischemia in 10 cases and rupture in one case. In the remaining four cases, aneurysm was asymptomatic including three that were detected following hemispheric stroke related to a contralateral aneurysm. The etiology was spontaneous dissection in four cases, blunt trauma in three cases, fibromuscular disease in five cases, and atheroma in three cases. The upper limit of the aneurysm was located at C1-C2 in six cases, at C1 in three cases, and above C1 (at the base of the skull) in six cases. The cervical approach was used to successfully perform 12 revascularizations and three ligations (including one after extra-intracranial bypass). There were no postoperative deaths. One transient ischemic attack (TIA) occurred after ligation. Peripheral facial paralysis (PFP) occurred in four of the nine cases in which an extended cervical approach was used. No patients were lost to follow-up. Mean duration of follow-up was 4 years (range: 2 months-10 years). Two patients died at 2 and 4 years of causes unrelated to the procedure. All carotid reconstructions are currently patent and no neurologic manifestations have occurred. PFP persisted in one case. The results of this series confirm that surgical therapy of aneurysms of the extracranial internal carotid artery achieves satisfactory short- and medium-term results and that the extended cervical approach allows treatment of lesions near the base of the skull.

Management of the vertebral artery in excision of extradural tumors of the cervical spine

Extradural tumors of the cervical spine may involve the vertebral artery on one or both sides, posing one of the limiting factors toward the radical resection of such neoplasms. A standard anterior approach may be inadequate for the management of such tumors. An anterolateral approach allows the dissection and mobilization of the vessel, which can then be preserved, resected, or reconstructed with a vein graft. An anterior approach can be supplemented with this for tumor resection and stabilization. This management strategy is described in 10 patients with a variety of tumors.