Experience from "double-insurance bypass." Surgical results and additional techniques to achieve complex aneurysm surgery in a safer manner

BACKGROUND: "Double-insurance bypass" was recently advocated to avoid the risk of cerebral ischemia during prolonged temporary occlusion of the carotid artery. For large aneurysms needing temporary but prolonged obliteration of the internal carotid artery (ICA). We have attempted the double-insurance bypass in 15 patients and, herein, report the efficacies and limitations of the procedure, and surgical techniques to make this procedure safer. METHODS: We treated 15 patients with complex internal carotid aneurysms by clipping surgery with the aid of radial artery (RA) to proximal middle cerebral artery (MCA) bypass, so-called double-insurance bypass. We analyzed surgical results of the procedure. RESULTS: In 11 patients, the duration of temporary occlusion of the ICA could be prolonged for as long as 110 minutes (mean, 45 minutes) without any ischemic complications. One patient in the earlier period of our experience suffered extended cerebral infarction due to possible restricted blood flow through the RA, because the brachial artery was compressed by the firm shoulder joint and neighboring structures. Thereafter, we routinely monitored the blood pressure of MCA (MCABP) and never experienced such cortical infarctions. Another 3 patients, however, experienced ischemia in the territory of perforating arteries that originated from a segment that could not be perfused by the RA-MCA bypass. CONCLUSIONS: In combination with monitoring of MCABP, the double-insurance bypass can be a safer and more potent adjunctive procedure for the treatment of complex internal carotid aneurysms which require prolonged temporary occlusion of the ICA.     

Double-insurance bypass for internal carotid artery aneurysm surgery

OBJECTIVE: The aim of this article is to present the usefulness of a double-bypass method in the surgical treatment of complex internal carotid artery (ICA) aneurysms. For patients with clippable but complex aneurysms of the ICA having poor collateral circulation, bypass surgery is needed before temporary occlusion of the ICA. We propose a double bypass for safety. METHODS: The superficial temporal artery was anastomosed to the distal cortical branch of the middle cerebral artery (MCA), followed by anastomosis between the radial artery and the inferior trunk of the MCA. For patients with clippable ICA aneurysms, the radial artery was temporarily anastomosed to the inferior trunk of the MCA by raising the ipsilateral forearm to the head after the radial artery was harvested. After the aneurysm had been clipped, the anastomosed radial artery was cut close to the anastomosed site and repositioned back to the original arm. RESULTS: This double-bypass procedure was performed in two patients, and no ischemic complications related to revascularization were observed. Temporary occlusion times of the MCA for superficial temporal artery-to-MCA anastomosis and radial artery-to-MCA anastomosis were 30 and 46 minutes in one patient and 28 and 55 minutes in another. CONCLUSION: This surgical procedure, which we called "double-insurance bypass," can reduce the risk of ischemic complications associated with revascularization of the ICA.     

Retinal artery pressure and cerebral artery perfusion pressure in cerebrovascular occlusive disease

The objectives of the investigation were to measure the retinal artery pressure (RAP) and cortical artery pressure (CAP) in patients undergoing superficial temporal artery to middle cerebral artery (STA-MCA) bypass, to study the relationship between these pressures, and to evaluate our ability to predict CAP on the basis of RAP. The 44 patients undergoing bypass surgery included 26 with ipsilateral internal carotid artery (ICA) occlusion (Group I), 5 with bilateral ICA occlusion (Group II), 4 with inaccessible ICA stenosis proximal to the ophthalmic artery (OA) (Group III), 2 with ICA stenosis distal to the OA (Group IV), 3 with ICA occlusion distal to the OA (Group V), 2 with MCA stenosis (Group VI), and 2 with MCA occlusion (Group VII). Five patients undergoing craniotomy for an asymptomatic saccular aneurysm were used as controls. Mean RAP (MRAP) was measured by ophthalmodynamometry (ODM) and was expressed as a ratio of the mean systemic arterial blood pressure (i.e., MRAP/MSAP). The mean MRAP/MSAP for combined Groups I, II, and III with ICA occlusion proximal to the OA was significantly lower than both the control group (P = 0.0001) and the combined Groups IV, V, VI, and VII with occlusive lesions distal to the OA (P = 0.0001). Six patients in Groups I and II with venous stasis retinopathy had a mean MRAP/MSAP of 0.18 +/- 0.11. Mean cortical artery pressure (MCAP) was measured by inserting a 26 gauge needle into a small cortical artery and was expressed as the MCAP/MSAP ratio. Mean MCAP/MSAP was less than 0.50 for all groups except Group III.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tandem middle cerebral artery-internal carotid artery occlusions: reduced occlusion-to-revascularization time using a trans-anterior communicating artery approach with a penumbra device

Rapid revascularization of tandem extracranial and intracranial acute thromboembolic occlusions can be challenging and can delay restoration of blood flow to the cerebral circulation. Taking advantage of collateral pathways in the circle of Willis for thrombectomy can reduce the occlusion-to-revascularization time significantly, thereby protecting brain tissue from ischemic injury. The authors report using the trans-anterior communicating artery (ACoA) approach by using the Penumbra microcatheter to rapidly restore blood flow to the middle cerebral artery (MCA) territory prior to treating the ipsilateral internal carotid artery (ICA) occlusion. Two patients with acute onset of tandem ipsilateral ICA and MCA occlusions and a competent ACoA underwent rapid revascularization of the MCA using a trans-ACoA approach for pharmaceutical and mechanical thrombolysis with the 0.026-in Penumbra microcatheter. Subsequently, once blood flow was reestablished in the MCA territory via cross-filling from the contralateral ICA, the proximally occluded ICA dissection was revascularized with a stent. Both patients had rapid revascularization of the MCA territory (both Thrombolysis in Myocardial Infarction Grade 3) with the trans-ACoA approach (19 and 36 minutes) followed by treatment of the ipsilateral proximal ICA occlusion. This prevented prolonged MCA ischemia time (72 and 47 minutes for ICA revascularization time saved) that would have otherwise occurred if the dissections were treated prior to revascularization of the MCA. Both patients had improved NIH Stroke Scale scores after the procedure. No adverse events from crossing the ACoA with the Penumbra microcatheter were encountered during the revascularization procedure. The trans-ACoA approach with the Penumbra microcatheter for rapid revascularization of an acutely thrombosed MCA in the setting of a simultaneous ipsilateral proximal ICA occlusion is feasible in patients with a competent ACoA. This technique can significantly minimize ischemic injury by reducing the occlusion-to-revascularization time and allow for MCA perfusion via collateral circulation while treating a proximal occlusion. To the best of the authors' knowledge, this is the first reported trans-ACoA approach with the Penumbra microcatheter and the first to report the utilization of the collateral intracranial circulation to reduce occlusion-to-revascularization time.     

Impact of cervical internal carotid clamping and radial artery graft bypass on cortical arterial perfusion pressure during craniotomy

Strategic cervical internal carotid occlusion is employed either temporarily or permanently in various neurosurgical procedures. The aim of the present study was to assess changes in cortical arterial pressure during cervical internal carotid cross-clamping before and after the placement of radial artery (RA) graft bypass in the treatment of complex carotid artery aneurysms. Perfusion pressure of the middle cerebral artery (MCA) was assessed in 22 patients with complex carotid aneurysm treated with RA graft bypass. Regional cerebral blood flow was assessed postoperatively using single-photon computed tomography. Mean cortical blood pressure (mcBP) was found to be 48.2?±?24.2 and 97.0?±?24.0 % of baseline after clamping the cervical internal carotid artery and opening the RA graft bypass, respectively. Cerebral perfusion pressure estimated by the mcBP failed to sustain a critical limit of greater than 70 mmHg under craniotomy in 16 out of 20 (80 %) patients. There was an inverse correlation in mcBP between the baseline and after the placement of the RA graft bypass (r?=?0.66, P?<?0.005). Postoperative regional cerebral blood flow in the MCA territory on the ipsilateral side of the aneurysm was 97?±?7 % of that of the contralateral side after internal carotid artery (ICA) ligation combined with RA graft bypass. Substantial pressure reductions in cerebral cortical arteries were observed during the cervical internal carotid cross-clamping. Perfusion pressure in peripheral cortical arteries after the placement of the RA graft bypass was comparable to the state before ICA clamping.     

Tailored flow sequestration treatment using high-flow and low-flow bypass for partially thrombosed giant internal carotid artery aneurysm—a technical case report

Direct clipping of giant partially thrombosed intracranial internal carotid artery (ICA) aneurysms is challenging, especially when important perforating arteries are involved. Proximal occlusion with bypass represents a possible alternative approach. An 80-year-old female presented with worsening visual acuity and severe headache caused by partially thrombosed giant (38 mm in diameter) aneurysms of the right ICA, suggestive of impending rupture. Direct clipping in conjunction with temporary occlusion of the lesion involving the anterior choroidal artery (AChA) was considered too risky. Thus, we sequestrated the ipsilateral ICA flow into a low-flow and a high-flow system using two external carotid artery (ECA)-ICA bypasses and one in situ bypass with cervical ICA ligation. As a result, the low-flow system by the superficial temporal artery-middle cerebral artery (MCA) bypass perfused mainly the proximal MCA lesions and aneurysm, whereas the high-flow system by ECA-radial artery-M2 bypass exclusively supplied the residual distal MCA area. This tailored flow sequestration successfully interrupted intra-aneurysmal flow and accelerated near-complete thrombosis of the aneurysm while preserving the AChA and avoiding any significant neurological deterioration. We conclude that this method is effective for the management of giant partially thrombosed aneurysms of the ICA, especially when direct clipping is difficult.     

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.     

Spontaneous intracranial internal carotid artery dissection treated by intra-arterial thrombolysis and superficial temporal artery-middle cerebral artery anastomosis in the acute stage--case report--

A 22-year-old man presented with sudden onset of right retro-orbital headache followed by left hemiparesis. Right carotid angiography demonstrated almost total occlusion of the intracranial internal carotid artery (ICA) and severe stenosis of the middle cerebral artery (MCA), presumably caused by arterial dissection. Local arterial injection of urokinase was performed 2 hours after onset. The ICA became patent, but the M2 portion of the MCA was still occluded, and the left hemiparesis did not improve. Superficial temporal artery-MCA anastomosis was immediately performed. The left hemiparesis disappeared completely 6 days after this procedure. Angiography 2 weeks after the onset revealed occlusion of the ICA, and maintenance of blood flow to the right cerebral hemisphere via the anastomosis. Magnetic resonance imaging showed small infarcts in the right cerebral cortex. Repeat angiography after 5 months showed recanalization of the right ICA and the right MCA. Combination of thrombolytic therapy and bypass surgery may be a useful treatment option for patients with sudden occlusion of the intracranial artery caused by dissection.     

Treatment strategy for giant aneurysms in the cavernous portion of the internal carotid artery

BACKGROUND: As direct surgery to treat giant aneurysms of the ICA is difficult, ICA occlusion is the conventional treatment in patients with BTO tolerance. To determine whether bypass surgery should be performed after carotid occlusion by trapping or proximal occlusion, we developed a treatment strategy that includes BTO and SPECT. METHODS: We report 19 patients with symptomatic giant aneurysms in the cavernous portion of ICA. The appropriate type of bypass surgery was determined by the results of BTO and SPECT. The type of ICA occlusion selected was based on the evaluation of retrograde filling of the aneurysm during BTO. RESULTS: In all 19 patients, the ICA was sacrificed; 10 patients also underwent bypass surgery (low-flow bypass with STA-MCA anastomosis, n = 7; medium-flow bypass with radial artery graft, n = 2; high-flow bypass with vein graft, n = 1). Coil trapping was performed in 11 patients; proximal occlusion in 8. In 18 patients, there were no ischemic complications after treatment; 1 patient who had been treated by proximal ICA occlusion developed transient ischemia due to an intra-aneurysmal thrombus. Cranial nerve palsies were improved in 16 patients. CONCLUSIONS: Based on our experience, we recommend that patients with giant aneurysms in the cavernous portion of the ICA be evaluated by BTO and SPECT. In conjunction with bypass surgery, ICA trapping or proximal occlusion constitutes an effective treatment strategy.     

Superficial temporal artery-middle cerebral artery anastomosis in a patient of temporal arteritis with internal carotid artery occlusion: a case report

Temporal arteritis is a rare systemic autoimmune disease and the arteritic process in this case of temporal arteritis involved large and medium-size arteries. Temporal arteritis with internal carotid artery (ICA) occlusion is very rare. We report a case of temporal arteritis with ICA occlusion following superficial temporal artery (STA) -middle cerebral artery (MCA) anastomosis, together with steroid therapy. A 73-year-old female presented with a headache, visual disturbance of left side, and suppression of activity. Left STA was inflammatory and overswelling. Magnetic resonance angiography (MRA) and angiography revealed occlusion of the left internal carotid artery (ICA) at the cervical portion and lowering of vascular reserve on PAO SPECT. Diagnosis as temporal arteritis was conclusive due to the clinical presentation, laboratory studies, and left temporal artery biopsy, so steroid pulse therapy was initiated. Inflammation of left STA disappeared after steroid therapy, but left ICA occlusion on angiography and lowering of vascular reserve on SPECT remained for 3 months afterwards. Because of this, STA-MCA anastomosis was performed. There were no complications after the operation and the donor artery has been patent for two years. Temporal arteritis with ICA occlusion that requires extracranial-intracranial bypass (EC-IC bypass) is very rare. STA-MCA anastomosis with steroid therapy is effective for the prevention of cerebral infarction.     

Regional cerebral ischemia by occlusion of the posterior communicating artery and the middle cerebral artery in gerbils

The authors have created an experimental model of regional cerebral ischemia in gerbils that is reproducible and has a low mortality rate. In gerbils, either the posterior communicating artery (PCoA) or the middle cerebral artery (MCA) was occluded, and the distribution of cerebral ischemia from each surgical procedure was compared with that produced by occlusion of the common carotid artery (CCA). In contrast to the widespread cortical and subcortical infarctions seen after occlusion of the CCA, occlusion of the PCoA caused infarction that was restricted to the hippocampus, the piriform cortex, and the posterior part of the thalamus, and occlusion of the MCA resulted in infarction that was restricted to the central part of the cerebral hemisphere and the caudate nucleus and putamen. Intracranial occlusion of the PCoA or MCA in the gerbil resulted in lesions that were reproducible with low mortality rates over a long-term period. Occlusion of the PCoA, MCA, or CCA also produces a model that is suitable for investigation of the postischemic period. A combination of these three experimental models is useful for investigation of regional vulnerability and for the study of regional metabolic differences in cerebral ischemia.     

Extracorporeal femoral to carotid artery perfusion in selective brain cooling for a giant aneurysm. Case report

Giant partially thrombosed intracranial aneurysms are a challenge to treat surgically, and they are also unsuitable for coil embolization. The current options for treatment include extracranial-intracranial bypass followed by parent artery occlusion or direct surgical occlusion in which deep hypothermic circulatory arrest is used. The authors report the use of another approach in the treatment of a giant anterior circulation aneurysm: selective brain cooling accomplished by extracorporeal perfusion. This facilitated direct surgery on a 4.2-cm, partially thrombosed aneurysm of the middle cerebral artery (MCA). A brain temperature of 22 degrees C was achieved after 20 minutes of perfusion with blood cooled using an extracorporeal technique of femoral-common carotid artery perfusion. This was followed by a 20-minute period of surgical trapping of the MCA, then evacuation and clip occlusion of the aneurysm. During the period of selective brain cooling the patient's core body temperature was maintained above 35 degrees C. This technique of selective brain cooling may be a useful alternative to currently available surgical and endovascular methods of treatment for giant aneurysms.     

Superficial temporal-middle cerebral artery bypass: clinical pre- and postoperative angiographic correlation

Between 1974 and 1982, an anastomosis between a pedicle of the superficial temporal artery (STA) and a cortical branch of the middle cerebral artery (MCA) was performed in 163 carotid systems in 157 patients for internal carotid artery occlusion in whom postoperative angiograms were available for analysis. The angiographic opacification of the arterial system was correlated with the patient's preoperative neurological function and stroke in the follow-up period. From this analysis, the following observations were made: 1) 96% of bypasses were patent; 2) 80% of bypasses achieved a high or medium MCA filling score; 3) there was hypertrophy of the STA in 70% of the cases; 4) greater bypass filling occurred in hemispheres with nonvisualized preoperative collateral circulation than in those with readily visualized collateral flow; 5) a meaningful correlation between angiographically assessed postoperative bypass function and stroke rate was not possible because only four patients suffered an ipsilateral hemispheric stroke in the 8-year follow-up period; and 6) patients who were neurologically unstable before the procedure were at greatest risk for a stroke in the follow-up period. It is apparent that objective analysis of the effectiveness of an STA-MCA bypass, or any other form of extracranial bypass, must await the development of new diagnostic studies in which high-resolution three-dimensional quantification of cerebral blood flow is possible. These studies will necessarily be correlated with preoperative and follow-up clinical data.     

Surgical management of acute complications and critical restenosis following carotid artery stenting

Carotid artery angioplasty with stenting (CAS) is being increasingly used in the treatment of extracranial carotid artery stenosis. As in other catheter-based approaches to the treatment of arterial disease, surgical intervention may be required because of either acute complications or correct critical restenosis. We have reviewed our experience managing early complications and critical in-stent restenoses after CAS in a tertiary care university hospital and a Veterans Affairs Medical Center. During the last 5 years, 22 carotid arteries (21 patients) underwent CAS. One patient developed thrombosis and rupture of the carotid artery during stenting. Two other patients (3 arteries) developed critical restenosis within 12 months. Subsequent surgical reconstructions included an internal carotid artery (ICA)–to–external carotid artery (ECA) transposition and a common carotid artery (CCA)–to–ICA bypass with reversed saphenous vein (RSV). The patient who underwent CCA–to–ICA bypass later required subclavian–to–ICA bypass because of rapidly progressive intimal hyperplasia and subsequent occlusion of the CCA. The other patient has not had surgical repair because of his deteriorating condition and significant co-morbidities. During the same time period, two additional patients were referred from outside institutions specifically for surgical intervention after carotid stenting. One had delayed rupture of the carotid artery 1 day after stenting and underwent urgent surgical repair. Another patient had early, critical restenosis within the stent and underwent placement of a CCA–to–ICA interposition graft using RSV. Acute treatment failures after CAS can be successfully managed using standard surgical techniques. Patients who develop critical in-stent restenosis requiring surgical repair may need more challenging surgical reconstructions to maintain cerebral perfusion.     

Treatment of hemodynamic insufficiency in chronic CCA occlusion using a short saphenous vein interposition graft: diagnostic and technical considerations

Extracranial–intracranial bypass surgery has been shown to reverse hemodynamic insufficiency on the basis of steno-occlusive disease of the internal carotid artery (ICA) or middle cerebral artery. In contrast, chronic occlusion of the common carotid artery (CCA) without extracranial donor vessels affords alternative revascularization procedures as well as a more elaborate preoperative workup. This case is intended to illustrate the specific diagnostic approach and considerations as well as a beneficial treatment modality in the setting of pronounced hemodynamic insufficiency as a consequence of a CCA occlusion, in conjunction with contralateral CCA and ICA stenoses. A 61-year-old man complaining of new onset aphasia underwent vascular imaging that revealed a proximal occlusion of the left CCA with a concomitant patent proximal ICA on ultrasound. Functional cerebral blood flow measurement including Xenon-enhanced computer tomography showed corresponding chronic hemodynamic insufficiency of the left hemisphere. The patient received a modified revascularization procedure, where a saphenous vein was used as interposition graft between the subclavian artery and the left proximal ICA. Postoperatively, both clinical and morphological improvement were noted. Successful treatment of hemodynamic insufficiency because of chronic CCA occlusion necessitates a thorough preoperative workup and application of alternative revascularization strategies.     

Treatment of hemodynamic insufficiency in chronic CCA occlusion using a short saphenous vein interposition graft: diagnostic and technical considerations. An illustrative case report

Extracranial-intracranial bypass surgery has been shown to reverse hemodynamic insufficiency on the basis of steno-occlusive disease of the internal carotid artery (ICA) or middle cerebral artery. In contrast, chronic occlusion of the common carotid artery (CCA) without extracranial donor vessels affords alternative revascularization procedures as well as a more elaborate preoperative workup. This case is intended to illustrate the specific diagnostic approach and considerations as well as a beneficial treatment modality in the setting of pronounced hemodynamic insufficiency as a consequence of a CCA occlusion, in conjunction with contralateral CCA and ICA stenoses. A 61-year-old man complaining of new onset aphasia underwent vascular imaging that revealed a proximal occlusion of the left CCA with a concomitant patent proximal ICA on ultrasound. Functional cerebral blood flow measurement including Xenon-enhanced computer tomography showed corresponding chronic hemodynamic insufficiency of the left hemisphere. The patient received a modified revascularization procedure, where a saphenous vein was used as interposition graft between the subclavian artery and the left proximal ICA. Postoperatively, both clinical and morphological improvement were noted. Successful treatment of hemodynamic insufficiency because of chronic CCA occlusion necessitates a thorough preoperative workup and application of alternative revascularization strategies.     

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.     

Cerebral revascularization to a main limb of the middle cerebral artery in the Sylvian fissure. An alternative approach to conventional anastomosis

Thirteen patients underwent an anastomosis of the superficial temporal artery (STA) or a saphenous vein graft to one of the secondary trunks of the middle cerebral artery (MCA). They included five patients with giant MCA trifurcation aneurysms, four patients in whom an earlier conventional STA-MCA anastomosis had become occluded, two patients who had stenosis of one of the secondary limbs of the MCA, and one patient who had a carotid-cavernous fistula. One patient had a saphenous vein graft from the common carotid artery to a secondary trunk of the MCA to bypass an occluded internal carotid artery and severely stenosed external carotid artery. The primary advantages of this procedure are that a large-caliber anastomosis to one of the secondary limbs of the MCA immediately restores flow into the MCA tree with a larger amount of vessel filling than with a standard cortical bypass, and large vessels can be used for the anastomosis. The disadvantages are that one of the secondary branches of the MCA must be occluded, the cerebral hemisphere around the Sylvian fissure must be retracted, a lumbar subarachnoid drain is needed, and the anastomosis must be performed deep within the Sylvian fissure. The procedure is a satisfactory alternative in cases in which a conventional STA-MCA anastomosis has either failed or would be less likely to succeed.     

Surgical approach to giant intracranial aneurysms. Operative experience with 80 cases.

The authors report experience with the surgical management of 80 giant intracranial aneurysms (greater than 2.5 cm in diameter) during a 10-year period in which they performed 594 operations for aneurysms. The overall incidence of giant aneurysms was 13% but varied according to location: 20% of aneurysms of the internal carotid artery (ICA); 13% of middle cerebral artery (MCA) aneurysms; 1% of anterior cerebral artery (ACA) aneurysms; 15% of aneurysms of the basilar artery caput (BAC); and 18% of vertebrobasilar trunk (VB) aneurysms. Twenty-five patients had a subarachnoid hemorrhage (SAH), 49 had mass effect from the aneurysm, and six had ischemic events. There was no apparent difference in results related to the presence or absence of an SAH. Poor results were attributable to the operation except in the two cases of ACA aneurysm in which preexisting dementia persisted. Mortality was 4% and morbidity was 14%, varying from a combined low morbidity-mortality of 8% for ICA lesions to a high to 50% for BAC aneurysms. During the period of the study, different techniques were developed in an attempt to lower the risks of surgery. Ultimately ICA aneurysms were monitored with cerebral blood flow measurements and electroencephalography before and after temporary ICA ligation, then approached following resection of the anterior clinoid or treated with bypass in combination with ICA ligation. Aneurysms of the MCA were either opened during temporary MCA occlusion or resected in combination with a bypass procedure. Bypass grafts and circulatory arrest with extracorporeal circulation may have a role in giant aneurysms of the posterior circulation.     

Transcranial Doppler ultrasound in internal carotid artery and middle cerebral artery disease

Using noninvasive transcranial Doppler sonography, we studied cerebral collateral patterns in 30 patients with stenosis and/or occlusion of the extracranial internal carotid artery (ICA). All patients with unilateral ICA stenosis ⩽ 80% had normal transcranial Doppler findings. 80% of patients with unilateral and 50% of patients with bilateral ICA stenosis of more than 80% including those with occlusion showed a collateralization via the ipsilateral anterior and/or posterior cerebral artery. 20% of patients with unilateral and 50% of patients with bilateral ICA stenoses of more than 80% (including occlusion) had two or three collateral pathways, including the ophthalmic artery. Another ten patients with stenosis or spasm of the middle cerebral artery (MCA) showed increased flow velocities with turbulence in the narrow segment. In four patients with severe MCA disease with a systolic peak velocity of more than 200 cm/s, the Doppler waveform distal to the lesion was damped. Decreased regional cerebral blood flow (rCBF) measured by^99mTc-HMPAO-SPECT was found in two patients with severe MCA stenosis. Another patient with moderate MCA stenosis with a systolic peak velocity of 140 cm/s showed a normal cerebral perfusion pattern.