Transcranial Doppler pulsatility in vasodilation and stenosis

Although blood velocity in the major intracranial vessels is readily measured with transcranial Doppler ultrasound (TCD), the interpretation of velocity changes is by no means straightforward. For example, a velocity increase can arise from either a local stenosis or a decrease in downstream resistance, and these mechanisms have contradictory implications for blood flow. To determine whether TCD pulsatility might distinguish these two mechanisms, Doppler ultrasonic readings were taken from an artificial vascular model under conditions of either stenosis or distal dilation. In addition, TCD studies of nine patients with unihemispheric arteriovenous malformations (AVM's) and 16 TCD studies of seven patients with unihemispheric aneurysmal vasospasm were reviewed, and pulsatilities of the AVM's (representing decreased resistance) were compared with those of the vasospastic vessels (representing stenosis). The average percentage drop in pulsatility in the vasodilated configuration of the model/percentage increase in velocity was 0.38 +/- 0.08 (+/- standard error of the mean), while that for stenosis was 0.20 +/- 0.01. Similar comparisons of the patient population yielded 0.67 +/- 0.16 for the AVM group and 0.26 +/- 0.04 for the vasospasm group. These differences were significant (p less than 0.05). The fall in pulsatility associated with a given increase in velocity is significantly greater when the velocity increase arises from diminished downstream resistance than from stenosis.

Preoperative embolization of cerebral arteriovenous malformations with polyvinyl alcohol particles: experience in 51 adults

In order to determine possible risk factors and to assess the value of platinum microcoils added to polyvinyl alcohol particles in preoperative embolization of cerebral arteriovenous malformations in adults, we reviewed our experience with this procedure. Between September 1985 and June 1989, we performed embolizations in 54 patients with cerebral arteriovenous malformations. Of these, procedures in 51 adults involved the use of polyvinyl alcohol particles, either alone (n = 29) or in combination with platinum microcoils (n = 21). A complication during catheterization precluded embolization in another patient. Beginning as flow-directed embolizations via carotid artery catheterizations (n = 12), newer catheters allowed progression to superselective intracerebral catheterizations (n = 38). Embolization has led to shorter surgical procedures, more clearly defined operative margins, and less bloody operative fields. We have not found recanalization to significantly hinder embolization results with polyvinyl alcohol when resection is undertaken within 1-4 weeks of embolization. Its relative safety and ease of manipulation at surgery argue for its use. We found no significant increase in complications based on patient age, venous drainage of the arteriovenous malformation, or the circulation embolized. Embolization results in cerebral arteriovenous malformations were improved with superselective catheterization and most improved with the combined use of polyvinyl alcohol for nidus embolization followed by occlusion of the feeding vessel with microcoils.

Enlarging thrombosed aneurysm of the distal basilar artery

The case of a 65-year-old man who had partial left third nerve palsy is reported. Radiographic examination disclosed a completely thrombosed giant suprasellar aneurysm. Although an angiogram appeared to indicate that his aneurysm arose from the distal basilar artery, he was also noted to have an unusual and ectatic distal internal carotid artery on the left side, and this was also felt to be a potential source of the aneurysm. Operative exploration was performed and confirmed the basilar artery as the sight of origin, and definitive therapy was deferred. The patient's progress was monitored, and for 3 years his neurological course was stable and there was no change in his radiographic abnormalities. During the 6 months following this period, the patient developed signs and symptoms of progressing hydrocephalus and was found to have significant enlargement of his still completely thrombosed giant aneurysm. This complicated case highlights the controversy regarding the management of this difficult condition, particularly with regard to endovascular therapies, and also provides insight into the evolution of this dynamic disease process.

Resolution of a recurrent/residual bacterial aneurysm during antibiotic therapy

Management of patients harboring infectious intracranial aneurysms remains controversial because of the technical problems associated with the obliteration of these lesions as well as their frequent regression during antibiotic therapy. A case of a ruptured bacterial aneurysm of the distal middle cerebral artery in which a segment of the artery was found to be inflamed and necrotic is presented. The ruptured portion of the sac was clipped, leaving a small tag of aneurysmal tissue. Five days later, this tag was found to have expanded into a second aneurysm. This second lesion resolved with antibiotic therapy. Because of the responsiveness of infected cerebral arteries to the appropriate antibiotics, a less than radical surgical tactic may be a successful alternative to excision of the diseased arterial segment followed by distal revascularization in treating these lesions.

Causes of morbidity and mortality from surgery of aneurysms of the distal basilar artery

Despite modern neurosurgical technology and neuroanesthetic care, treatment of aneurysms of the distal basilar artery remains fraught with complications. Between 1982 and 1988, 126 patients with aneurysms of the distal basilar artery who had been treated by 2 surgeons were retrospectively analyzed to determine the causes of morbidity and mortality from this disease and its treatment. Ten patients (8%) died, and 14 patients (11%) suffered permanent neurological disability after treatment. The causes of failed management could be grouped into the following categories: 1) direct effects of hemorrhage; 2) errors in surgical timing; 3) conceptual errors; 4) technical errors; 5) morbidity from delayed cerebral ischemia; and 6) complications of hypertensive/hypervolemic therapy for symptomatic vasospasm; a small group of patients who died despite having received what we consider excellent management were grouped under a seventh category, "bad luck." Frequently, patients who did poorly suffered from multiple complications, each of which contributed to their overall morbidity. It is our hope that increased awareness of these potential pitfalls and the further evolution of intravascular technique in selected cases will, in time, improve the outlook for patients suffering from these dangerous lesions.

Evidence of redistribution of cerebral blood flow during treatment for an intracranial arteriovenous malformation

The presence of an intracranial arteriovenous malformation has a dramatic impact on local circulatory dynamics. Treatment of some arteriovenous malformations can result in disastrous hyperemic states caused by redistribution of previously shunted blood. This report describes serial hemodynamic measurements of both cerebral blood flow and flow velocity in 3 patients during treatment for arteriovenous malformations. Measurements of cerebral blood flow were made by computed tomographic scan employing the stable xenon inhalation technique; flow velocity, including autoregulatory characteristics, was measured by transcranial Doppler ultrasonogram. Substantial hyperemia developed in one patient (Case 1) after resection and in another (Case 3) after embolization. Embolization resulted in restoration of normal regional cerebral blood flow in a patient who demonstrated hypoperfusion before treatment (Case 2). In Patient 1, postoperative hyperemia was associated with persistently elevated flow velocities, and may have been accompanied by hemispheric neurological deficits. Sequential hemodynamic measurements may predict patients at risk of perioperative complications, and may become useful clinical guidelines for the extent and timing of embolization and for the timing of surgery after intracranial hemorrhage or preoperative embolization procedures.

Reversible middle cerebral artery embolization in dogs without intracranial surgery

Using dogs, we developed an intravascular model for reversible middle cerebral artery occlusion that does not involve intracranial surgery or enucleation. Using silicone plastic plugs with a suture embedded within them, we embolized the middle cerebral artery in 19 dogs via the cervical carotid artery. The free end of the suture remained accessible in the neck, and after variable dwell times traction was placed on the suture and the plug was withdrawn. Placement of the plug in the middle cerebral artery produced ischemia in the basal ganglia. The degree and distribution of cortical ischemia were variable as evidence by the pathologically documented scattered nature of infarcts that resulted when the plug was left permanently in the middle cerebral artery and when it was removed after 1 or 2 hours. Angiography demonstrated occlusion of the middle cerebral artery with the plug in place as well as reperfusion when the plug was withdrawn. This modification of a previously described model of middle cerebral artery occlusion provides an opportunity to study structural, physiologic, and biochemical events occurring in acutely hypoperfused cerebral tissue as well as critical changes leading to irreversible injury without the disadvantages of surgical manipulation required by all previous models of reversible cerebral ischemia.

Microfibrillar collagen model of canine cerebral infarction

A new canine model of focal cerebral ischemia has been developed employing intravascular delivery of microfibrillar collagen via femoral catheterization. In 13 dogs, dose-effect studies showed neurologic deficits (ranging from mild hemiparesis to death) related to the dose of microfibrillar collagen delivered. In another 10 dogs, 0.5 ml of 60 mg/ml microfibrillar collagen was injected into the common carotid artery; neurologic assessment over 48 hours revealed a survivable stroke syndrome in seven dogs, death at 40 hours in one dog and at less than 12 hours in another, and no clinical effect in one dog. The eight surviving dogs were sacrificed at 48 hours; nine of the 10 dogs had middle cerebral artery distribution infarcts (two grossly hemorrhagic and five grossly nonhemorrhagic) on histologic examination. Angiography in three dogs demonstrated no significant major vascular occlusion. All seven dogs with survivable strokes demonstrated a dense hemiparesis at 24 hours that improved to ambulatory status at 48 hours. The use of microfibrillar collagen to produce middle cerebral artery strokes in dogs provides a new opportunity to study cerebral ischemia without surgery involving the cervical or cranial vasculature. Dogs have larger brains than other common animal models and thus are more amenable to study with imaging modalities. A model with a measurable but survivable insult provides an opportunity for short- and long-term clinical follow-up and for the investigation of therapeutic interventions.

Hemodynamic assessment of the spinal cord arteriovenous malformation with intraoperative microvascular Doppler ultrasound: case report

Microvascular Doppler recordings were taken from the nidus and draining system of a dural spinal cord arteriovenous malformation during operative treatment. Doppler signals readily showed the direction of blood flow in the draining vein and the hemodynamic effects of surgical maneuvers. Recording during alterations of mean arterial blood pressure and partial carbon dioxide pressure (pCO2) demonstrated lack of autoregulation and impaired CO2 reactivity in the AVM nidus. Microvascular Doppler techniques provide useful intraoperative assessment of the hemodynamics of arteriovenous malformations of the spinal cord.

Intracranial arteriovenous malformation: contralateral steal phenomena

Sixty-two patients with radiographically proven intracranial arteriovenous malformations underwent preoperative regional cerebral blood flow measurement with 133Xe single-photon emission computed tomography. Contralateral regions of hypoperfusion were detected in all cases. Steal severity was assessed according to the contralateral steal index [ISteal(c)]. ISteal(c) was greater than 0.7 (severe) in 22 (35%), 0.7-0.8 (intermediate) in 18 (29%), and greater than 0.8 (mild) in 22 (35%). ISteal(c) was more frequently severe or mild in females and more often intermediate in males (p less than 0.05). Hyperemic complications were encountered more frequently in patients with intermediate ISteal(c) (p = 0.086). An unfavorable outcome was associated with less severe contralateral steal (p = 0.12). A detailed clinical, radiographic, and hemodynamic profile may help to preoperatively identify patients at high risk for a poor surgical outcome.

Intracranial arteriovenous malformation: relationships between clinical and radiographic factors and cerebral blood flow

Arteriovenous malformations (AVMs) dramatically alter normal cerebral circulatory dynamics. Clinical and radiographic data from 62 patients were analyzed to determine their impact on total brain blood flow (TBF) measured by single-photon emission computed tomography. 48% of patients presented with hemorrhage and 34% with progressive deficits. 37% had angiographic steal and 21% developed postoperative hyperemic complications. 40% were under 30 years old, 45% were between 30 and 50 years of age, and 15% were over 50. TBF was less than 70 ml/100 gm/min in 32% of patients, between 70 and 84 ml/100 gm/min in 40%, and greater than 84 ml/100 gm/min in 27%. Female patients had higher TBF than males; 42% of females but only 17% of males had values greater than 84 ml/100 gm/min (p less than 0.05). A trend toward decreased TBF with advancing age was noted. Intracranial hemorrhage was associated with lower TBF; 47% of patients with hemorrhage and 19% of those without had TBF of less than 70 ml/100 gm/min (p less than 0.05). 89% of patients with AVMs less than 5 cm in diameter had TBF of less than or equal to 84 ml/100 gm/min, and 65% of those with larger AVMs had similarly low flows (p less than 0.05). A trend toward lower TBF was observed in patients with unfavorable outcomes.

Intracranial arteriovenous malformation: relationship between clinical factors and surgical complications

Serious morbidity and hyperemic states continue to complicate the treatment of certain intracranial arteriovenous malformations (AVMs). Clinical and radiographic characteristics of 62 patients treated over 3 years were analyzed to determine if hyperemic complications (HCs) (defined as unusual perioperative edema or hemorrhage) and outcome could be predicted. Twenty-five (40%) of the patients were less than 30 years old, 28 (45%) were between 30 and 50, and 9 (15%) were more than 50. A history of hemorrhage was found in 48%, and 34% presented with progressive deficits. Thirteen (21%) developed evidence of HCs; 51 (82%) ultimately had a good outcome, 4 (6%) had a poor outcome, and 7 (11%) died. The incidence of HCs was higher in patients whose AVMs recruited perforating vessels (53%) than those without (7%) (P less than 0.001). The presence of preoperative angiographic steal carried a 35% risk of HCs whereas its absence carried a 13% risk (P less than 0.05). The sum of the diameters of the feeding vessels was also predictive (P less than 0.05). Outcome was clearly age-related: good outcome was achieved in 92% of the patients less than 30 years old, 86% of those 30 to 50, and 44% of patients older than 50 (P less than 0.05). Left hemispheric AVMs showed less morbidity than right (P less than 0.05) as did those without perforating vessel recruitment (P less than 0.07). HCs had a dramatic impact on outcome with 92% of patients without HCs having good outcome and 46% of those with HCs recovering well (P less than 0.001).

Intracranial arteriovenous malformation: relationships between clinical and radiographic factors and ipsilateral steal severity

Intracranial arteriovenous malformations (AVMs) are high flow shunts that may jeopardize the perfusion of adjacent tissue. Clinical and radiographic data from 62 patients were analyzed to determine their relationship to the severity of steal measured by single photon emission computed tomography (SPECT). The ipsilateral steal index [ISteal(i)] was determined by dividing regional cerebral blood flow (rCBF) values within hand-drawn regions of hypoperfusion in the ipsilateral hemisphere by total brain flow, which was calculated as the average rCBF of each hemisphere. Of the patients, 40% were less than 30 years of age, 45% were 30 to 50 years old, and 15% were over 50. Forty-eight per cent presented with hemorrhage and 34% presented with progressive deficits. There was angiographic steal in 37%, and postoperative hyperemic complications developed in 21%. All patients had ipsilateral regions of hypoperfusion. The ISteal(i) was less than 0.7 in 23 (37%), 0.7 to 0.8 in 20 (32%), and greater than 0.8 in 19 (31%). The ISteal(i) was significantly less severe in the patients over 50; 78% of these patients had an ISteal(i) of greater than 0.8 (P less than 0.01). A history of hemorrhage was associated with less severe steal than that in patients who had not bled (P = 0.088). Patients presenting with a history of progressive deficits had increased severity of steal compared with those without progressive deficits (P less than 0.05). A trend toward decreased severity of steal was noted in patients with unfavorable outcomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraoperative ventricular puncture

Modern neuroanesthetic techniques frequently provide the neurosurgeon with adequate brain relaxation for an atraumatic frontotemporal or transylvian dissection. Circumstances such as recent subarachnoid hemorrhage with brain edema and acute hydrocephalus can mandate significant frontal lobe retraction before access to cerebrospinal fluid (CSF) drainage from the basal cisterns is gained. A simple technique can give the "early" aneurysm surgeon reliable access to the frontal horn of the lateral ventricle for intraoperative drainage of CSF before brain retraction.

Improvement in regional cerebral blood flow and cerebral vasoreactivity after extracranial-intracranial arterial bypass

Regional cerebral blood flow was measured with xenon-133 inhalation single photon emission computed tomography in a patient who developed a neurological deficit after carotid ligation. Hemispheric hypoperfusion was noted in resting studies and impaired vasoreactivity was suggested by lack of symmetrical flow augmentation after acetazolamide administration. Because of progressive neurological deterioration, an extracranial-intracranial bypass was performed. After prompt neurological improvement, repeat cerebral blood flow measurements at 1 and 9 weeks postoperatively confirmed improvement in resting flow and vasoreactivity. It is possible that decreased cerebrovascular reserve implied by measurements of vasoreactivity can identify patients who will benefit from surgical revascularization.

Cerebrovascular hemodynamics in arteriovenous malformation complicated by normal perfusion pressure breakthrough

Catastrophic hyperemic states are known complications after the treatment of certain types of intracranial arteriovenous malformations (AVMs). A case is presented in which a large AVM was preoperatively embolized and later resected. There was clear intra- and postoperative evidence of edema and hemorrhage, which resulted in a fatal outcome. Regional cerebral blood flow (rCBF) data from this patient obtained with single photon emission computed tomography (SPECT) both before and after embolization were compared with data from four patients with similar size supratentorial AVMs treated and studied in a similar protocol who did not develop perfusion breakthrough. Pretreatment hemispheric rCBF was significantly reduced in this patient's ipsilateral hemisphere (50 ml/100 g/min) compared to the control group mean (83 +/- 9.5 ml/100 g/min). A similar relative depression was found in the contralateral hemisphere. After therapeutic embolization, the ipsilateral rCBF increased by 33 ml/100 g/min and the contralateral hemispheric rCBF increased by 30 ml/100 g/min; this embolization-induced increase in rCBF was significantly higher than in the control group. Acetazolamide, known to increase rCBF in normal tissue by 35 +/- 3%, resulted in a 56% augmentation of ipsilateral hemispheric flow before embolization in the reported patient vs. a 22 +/- 10% increase for the control group. Postembolization, this hyperresponsiveness to acetazolamide remained unchanged. It is possible that these hemodynamic derangements may indicate a dissociation between the vasoconstrictive and vasodilatory reactivity in chronically hypoperfused territories adjacent to AVMs such that pharmacological or metabolic stimuli may induce further vasodilation, but sudden redistribution of large volumes of flow will not promote protective vasoconstriction.

Use of etomidate, temporary arterial occlusion, and intraoperative angiography in surgical treatment of large and giant cerebral aneurysms

The operative management of large and giant aneurysms is complicated by their typically atheromatous and thick walls, frequent intramural thrombosis with calcification, and broad-based necks that often incorporate perforating and other vital vessels. Not infrequently, it is necessary to at least focally arrest the intracranial circulation and open or excise these aneurysms to facilitate vascular reconstruction. This maneuver, in patients whose disease processes have destroyed autoregulatory function or who have inadequate sources of anatomical collateral supply, may cause the threshold for permanent ischemic injury to be exceeded. The authors have recently treated 14 such patients while under electroencephalographic monitoring to document electrical burst suppression induced by the administration of etomidate, followed by temporary clipping to permit vascular repair and intraoperative angiography to document patency of parent arteries. Up to 60 minutes of internal carotid artery occlusion, 35 minutes of middle cerebral artery occlusion, 19 minutes of upper basilar artery occlusion, and 4 1/2 minutes of lower basilar artery occlusion have been well tolerated using this protocol. In such situations, etomidate may be effective in protecting the cerebral circulation without the detrimental cardiotoxicity observed with protective doses of barbiturates.

Subtemporal transdural use of detachable balloons for traumatic carotid-cavernous fistulas

Endovascular use of detachable balloons has revolutionized the management of carotid-cavernous fistulas so that the goals of angiographic elimination of fistula and preservation of carotid patency can usually be achieved nonsurgically. Certain circumstances of flow dynamics and anatomy, however, make an endovascular approach difficult for even an experienced interventional neuroradiologist. Fistulas involving the posterior carotid wall at its proximal cavernous entry and the anterior carotid wall in its initial horizontal intracavernous segment, as well as very low flow fistulas at other sites, have posed particular problems. Three patients with such traumatic fistulas whose endovascular treatment failed were managed by the direct transdural introduction of balloons. Intraoperative angiography was accomplished with open internal carotid artery (ICA) catheterization and the use of a portable C-arm with a 6-in. image intensifier. After temporal craniectomy and subtemporal exposure, the course of the cavernous ICA was mapped out with spinal needles and the site of the fistula was localized by intraoperative angiography. An incision was then made in the lateral wall of the cavernous sinus, and latex balloons were manually introduced via a 7 French introducer sheath. The balloons were inflated under angiographic control and detached when the fistula was obliterated. This simple technique was initially successful in three patients; the fistula was eliminated with preservation of carotid patency. One patient suffered a recurrence of his fistula 2 months postoperatively while lifting weights, and one patient developed a new 3rd nerve palsy after operation.

Use of the extracranial-intracranial arterial bypass in the management of refractory vasospasm: a case report

Cerebral arterial vasospasm after aneurysmal subarachnoid hemorrhage remains one of the major causes of morbidity and mortality in patients surviving the initial hemorrhage. Once established, no known method has been shown to reverse this process in humans. Although intravascular volume expansion and induced arterial hypertension have been shown to be effective in the reversal of neurological deficits secondary to vasospasm, a large proportion of patients remain refractory to these methods. We report one such case successfully managed by the establishment of an extracranial-intracranial anastomosis in an attempt to augment collateral flow.

Recurrent subarachnoid hemorrhage complicating a traumatic carotid-cavernous fistula

Recurrent subarachnoid hemorrhage complicated a traumatic carotid-cavernous fistula in a young man. The fistula drained predominantly into the deep venous system of the brain, where the hemorrhage was thought to have occurred.