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✓ Arteriovenous (AV) fistulas of cerebral and spinal arteries are characterized angiographically by an immediate AV transition without a capillary bed or “nidus” as occurs in AV malformations (AVM's). The clinical presentation, morphology, radiology, and treatment of 12 patients with cerebral AV fistulas and of 12 patients with spinal AV fistulas are reviewed. In the patients with cerebral lesions, headache and seizure disorders were the most common presentations followed by subarachnoid hemorrhage, cardiac failure, progressive neurological dysfunction, and incidental detection on prenatal ultrasound study. In patients with spinal AV fistulas, weakness and sensory disturbance in the lower extremities were the most frequent clinical presentations followed by back pain, disturbances of micturition, and grand mal seizure. The etiology of the symptom complex produced by AV fistulas in each of these locations differed, with venous hypertension being important in spinal cord lesions. Of the patients with cerebral lesions, nine had a single AV fistula, one had two fistulas, and two had multiple fistulas. An AVM was observed in five patients with fistulas (two large, three small). Nine patients exhibited extramedullary AV fistulas of the spine, of whom eight had a single fistula and one had three fistulas; three patients had intramedullary spinal AV fistulas. An arterial aneurysm was found in association with two fistulas, one cerebral and one spinal. Venous ectasias or varices, frequently exhibiting mural calcification, were observed to be prominent in all AV fistulas involving cerebral arteries and in two involving spinal arteries. The location and size of the venous complexes reflected the diameter of the fistula. In addition to conventional imaging techniques (cerebral angiography, computerized tomography, and magnetic resonance (MR) imaging), MR angiography was a helpful adjunct in the evaluation of fistulas. Treatment strategies employed for AV fistulas in both locations included open surgical and endovascular procedures, frequently used in combination. A satisfactory outcome was observed in all patients.

✓ The objective of this study was to assess the effect of referral bias on survival in patients with subarachnoid hemorrhage (SAH). The characteristics of 49 patients with aneurysmal SAH from a single community were compared with those of 328 patients referred from outside the community, all treated in the same medical care setting. In addition, referral patients who received surgery were compared by differential survival analysis with those still awaiting surgery at Days 1 to 3, Days 4 to 10, and Days 11 to 15. There was a dramatic difference in the 30-day survival rate between referral patients (83%) and community patients (59%), but most of the difference had occurred by the 2nd day after SAH. In the referral patients, the variables present at first medical attention that were found to have an independent effect on survival were clinical grade, presence of coma, number of days from SAH to referral, diastolic blood pressure, and patient age. There was a higher survival rate at 1 year for patients who were surgically treated compared with those awaiting surgery for each of the three time periods. Patients who underwent early surgical treatment had a 1-year survival rate almost identical to that of patients with late surgery. Referral patients had a better early survival rate than did community patients because the referral group did not include patients who died and some who were in poor clinical condition before the opportunity for referral. The differential survival analysis described provides a new method for estimating survival for treated and untreated patients with SAH.

✓ An alternative theory is proposed to explain the brain edema and hemorrhage that may occur after resection of high-flow intracerebral arteriovenous malformations (AVM's). This theory, termed “occlusive hyperemia,” is based on a retrospective analysis of operative dictations along with postoperative imaging studies (191 angiograms and 273 computerized tomography scans) in 295 cases of intracerebral AVM's operated on at the Mayo Clinic between 1970 and 1990. In this series, 34 cases (12%) of postoperative deterioration were documented, of which 15 were due to incomplete resection of the AVM. Of the remaining 19 cases, six had brain edema alone and 13 had hemorrhage with edema, despite complete excision of the AVM. In these 19 cases, the AVM's were greater than 6 cm in diameter in 10 patients, between 3 and 6 cm in six, and less than 3 cm in three. Obstruction of the venous drainage system was observed in 14 (74%) of the 19 cases. Ten of these 14 were due to obstruction of the primary venous drainage of the brain parenchyma immediately surrounding the lesions, while four were due to obstruction of other venous structures. In no case was a rapid circulation identified on postoperative angiograms. The flow pattern was slow or stagnant in former AVM feeders and their parenchymal branches. It is proposed that postoperative intracranial hemorrhage and/or brain edema in AVM patients may be due to: 1) obstruction of the venous outflow system of brain adjacent to the AVM, with subsequent passive hyperemia and engorgement; and 2) stagnant arterial flow in former AVM feeders and their parenchymal branches, with subsequent worsening of the existing hypoperfusion, ischemia, and hemorrhage or edema into these areas. Supportive hemodynamic evidence for this theory was derived from the literature.

✓ A series of 280 cases of cerebral arteriovenous malformations (AVM's) treated surgically between June, 1970, and June, 1989, is reviewed with particular focus on the preoperative seizure history and follow-up seizure status. Follow-up evaluation (mean duration 7.5 years) was achieved in 98% of cases and was accomplished through re-examinations, telephone interviews, and written questionnaires. Overall, 89% of the surviving patients with a follow-up period of greater than 2 years were free of seizures at last examination. Of the 280 patients in this series. 163 had experienced no seizures preoperatively. A recent follow-up study (with a minimum duration of 2 years or to death) was available in 157 of these 163 cases; 21 patients had died. Of the 136 surviving patients, only eight (6%) were having new ongoing seizures. In the 128 (94%) who had remained seizure-free, 73% were receiving no anticonvulsant agents while 27% were taking anticonvulsant prophylaxis. The 2-year minimum follow-up study in 110 of the 117 patients with preoperative seizures revealed that eight (7%) had died. Of the 102 surviving patients, 85 (83%) were seizure-free (with 48% no longer receiving anticonvulsant therapy), while 17 (17%) still suffered intermittent seizures. However, of these 17 patients, 13 reported their seizures to be improved compared to preoperatively; the seizures were the same in two patients and were worse in two patients. An actuarial analysis was conducted comparing the life expectancy of patients following surgery for AVM's with the expected survival of a general white population of the same age and sex in the West Northcentral region of the United States. No statistically significant difference was found. There were seven perioperative deaths (three from cerebral hemorrhage, two from pulmonary emboli, and two from obstruction of venous drainage) and 22 deaths during the follow-up period. Of these 22 deaths, the cause was unknown in four patients, apparently unrelated to the AVM in 13, and directly or indirectly related to the patient's neurological condition prior to surgery or due to surgery performed for resection of the AVM in five. There was a statistically significant relationship between the size and location of the AVM and the clinical presentation. Patients with small AVM's (< 3 cm) were more likely to present with hemorrhage whereas those with large AVM's were more likely to present with seizures. Conclusions from this study are: 1) there is a low incidence of a new seizure disorder following surgery: 2) chances for resolution or control of a pre-existing seizure disorder are good: 3) although resolution of seizures or seizure control was achieved postoperatively in AVM's of all sizes, this benefit was highest in smaller as opposed to larger AVM's; and 4) ultimately, there is a good capacity for recovery from pre-existing neurological deficits or those resulting from surgery.

✓ High-energy phosphate levels were measured in the canine cerebral artery during chronic vasospasm. Subarachnoid hemorrhage and vasospasm were induced by percutaneous injections of autologous venous blood into the cisterna magna. Narrowing of the artery was confirmed by angiography 7 days later. Levels of adenosine phosphates (adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP)), guanosine phosphates (guanosine triphosphate (GTP) and guanosine diphosphate (GDP)), and creatine phosphate (CrP) in the basilar artery were quantified using high-performance liquid chromatography. The total creatine (Crtotal) content was measured by a spectrophotometric method after acid hydrolysis of CrP. Levels of ATP, GTP, and CrP were markedly reduced in the spastic arteries, and ratios of ATP:ADP, GTP:GDP, and CrP:Crtotal were significantly decreased. The results indicate a serious disturbance in the energy metabolism that takes place in the cerebral artery during chronic vasospasm.

✓ Because of a suspicion that intraoperative penicillin antibiotics might be causing early postoperative seizures in craniotomy patients, a deliberate effort was initiated in 1987 to avoid these agents in favor of nonpenicillin antibiotics. This permitted a retrospective comparison of the incidence of early postoperative seizures in craniotomy patients who did and who did not receive intraoperative penicillins. Records of patients treated between July 1, 1984, and July 1, 1985, and between July 1, 1987, and July 1, 1988, were reviewed, for a total of 1316 procedures. There were no seizures in the 323 patients who underwent suboccipital craniectomy. However, among the 993 patients receiving supratentorial procedures there were 30 with seizures within the first 6 hours postoperatively, 19 of which were generalized seizures. The incidence of early seizures was 4.7% (20 cases) of the 427 patients given penicillins and only 1.8% (10 cases) of the 566 not given penicillins (p < 0.01). Since patients undergoing surgery for intractable seizures have a high incidence of early postoperative seizures (11 of 92 in this series, or 12%), creation of a subgroup eliminated these from consideration but did not alter the relationship of penicillins to early seizures (p < 0.02). The authors conclude that intraoperative (and early postoperative) penicillin antibiotic administration should be avoided, if possible, in patients undergoing craniotomy for supratentorial pathology.

✓ On June 30, Mrs. Jean Lawe will step down as Managing Editor of the Journal of Neurosurgery. She has worked on the Journal since 1965, when Dr. Louise Eisenhardt retired as the first Editor. Since that time the Journal has grown in size and circulation, and production has become fully computerized. In her valedictory, Mrs. Lawe summarizes her years with the Journal and her approach to scientific editing.

✓ In this study, 24 aneurysms occurring in 23 patients under the age of 18 years (mean 12 years) are analyzed. The male:female ratio was 2.8:1, and the youngest patient was 3 months old. Mycotic lesions and those associated with other vascular malformations were excluded. Forty-two percent of the aneurysms were located in the posterior circulation, and 54% were giant aneurysms. Presenting symptoms included subarachnoid hemorrhage in 13 and mass effect in 11. Several of these aneurysms were documented to rapidly increase in size over a 3-month to 2-year period of observation. All aneurysms were surgically treated: direct clipping was performed in 14; trapping with bypass in four; trapping alone in four; and direct excision with end-to-end anastomosis in two. The postoperative results were excellent in 21 aneurysms (87%), good in two (8%), and poor in one. The pathogenesis of cerebral aneurysms is reviewed.

✓ Intracellular brain pH, cortical blood flow (CBF), and electrocorticograms were recorded in regions of severe and moderate ischemia in 10 control rabbits and 10 rabbits given mannitol, 1 gm/kg, after occlusion of a major branch of the middle cerebral artery. Pooling the data from all 20 animals, preocclusion CBF was 46.4 ±3.6 ml/100 gm/min and intracellular brain pH was 7.01 ± 0.04 (means ± standard error of the means). Although mannitol administration mildly improved CBF in regions of severe ischemia, this increase was not sufficient to prevent metabolic deterioration as assessed by brain pH. However, in regions of moderate ischemia, CBF improved significantly with mannitol and the gradual decline in brain pH observed in control animals was prevented. For example, in the treated moderate ischemia sites 4-hour postocclusion CBF and pH values were 31.8 ml/100 gm/min and 6.89 ± 0.09, respectively, as compared to control values of 14.3 ml/ 100 gm/min and 6.75 ± 0.06. These results suggest that mannitol may be of benefit in stabilizing regions of moderate, but not severe, ischemia after vessel occlusion.

✓ The authors report their initial experience with the use of interposition saphenous vein grafts between the external carotid artery and the proximal posterior cerebral artery. The indications, results, and technical aspects of the operation are reviewed. All patients accepted for surgery were at high risk for a posterior circulation infarct, and all patients with ischemic symptomatology had continued to progress while on anticoagulant drugs or anti-platelet agents. Thus, all patients were at high risk, and 11 of the 14 patients operated on were confined to bed before surgery. Intraoperative graft flows varied from 35 to 170 ml/min, and postoperative graft flows ranged from 75 to 311 ml/min in the patent grafts. There were three early graft occlusions and two late graft occlusions; these all occurred in patients with relatively low flows at the time of surgery (40 ml/min or lower). Subdural hygroma was the next most frequent complication to graft occlusion. It was thought to be caused by the pulsating graft anastomosed to a major vessel through a small opening in the basal arachnoid, which provided a new path for cerebrospinal fluid flow in patients with a degree of preexisting atrophy. One patient with a large aneurysm in the posterior circulation underwent proximal intracranial clipping of the vertebral artery and bypass grafting simultaneously. There were seven excellent results and two good results in nine patients in whom the graft remained patent. In the five patients with graft occlusion, there were two minor strokes, two major strokes, and one death.

✓ The authors describe their experience using booster clips to secure the closure of primary clips in the repair of giant and other thick-walled aneurysms. These clips were used for 21 aneurysms in 20 patients, comprising 12% of all aneurysms operated on during the 15-month period of the report, but representing about 50% of all giant aneurysms operated on during the same time frame. These clips are designed to encircle the primary clip and have fixation “shoes” to close upon the jaws of the primary clip. All aneurysms were opened for decompression and thrombectomy when necessary following temporary major vessel occlusion before placement of the primary clip. Cerebral blood flow measurements and continuous electroencephalographic monitoring were utilized to predict the brain's tolerance to temporary ligation of the internal carotid artery (ICA) in those cases with a giant aneurysm arising from that vessel. There were no complications attributable to the periods of intracranial or cervical ICA occlusion; these periods varied but did not exceed 8 minutes for the former nor the tolerance period for the latter, which was calculated as from 5 to 30 minutes. It was necessary to reoperate on two patients and reposition clips because of stenoses or occlusions identified on immediate postoperative angiography. Fifteen patients had normal neurological function at the time of discharge. Three patients had minor deficits which did not prevent employment; two of these were related to a preoperative deficit and one was a complication of delayed ischemia. There were two deaths: one from bleeding complications and probable damage to perforating vessels in a patient operated on under profound hypothermia (the only case in the series so managed), and one from respiratory complications in a patient with severe pulmonary problems.

✓ A series of 14 patients with intracerebral hemorrhage after carotid endarterectomy is reviewed. This complication occurred in 0.6% of 2362 consecutive carotid endarterectomies performed at the Mayo Clinic from 1972 through 1986. All hemorrhages occurred within the first 2 weeks after operation and were ipsilateral to the side of the operation. Eight patients died, and only two made a good recovery. Significant risk factors are hypertension and chronic hemispheric hypoperfusion with impaired autoregulation. The “normal pressure-hyperperfusion breakthrough” syndrome was considered to be operative in 12 of the 14 patients. Nine patients had documented hyperperfusion (at least 100% increase of baseline cerebral blood flow) at the time of surgery. In an additional three patients, normal perfusion-pressure breakthrough was inferred by the clinical course and radiological findings, as well as by the absence of alternative explanations. Patients at risk for postendarterectomy intracerebral hemorrhage include those who have a clinical history suggestive of hemodynamic cerebral ischemia, severe carotid stenosis with limited hemispheric collateral flow, and postendarterectomy hyperperfusion, as measured by intraoperative cerebral blood flow. To minimize the risk of hemorrhage in these patients, strict maintenance of blood pressure at normotensive or even relatively hypotensive levels during the intraoperative and early postoperative periods is advised.

✓ Ninety-three endarterectomies for carotid stenosis were monitored with cerebral blood flow (CBF) measurements, and 113 with both CBF measurements and a continuous electroencephalogram (EEG). Significant CBF increase occurred only when carotid endarterectomy was for a stenosis greater than 90%. A high correlation between CBF and EEG indicated when a shunt was required. To sustain a normal EEG, the CBF ascertained by the initial slope technique must be 18 ml/100 gm/min at an arterial carbon dioxide tension (PaCO2) of 40 torr. The degree of EEG change below this level during occlusion reflected the severity of reduced blood flow and was reversible with replacement of a shunt. The value and limitations of these monitoring techniques and a concept of ischemic tolerance and critical CBF are discussed.

✓ Twenty cases treated with emergency embolectomy for acute occlusion of the middle cerebral artery were reviewed. There were 10 males and 10 females, with an average age of 55 years. The left middle cerebral artery was involved in 17 patients and the right in three. Flow was restored in 16 patients (75%). The embolus originated in the heart in seven, the carotid artery in seven, the aorta in three, an aneurysm in one, and an indeterminate source in two. It was technically most difficult to achieve patency with atheromatous emboli from the aorta. Two patients (10%) had an excellent result with no neurological deficit, five (25%) were left with a minimal deficit but were employable, seven (35%) had a fair result but were still independent and employable, four (20%) did poorly, and two (10%) died. Patients with an associated ipsilateral carotid artery occlusion did poorly. Collateral flow, as judged from preoperative angiograms, was the best predictor of outcome.

✓ The sequential neuronal alterations that occur during the early phase of developing cortical infarction in the squirrel monkey were studied by light and electron microscopy. A technique used to select ischemic tissue based on spectrophotometry is described. Neuronal shrinkage, characterized by angularity, cytoplasmic eosinophilia, and nuclear pyknosis on light microscopy and by an increase in electron density of the cytoplasmic and nucleoplasmic matrix on electron microscopy, was the predominant reaction. The increased electron density of the cytoplasm and nucleoplasm suggested a diffuse alteration at the molecular level and the appearance of this abnormality between 3 and 6 hours corresponded with the development of an irreversible neurological deficit. In contrast, approximately 10% of the neurons became very swollen and pale. The pattern of perineuronal astrocytic alterations suggested that some form of interaction involving fluid transfer may exist between astrocyte and neuron and that shrinkage or swelling of neurons may depend in part upon the presence or absence of direct fluid exchange with astrocytes. Most terminal boutons became progressively shrunken and dense resembling the changes which occur in anterograde axonal degeneration. Swelling and fragmentation of large lysosomes occurred at 12 hours. Disruption of neural membranes was widespread by 24 hours and was more severe in swollen neurons.

✓ Intracellular brain pH, cortical blood flow, and electroencephalograms (EEG's) were recorded in severely and moderately ischemic regions in 10 control and 10 nimodipine-treated rabbits prior to and following major branch occlusion of the middle cerebral artery (MCA). Preocclusion cortical blood flow was 51 ml/100 gm/min and intracellular brain pH was 7.01 in both the control and the treated animals. After MCA occlusion, the severely ischemic regions in the control group showed initial and 4-hour postocclusion flows of 12.7 and 5.2 ml/100 gm/min with a brain pH of 6.64 and 6.08, respectively. In animals given nimodipine after MCA occlusion, blood flow increased from 10.5 to 18.8 ml/100 gm/min, with an associated elevation in intracellular brain pH from 6.57 to 6.91. Comparable findings were observed in areas of moderate ischemia. Improvements in cortical blood flow, intracellular brain pH, and EEG attenuations produced by nimodipine were all statistically significant. Inspection of the cortex revealed reversal of cortical pallor and small-vessel spasm following treatment with nimodipine. It is hypothesized that nimodipine exerts its effects through reversal of ischemia-induced secondary vasoconstriction, and that this drug may be an important adjunctive treatment for patients with focal cerebral ischemia.

✓ Scanning electron microscopy of feline basilar arterial endothelium 4 hours and 1, 3, 5, and 7 days after subarachnoid hemorrhage (SAH) showed longitudinal furrows that correlated with angiographically demonstrated vasospasm. These ridges persisted after fixation at physiological pressure, and probably reflected medial contraction with undulation of the underlying elastic lamina. No change in endothelial cell morphology or thrombogenesis was observed as long as 7 days after SAH. There is no evidence from this study to suggest that ischemia from vasospasm is a product of thromboembolism from damaged endothelial surfaces.

✓ The relationship among cerebral blood flow (CBF), blood volume, cardiac output (CO), and mean arterial blood pressure (MABP) at varying levels of arterial CO2 tensions (PaCO2) were studied in 70 normal cats. The CBF was measured from the clearance curve of xenon−133 and CO with a thermal dilution catheter placed in the pulmonary artery. The CBF, CO, and MABP values varied appropriately with changes in PaCO2, confirming the reliability of the preparations and the presence of normal autoregulatory responses. Moderate hypovolemia that did not change MABP did, nevertheless, significantly decrease CO and CBF. In an effort to determine if this decrease in CO and CBF were coupled responses, the effects of beta stimulation, hypervolemia, and alpha and beta blockade were investigated. Propranolol, in a dosage insufficient to change MABP, decreased both CO and CBF. This agent abolished the CO response to elevations in PaCO2 but not the CBF response, making it unlikely that this CBF reduction resulted from impaired cerebral autoregulation. Isoproterenol, which, in contrast to propranolol, does not cross the normal blood-brain barrier, alone or in combination with phenoxybenzamine, produced a 38% and 72% increase in CO, respectively, without a change in CBF. Alpha blockade (no major change in CO) and beta blockade (major decrease in CO) did not significantly effect cerebral autoregulation to changes in MABP from angiotensin. The ability of the brain to resist increases in MABP and CO and maintain normal CBF is explained by normal cerebral autoregulation. However, its vulnerability to modest decreases in blood volume, which cannot be attributed to variations in perfusion pressure, is unexplained but obviously has important therapeutic implications. This may be related to reduction in CO, changes in autonomic activity, or a decrease in the size of the perfused capillary bed.

✓ The healing of the canine carotid endarterectomy was defined at intervals from 30 minutes to 3 months after surgery by means of angiography, light microscopy, and scanning electron microscopy. Immediately after flow was established, a fibrin-platelet carpet formed on the endarterectomized surface. A typical thrombus formed on this initial layer resulting in vessel occlusion in 52% of non-heparinized animals. By 48 hours after surgery, there was little evidence of active thrombus formation, and reendothelialization from existing endothelial cells was noted. One week later, most of the mural thrombus had disappeared and re-endothelialization was well underway; by 3 months after surgery, re-endothelialization was complete. Intraoperative heparinization resulted in a striking reduction in mural thrombus formation and 100% patency rate. Vessel closure with vein-patch grafts resulted in no improvement of vessel patency. However, the results of this aspect of the study cannot be totally extrapolated to human carotid endarterectomy for the reasons discussed. The survival of the vein-patch grafts was investigated.

✓The comparative effectiveness of isoproterenol (Isuprel), phentolamine (Regitine), and phenoxybenzamine (Dibenzyline) in modifying basilar arterial spasm induced by the topical application of arterial blood was studied in cats. None of these agents was effective in inhibiting initial peak constriction. Each reduced the duration of the vasospasm. The results indicate that both alpha-blockade and beta-stimulation can alter the course of blood-induced cerebral vasospasm.

✓ The author reviews a form of management for patients deteriorating preoperatively or postoperatively from apparent ischemia attributed to progressive vasospasm after a subarachnoid hemorrhage. The clinical picture and relative frequency of this complication are considered in relationship to the status (grade) of the patient, location of the aneurysm, and ultimate neurological recovery. Experience suggests that the drug regimen reported is useful when instituted early after the onset of symptoms and is safe with proper monitoring techniques. The data do not justify early operative intervention after a subarachnoid hemorrhage, operation when there is angiographic evidence of severe spasm, or expectation of a dramatic effect in patients with a profound deficit or a fixed deficit several hours old.

✓ Nimodipine, a dihydropyridine that interacts with a Ca++ channel-associated binding site, when delivered (30 to 150 µg/kg) intra-arterially (ia) to enflurane-anesthetized cats, produced a dose-dependent suppression of seizures evoked by pentylenetetrazol. A comparable suppression was produced by clonazepam (1 to 30 µg/kg, ia). Phenytoin was maximally effective only at nearly lethal doses (90 mg/kg, ia). Verapamil, a diphenyl-alkylamine that interacts with a separate Ca++ channel-associated site, at the maximum nonlethal dose (6 mg/kg, ia) resulted in a mild facilitation of seizure activity. The drug vehicle used in these studies (50% polyethylene glycol-400) had no effect when given alone. Regional cerebral blood flow (rCBF) as measured by the clearance of xenon-133 was markedly elevated immediately after the onset of seizure activity (89 ± 3 to 168 ± 4 ml/100 gm/min). Concurrent with their resolution of the seizure activity, both nimodipine and clonazepam reduced rCBF to near preseizure levels and preserved the rCBF response to hypercarbia which would otherwise have been abolished following prolonged seizure activity. Moreover, the effect of nimodipine on rCBF and seizures occurred without any prominent alterations in mean arterial blood pressure as compared to preseizure levels. These data support the proposition that a dihydropyridine Ca++ channel binding site may play a role in modulating paroxysmal neuronal activity, and suggest that this class of agents may reflect a novel group of antiepileptic drugs.

✓ The authors report the results of a long-term follow-up study of 130 patients with 161 unruptured intracranial saccular aneurysms. Their findings suggest that unruptured saccular aneurysms less than 10 mm in diameter have a very low probability of subsequent rupture; The mean diameter of the aneurysms that subsequently ruptured was 21.3 mm, compared with a diameter of 7.5 mm for aneurysms defined after rupture at the same institution. Part of the explanation for this discrepancy may be that the size of the filling compartment of the aneurysm decreases after rupture. There is also evidence from the present study that intracranial saccular aneurysms develop with increasing age of the patient and stabilize over a relatively short period, if they do not initially rupture, and that the likelihood of subsequent rupture decreases considerably if the initial stabilized size is less than 10 mm in diameter. Consequently, the critical size for aneurysm rupture is likely to be smaller if rupture occurs at the time of or soon after aneurysm formation. There seems to be a substantial difference in potential for growth and rupture between previously ruptured and unruptured aneurysms.

✓ To investigate the alteration of endothelium-dependent responses in chronic vasospasm after subarachnoid hemorrhage (SAH), experiments were carried out in the double-hemorrhage canine model. After the presence of vasospasm was confirmed by cerebral angiography on Days 0 and 7, pharmacological studies on the basilar artery were conducted in vitro on Day 8. In the SAH group, endothelium-dependent relaxation was abolished in response to arginine vasopressin and was significantly reduced in response to thrombin. Endothelium-independent relaxation in the SAH group was preserved in response to papaverine and was minimally reduced in response to sodium nitroprusside. Endothelium-dependent contraction in response to arachidonic acid, acetylcholine, the calcium ionophore A23187, adenosine diphosphate, mechanical stretching, and hypoxia persisted in the SAH group. The maximal contraction to KCl and uridine triphosphate, which is endothelium-independent, was diminished in the SAH group, but no changes in sensitivity were noted in the concentration-response relationships. A significant correlation was observed between the degree of vasospasm determined angiographically and the loss of endothelium-dependent relaxation. The loss of endothelium-dependent relaxation and the persistence of endothelium-dependent contraction suggest that the deterioration in the endothelium-dependent responses may be an important component in the pathogenesis of cerebral vasospasm.

✓ Results, complications, and operative techniques of the surgical management of 20 aneurysms of the distal extracranial internal carotid artery (ICA) in 19 patients are reviewed. The proximity of these aneurysms to the styloid process is not considered as a chance occurrence, and the possibility is raised that these lesions are related to trauma from that structure. False aneurysms from spontaneous dissections are believed to occur only in those dissections that begin distally; they are not found in dissections that begin proximally. Treatment was individualized and dependent upon: 1) the size and location of the aneurysm; 2) symptomatology; and 3) hemodynamic considerations based upon intraoperative cerebral blood flow (CBF) measurements determined from the clearance of xenon-133 injected into the ipsilateral ICA. Methods of treatment included: resection of the aneurysm with placement of an interposition saphenous vein graft in seven patients; resection of the aneurysm with end-to-end anastomosis of the ICA in five; ICA ligation in three; clipping of the aneurysm in one; and extracranial-to-intracranial bypass in four. One patient sustained a postoperative cerebral ischemic complication from embolization which resulted in a mild permanent impairment in right hand dexterity. There were no other cerebral ischemic complications in the group, largely attributable, it is thought, to the use of intraoperative CBF measurements and continuous electroencephalograms. Four patients had transient dysphagia from traction damage to the pharyngeal and superior laryngeal nerves, and one patient with preoperative difficulty in swallowing required a gastrostomy. Long-term results have been excellent. Use of the operating microscope facilitated the suturing of the distal anastomosis in cases in which the ICA was reconstructed by an interposition vein graft or end-to-end anastomosis.

✓ A case of giant traumatic false aneurysm of the intracranial internal carotid artery (ICA) with a concomitant carotid-cavernous fistula is reported. The fistula and the aneurysm persisted after ipsilateral cervical ICA ligation was performed elsewhere. Successful obliteration of the aneurysm and the fistula, with preservation of cross filling of the ipsilateral middle cerebral artery system, was accomplished by ligation of the intracranial ICA proximal to the origin of the posterior communicating artery with a 7–0 prolene suture, followed by transaneurysmal packing of the fistula.

✓ The authors report their experience with the use of saphenous vein bypass grafts for treating advanced occlusive disease in the posterior circulation (77 patients, all of whom had failed medical management and showed severe ischemic symptoms), deteriorating patients with giant aneurysms of the posterior circulation (nine patients), progressive ischemia in the anterior circulation (26 patients, none of whom had a normal examination), and giant aneurysms in the anterior circulation (20 patients, all of whom presented with mass effect or subarachnoid hemorrhage). Graft patency in the first 65 cases treated was 74%. However, after significant technical changes of vein-graft preparation and construction of the proximal anastomosis, patency in the following 67 cases was 94%. Excellent or good results (including relief of deficits existing prior to surgery) were achieved in 71% of patients with advanced occlusive disease in the posterior circulation, 44% of those with giant aneurysms of the posterior circulation, 58% of those with ischemia of the anterior circulation, and 80% of those with giant aneurysms of the anterior circulation. Mean graft blood flow at surgery in the series was 100 ml/min for posterior circulation grafts and 110 ml/min for anterior circulation grafts. Experience to date indicates that this is a useful operation, and is particularly applicable to patients who are neurologically unstable from advanced intracranial occlusive disease in the posterior circulation or with giant aneurysms in the anterior circulation. The risk of hyperperfusion breakthrough with intracerebral hematoma restricts the technique in patients with progressing ischemic symptoms in the anterior circulation, and the intolerance of patients with fusiform aneurysms in the posterior circulation to the iatrogenic vertebrobasilar occlusion limits the applicability of this approach to otherwise inoperable lesions in that system.

✓ Various straight-jawed aneurysm clips were tested for occluding capabilities on a vascular tissue model. Occluding pressures varied markedly among the clip styles and were altered by changes in the lumen and tissue composition of the model. Mechanical characteristics are highly variable between clip styles, but fall within a narrow range for clips of a similar style. The complex interplay of the unique aspects of clip design and force generated by the spring in conjunction with tissue characteristics and precise clip placement upon the tissue are major variables in the apparent ability of a particular clip to occlude the neck of an aneurysm.

ThE introduction of the operating microscope to the field of neurosurgery has opened a new era3 ,6 Intracranial neurovascular surgery on major vessels seems technically feasible. Yet the necessity for rapid work, the position of these vessels, the friable vessel wall, and uncontrolled bleeding make microsuture techniques most difficult. The purpose of the clip-graft is to provide the neurosurgeon with a rapid non-suture technique for the repair of diseased major intracranial vessels. It is anticipated that there will be application to endarterectomies, embolectomies, aneurysms, and the repair of major vessels injured in tumor surgery. The clip-graft utilizes a teflon or dacron graft attached to a circular spring metal clip. The stainless steel metal clip is merely the carrier for the graft and provides a non-suture method of application, This report resolves itself therefore to a study of these fabric grafts in the repair of segmental defects in small arteries of the sizes of the human internal carotid and middle cerebral. The previously reported concept of intraluminal pressure-sealing is utilized2

✓ Representative enzymes in brain were studied by histochemical techniques at intervals varying between 6 hours and 8 weeks after permanent middle cerebral artery occlusion in 18 cats. Unequivocal enzyme changes did not develop until 12 hours after occlusion, and no specific enzyme system was demonstrated to fail prior to others. That the ischemia of the first 6 hours is reversible in the cat was further substantiated by histological studies in a separate group of animals subjected to temporary middle cerebral artery occlusion for 6 hours. This study demonstrated progressive axonal changes, after the period of reversibility, bordering the core area of ischemia and resembling neural tissue reaction to injury in the spinal cord. Correlation of this study with previous biochemical determinations suggests that a self-induced and self-perpetuated toxicity might explain, in part, progressive changes in ischemic areas.

✓ Analysis of the use of the clip-graft for intracranial aneurysms indicates that the clip-graft is chiefly applicable to internal carotid and anterior communicating artery aneurysms. The development of the right-angle clip holder has extended its use to anterior communicating artery aneurysms that project posteriorly or superiorly. The dangers of dissection in the septal region are discussed. With few exceptions, the clip-graft is not applicable to the vertebrobasilar system or middle cerebral artery trifurcation aneurysms, although it has been used for aneurysms arising from the trunk of the latter vessel.

tran, has been used to treat experimental cerebral infarction in dogs, with somewhat favorable results. ~ In this paper we shall report the results of the modification of cerebral infarction in cats by a variety of agents. The agents include: hyperoncotic solutions of low-molecular-weight dextran, serum albumin, and urea, individually and in combination; honmlogous serum; physiologic saline; and packed erythrocytes.

✓ Experience in cardiovascular and peripheral vascular surgery with saphenous vein bypass conduits is reviewed. It is clear that meticulous technique and graft preparation are crucial to short-term and long-term patency. The risk of early thrombosis is related to damage to the graft 's native intima, graft flow, and coagulability of the patient 's blood. Attention to atraumatic harvesting techniques and perfection of anastomoses are crucial to minimizing intimal damage. Graft inflow and outflow are fundamental principles. The use of vitamin K antagonists and platelet inhibitors may improve graft survival. Subacute occlusion is related to structural alterations in the grafts themselves. These include intimal hyperplasia and medial fibrosis as the grafts become “arterialized,” valve fibrosis, aneurysmal dilatation, clamp stenosis, and suture stenosis. Long-term patency is threatened primarily by atherosclerosis in the graft itself. There is some evidence that care in vein harvesting and implantation as well as the use of anticoagulant agents affect the development of this complication. A technique for graft preparation is presented that is based on the experience of the authors in harvesting grafts for both cerebral and coronary bypass conduits.

✓ The biological response of normal cat brain to Nd:YAG laser light was studied both in vitro and in vivo to evaluate the potential safety of this laser for coagulation in brain tissue. Transmission studies revealed a blood:brain absorption ratio of 100:1 indicating the selective absorption of Nd:YAG light by hemoglobin and enabling Nd:YAG light to selectively heat blood vessels compared to brain tissue. In vivo temperature recordings and pathological evaluation demonstrated a remarkable ability of the brain to dissipate the thermal energy produced by Nd:YAG light with only a small amount of structural damage. Powers of 10 W applied for 8 seconds using a 1.2-mm focused probe resulted in a penetration depth in normal brain of only 2 mm. Thermal recordings also revealed that blood is heated to 90% of its maximum temperature within 3 seconds, while the brain temperature increases linearly as the duration of the laser pulse is increased. In addition, the localized heating of brain tissue was cooled rapidly within seconds following cessation of the laser pulse. These findings indicate that by using short, intermittent pulses of light focused upon blood vessels, damage to the surrounding tissue can be minimized, and the Nd:YAG laser can be used safely as an adjunctive measure for hemostasis in many neurosurgical procedures.

✓ A retrospective angiographic analysis was designed to extrapolate the frequency of angiographically defined asymptomatic intracranial aneurysms in the anterior circulation from a relatively unbiased clinical series. A total of 9295 angiograms were reviewed from January, 1980, to January, 1987, and, based on these, 278 patients with minimal bias for the presence of an aneurysm were selected. Three patients were found to have incidental aneurysms; thus, the angiographic frequency of patients with asymptomatic aneurysms in this series was 1%. This patient population is skewed toward the older age groups and probably over-represents the incidence of these aneurysms in the population at large. Comparing current subarachnoid hemorrhage statistics and the low frequency of asymptomatic aneurysms suggests that a larger percentage of these aneurysms than was previously thought subsequently rupture. This study contrasts sharply with previous reports quoting a high incidence of aneurysms, and significantly alters the concept and treatment of this disease.

✓ Arteriovenous malformations (AVM's) of lateral and sigmoid sinuses are acquired lesions evolving from a previously thrombosed dural sinus. Their natural history is usually that of gradual progression and hence surgery is frequently necessary. The preferred surgical treatment is complete excision coupled with packing of the sigmoid sinus. The operative approach is illustrated and discussed in detail. Results and complications are reviewed in 27 patients whose symptomatology had progressed under conservative management; 22 of these cases harbored primary lesions and five had recurrences. There were 22 excellent, one good, and two poor results (both of the latter from blindness that preceded surgery). There were two deaths, both in patients previously operated on with incomplete removal or obliteration of the AVM by attempted embolization.

✓ The purpose of this study was to examine the hypotheses that structural stiffening of the arterial wall contributes to chronic cerebral vasospasm, and that alteration in properties of smooth muscle takes place after subarachnoid hemorrhage (SAH). Subarachnoid hemorrhage and subsequent chronic vasospasm were induced in dogs by two cisternal injections of autologous blood (on Day 0 and Day 2). Vasospasm was confirmed by angiography performed on Day 0 and Day 7. Animals in the control group underwent angiography only. On Day 8, the mechanical properties of the basilar arteries were studied in vitro. Passive compliance, measured under total inhibition of spontaneous myogenic tone with diltiazem (10−4 M) plus papaverine (10−4 M) was smaller in the SAH group. The length-contraction curve was shifted to the left and the optimum length for maximum contraction (Lmax) was significantly shorter in the spastic blood vessels. The spontaneous myogenic tone was augmented in the SAH group, resulting in an increase in resting tension at each length. By contrast, the maximum contractions in response to KCl and uridine 5′-triphosphate were markedly reduced in the SAH group, without changes in sensitivity to these agents. These differences in mechanical properties were observed in rings both with and without endothelium. The results indicate that, in chronic vasospasm, stiffening of the noncontractile component of the vasculature takes place as well as alterations in the contractile component, both of which presumably contribute to the shift in resting length-tension relationship and length-contraction relationship of the artery. The decreased distensibility, the increase in resting tension, and the shortening of the Lmax all favor a smaller diameter of the artery after SAH, possibly contributing to vasospasm.

✓ Severe chronic cerebral vasospasm was reliably induced in dogs by two injections, 2 days apart, of autologous blood into the cisterna magna. Treatment with ibuprofen or high-dose methylprednisolone after the first injection prevented or reduced vasospasm. Both drugs reduced meningismus and accelerated the rate of neurological recovery. Compared with specimens from normal dogs, rings of basilar arteries obtained from untreated dogs contracted weakly in response to 5-hydroxytryptamine, prostaglandin F2α, potassium chloride, and barium chloride. Rings of arteries from dogs who received ibuprofen or methylprednisolone contracted more strongly. Electron micrographs of basilar arteries from untreated dogs showed degeneration of smooth muscle, whereas those from treated dogs did not. Thus, what is termed “chronic cerebral vasospasm” probably represents a structural derangement of the blood vessel wall leading to its narrowing, rather than a sustained contraction of the vascular smooth muscle. Administration of high-dose methylprednisolone and ibuprofen can prevent its occurrence.

✓ The management results in 244 patients admitted to one institution within 3 days of aneurysmal subarachnoid hemorrhage (SAH) from January, 1979, to December, 1985, were analyzed with respect to the timing of surgical intervention. Twenty-six patients died prior to surgery. Patients surviving to surgery were divided into three groups according to the interval between preadmission SAH and surgery: 0 to 3 days (85 cases), 4 to 9 days (83 cases), and 10 or more days (50 cases). Of the patients who were categorized neurologically into Botterell Grades 1 and 2 (Hunt and Hess Grades I to III) on admission, 87% had an excellent or good result on follow-up evaluation. Patients undergoing surgery 0 to 3 days after SAH had a statistically significant increase in the incidence of postoperative ischemic symptoms (p < 0.005), which was balanced by similar complications preoperatively in the 10-day post-SAH surgical group. Most rebleeds occurred before admission but delaying surgery did increase the risk of rebleeding in the hospital (p < 0.0005). Management morbidity and mortality occurred primarily as a direct result of a severe initial hemorrhage; thus, the measured benefits of early surgery were less than might have been predicted.

✓ Carotid body tumors are a rare but potentially difficult surgical entity. Their pathology, physiology, and natural history are reviewed along with surgical results reported in the literature. A surgical approach for removal of these tumors is presented which differs significantly from the recommended techniques in that emphasis is placed on intraoperative monitoring of cerebral blood flow, the selective use of shunts, a tumor-adventitial plane of dissection, preservation of the carotid artery complex, and mobilization of the parotid gland. Thirteen cases using these techniques are reviewed. The mortality rate and the incidence of cerebrovascular sequelae were both 0%. The major morbidity consisted of injury to the lower cranial nerves in five patients (39%) with tumors larger than 5 cm in length.

✓ The authors report experience with the surgical management of 80 giant intracranial aneurysms (> 2.5cm 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 of 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.

✓ The purpose of this study was to determine the cause of the loss of endothelium-dependent relaxation observed in chronic cerebral vasospasm. A bioassay system was developed to measure the release of endothelium-derived relaxing factor (EDRF) from canine basilar arteries. Subarachnoid hemorrhage (SAH) was induced in dogs by two injections of autologous blood into the cisterna magna. Angiograms were performed on the 7th day after SAH to check the presence of chronic vasospasm. The animals were sacrificed on the 8th day, and in vitro experiments were performed on rings harvested from the basilar artery. These confirmed loss of endothelium-dependent relaxation in response to bradykinin and arginine vasopressin in the group with SAH. The basilar arteries were perfused with modified Krebs-Ringer solution. The perfusate was bioassayed with a ring of coronary artery without endothelium (bioassay ring). The release of the EDRF was detected by relaxation of the bioassay ring contracted with prostaglandin F2α. Arginine vasopressin and bradykinin added to the perfusate upstream of the basilar artery caused concentration-dependent release of the EDRF. The direct effect of these peptides on the smooth muscle of the bioassay ring was to cause contraction. The release of the EDRF was identical in basilar arteries from the control and the SAH groups. These results indicate that the release of the EDRF is not impaired during chronic vasospasm, and thus that the loss of the endothelium-dependent relaxation is due to a decreased transfer of the EDRF or a reduced responsiveness of the smooth muscle to the factor.

✓ Data from 722 consecutive cases with intracranial aneurysms were stored in a computer and later retrieved for analysis. Results and complications (including preoperative death and morbidity) of the surgical management of these patients were correlated with the Botterell grade of the patient in individuals with a recent subarachnoid hemorrhage (SAH), with the type of aneurysm, and with the timing of the surgical procedure. Patients with no SAH within 30 days prior to hospital admission were classified as “no SAH.” Approximately 30% of all patients had sustained more than one hemorrhage. Death and morbidity rates prior to surgery in good-grade patients with a recent SAH exceeded the risk of surgery itself. Rebleeding was the primary cause for death and morbidity in Grade 1 patients: 3% of Grade 1 patients died from a recurrent hemorrhage and 7% deteriorated to a lower grade. Deterioration from ischemia produced by vasospasm related or unrelated to rebleeding exceeded the risks of rebleeding in Grade 2 patients. There was an operative morbidity of 2% and mortality of 2% in patients who were classified as Grade 1 at the time of surgery, but an overall management morbidity of 3% and mortality of 6% in patients who were in Grade 1 at the time of hospital admission. Early surgery in Grade 1 patients was not associated with an increased incidence of delayed ischemia postoperatively. In Grade 2 patients, the operative morbidity and mortality was 7% and 4%, respectively, and the management morbidity and mortality 16% and 11%, respectively. Early surgery in this group was associated with a high frequency of postoperative delayed ischemia (particularly in patients with more than one SAH). Epsilon-aminocaproic acid appeared to protect against a rebleed, but was associated with a higher incidence of postoperative pulmonary emboli. Intraoperative complications were related both to the size of the aneurysm and to its location. Repair of multiple aneurysms did not adversely affect the result. The surgical approach, the importance of using a self-retaining brain retractor, and the technical complications in these cases are discussed.

✓ The adverse effect of a minimal cerebral blood flow (CBF) in models of global ischemia has been noted by many investigators. One factor believed important in this situation is the level of blood glucose, since a continued supply of this metabolite results in increased tissue lactate, decreased brain pH, and increased cell damage. The authors have extended these observations to a model of focal incomplete ischemia. Brain pH was measured in fasted squirrel monkeys in regions of focal incomplete ischemia after transorbital occlusion of the middle cerebral artery (MCA). In both control and hyperglycemic animals, CBF was reduced to less than 30% of baseline. At 3 hours after MCA occlusion, brain pH in the control group was 6.66 ± 0.68 as compared to 6.27 ± 0.26 in the glucose-treated group. This difference was statistically significant by Student's unpaired t-test (p < 0.05). Thus, hyperglycemia results in decreased tissue pH in regions of focal incomplete cerebral ischemia in monkeys.

✓ Ten patients with intracranial internal carotid artery (ICA) aneurysms were managed by combining ICA ligation with an extracranial to intracranial bypass procedure. Nine of these grafts were proven patent by angiogram. One patient was unable to return for postoperative angiograms; his graft had appeared patent on physical examination. Seven aneurysms were intracavernous, two were giant carotid-ophthalmic aneurysms, and one aneurysm was at the intracranial bifurcation of the ICA. Despite occlusion cerebral blood flow (CBF) measurements of 20 ml/100 gm/min or less in six patients, only one patient was unable to tolerate ICA ligation. Three patients developed transient aphasia, but there were no permanent neurological deficits associated with the carotid occlusion. Seven patients had improvement in pre-existing extraocular palsies or visual field defects. Others remained stable. The combination of an extracranial to intracranial microvascular bypass procedure with ICA ligation seems to be an effective method of treatment for aneurysms near the base of the skull that cannot be obliterated by a direct intracranial approach. The addition of the bypass procedure permits ICA ligation in patients who would not otherwise have tolerated occlusion of that vessel. Intraoperative xenon CBF measurements are an important adjunct to the operation.

✓ A method is described for the protection of the trigeminal root from recurrent vascular irritation or compression after posterior fossa microvascular decompression. A vascular clip-graft, using a Sundt clip of suitable size, is applied to the sensory root of the trigeminal nerve. The technique has proven safe and effective in a series of nine patients followed for up to 28 months.

✓ A case of spontaneous vertebral arteriovenous fistula in association with fibromuscular dysplasia is reported. The patient presented with progressive cervical myelopathy and cervical bruit. The pathogenesis of the fistula development and the spinal cord symptoms is discussed. Symptoms subsided after obliteration of the fistula.

✓ A combination of the Sundt-Kees reinforcing aneurysm clip applied to a Drake aneurysm clip in a piggyback fashion was studied for possible defects due to corrosion and or tissue toxicity. These two clips, which are made of similar metal (301 stainless steel), showed little or no defects when immersed in 5% saline or when implanted in rats for 6 months. This study demonstrates that clips made of similar metals can be used piggyback in patients without ill effects provided that they are carefully handled to avoid any abrasion or misbends which could conceivably lead to corrosion.