✓ 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.
Thoralf M. Sundt Jr., David G. Piepgras, W. Richard Marsh and Nicolee C. Fode
David O. Wiebers, Jack P. Whisnant, Thoralf M. Sundt Jr. and W. Michael O'Fallon
✓ 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.
Max E. Ots, Tony L. Yaksh, Robert E. Anderson and Thoralf M. Sundt Jr.
✓ 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.
Assessment by intracellular brain pH, cortical blood flow, and electroencephalography
Fredric B. Meyer, Robert E. Anderson, Thoralf M. Sundt Jr. and Tony L. Yaksh
✓ 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.
Fredric B. Meyer, Robert E. Anderson, Tony L. Yaksh and Thoralf M. Sundt Jr.
✓ 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.
Fredric B. Meyer, Thoralf M. Sundt Jr., Nicolee C. Fode, Michael K. Morgan, Glen S. Forbes and James F. Mellinger
✓ 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.
Francis H. Tomlinson, Daniel A. Rüfenacht, Thoralf M. Sundt Jr., Douglas A. Nichols and Nicolee C. Fode
✓ 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.
Nayef R. F. Al-Rodhan, Thoralf M. Sundt Jr., David G. Piepgras, Douglas A. Nichols, Daniel Rßfenacht and Lorna N. Stevens
✓ 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.
Jack P. Whisnant, Sara E. Sacco, W. Michael O'Fallon, Nicolee C. Fode and Thoralf M. Sundt Jr.
✓ 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.