STA-MCA Bypass Surgery for Internal Carotid Artery Occlusion Comparative Follow-up — Study— Tatsuya Hiromu
ISHIKAWA, HADEISHI,
Nobuyuki Fumio
YASUI,
SHISHIDO*
Akifumi and
Kazuo
SUZUKI, UEMURA*
Departments of Surgical Neurology and *Radiology and Nuclear Medicine, Research Institute for Brain and Blood Vessels-A kita, Akita
Abstract Sixty-three patients with internal carotid artery occlusion manifesting as transient ischemic attack or minor stroke received superficial temporal artery-middle cerebral artery bypass surgery and medical treatment (n = 27) or medical treatment only (n = 36). Long-term follow-up showed that there was no significant difference in the outcomes. However, positron emission tomography studies suggested that patients with misery perfusion in the chronic stage benefited from extracranial-intracranial bypass surgery. Key words:
internal
non-surgical
therapy,
carotid positron
artery
occlusion,
emission
long-term
follow-up,
STA-MCA
bypass,
tomography
Introduction
Materials
and
Methods
This retrospective study included 63 patients who presented at our institute with cerebrovascular steno occlusive diseases manifesting as TIA or minor stroke between 1977 and 1988. Angiography diag gery.9"15) However, a large prospective randomized trial') has demonstrated that this surgery does not nosed arteriosclerotic occlusion of either the uni help prevent subsequent stroke even in a subgroup of lateral or bilateral ICA in all cases. All patients re ICA occlusion patients. In contrast, EC-IC bypass ceiving surgery were independent prior to surgery. surgery is considered effective in patients with hemo All medically treated patients were independent at dynamic cerebrovascular ischemic diseases 2,8,10,13,17,18) discharge, although some needed rehabilitation. Pa About 75% of ICA occlusion patients are thought to tients with major completed stroke because of ICA have abnormal cerebral hemodynamics.16) occlusion were excluded whether they had surgery or Our study followed patients with ICA occlusion not. Patients with a diagnosis of embolic ICA occlu suffering either transient ischemic attack (TIA) or sion originating extracranially, moyamoya disease, minor stroke for a long period. Groups of patients arteritis, or traumatic ICA occlusion were also ex receiving EC-IC bypass surgery and medical treat cluded. Bilateral carotid angiography was performed ment were compared to assess the effectiveness of on all patients, and vertebral angiography on many EC-IC bypass in preventing recurrent ischemic to confirm side and site of the ICA occlusion. Any stroke and the final outcome. Positron emission past history of hypertension, diabetes mellitus, and ischemic heart disease was considered. Cases with tomography (PET) was used to investigate the occur rence of recurrent ischemic stroke and the cerebral clinical symptoms not necessarily caused by the ICA blood flow (CBF) and oxygen metabolism in some pa occlusion were also included in the study. tients. Twenty-seven patients received EC-IC bypass surgery (surgical group). The other 36 patients re Received January 7, 1991; Accepted May 2, 1991 ceived only medical treatment (non-surgical group).
Internal carotid artery (ICA) occlusion is the most common arterial lesion considered suitable for ex tracranial-intracranial (EC-IC) arterial bypass sur
The EC-IC bypass surgery was expected to prevent recurrent ischemic stroke. Patients were placed in the non-surgical group when: 1) the patient or family rejected surgery, 2) the patient was included in the non-surgical group in the EC-IC Bypass Study,') 3) the attending neurologist was not inclined to surgical treatment, 4) PET studies contraindicated EC-IC bypass surgery. All 63 patients were followed for a long period. Clinical course following discharge and the final out come were evaluated using medical records and in terviews with the patient or family by telephone or letter. The occurrence of recurrent ischemic stroke,
Table
1
Clinical
profiles
bypass
group
of
patients
and non-surgical
progression of dementia, functional level of the pa tient, and the cause of death (if applicable) were investigated. Death was considered stroke-related if occurring as a result of ischemic stroke or related complications. Since 1984, a PET study was made in 17 of the 63 patients for a quantitative evaluation of CBF and oxygen metabolism. The relationship between the PET study and the clinical course was also evalu ated. Table
2
Medical
treatment
Table
3
Outcome
Table
4
Final
for patients
Results Table 1 summarizes
the clinical profiles of the two
groups. No significant difference was recognized be tween the clinical profiles of these two groups, except for the sex distribution (p < 0.05). A superficial temporal artery-middle cerebral artery (STA-MCA) bypass was performed on a total of 28 sides among the 27 patients in surgical group. A double STA-MCA anastomosis was made on 22 sides, and on one side a triple anastomosis. The other four sides in four patients were single anastomoses. No perioperative death occurred. Only one patient developed occlusion of a MCA branch perioperatively, resulting in permanent neurological deficit. Postoperative angiography demonstrated asymptomatic occlusion of one of the double STA MCA bypasses in two patients. No standard medical treatment for the prevention of further cerebral infarction has been established at our institute. Therefore, various agents were given to the patients in each group (Table 2). Antiplatelet agents, such as acetylsalicylic acid and ticlopidine, which are believed to prevent ischemic strokes, were prescribed for about two-thirds of the patients in both groups. However, whether all these patients continued to receive these medicines during follow up is unclear. Aggressive hypertension was also con trolled if necessary. Table 3 summarizes the observations during the
of the patients
outcome
of patients
in
the group
EC-IC
Table
5
Outcomes
and
results
from
the PET
study
follow-up period in both groups. Recurrent ischemic stroke includes perioperative ischemic attacks. The total recurrent ischemic stroke incidence in the surgical group was 4.7% per year. The incidence ipsilateral to the ICA occlusion was 3.1 % per year. The total recurrent ischemic stroke incidence in the non-surgical group was 6.4% per year. The incidence ipsilateral to the ICA occlusion was 4.0% per year. There were no significant difference in the incidence of recurrent ischemic strokes and in the incidence of death or stroke-related death between the two groups. Table 4 summarizes the outcome at the time of the survey. There were no significant differences between the two groups. The regional CBF (rCBF), the regional oxygen ex traction fraction (rOEF), regional metabolic rate of oxygen (rCMR02), and the regional cerebral blood volume (rCBV) were quantitatively measured by PET using the continuous inhalation of C1502 and 150 2 and single inhalation of C150 (Table 5). All 17 patients had a unilaterally occluded ICA. The PET study was performed preoperatively in the surgical group. The time delay between the most recent stroke and PET study was significantly longer in the surgical group, but all PET studies were performed during either the subacute or chronic stage of cerebral infarction. The OEF values in the perfusion territory of the MCA distal to the occluded ICA were compared to those of the non-affected side. The four surgical patients with higher OEF suffered no recur rent ischemic stroke during follow-up. One month after the operation they were re-examined. Three demonstrated normalized OEF due to increased
CBF. Five patients in the non-surgical group had a higher OEF. Two suffered recurrent ischemic stroke ipsilateral to the ICA occlusion, and in another two mild dementia progressed. The incidence of ipsi lateral recurrent ischemic stroke was 12.2% per year. If progressive dementia is included, this in cidence was 24.4% per year. No patient with normal OEF in either group suffered recurrent ischemic stroke or progressive dementia. Discussion This study was not a randomized
trial, but the two
groups had well-matched epidemiological factors (age and past history) and clinical features (type of ischemic stroke, side and site of ICA occlusion). In this study the patients of both groups received medical treatment and more than half received an tiplatelet agents. This study, therefore, investigated the combined effects of EC-IC bypass surgery and medical treatment. In this respect, this study is different from the EC-IC Bypass Study." Table 6 summarizes published data on the long-term out come of common carotid artery and ICA occlu sion. 3,5,7,9,1'''4 The incidence of recurrent ischemic stroke in pa tients with carotid occlusion was about 3-6% per year, with 0-5% per year of strokes occurring ipsi lateral to the carotid occlusion. Our results in the non-surgical group showed the incidence of recur rent ischemic stroke is 6.4% per year, with 4.0% per year occurring ipsilateral to the ICA occlusion. Our results therefore correspond with previous reports. The EC-IC Bypass Study" found no benefits from
Table
6
Outcomes
in cases
of common
and internal
carotid
surgery for the subgroup of patients with ICA occlu sion. The incidence of recurrent ischemic stroke for the "medical group" was 5.2% per year for patients with no symptoms between the angiographic demonstration and randomization, and 6.9% per year for patients with symptoms. For the "surgical group," the incidences were 4.7% per year and 9.1 % per year, respectively. In our study, the total in cidence of recurrent ischemic stroke in the surgical group was 4.7% per year, and ipsilaterally 3.1 % per year. These incidences were somewhat better than those in the non-surgical group. However, the difference was not significant. Final outcome and incidence of stroke related death were also not significantly different. Our study therefore fails to prove any benefit from EC-IC bypass surgery for the prevention of recurrent ischemic stroke and stroke related death in patients with ICA occlusion. Hemodynamic stroke has been considered a good indication for EC-IC bypass surgery.2.g,1o,'3,",'8' However, it is not effective for thromboembolic stroke.') EC-IC bypass surgery can achieve hemodynamic improvement in patients with a hemodynamic abnormality .2,1,11,11,16 's' However, there is no epidemiological proof that EC-IC bypass surgery is effective for hemodynamic stroke. Powers et al. ") used an abnormal rCBV/rCBF ratio measured by PET, to define abnormal cerebral hemodynamics. About 75% of patients with carotid artery occlusion have an abnormal rCBV/rCBF ratio. However, EC-IC bypass surgery was not effec tive in preventing recurrent ischemic stroke, even when the patient had an abnormal rCBV/rCBF ratio. 16) Frackowiak6) concluded that patients with acute occlusion of a major cerebral artery sequentially call on a hemodynamic reserve by vascular dilation, quantifiable by rCBF and rCBV. When the CBF fur ther decreases, the oxygen carriage reserve is called on, quantifiable by rOEF. The cerebral tissue which
artery
occlusion
calls on the oxygen carriage reserve is supplied with insufficient CBF, and the rCMRO2 is only maintain ed by increased rOEF. Cerebral tissue in this condi tion, misery perfusion,2' is particularly susceptible to ischemia and, therefore, infarction. Usually, misery perfusion is recognized only in the superacute stage, and subsequently becomes infarction after a decrease in rCMRO2.22) Only rarely does calling on the oxygen carriage reserve persist to the subacute or chronic state.6) Powers et al.16' considered less than 10% of symptomatic patients are in this condition. Such chronic hypoperfusion due to ICA occlusion could cause progressive dementia, as generally occurs in bilateral carotid occlusion patients.") EC-IC bypass surgery has been considered effective in improving neuropsychological functions.'s.'9.23) In our study, four of five (80%) non-surgical patients with a higher OEF on the affected side suffered either recurrent ischemic stroke or progression of dementia. EC-IC bypass surgery patients with a higher OEF had no such ischemic events. Recurrent ischemic stroke did not occur in patients with a normal OEF, whether they had surgery or not. As described above, chronically ischemic cerebral tissue that calls on the oxygen carriage reserve is very fragile and is easily damaged, even by minor hemodynamic compromise and hypoxia, if appropriate vascular reconstruction surgery is not performed. Therefore, a high OEF compared to the contralateral side distal to the ICA occlusion in the chronic stage indicates that EC-IC bypass surgery may prevent both recurrent ischemic stroke and intellectual impairment. The effect of EC-IC bypass surgery on a mild to moderate hemodynamic compromise, such as calling on the hemodynamic reserve, was not determined because the vascular reactions of only a few patients were studied. Hemodynamic abnormality can now be evaluated by another method, single photon emis sion tomography, measuring either the rCBV/rCBF ratio or the vascular reactivity to CO2 inhalation 121
and injection of acetazolamide.20' Whether or not pa tients with mild or moderate hemodynamic abnor mality should receive EC-IC bypass surgery should be clarified.
13)
14)
References 1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
Barnett HJM: Delayed cerebral ischemic episodes distal to occlusion of major cerebral arteries. Neurology (Minneap) 28: 769-774, 1978 Baron JC, Bousser MG, Rey A, Guillard A, Comar D, Castaigne P: Reversal of focal “misery-perfusion syndrome” by extra-intracranial arterial bypass in hemodynamic cerebral ischemia. Stroke 12: 454-459, 1981 Dyken ML, Klatte E, Kolar OJ, Spurgeon C: Com plete occlusion of common or internal carotid arteries: Clinical significance. Arch Neurol 30: 343 346, 1974 The EC⁄IC Bypass Group: Failure of extracranial intracranial arterial bypass to reduce the risk of ischemic stroke. Results of an international random ized trial. N Engl J Med 313: 1191-1200, 1985 Fields WS, Lemak NA: Joint study of extracranial arterial occlusion: X. Internal carotid artery occlu sion. JAMA 235: 2734-2738, 1976 Frackowiak RSJ: Pathophysiology of human cerebral ischemia: Studies with positron tomography and 15oxygen, in Skoloff L (ed): Brain Imaging and Brain Function. New York, Raven Press, 1985, pp 139-161 Furlan AJ, Whisnatt JP, Backer HL Jr: Long-term prognosis after carotid artery occlusion. Neurology (NY) 30: 986-988, 1980 Gibbs JM, Wise RJS, Thomas DJ, Mansfield AO, Russel RWR: Cerebral hemodynamic changes after extracranial-intracranial bypass surgery. J Neurol Neurosurg Psychiatry 50: 140-150, 1987 Grillo P, Patterson RH Jr: Occlusion of the carotid artery: Prognosis (natural history) and the possibilities of surgical revascularization. Stroke 6: 17-20, 1975 Halsey JH, Morawetz RB, Blauenstein UW: The hemodynamic effect of STA-MCA bypass. Stroke 13: 163-167, 1982 Hardy WG, Lindner DW, Thomas LM, Gurdjian ES: Anticipated clinical course in carotid artery occlu sion. Arch Neurol (Chicago) 6: 138-150, 1962 Herold S, Brown MM, Frackowiak RSJ, Mansfield AO, Thomas DJ, Marshall J: Assessment of cerebral haemodynamic reserve: Correlation between PET parameters and CO2 reactivity measured by the intravenous 133Xe injection technique. J Neurol Neurosurg Psychiatry 51: 1045-1050, 1988
Leblanc R, Tyler JL, Mohr G, Meyer E, Diksic M, Yamamoto L, Taylor L, Gauthier S, Hakim A: Hemodynamic and metabolic effects of cerebral revascularization. J Neurosurg 66: 529-535, 1987 McDowell FH, Potes J, Groch S: The natural history of internal carotid and vertebral-basilar artery occlu sion. Neurology (Minneap) 11: 153-157, 1961
15) Peerless SJ, Chater NL, Ferguson GF: Multiple vessel occlusion in cerebrovascular disease. A follow up of the effects of bypass surgery on the quality of life and the incidence of stroke, in Schmiedek P (ed): Microsurgery for Stroke. New York, Springer Verlag, 1977, pp 251-259 16)
17)
18)
19)
20)
21)
22)
23)
Powers WJ, Grubb RL Jr, Raichle ME: Clinical results of extracranial-intracranial bypass surgery in patients with hemodynamic cerebrovascular disease. J Neurosurg 70: 61-67, 1989 Powers WJ, Martin WRW, Herscovitch P, Raichle ME, Grubb RL Jr: Extracranial-intracranial bypass surgery: Hemodynamic and metabolic effects. Neurology (NY) 34: 1168-1174, 1984 Samson Y, Baron JC, Bousser MG, Derlon JM, David P, Comoy J: Effects of extra-intracranial arterial bypass on cerebral blood flow and oxygen metabolism in humans. Stroke 16: 609-616, 1985 Sundt TM Jr, Fode NC, Jack CR Jr: The past, pre sent, and future of extracranial to intracranial bypass surgery. Clin Neurosurg 35: 134-153, 1988 Vorstrup S, Brun B, Lassen NA: Evaluation of the cerebral vasodilatory capacity by the Acetazolamide test before EC-IC bypass surgery in patients with oc clusion of the internal carotid artery. Stroke 17: 1291-1298, 1986 Williams M, McGee TF: Psychological study of carotid occlusion and endarterectomy. Arch Neurol (Chicago) 10: 293-297, 1964 Wise JS, Bernaddi S, Frackowiak RSJ, Legg NJ, Jones T: Serial observations on the pathophysiology of acute stroke. The transition from ischemia to in farction as reflected in regional oxygen extraction. Brain 106: 197-222, 1983 Younkin D, Hungerbuhler JP, O'Connor M, Goldberg H, Burke A, Kushner M, Hurtig H, Orbist W, Gordon J, Gur R, Reivich M: Superficial tem poral-middle cerebral artery anastomosis: Effects on vascular, neurologic, and neuropsychological func tions. Neurology (NY) 35: 462-469, 1985
Address
reprint
ment Brain
of
requests Surgical
and
kubota-machi,
to: T. Ishikawa, Neurology,
Blood Akita
Research
Vessels-Akita, 010,
Japan.
M.D.,
Depart
Institute 6-10
for
Senshu
ISHIKAWA, HADEISHI,
Nobuyuki Fumio
YASUI,
SHISHIDO*
Akifumi and
Kazuo
SUZUKI, UEMURA*
Departments of Surgical Neurology and *Radiology and Nuclear Medicine, Research Institute for Brain and Blood Vessels-A kita, Akita
Abstract Sixty-three patients with internal carotid artery occlusion manifesting as transient ischemic attack or minor stroke received superficial temporal artery-middle cerebral artery bypass surgery and medical treatment (n = 27) or medical treatment only (n = 36). Long-term follow-up showed that there was no significant difference in the outcomes. However, positron emission tomography studies suggested that patients with misery perfusion in the chronic stage benefited from extracranial-intracranial bypass surgery. Key words:
internal
non-surgical
therapy,
carotid positron
artery
occlusion,
emission
long-term
follow-up,
STA-MCA
bypass,
tomography
Introduction
Materials
and
Methods
This retrospective study included 63 patients who presented at our institute with cerebrovascular steno occlusive diseases manifesting as TIA or minor stroke between 1977 and 1988. Angiography diag gery.9"15) However, a large prospective randomized trial') has demonstrated that this surgery does not nosed arteriosclerotic occlusion of either the uni help prevent subsequent stroke even in a subgroup of lateral or bilateral ICA in all cases. All patients re ICA occlusion patients. In contrast, EC-IC bypass ceiving surgery were independent prior to surgery. surgery is considered effective in patients with hemo All medically treated patients were independent at dynamic cerebrovascular ischemic diseases 2,8,10,13,17,18) discharge, although some needed rehabilitation. Pa About 75% of ICA occlusion patients are thought to tients with major completed stroke because of ICA have abnormal cerebral hemodynamics.16) occlusion were excluded whether they had surgery or Our study followed patients with ICA occlusion not. Patients with a diagnosis of embolic ICA occlu suffering either transient ischemic attack (TIA) or sion originating extracranially, moyamoya disease, minor stroke for a long period. Groups of patients arteritis, or traumatic ICA occlusion were also ex receiving EC-IC bypass surgery and medical treat cluded. Bilateral carotid angiography was performed ment were compared to assess the effectiveness of on all patients, and vertebral angiography on many EC-IC bypass in preventing recurrent ischemic to confirm side and site of the ICA occlusion. Any stroke and the final outcome. Positron emission past history of hypertension, diabetes mellitus, and ischemic heart disease was considered. Cases with tomography (PET) was used to investigate the occur rence of recurrent ischemic stroke and the cerebral clinical symptoms not necessarily caused by the ICA blood flow (CBF) and oxygen metabolism in some pa occlusion were also included in the study. tients. Twenty-seven patients received EC-IC bypass surgery (surgical group). The other 36 patients re Received January 7, 1991; Accepted May 2, 1991 ceived only medical treatment (non-surgical group).
Internal carotid artery (ICA) occlusion is the most common arterial lesion considered suitable for ex tracranial-intracranial (EC-IC) arterial bypass sur
The EC-IC bypass surgery was expected to prevent recurrent ischemic stroke. Patients were placed in the non-surgical group when: 1) the patient or family rejected surgery, 2) the patient was included in the non-surgical group in the EC-IC Bypass Study,') 3) the attending neurologist was not inclined to surgical treatment, 4) PET studies contraindicated EC-IC bypass surgery. All 63 patients were followed for a long period. Clinical course following discharge and the final out come were evaluated using medical records and in terviews with the patient or family by telephone or letter. The occurrence of recurrent ischemic stroke,
Table
1
Clinical
profiles
bypass
group
of
patients
and non-surgical
progression of dementia, functional level of the pa tient, and the cause of death (if applicable) were investigated. Death was considered stroke-related if occurring as a result of ischemic stroke or related complications. Since 1984, a PET study was made in 17 of the 63 patients for a quantitative evaluation of CBF and oxygen metabolism. The relationship between the PET study and the clinical course was also evalu ated. Table
2
Medical
treatment
Table
3
Outcome
Table
4
Final
for patients
Results Table 1 summarizes
the clinical profiles of the two
groups. No significant difference was recognized be tween the clinical profiles of these two groups, except for the sex distribution (p < 0.05). A superficial temporal artery-middle cerebral artery (STA-MCA) bypass was performed on a total of 28 sides among the 27 patients in surgical group. A double STA-MCA anastomosis was made on 22 sides, and on one side a triple anastomosis. The other four sides in four patients were single anastomoses. No perioperative death occurred. Only one patient developed occlusion of a MCA branch perioperatively, resulting in permanent neurological deficit. Postoperative angiography demonstrated asymptomatic occlusion of one of the double STA MCA bypasses in two patients. No standard medical treatment for the prevention of further cerebral infarction has been established at our institute. Therefore, various agents were given to the patients in each group (Table 2). Antiplatelet agents, such as acetylsalicylic acid and ticlopidine, which are believed to prevent ischemic strokes, were prescribed for about two-thirds of the patients in both groups. However, whether all these patients continued to receive these medicines during follow up is unclear. Aggressive hypertension was also con trolled if necessary. Table 3 summarizes the observations during the
of the patients
outcome
of patients
in
the group
EC-IC
Table
5
Outcomes
and
results
from
the PET
study
follow-up period in both groups. Recurrent ischemic stroke includes perioperative ischemic attacks. The total recurrent ischemic stroke incidence in the surgical group was 4.7% per year. The incidence ipsilateral to the ICA occlusion was 3.1 % per year. The total recurrent ischemic stroke incidence in the non-surgical group was 6.4% per year. The incidence ipsilateral to the ICA occlusion was 4.0% per year. There were no significant difference in the incidence of recurrent ischemic strokes and in the incidence of death or stroke-related death between the two groups. Table 4 summarizes the outcome at the time of the survey. There were no significant differences between the two groups. The regional CBF (rCBF), the regional oxygen ex traction fraction (rOEF), regional metabolic rate of oxygen (rCMR02), and the regional cerebral blood volume (rCBV) were quantitatively measured by PET using the continuous inhalation of C1502 and 150 2 and single inhalation of C150 (Table 5). All 17 patients had a unilaterally occluded ICA. The PET study was performed preoperatively in the surgical group. The time delay between the most recent stroke and PET study was significantly longer in the surgical group, but all PET studies were performed during either the subacute or chronic stage of cerebral infarction. The OEF values in the perfusion territory of the MCA distal to the occluded ICA were compared to those of the non-affected side. The four surgical patients with higher OEF suffered no recur rent ischemic stroke during follow-up. One month after the operation they were re-examined. Three demonstrated normalized OEF due to increased
CBF. Five patients in the non-surgical group had a higher OEF. Two suffered recurrent ischemic stroke ipsilateral to the ICA occlusion, and in another two mild dementia progressed. The incidence of ipsi lateral recurrent ischemic stroke was 12.2% per year. If progressive dementia is included, this in cidence was 24.4% per year. No patient with normal OEF in either group suffered recurrent ischemic stroke or progressive dementia. Discussion This study was not a randomized
trial, but the two
groups had well-matched epidemiological factors (age and past history) and clinical features (type of ischemic stroke, side and site of ICA occlusion). In this study the patients of both groups received medical treatment and more than half received an tiplatelet agents. This study, therefore, investigated the combined effects of EC-IC bypass surgery and medical treatment. In this respect, this study is different from the EC-IC Bypass Study." Table 6 summarizes published data on the long-term out come of common carotid artery and ICA occlu sion. 3,5,7,9,1'''4 The incidence of recurrent ischemic stroke in pa tients with carotid occlusion was about 3-6% per year, with 0-5% per year of strokes occurring ipsi lateral to the carotid occlusion. Our results in the non-surgical group showed the incidence of recur rent ischemic stroke is 6.4% per year, with 4.0% per year occurring ipsilateral to the ICA occlusion. Our results therefore correspond with previous reports. The EC-IC Bypass Study" found no benefits from
Table
6
Outcomes
in cases
of common
and internal
carotid
surgery for the subgroup of patients with ICA occlu sion. The incidence of recurrent ischemic stroke for the "medical group" was 5.2% per year for patients with no symptoms between the angiographic demonstration and randomization, and 6.9% per year for patients with symptoms. For the "surgical group," the incidences were 4.7% per year and 9.1 % per year, respectively. In our study, the total in cidence of recurrent ischemic stroke in the surgical group was 4.7% per year, and ipsilaterally 3.1 % per year. These incidences were somewhat better than those in the non-surgical group. However, the difference was not significant. Final outcome and incidence of stroke related death were also not significantly different. Our study therefore fails to prove any benefit from EC-IC bypass surgery for the prevention of recurrent ischemic stroke and stroke related death in patients with ICA occlusion. Hemodynamic stroke has been considered a good indication for EC-IC bypass surgery.2.g,1o,'3,",'8' However, it is not effective for thromboembolic stroke.') EC-IC bypass surgery can achieve hemodynamic improvement in patients with a hemodynamic abnormality .2,1,11,11,16 's' However, there is no epidemiological proof that EC-IC bypass surgery is effective for hemodynamic stroke. Powers et al. ") used an abnormal rCBV/rCBF ratio measured by PET, to define abnormal cerebral hemodynamics. About 75% of patients with carotid artery occlusion have an abnormal rCBV/rCBF ratio. However, EC-IC bypass surgery was not effec tive in preventing recurrent ischemic stroke, even when the patient had an abnormal rCBV/rCBF ratio. 16) Frackowiak6) concluded that patients with acute occlusion of a major cerebral artery sequentially call on a hemodynamic reserve by vascular dilation, quantifiable by rCBF and rCBV. When the CBF fur ther decreases, the oxygen carriage reserve is called on, quantifiable by rOEF. The cerebral tissue which
artery
occlusion
calls on the oxygen carriage reserve is supplied with insufficient CBF, and the rCMRO2 is only maintain ed by increased rOEF. Cerebral tissue in this condi tion, misery perfusion,2' is particularly susceptible to ischemia and, therefore, infarction. Usually, misery perfusion is recognized only in the superacute stage, and subsequently becomes infarction after a decrease in rCMRO2.22) Only rarely does calling on the oxygen carriage reserve persist to the subacute or chronic state.6) Powers et al.16' considered less than 10% of symptomatic patients are in this condition. Such chronic hypoperfusion due to ICA occlusion could cause progressive dementia, as generally occurs in bilateral carotid occlusion patients.") EC-IC bypass surgery has been considered effective in improving neuropsychological functions.'s.'9.23) In our study, four of five (80%) non-surgical patients with a higher OEF on the affected side suffered either recurrent ischemic stroke or progression of dementia. EC-IC bypass surgery patients with a higher OEF had no such ischemic events. Recurrent ischemic stroke did not occur in patients with a normal OEF, whether they had surgery or not. As described above, chronically ischemic cerebral tissue that calls on the oxygen carriage reserve is very fragile and is easily damaged, even by minor hemodynamic compromise and hypoxia, if appropriate vascular reconstruction surgery is not performed. Therefore, a high OEF compared to the contralateral side distal to the ICA occlusion in the chronic stage indicates that EC-IC bypass surgery may prevent both recurrent ischemic stroke and intellectual impairment. The effect of EC-IC bypass surgery on a mild to moderate hemodynamic compromise, such as calling on the hemodynamic reserve, was not determined because the vascular reactions of only a few patients were studied. Hemodynamic abnormality can now be evaluated by another method, single photon emis sion tomography, measuring either the rCBV/rCBF ratio or the vascular reactivity to CO2 inhalation 121
and injection of acetazolamide.20' Whether or not pa tients with mild or moderate hemodynamic abnor mality should receive EC-IC bypass surgery should be clarified.
13)
14)
References 1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
Barnett HJM: Delayed cerebral ischemic episodes distal to occlusion of major cerebral arteries. Neurology (Minneap) 28: 769-774, 1978 Baron JC, Bousser MG, Rey A, Guillard A, Comar D, Castaigne P: Reversal of focal “misery-perfusion syndrome” by extra-intracranial arterial bypass in hemodynamic cerebral ischemia. Stroke 12: 454-459, 1981 Dyken ML, Klatte E, Kolar OJ, Spurgeon C: Com plete occlusion of common or internal carotid arteries: Clinical significance. Arch Neurol 30: 343 346, 1974 The EC⁄IC Bypass Group: Failure of extracranial intracranial arterial bypass to reduce the risk of ischemic stroke. Results of an international random ized trial. N Engl J Med 313: 1191-1200, 1985 Fields WS, Lemak NA: Joint study of extracranial arterial occlusion: X. Internal carotid artery occlu sion. JAMA 235: 2734-2738, 1976 Frackowiak RSJ: Pathophysiology of human cerebral ischemia: Studies with positron tomography and 15oxygen, in Skoloff L (ed): Brain Imaging and Brain Function. New York, Raven Press, 1985, pp 139-161 Furlan AJ, Whisnatt JP, Backer HL Jr: Long-term prognosis after carotid artery occlusion. Neurology (NY) 30: 986-988, 1980 Gibbs JM, Wise RJS, Thomas DJ, Mansfield AO, Russel RWR: Cerebral hemodynamic changes after extracranial-intracranial bypass surgery. J Neurol Neurosurg Psychiatry 50: 140-150, 1987 Grillo P, Patterson RH Jr: Occlusion of the carotid artery: Prognosis (natural history) and the possibilities of surgical revascularization. Stroke 6: 17-20, 1975 Halsey JH, Morawetz RB, Blauenstein UW: The hemodynamic effect of STA-MCA bypass. Stroke 13: 163-167, 1982 Hardy WG, Lindner DW, Thomas LM, Gurdjian ES: Anticipated clinical course in carotid artery occlu sion. Arch Neurol (Chicago) 6: 138-150, 1962 Herold S, Brown MM, Frackowiak RSJ, Mansfield AO, Thomas DJ, Marshall J: Assessment of cerebral haemodynamic reserve: Correlation between PET parameters and CO2 reactivity measured by the intravenous 133Xe injection technique. J Neurol Neurosurg Psychiatry 51: 1045-1050, 1988
Leblanc R, Tyler JL, Mohr G, Meyer E, Diksic M, Yamamoto L, Taylor L, Gauthier S, Hakim A: Hemodynamic and metabolic effects of cerebral revascularization. J Neurosurg 66: 529-535, 1987 McDowell FH, Potes J, Groch S: The natural history of internal carotid and vertebral-basilar artery occlu sion. Neurology (Minneap) 11: 153-157, 1961
15) Peerless SJ, Chater NL, Ferguson GF: Multiple vessel occlusion in cerebrovascular disease. A follow up of the effects of bypass surgery on the quality of life and the incidence of stroke, in Schmiedek P (ed): Microsurgery for Stroke. New York, Springer Verlag, 1977, pp 251-259 16)
17)
18)
19)
20)
21)
22)
23)
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Address
reprint
ment Brain
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requests Surgical
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Blood Akita
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Japan.
M.D.,
Depart
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