the online version of this article ( doi:10.1007/s00415 - 012 - 6498 - 2 ) contains supplementary material , which is available to authorized users .
patients with an acute basilar artery occlusion ( bao ) have a high risk of long - lasting disability and death [ 1 , 2 ] .
although higher age , analyzed as a continuous variable , has been associated with poor functional outcome after bao , only limited data are available on functional outcome in elderly patients [ 38 ] .
one small case series suggested that all patients 75  years have poor functional outcome . in another study ,
we analysed data from the basilar artery international cooperation study ( basics ) to determine outcomes in patients with bao 75  years .
basics is a prospective , observational , registry of 619 consecutive patients 18  years with an acute symptomatic bao [ 2 , 9 ] .
the protocol was approved by the ethics committee of the university medical center utrecht , the netherlands .
embolic bao was defined as complete recanalization on follow - up and no indication of dissection , or maximum deficit from onset and cardiac or vertebral source of embolism , or maximum deficit from onset with complete absence of other atherosclerotic cerebrovascular lesions .
atherosclerotic bao was defined as known symptomatic basilar artery stenosis ( > 50  % ) prior to occlusion , or residual stenosis after recanalization and no evidence of cardiac or vertebral artery source of embolism , or prior tias or stroke in the basilar artery territory and no evidence of cardiac or vertebral artery source of embolism .
primary outcome was poor functional outcome after 1  month [ predefined as modified rankin scale ( mrs ) score 46 ] .
secondary outcomes were death , insufficient vessel recanalization [ defined as thrombolysis in myocardial infarction ( timi ) score 01 ] and symptomatic intracranial hemorrhage ( sich ) .
we also investigated if our conclusions changed if poor functional outcome was defined as an mrs of 36 .
sich was not predefined by the registry , and the reporting of sich was done on the basis of each investigator s judgment . for the purpose of this study , patients were divided into four age - groups , based on quartiles : 1854 , 5564 , 6574 , and 75  years .
. risk ratios ( rr ) and corresponding 95  % confidence intervals ( ci ) were calculated .
variables that affected the crude risk ratio most were used simultaneously in poisson regression analyses to calculate adjusted risk ratios ( arr ) . missing baseline data (
finally , we explored the incidence of poor functional outcome in patients 7579 , 8084 , 8589 , and 90  years or older .
baseline characteristics are listed in table  1 . in total , 162 patients ( 26  % of total cohort ) were 75  years . in this group of patients , the most common cause of stroke was embolism and 64  % had an nihss score > 20 .
treatment of any kind was initiated in 148 patients ( 91  % ) .table  1baseline characteristics according to age groupvariableall patientsn  =  6191854  yearsn  =  1535564  yearsn  =  1336574  yearsn  =  17175  yearsn  =  162male sex390 ( 63  % ) 94 ( 61  % ) 105 ( 79  % ) 116 ( 68  % ) 75 ( 46  % ) hypertension383 ( 62  % ) 41 ( 27  % ) 87 ( 65  % ) 133 ( 78  % ) 122 ( 75  % ) diabetes mellitus135 ( 22  % ) 13 ( 8  % ) 31 ( 23  % ) 49 ( 29  % ) 42 ( 26  % ) hyperlipidemia167 ( 27  % ) 30 ( 20  % ) 45 ( 34  % ) 55 ( 32  % ) 37 ( 23  % ) atrial fibrillation133 ( 21  % ) 3 ( 2  % ) 20 ( 15  % ) 42 ( 25  % ) 68 ( 42  % ) coronary artery disease109 ( 18  % ) 12 ( 8  % ) 21 ( 16  % ) 35 ( 20  % ) 41 ( 25  % ) location of basilar artery occlusion  distal third202 ( 33  % ) 42 ( 27  % ) 30 ( 23  % ) 55 ( 32  % ) 75 ( 46  % )  middle third143 ( 23  % ) 37 ( 24  % ) 29 ( 22  % ) 46 ( 27  % ) 31 ( 19  % )  proximal third274 ( 44  % ) 74 ( 48  % ) 74 ( 56  % ) 70 ( 41  % ) 56 ( 35  % ) median nihss score ( iqr)22 ( 1230)20 ( 930)20 ( 1230)22 ( 1328)25 ( 1630)nihss score > 20336 ( 54  % ) 73 ( 48  % ) 66 ( 50  % ) 93 ( 54  % ) 104 ( 64  % ) type of treatment  antithrombotics183 ( 30  % ) 47 ( 31  % ) 33 ( 25  % ) 52 ( 30  % ) 51 ( 31  % )  iv tpa or iv tpa / iat121 ( 20  % ) 25 ( 16  % ) 37 ( 28  % ) 24 ( 14  % ) 35 ( 22  % )  iat only288 ( 47  % ) 78 ( 51  % ) 59 ( 44  % ) 89 ( 52  % ) 62 ( 38  % )  no treatment27 ( 4  % ) 3 ( 2  % ) 4 ( 3  % ) 6 ( 4  % ) 14 ( 9  % ) time to treatment  03  h179 ( 29  % ) 41 ( 27  % ) 39 ( 29  % ) 49 ( 29  % ) 50 ( 31  % )  46  h190 ( 31  % ) 45 ( 29  % ) 37 ( 28  % ) 58 ( 34  % ) 50 ( 31  % )  79  h84 ( 14  % ) 22 ( 14  % ) 19 ( 14  % ) 26 ( 15  % ) 17 ( 10  % )  1012  h57 ( 9  % ) 14 ( 9  % ) 14 ( 11  % ) 16 ( 9  % ) 13 ( 8  % )  1324  h55 ( 9  % ) 17 ( 11  % ) 15 ( 11  % ) 9 ( 5  % ) 14 ( 9  % )  > 24  h27 ( 4  % ) 11 ( 7  % ) 5 ( 4  % ) 7 ( 4  % ) 4 ( 2  % ) cause of stroke  embolism224 ( 36  % ) 42 ( 27  % ) 38 ( 29  % ) 59 ( 35  % ) 85 ( 52  % )  atherosclerosis215 ( 35  % ) 39 ( 25  % ) 57 ( 43  % ) 72 ( 42  % ) 47 ( 29  % )  dissection32 ( 5  % ) 24 ( 16  % ) 5 ( 4  % ) 3 ( 2  % ) 0 ( 0  % )  other6 ( 1  % ) 2 ( 1  % ) 1 ( 1  % ) 2 ( 1  % ) 1 ( 1  % )  unknown142 ( 23  % ) 44 ( 29  % ) 30 ( 23  % ) 31 ( 18  % ) 27 ( 17  % ) nihss national institutes of health stroke scale , iqr interquartile range , iv intravenous , tpa tissue plasminogen activator , iat any intra - arterial treatment ( either intra - arterial tpa , mechanical clot disruption , or both ) baseline characteristics according to age group nihss national institutes of health stroke scale , iqr interquartile range , iv intravenous , tpa tissue plasminogen activator , iat any intra - arterial treatment ( either intra - arterial tpa , mechanical clot disruption , or both ) modified rankin scale scores for all age groups are presented in fig .  1 .
patients 75  years had a higher risk of poor functional outcome [ arr 1.33 ( 1.141.55 ) , table  2 ] and death [ arr 2.47 ( 1.753.51 ) , table  3 ] than patients aged 1854  years .
nevertheless , 35 patients ( 22  % , 95  % ci 1528  % ) of those 75  years had a good functional outcome .
no significant differences between age groups were observed for insufficient recanalization [ patients 75 vs. 1854  years arr 1.69 ( 0.953.03 ) ] and sich [ patients 75 vs. 1854  years rr 1.77 ( 0.774.06 ) ] .
since sich occurred in only 42 ( 7  % ) patients , no further analyses were performed for this outcome measure.fig .  1modified rankin scale scores according to age group .
mrs modified rankin scale scoretable  2poor functional outcome ( mrs 46 ) according to age - group1854  years5564  years6574  years75  yearstotal153 ( 25  % ) 133 ( 21  % ) 171 ( 28  % ) 162 ( 26  % ) poor outcome91/153 ( 60  % ) 85/133 ( 64  % ) 126/171 ( 74  % ) 127/162 ( 78  % ) unadjusted11.08 ( 0.901.29)1.24 ( 1.061.45)1.32 ( 1.131.54)adjusted  male sex11.06 ( 0.881.28)1.23 ( 1.051.45)1.33 ( 1.141.55 )  location of occlusion11.06 ( 0.891.27)1.26 ( 1.081.47)1.37 ( 1.181.60 )  nihss11.06 ( 0.901.25)1.22 ( 1.061.41)1.23 ( 1.061.41 )  time to treatment ( h)11.08 ( 0.901.30)1.26 ( 1.071.49)1.33 ( 1.131.56 )  type of treatment11.07 ( 0.891.29)1.24 ( 1.051.46)1.32 ( 1.121.55 )  3 factors11.05 ( 0.891.24)1.24 ( 1.071.43)1.28 ( 1.111.48 )  5 factors11.06 ( 0.901.25)1.28 ( 1.101.49)1.33 ( 1.141.55)reference group . data are number ( % ) or risk ratio ( 95  % ci)adjustment for national institutes of health stroke scale ( nihss ) score , sex , and location of occlusionadjustment for nihss score , sex , location of occlusion , time to treatment , and type of treatmenttable  3mortality according to age group1854  years5564  years6574  years75  yearstotal153 ( 25  % ) 133 ( 21  % ) 171 ( 28  % ) 162 ( 26  % ) mortality33/153 ( 22  % ) 43/133 ( 32  % ) 80/171 ( 47  % ) 84/162 ( 52  % ) unadjusted11.50 ( 1.022.21)2.17 ( 1.543.05)2.40 ( 1.723.37)adjusted  male sex11.48 ( 1.0022.19)2.16 ( 1.533.04)2.43 ( 1.733.40 )  location of occlusion11.47 ( 0.9982.16)2.22 ( 1.583.11)2.55 ( 1.833.56 )  nihss11.46 ( 1.0082.12)2.13 ( 1.552.94)2.16 ( 1.572.98 )  time to treatment ( h)11.56 ( 1.042.35)2.28 ( 1.593.27)2.41 ( 1.683.46 )  type of treatment11.55 ( 1.032.34)2.24 ( 1.563.21)2.42 ( 1.683.47 )  3 factors11.47 ( 1.022.12)2.22 ( 1.613.05)2.31 ( 1.683.17 )  5 factors11.56 ( 1.052.31)2.41 ( 1.713.39)2.47 ( 1.753.51)reference group .
data are number ( % ) or risk ratio ( 95  % ci)adjustment for national institutes of health stroke scale ( nihss ) score , sex and location of occlusionadjustment for nihss score , sex , location of occlusion , time to treatment , and type of treatment modified rankin scale scores according to age group .
mrs modified rankin scale score poor functional outcome ( mrs 46 ) according to age - group reference group .
data are number ( % ) or risk ratio ( 95  % ci ) adjustment for national institutes of health stroke scale ( nihss ) score , sex , and location of occlusion adjustment for nihss score , sex , location of occlusion , time to treatment , and type of treatment mortality according to age group reference group .
data are number ( % ) or risk ratio ( 95  % ci ) adjustment for national institutes of health stroke scale ( nihss ) score , sex and location of occlusion adjustment for nihss score , sex , location of occlusion , time to treatment , and type of treatment if poor functional outcome was defined as an mrs of 36 , the proportion of patients with poor functional outcome in each age group was 108/153 ( 71  % ) in patients 1854  years of age , 101/133 ( 76  % ) in patients
5564  years , 142/171 ( 83  % ) in patients 6574  years , and 137/162 ( 85  % ) in patients 75  years .
also when this definition was used , patients 75  years had a higher risk of poor functional outcome [ arr 1.21 ( 1.071.36 ) ] than patients aged 1854  years .
baseline characteristics of patients 75  years and their relationship with functional outcome are shown in table  4 .
the following variables were associated with an increased risk of poor functional outcome after 1  month : male sex ( rr 1.18 , 95  % ci 1.001.38 ) , location of occlusion ( middle third vs. distal third : rr 1.21 , 95  % ci 1.021.44 ) , nihss score > 20 on presentation ( rr 1.36 , 95  % ci 1.101.67 ) , type of treatment ( no treatment vs. intra - arterial thrombolytic therapy ( iat ) only : rr 1.32 , 95  % ci 1.151.52 ) , sich ( rr 1.21 , 95  % ci 1.031.43 ) , and insufficient recanalization ( rr 1.38 , 95  % ci 1.071.77).table  4characteristics of patients 75  years and risk of poor functional outcomevariablerisk of poor functional outcome ( mrs 46)rr ( 95  % ci)characteristic presentcharacteristic absentmale sex64/75 ( 85  % ) 63/87 ( 72  % ) 1.18 ( 1.001.38)hypertension98/122 ( 80  % ) 29/40 ( 73  % ) 1.11 ( 0.901.37)diabetes mellitus29/42 ( 69  % ) 98/120 ( 82  % ) 0.85 ( 0.681.05)hyperlipidemia27/37 ( 73  % ) 100/125 ( 80  % ) 0.91 ( 0.741.13)atrial fibrillation57/68 ( 84  % ) 70/94 ( 74  % ) 1.13 ( 0.96 - 1.32)coronary artery disease35/41 ( 85  % ) 92/121 ( 76  % ) 1.12 ( 0.961.32)location of basilar artery occlusion  proximal third43/56 ( 77  % ) 56/75 ( 75  % ) 1.03 ( 0.851.25 )  middle third28/31 ( 90  % ) 56/75 ( 75  % ) 1.21 ( 1.021.44)nihss score > 2090/104 ( 87  % ) 37/58 ( 64  % ) 1.36 ( 1.101.67)type of treatment  antithrombotics38/51 ( 75  % ) 47/62 ( 76  % ) 0.98 ( 0.791.22 )  iv tpa or iv tpa / iat28/35 ( 80  % ) 47/62 ( 76  % ) 1.06 ( 0.851.31 )  no treatment14/14 ( 100  % ) 47/62 ( 76  % ) 1.32 ( 1.151.52)time to treatment  46  h35/50 ( 70  % ) 38/50 ( 76  % ) 0.92 ( 0.731.17 )  79  h13/17 ( 76  % ) 38/50 ( 76  % ) 1.01 ( 0.741.37 )  10  h27/31 ( 87  % ) 38/50 ( 76  % ) 1.15 ( 0.931.41)cause of stroke  embolism65/85 ( 76  % ) 38/47 ( 81  % ) 0.95 ( 0.791.14)symptomatic intracranial hemorrhage14/15 ( 93  % ) 113/147
( 77  % ) 1.21 ( 1.031.43)insufficient recanalization18/20 ( 90  % ) 32/49 ( 65  % ) 1.38 ( 1.071.77)distal occlusion was taken as reference and is recorded under 
characteristic absent  characteristics of patients 75  years and risk of poor functional outcome distal occlusion was taken as reference and is recorded under 
characteristic absent  the proportion of patients with poor functional outcome in age subgroups 75  years was as follows : 64/82 ( 78  % ) in patients 7579  years of age , 40/49 ( 82  % ) in patients 8084  years , 16/23 ( 70  % ) in patients 8589  years , and 7/8 ( 88  % ) in patients 90  years or older .
the oldest patient with good functional outcome was 91  years of age , despite an nihss score of 21 on admission .
this patient was treated with intravenous recombinant tissue plaminogen activator ( rtpa ) only , and had an mrs score of 2 at 1  month follow - up .
the basics study shows that patients 75  years with bao have an increased risk of poor functional outcome and death compared with younger patients , despite comparable recanalization rates .
in contrast with a small previous study , our data show that a substantial group of patients 75  years survives with good functional outcome .
previously , it has been suggested that the increased risk of poor functional outcome in elderly patients resulted from a higher prevalence of atherosclerotic occlusions and consequently lower recanalization rates .
however , in our study population patients 75  years were more likely to have an embolic rather than an atherosclerotic cause of bao , mainly due to a higher prevalence of atrial fibrillation .
patients 75  years with an embolic cause of bao had a similar risk of poor functional outcome compared with patients in this age group with an atherosclerotic cause of bao .
sufficient recanalization was achieved in 71  % of patients in this age group . in patients
75  years , several baseline- and treatment - related characteristics were associated with an increased risk of poor functional outcome .
a recent large case series of patients with bao , in which only a minority of patients was 75  years , identified similar risk factors for poor functional outcome and death .
the strength of this study is that basics was a prospective registry of consecutive patients , and therefore our results are representative for daily practice .
a limitation of this study is that this was a post hoc analysis of non - randomized data , and therefore the data regarding treatment - dependent outcomes are prone to bias . due to the prospective collection of detailed data , we were able to perform poisson regression analyses to adjust for important confounding baseline characteristics .
we conclude that a substantial group of elderly patients survives with a good functional outcome .
this study can not answer the question which treatment option is superior in elderly patients , nor can it define an upper age limit above which treatment is no longer effective . these and other questions may be answered in the recently started basics trial in which patients with bao of up to 85  years of age are randomized between intravenous thrombolysis ( ivt ) alone vs. ivt followed by additional intra - arterial therapy ( http://www.trialregister.nl/trialreg/admin/rctview.asp?tc=2617 ; accessed february 1 , 2012 ) .
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this article is distributed under the terms of the creative commons attribution license which permits any use , distribution , and reproduction in any medium , provided the original author(s ) and the source are credited .
 patients with an acute basilar artery occlusion ( bao ) have a high risk of long - lasting disability and death . 
 only limited data are available on functional outcome in elderly patients with bao . using data from the basilar artery international cooperation study 
 , we aimed to determine outcomes in patients 75  years . 
 primary outcome measure was poor functional outcome ( modified rankin scale score 46 ) . 
 secondary outcomes were death , insufficient vessel recanalization ( defined as thrombolysis in myocardial infarction score 01 ) and symptomatic intracranial hemorrhage ( sich ) . 
 patients were divided into four age - groups , based on quartiles : 1854 , 5564 , 6574 , and 75  years . 
 outcomes were compared between patients 75  years and patients aged 1854  years 
 . risk ratios with corresponding 95  % confidence intervals ( ci ) were calculated and poisson regression analyses were performed to calculate adjusted risk ratios ( arr ) . 
 we included 619 patients [ 1854  years n  =  153 ( 25  % ) , 5564  years n  =  133 ( 21  % ) , 6574  years n  =  171 ( 28  % ) , and 75  years n  =  162 ( 26  % ) ] . compared with patients aged 1854  years , patients 75  years were at increased risk of poor functional outcome [ arr 1.33 ( 1.141.55 ) ] and death [ arr 2.47 ( 1.753.51 ) ] . 
 nevertheless , 35/162 ( 22  % , 95  % ci 1528  % ) of patients 75  years had good functional outcome . 
 no significant differences between age groups were observed for recanalization rate and incidence of sich . 
 although patients 75  years with bao have an increased risk of poor outcome compared with younger patients , a substantial group of patients 75  years survives with a good functional outcome.electronic supplementary materialthe online version of this article ( doi:10.1007/s00415 - 012 - 6498 - 2 ) contains supplementary material , which is available to authorized users . 
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Introduction
Methods
Results
Discussion
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