with the improvement of diagnostic imaging , the incidence of uia diagnosis is increasing , along with the national cost containment pressures associated with treatment and management . economic considerations are important in the cost - benefit evaluation of treatments , and influence healthcare coverage , reimbursement , and policy . while many studies have already compared the treatment modalities for intracranial aneurysms , surgical clipping and endovascular coiling , in terms of the procedural invasiveness , clinical and functional outcomes , and durability , few studies have investigated the economic costs for such treatments23713 ) . plus , treatment costs show distinct disparities between countries313).during the process of informed consent for clipping or coiling , uia patients are also concerned about the cost implications . therefore , the authors performed a cost comparison , and investigated the principal cost determinants of uia treatment in south korea . this study conducted a retrospective review of data from a series of consecutive patients who underwent surgical clipping or endovascular coiling of a uia at the authors ' institution between january 2011 and may 2014 . the exclusion criteria included a recent ( < 1 month ) subarachnoid hemorrhage caused by a concomitant aneurysm , giant aneurysm with a diameter > 2.5 cm , poor preoperative neurological state affecting postoperative management , and another disease or medical condition significantly increasing the hospital costs . the medical records were reviewed to obtain relevant clinical information , and all the radiological data were obtained using an electronic picture archiving and communication system . the treatment decision , surgical coiling versus endovascular coiling , was made primarily based on the findings of the digital subtraction angiography . surgical treatment was favored over endovascular treatment for patients with the following findings : 1 ) difficult navigation of the microcatheter into the aneurysm19 ) , 2 ) very small ( <3 mm ) aneurysm149 ) , 3 ) complex and wide - neck aneurysm requiring y or x stent - assisted coiling610 ) , 4 ) aneurysm with an arterial branch incorporated into the sac58 ) , 5 ) fusiform or complex aneurysmal configuration , or 6 ) aneurysmal compression of an adjacent cranial nerve11 ) , as long as the patients had no problems related to surgical accessibility or comorbidity . all the patients completed an angiographic examination , chest x - ray , and laboratory tests as a preoperative evaluation before admission , and were admitted to hospital one day before the surgical or endovascular procedure . the operative and perioperative management procedures were uniformly applied to each uia patient . for the patients who underwent surgical clipping , a postoperative computed tomography ( ct ) and ct angiography another ct scan was performed on the day of discharge to check for the occurrence of any subdural hygromas . for most surgical patients , the length of the hospital stay was 3 - 6 days . in the case of elderly patients , a longer hospital stay was usually required due to fatigue and general weakness . meanwhile , for the patients who underwent endovascular coiling , diffusion - weighted magnetic resonance imaging was commonly performed on day 1 following the procedure to evaluate any procedure - related thromboembolic phenomena . the length of the hospital stay after coiling was 3 - 4 days for most patients , irrespective of the patient 's age . the treatment costs for each patient were calculated based on the expenses incurred during the time spent as an inpatient for aneurysm treatment , including the operative and postoperative costs . the operative costs covered the neurosurgical or endovascular procedure , anesthesia , and all the materials ( e.g. , aneurysm clip , endovascular coil , and other surgical supplies ) , while the perioperative costs included the costs for the bed occupancy in the intensive care unit and regular hospital ward , radiological imaging studies , laboratory tests , and all the medications . the costs affected by patient selection ( e.g. , bed occupancy in the regular hospital ward ) were made uniform to the basic lowest cost . all the costs are all presented in korean won and us dollars based on an international conversion rate of 1100=$1 . the statistical analyses were performed using an spss software package ( version 18.0 for windows ; spss inc . , chicago , il , usa ) . plus , scientific data analysis and graphing software ( sigmaplot , version 10.0 ; systat software inc . , chicago , il , usa ) was applied for the statistical linear regression analysis . an independent t - test was used for the mean comparison between the surgical and endovascular groups . the correlation between the aneurysm diameter and the total hospital costs was assessed using a pearson correlation analysis . this study conducted a retrospective review of data from a series of consecutive patients who underwent surgical clipping or endovascular coiling of a uia at the authors ' institution between january 2011 and may 2014 . the exclusion criteria included a recent ( < 1 month ) subarachnoid hemorrhage caused by a concomitant aneurysm , giant aneurysm with a diameter > 2.5 cm , poor preoperative neurological state affecting postoperative management , and another disease or medical condition significantly increasing the hospital costs . the medical records were reviewed to obtain relevant clinical information , and all the radiological data were obtained using an electronic picture archiving and communication system . the treatment decision , surgical coiling versus endovascular coiling , was made primarily based on the findings of the digital subtraction angiography . surgical treatment was favored over endovascular treatment for patients with the following findings : 1 ) difficult navigation of the microcatheter into the aneurysm19 ) , 2 ) very small ( <3 mm ) aneurysm149 ) , 3 ) complex and wide - neck aneurysm requiring y or x stent - assisted coiling610 ) , 4 ) aneurysm with an arterial branch incorporated into the sac58 ) , 5 ) fusiform or complex aneurysmal configuration , or 6 ) aneurysmal compression of an adjacent cranial nerve11 ) , as long as the patients had no problems related to surgical accessibility or comorbidity . all the patients completed an angiographic examination , chest x - ray , and laboratory tests as a preoperative evaluation before admission , and were admitted to hospital one day before the surgical or endovascular procedure . the operative and perioperative management procedures were uniformly applied to each uia patient . for the patients who underwent surgical clipping , a postoperative computed tomography ( ct ) and ct angiography another ct scan was performed on the day of discharge to check for the occurrence of any subdural hygromas . for most surgical patients , the length of the hospital stay was 3 - 6 days . in the case of elderly patients , a longer hospital stay was usually required due to fatigue and general weakness . meanwhile , for the patients who underwent endovascular coiling , diffusion - weighted magnetic resonance imaging was commonly performed on day 1 following the procedure to evaluate any procedure - related thromboembolic phenomena . the length of the hospital stay after coiling was 3 - 4 days for most patients , irrespective of the patient 's age . the treatment costs for each patient were calculated based on the expenses incurred during the time spent as an inpatient for aneurysm treatment , including the operative and postoperative costs . the operative costs covered the neurosurgical or endovascular procedure , anesthesia , and all the materials ( e.g. , aneurysm clip , endovascular coil , and other surgical supplies ) , while the perioperative costs included the costs for the bed occupancy in the intensive care unit and regular hospital ward , radiological imaging studies , laboratory tests , and all the medications . the costs affected by patient selection ( e.g. , bed occupancy in the regular hospital ward ) were made uniform to the basic lowest cost . all the costs are all presented in korean won and us dollars based on an international conversion rate of 1100=$1 . the statistical analyses were performed using an spss software package ( version 18.0 for windows ; spss inc . , chicago , il , usa ) . plus , scientific data analysis and graphing software ( sigmaplot , version 10.0 ; systat software inc . , chicago , il , usa ) was applied for the statistical linear regression analysis . an independent t - test was used for the mean comparison between the surgical and endovascular groups . the correlation between the aneurysm diameter and the total hospital costs was assessed using a pearson correlation analysis . surgical clipping was applied to 222 patients , where a single aneurysm was clipped in 188 patients and 2 - 3 multiple aneurysms were clipped in 34 patients . while most patients underwent a superciliary keyhole approach ( n=180 , 81.1% ) , the others experienced a pterional approach ( n=31 ) , interhemispheric approach ( n=8 ) , or combined pterional and interhemispheric approach ( n=3 ) . meanwhile , the demographic and aneurysmal characteristics of the 376 patients who underwent surgical clipping ( n=188 ) or endovascular coiling ( n=188 ) for a single uia are summarized in table 1 . the ages , genders , and aneurysm locations were comparable between the surgical and endovascular groups . however , the diameters of the endovascularly - treated aneurysms were larger than those of the surgically - treated aneurysms , although the difference was small ( meansd , range : 5.92.8 mm , 2.2 - 16.0 mm vs. 5.12.2 mm , 2.0 - 14.0 mm ) when comparing the total hospital costs for surgical clipping of a single uia ( n=188 ) and endovascular coiling of a single uia ( n=188 ) , surgical treatment [ meansd : 8,280,0001,490,000 ( $ 75271355 ) ] showed significantly lower total hospital costs than endovascular treatment [ meansd : 11,700,0003,050,000 ( $ 106362773 ) , p<0.001 ] ( table 2 ) . the median and interquartile range ( iqr ) of the total hospital costs for surgical versus endovascular treatment were 7,770,000 ( $ 7064 ) and 1,440,000 ( $ 1309 ) vs. 11,440,000 ( $ 10400 ) and 3,460,000 ( $ 3145 ) , respectively . thus , the median of the total hospital costs for coiling was 47% higher than that for clipping . the higher total hospital costs for endovascular treatment were due to higher operative costs , including the medical equipment and endovascular coils . the operative costs for surgical clipping [ meansd : 5,800,000680,000 ( $ 5273618 ) ] were significantly lower than the operative costs for endovascular coiling [ meansd : 9,310,0002,800,000 ( $ 84642545 ) , p<0.001 ] . the median and iqr of the operative costs for surgical versus endovascular treatment were 5,600,000 ( $ 5091 ) and 730,000 ( $ 664 ) vs. 9,140,000 ( $ 8309 ) and 3,430,000 ( $ 3118 ) , respectively . the price of one endovascular coil was approximately 550,000 ( $ 500 ) , while the price of one surgical clip was approximately 140,000 ( $ 127 ) . in addition , endovascular treatment of a single aneurysm required a considerable increase in the number of coils according to the diameter of the aneurysm , whereas most surgical cases only required one to three aneurysm clips . notwithstanding , there was no statistical difference in the perioperative costs between the surgical and endovascular groups [ meansd : 2,480,0001,070,000 ( $ 2255973 ) vs. 2,400,0001,310,000 ( $ 21821191 ) ] . in the multi regression analysis , the factors significantly associated with the total hospital costs for endovascular treatment of a single uia were the aneurysm diameter ( p<0.001 ) and patient age ( p=0.014 ) , while the patient gender and aneurysm location were not associated . in the case of surgical treatment , the only factor significantly associated with the total hospital costs was the aneurysm diameter ( p<0.001 ) , while the patient age , gender , and aneurysm location were not associated . the pearson correlation analysis of the endovascular group showed a strong positive correlation ( r=0.77 ) between the aneurysm diameter and the total hospital costs ( fig . 1a ) , whereas only a weak positive correlation ( r=0.16 ) was revealed between the patient age and the total hospital costs . meanwhile , the pearson correlation analysis of the surgical group showed a weak positive correlation ( r=0.26 ) between the aneurysm diameter and the total hospital costs ( fig . a simple linear regression analysis was used to develop an equation for predicting the dependent variable ( y , total hospital costs ) given a value ( x , aneurysm diameter ) for the independent variable . for the endovascular group , this equation was y ( )= 6,658,630 + 855,250x ( mm ) or y ( $ ) = 6053.3 + 777.5x ( mm ) . the value of r was 0.6004 . thirty four patients were surgically treated for two ( n=27 ) or three ( n=7 ) uias during a single operation , however , no patient received endovascular treatment for multiple uias during a single session . the mean value of the total hospital costs for the surgical treatment of two uias was 10,810,0002,960,000 ( $ 98272691 ) , while the mean value for the surgical treatment of three uias was 11,540,0001,430,000 ( $ 104911300 ) . for both treatment groups , no direct mortality or permanent morbidity adversely affecting the glasgow outcome scale ensued from the treatments . two patients in the surgical group developed venous infarction and transient somnolence after clipping a pericallosal artery aneurysm , yet both patients recovered without neurological deficits . meanwhile , a patient in the endovascular group developed a thromboembolism and transient leg monoparesis after coiling an anterior communicating artery aneurysm . surgical clipping was applied to 222 patients , where a single aneurysm was clipped in 188 patients and 2 - 3 multiple aneurysms were clipped in 34 patients . while most patients underwent a superciliary keyhole approach ( n=180 , 81.1% ) , the others experienced a pterional approach ( n=31 ) , interhemispheric approach ( n=8 ) , or combined pterional and interhemispheric approach ( n=3 ) . meanwhile , the demographic and aneurysmal characteristics of the 376 patients who underwent surgical clipping ( n=188 ) or endovascular coiling ( n=188 ) for a single uia are summarized in table 1 . the ages , genders , and aneurysm locations were comparable between the surgical and endovascular groups . however , the diameters of the endovascularly - treated aneurysms were larger than those of the surgically - treated aneurysms , although the difference was small ( meansd , range : 5.92.8 mm , 2.2 - 16.0 mm vs. 5.12.2 mm , 2.0 - 14.0 mm ) when comparing the total hospital costs for surgical clipping of a single uia ( n=188 ) and endovascular coiling of a single uia ( n=188 ) , surgical treatment [ meansd : 8,280,0001,490,000 ( $ 75271355 ) ] showed significantly lower total hospital costs than endovascular treatment [ meansd : 11,700,0003,050,000 ( $ 106362773 ) , p<0.001 ] ( table 2 ) . the median and interquartile range ( iqr ) of the total hospital costs for surgical versus endovascular treatment were 7,770,000 ( $ 7064 ) and 1,440,000 ( $ 1309 ) vs. 11,440,000 ( $ 10400 ) and 3,460,000 ( $ 3145 ) , respectively . thus , the median of the total hospital costs for coiling was 47% higher than that for clipping . the higher total hospital costs for endovascular treatment were due to higher operative costs , including the medical equipment and endovascular coils . the operative costs for surgical clipping [ meansd : 5,800,000680,000 ( $ 5273618 ) ] were significantly lower than the operative costs for endovascular coiling [ meansd : 9,310,0002,800,000 ( $ 84642545 ) , p<0.001 ] . the median and iqr of the operative costs for surgical versus endovascular treatment were 5,600,000 ( $ 5091 ) and 730,000 ( $ 664 ) vs. 9,140,000 ( $ 8309 ) and 3,430,000 ( $ 3118 ) , respectively . the price of one endovascular coil was approximately 550,000 ( $ 500 ) , while the price of one surgical clip was approximately 140,000 ( $ 127 ) . in addition , endovascular treatment of a single aneurysm required a considerable increase in the number of coils according to the diameter of the aneurysm , whereas most surgical cases only required one to three aneurysm clips . notwithstanding , there was no statistical difference in the perioperative costs between the surgical and endovascular groups [ meansd : 2,480,0001,070,000 ( $ 2255973 ) vs. 2,400,0001,310,000 ( $ 21821191 ) ] . in the multi regression analysis , the factors significantly associated with the total hospital costs for endovascular treatment of a single uia were the aneurysm diameter ( p<0.001 ) and patient age ( p=0.014 ) , while the patient gender and aneurysm location were not associated . in the case of surgical treatment , the only factor significantly associated with the total hospital costs was the aneurysm diameter ( p<0.001 ) , while the patient age , gender , and aneurysm location were not associated . the pearson correlation analysis of the endovascular group showed a strong positive correlation ( r=0.77 ) between the aneurysm diameter and the total hospital costs ( fig . 1a ) , whereas only a weak positive correlation ( r=0.16 ) was revealed between the patient age and the total hospital costs . meanwhile , the pearson correlation analysis of the surgical group showed a weak positive correlation ( r=0.26 ) between the aneurysm diameter and the total hospital costs ( fig . a simple linear regression analysis was used to develop an equation for predicting the dependent variable ( y , total hospital costs ) given a value ( x , aneurysm diameter ) for the independent variable . for the endovascular group , this equation was y ( )= 6,658,630 + 855,250x ( mm ) or y ( $ ) = 6053.3 + 777.5x ( mm ) . thirty four patients were surgically treated for two ( n=27 ) or three ( n=7 ) uias during a single operation , however , no patient received endovascular treatment for multiple uias during a single session . the mean value of the total hospital costs for the surgical treatment of two uias was 10,810,0002,960,000 ( $ 98272691 ) , while the mean value for the surgical treatment of three uias was 11,540,0001,430,000 ( $ 104911300 ) . for both treatment groups , no direct mortality or permanent morbidity adversely affecting the glasgow outcome scale ensued from the treatments . two patients in the surgical group developed venous infarction and transient somnolence after clipping a pericallosal artery aneurysm , yet both patients recovered without neurological deficits . meanwhile , a patient in the endovascular group developed a thromboembolism and transient leg monoparesis after coiling an anterior communicating artery aneurysm . previous cost comparisons of surgical clipping and endovascular coiling of intracranial aneurysms have revealed distinct disparities between different countries . the international subarachnoid aneurysm trial ( isat ) , primarily conducted in europe , showed no significant cost difference between surgical and endovascular groups at a 1-year or 2-year follow - up13 ) . while the endovascular patients had higher costs related to the initial intervention and subsequent procedures due to recurrences , this was offset by lower costs related to the shorter hospital stay and fewer complications . however , a national analysis using a nationwide inpatient sample in the united states showed significantly higher total hospital costs for surgical clipping of both ruptured and unruptured aneurysms when compared with endovascular coiling3 ) . in contrast , the present study showed significantly lower costs for surgical clipping of uias , attributable to the lower device cost of clips over coils and good surgical results with minimal complications . in the present surgical case series , the advantage of lower economic costs was also enhanced by the reduced surgical invasiveness of a keyhole approach used on 81% of the patients . radovanovic et al.12 ) previously reported that minimally invasive surgery reduced hospital costs by decreasing the operative time and length of the hospital stay when compared with conventional surgery . however , in the present study , the impact of minimally invasive surgery on the treatment costs was not critical , as postoperative costs including hospital bed charges are not high in south korea . since the total hospital costs associated with endovascular coiling of a uia varied predictably as a function of the aneurysm diameter , the costs for endovascular coiling of a uia can be estimated before the procedure using the suggested equation provided by a simple linear regression analysis , where r is a statistical measure of the closeness of the data to the fitted regression line . thus , when the value of r is 0.6 , 60% of the data is on the straight line . first , it is based on a retrospective review of a case series from a single institution . as the surgical techniques and results affecting treatment costs can vary significantly between medical institutions , it is difficult to make generalizations . second , it does not include any long - term economic impact related to the surgical and endovascular treatment of uias . for example , the number of postoperative angiograms , outpatient services , and retreatments can be higher in the case of endovascular treatment . in south korea , the surgical clipping of uias was found to incur lower total hospital costs than endovascular coiling when the surgical results were favorable without significant complications . plus , a strong positive correlation was noted between an increase in the aneurysm diameter and a dramatic increase in the costs of endovascular coiling .