only one did well and , accordingly , he emphasized a high surgical risk in dealing with infratentorial meningiomas25 ) . because of its deep location , narrow visual field of operation and proximity to cranial nerves , brain stem and important blood vessels , surgical intervention for this pathology have a high lethal and crippled rate16 ) .
clinical presentation and microsurgical anatomy , particularly in regard to cranial nerve dislocation , critically depend on the tumor 's dural origin22 ) .
infratentorial meningiomas include cerebellar convexity , tentorial , cerebellopontine angle , jugular foramen , petroclival , peritorcula , and foramen magnum .
however , infratentorial meningiomas have been a challenge for operation , because of its close proximity to critical vascular and neurologic structures and slow growth25 ) . in the early series ,
the surgical try to remove these lesions was associated with high rates of morbidity and mortality9 ) . as developing radiologic tools , microsurgical techniques and surgical approaches of these tumors ,
surgical management has been evolving and shown good outcomes along with a decrease in surgical morbidity and pamortality2,11,20,28 ) . despite these improvements , surgery for infratentorial meningiomas
, we analyzed surgical outcomes of patients with infratentorial meningiomas surgically treated at our institution to postulate the predictors for surgical resection , recurrence , complication , and survival .
the study is in compliance with the declaration of helsinki ( sixth revision , 2008 ) .
this study fulfils all the requirements for patient anonymity was approved by the institutional review board . between april 1993 and may 2013 , 782 case of intracranial meningioma
were surgically resected at our institution . among these cases , 158 patients ( 20.2% )
were diagnosed with infratentorial meningioma by means of radiological studies [ non - enhanced and enhanced computed tomographic ( ct ) scanning and magnetic resonance imaging ( mri ) ] and their surgical records .
recurred cases were excluded from this study . to define the clinical and radiological characteristics of the patients , several variables such as age , sex , presenting symptoms , pathology , tumor features ( size , location , peritumoral edema ) , preoperative and postoperative kps , postoperative transient / permanent complications , recurrence and survival rate were evaluated .
the patients consisted of 32 males and 126 females ( female predominance , 79.7% ) , with a median age of 57.1 years ( range , 16 - 77 years ) .
the most common presenting symptoms were headache , followed by dizziness and disturbance of gait .
the exact location of the patients was decided by radiological study and operation records , with regard to the origin of the mass , including tentorial meningioma in 39 patients , cerebellopontine angle ( cpa ) in 75 patietns , petroclival in 21 patients , peritorcular in 8 patients , cerebellar convexity in 7 patients , foramen magnum in 6 patients , and jugular foramen in 2 patients .
tumor locations were classified into 3 groups according to their origin site ( group i , cerebellopontine angle & cerebellar convexity ; group ii , tentorial & peritorcular ; group iii , petroclival & other skull base location ) . based on t1-weighted enhanced & t2-weighted non - enhanced mri , the maximal size of the tumor and peri - tumoral edema was evaluated .
four centimeter was cut - off value as the size parameter ( < 4 cm vs. 4 cm ) . according to the peri - tumoral edema , the patients were divided into two groups [ none or minimal ( < 5 mm in edema thickness ) vs. moderate or severe ( 5 mm in edema thickness ) ] .
gross total resection was defined as simpson 's grades i and ii resection without any visible tumor remnant on surgical finding and follow - up mri .
all tumors were graded pathologically according to the world health organization ( who ) classification system . according to the pamortality
had been classified by who grade that grade i in 148 patients , grade ii & iii in 10 ( 9 patients in grade ii & 1 in iii ) . on follow - up mri ,
new enhancing mass in completely resected case or re - growing symptomatic mass in non - completely resected case was regarded as a recurred lesion .
surgery - related complication was defined as a new developed neurological deficit or aggravated pre - existing deficit .
the transient complication was defined as the new or aggravated postoperative problem resolved generally within 3 - 6 months after the operation . if the problem persisted or needed another operation , it was regarded as the permanent complication .
the time to measure of post - operative kps was 6 months after the operation .
all surviving patients were monitored ; the mean duration of follow - up was 48.4 months with a range of 0.8 to 242.2 months .
recurrence - free survival ( rfs ) was calculated as the time from surgery to the date of recurrence .
the probability of rfs was analyzed according to the kaplan - meier method and compared with the log - rank test .
overall survival was also calculated as the time from surgery to the date of death or last follow - up visit .
for the multivariate analysis , independent prognostic factors were determined using the cox 's proportional hazards model .
the relation between resection degree / permanent complication occurrence and categorical variables was compared by using a chi - square test or fisher - exact probability test .
all statistical analyses were performed using spss version 20.0 software program for windows ( chicago , il , usa ) .
the study is in compliance with the declaration of helsinki ( sixth revision , 2008 ) .
this study fulfils all the requirements for patient anonymity was approved by the institutional review board . between april 1993 and may 2013 , 782 case of intracranial meningioma
were surgically resected at our institution . among these cases , 158 patients ( 20.2% )
were diagnosed with infratentorial meningioma by means of radiological studies [ non - enhanced and enhanced computed tomographic ( ct ) scanning and magnetic resonance imaging ( mri ) ] and their surgical records .
to define the clinical and radiological characteristics of the patients , several variables such as age , sex , presenting symptoms , pathology , tumor features ( size , location , peritumoral edema ) , preoperative and postoperative kps , postoperative transient / permanent complications , recurrence and survival rate were evaluated .
the patients consisted of 32 males and 126 females ( female predominance , 79.7% ) , with a median age of 57.1 years ( range , 16 - 77 years ) .
the most common presenting symptoms were headache , followed by dizziness and disturbance of gait .
the exact location of the patients was decided by radiological study and operation records , with regard to the origin of the mass , including tentorial meningioma in 39 patients , cerebellopontine angle ( cpa ) in 75 patietns , petroclival in 21 patients , peritorcular in 8 patients , cerebellar convexity in 7 patients , foramen magnum in 6 patients , and jugular foramen in 2 patients .
tumor locations were classified into 3 groups according to their origin site ( group i , cerebellopontine angle & cerebellar convexity ; group ii , tentorial & peritorcular ; group iii , petroclival & other skull base location ) . based on t1-weighted enhanced & t2-weighted non - enhanced mri , the maximal size of the tumor and peri - tumoral edema was evaluated .
four centimeter was cut - off value as the size parameter ( < 4 cm vs. 4 cm ) . according to the peri - tumoral edema , the patients were divided into two groups [ none or minimal ( < 5 mm in edema thickness ) vs. moderate or severe ( 5 mm in edema thickness ) ] .
gross total resection was defined as simpson 's grades i and ii resection without any visible tumor remnant on surgical finding and follow - up mri .
all tumors were graded pathologically according to the world health organization ( who ) classification system . according to the pamortality
had been classified by who grade that grade i in 148 patients , grade ii & iii in 10 ( 9 patients in grade ii & 1 in iii ) . on follow - up mri ,
new enhancing mass in completely resected case or re - growing symptomatic mass in non - completely resected case was regarded as a recurred lesion .
surgery - related complication was defined as a new developed neurological deficit or aggravated pre - existing deficit .
the transient complication was defined as the new or aggravated postoperative problem resolved generally within 3 - 6 months after the operation . if the problem persisted or needed another operation , it was regarded as the permanent complication .
the time to measure of post - operative kps was 6 months after the operation .
all surviving patients were monitored ; the mean duration of follow - up was 48.4 months with a range of 0.8 to 242.2 months .
recurrence - free survival ( rfs ) was calculated as the time from surgery to the date of recurrence .
the probability of rfs was analyzed according to the kaplan - meier method and compared with the log - rank test .
overall survival was also calculated as the time from surgery to the date of death or last follow - up visit . for the multivariate analysis
the relation between resection degree / permanent complication occurrence and categorical variables was compared by using a chi - square test or fisher - exact probability test .
all statistical analyses were performed using spss version 20.0 software program for windows ( chicago , il , usa ) .
for some cases , far lateral , subtemporal , or orbitozygomatic route was selected to resect the lesion located on skull base region . in our series ,
129 patients ( 81.6% , 129/158 ) were classified into simpson 's grade i and ii , 28 patients ( 17.7% ) into grade iii and iv and 1 patient ( 0.6% ) into grade v. on univariate analysis , female ( p=0.019 ) , non - skull base location ( p<0.001 ) and postoperative kps over than 90 ( p=0.012 ) were significantly related with the possibility of complete resection ( table 2 ) .
however , only non - skull base location was associated with complete resection , on multivariate analysis [ hazard ratio ( hr ) : 0.162 , 95% confidence index ( ci ) : 0.065 - 0.405 , p<0.001 ] . in this study ,
recurrence rate was 13.3% ( 21/158 ) and the 5- , 10- , and 15-year recurrence rates were 8.2% , 12.0% , and 13.3% , respectively ( fig .
the results of analyses of the variables that could be correlated with recurrence are shown in fig . 2 and table 3 .
on univariate analysis , age , pathology , postoperative kps , postoperative complication , edema , size , preoperative symptom and simpson 's grade showed statistical significance .
the patient 's age at the operation was important factor for rfs [ mean value , 36.55.2 months ( group < 40 years ) vs. 155.512.9 months ( 40 group < 60 years ) , 107.66.5 months ( group 60 years ) , p=0.004 ] .
the younger - aged group showed shorter rfs than the older - aged group ( mean value , 36.55.2 months vs. 153.411.1 months , p=0.001 ) .
the more aggressive pathology group ( who grade ii and iii ) showed the recurrence in earlier postoperative period than the benign group ( mean value , 45.612.5 months vs. 155.711.1 months , p<0.001 ) .
the size of tumor was also an important factor [ mean value , 175.29.8 months ( group < 4 cm ) vs. 107.712.9 months ( 4 cm group < 6 cm ) , 106.322.8 months ( group 6 cm ) , p=0.026 ] . in the group with large - size tumor ( 4 cm ) ,
the rfs was shorter than small - size group ( mean value , 175.29.8 months vs. 113.311.1 months , p=0.007 ) .
the patient with brain stem or cranial nerve sign showed a shorter rfs time , compared to the patient with other minor symptoms ( value , 157.912.8 months vs. 113.811.4 months , p=0.038 ) . in regard to the peritumoral edema , higher edema group ( moderate or severe ) was significantly associated with shorter rfs ( mean value , 168.111.4 months vs. 73.08.6 months , p<0.001 ) . not surprisingly , non - complete resection group ( simpson 's grade iii - v ) demonstrated a shorter rfs compared to complete resection group ( mean value , 154.012.1 months vs. 114.021.9 months , p=0.002 ) .
the absence of postoperative complication ( mean value , 157.611.3 months vs. 70.412.4 months , p=0.001 ) and postoperative kps over 90 ( mean value , 163.212.0 months vs. 71.59.7 months , p<0.001 ) were significantly related with recurrence in a longer follow - up period .
on multivariate analysis , pathologic grade , postoperative kps , peritumoral edema and resection degree were independent predictable factors for tumor recurrence . benign pathology ( hr 0.109 , 95% ci 0.026 - 0.453 , p=0.002 ) , postoperative kps over 90 ( hr 0.078 , 95% ci 0.025 - 0.243 , p<0.001 ) , low peritumoral edema ( hr 0.134 , 95% ci 0.046 - 0.392 , p<0.001 ) , and complete resection ( hr 0.226 , 95% ci 0.077 - 0.669 , p=0.007 ) were significantly associated with longer rfs time .
the incidence of death rate was 5.0% over follow - up period ( 8/158 ) .
the surgery - related mortality which the death occurred within one month after resection was 3.16% in this study ( 5/158 ) .
the 5- , 10- , and 15-year survival rates were 96.2% , 94.9% , and 94.9% , respectively ( fig .
the results of analyses of the variables that could be correlated with survival time are shown in fig . 4 and table 4 .
on univariate analysis , pathology , location , size , postoperative complication and kps , and simpson 's grade showed statistical significance .
the more aggressive pathology group ( who grade ii and iii ) showed a shorter survival time than the benign group ( mean value , 40.116.2 months vs. 227.46.2 months , p<0.001 ) .
the tumor location was important factor for survival time [ mean value , 167.16.7 months ( group i ) vs. 236.65.5 months ( group ii ) , 98.08.6 months ( group iii ) , p=0.009 ] .
the group located at skull base showed shorter survival time than the non - skull base group ( mean value , 98.08.6 months vs. 232.36.3 months , p=0.002 ) .
the size of tumor is also important variable in survival time [ mean value , 200.52.6 months ( group < 4 cm ) vs. 192.120.8 months ( 4 cm group < 6 cm ) , 152.711.2 months ( group 6 cm ) , p=0.023 ] . in larger - sized group
( 4 cm ) , the survival time was shorter compared that of small - size group ( mean value , 200.52.6 months vs. 200.815.9 months , p=0.008 ) . interestingly , non - complete resection group ( simpson 's grade iii - v ) demonstrated a shorter survival time than the complete resection group ( mean value , 232.85.7 months vs. 139.117.2 months , p<0.001 ) . with regard of permanent complication after surgical resection , the presence of complication was significantly related with shorter survival time ( mean value , 233.14.5 months vs. 85.912.9 months , p=0.001 ) .
the patient with low level of postoperative kps ( < 90 ) also showed shorter survival time , compared to the patient with higher score ( mean value , 239.42.8 months vs. 89.79.2 months , p<0.001 ) .
our study showed that the patient lesser than 90 in preoperative kps survived shorter than the patients of high level kps , with a marginal statistical significance ( mean value , 234.54.4 months vs. 132.910.2 months , p=0.051 ) .
on multivariate analysis , pathology , resection degree and postoperative kps were independent predictable factors for survival rate .
benign pathology ( hr 0.041 , 95% ci 0.005 - 0.343 , p=0.003 ) , complete resection ( hr 0.150 , 95% ci 0.029 - 0.769 , p=0.023 ) and postoperative kps over 90 ( hr 0.041 , 95% ci 0.005 - 0.351 , p=0.004 ) were significantly associated with a longer survival rate .
most common permanent complication is cranial nerve injury ( 42.9% ) followed by operation - related hemorrhage or infarction , motor weakness , hydrocephalus , and infection .
the results of analyses of the variables that could be correlated with permanent complications are shown in table 5 .
on univariate analysis , location , preoperative symptom , and preoperative kps showed statistical significance .
the tumor location was important factor for development of permanent complication ( 8.1% in group i vs. 2.3% in group ii , 28.0% in group iii , p=0.002 ) .
the group located at skull base showed higher possibility of permanent complication than the non - skull base group ( 28.0% vs. 6.0% , p=0.001 ) . the patient with brain stem or cranial nerve sign showed higher possibility for postoperative complication , compared to the patient with other minor symptoms ( 19.0% vs. 7.4% , p=0.043 ) .
the patient with low level of postoperative kps ( < 90 ) was also significantly associated with permanent complication ( 37.1% vs. 3.5% , p<0.001 ) .
on multivariate analysis , location and postoperative kps were independent predictable factors for development of permanent complication .
non - skull base location ( hr 0.206 , 95% ci 0.058 - 0.727 , p=0.014 ) and postoperative kps over 90 ( hr 0.048 , 95% ci 0.012 - 0.197 , p<0.001 ) were significantly related with a higher complication rate .
for some cases , far lateral , subtemporal , or orbitozygomatic route was selected to resect the lesion located on skull base region . in our series ,
129 patients ( 81.6% , 129/158 ) were classified into simpson 's grade i and ii , 28 patients ( 17.7% ) into grade iii and iv and 1 patient ( 0.6% ) into grade v. on univariate analysis , female ( p=0.019 ) , non - skull base location ( p<0.001 ) and postoperative kps over than 90 ( p=0.012 ) were significantly related with the possibility of complete resection ( table 2 ) .
however , only non - skull base location was associated with complete resection , on multivariate analysis [ hazard ratio ( hr ) : 0.162 , 95% confidence index ( ci ) : 0.065 - 0.405 , p<0.001 ] .
in this study , recurrence rate was 13.3% ( 21/158 ) and the 5- , 10- , and 15-year recurrence rates were 8.2% , 12.0% , and 13.3% , respectively ( fig .
the results of analyses of the variables that could be correlated with recurrence are shown in fig . 2 and table 3 .
on univariate analysis , age , pathology , postoperative kps , postoperative complication , edema , size , preoperative symptom and simpson 's grade showed statistical significance .
the patient 's age at the operation was important factor for rfs [ mean value , 36.55.2 months ( group < 40 years ) vs. 155.512.9 months ( 40 group < 60 years ) , 107.66.5 months ( group 60 years ) , p=0.004 ] .
the younger - aged group showed shorter rfs than the older - aged group ( mean value , 36.55.2 months vs. 153.411.1 months , p=0.001 ) .
the more aggressive pathology group ( who grade ii and iii ) showed the recurrence in earlier postoperative period than the benign group ( mean value , 45.612.5 months vs. 155.711.1 months , p<0.001 ) .
the size of tumor was also an important factor [ mean value , 175.29.8 months ( group < 4 cm ) vs. 107.712.9 months ( 4 cm group < 6 cm ) , 106.322.8 months ( group 6 cm ) , p=0.026 ] . in the group with large - size tumor ( 4 cm ) , the rfs was shorter than small - size group ( mean value , 175.29.8 months vs. 113.311.1 months , p=0.007 ) .
the patient with brain stem or cranial nerve sign showed a shorter rfs time , compared to the patient with other minor symptoms ( value , 157.912.8 months vs. 113.811.4 months , p=0.038 ) . in regard to the peritumoral edema , higher edema group ( moderate or severe ) was significantly associated with shorter rfs ( mean value , 168.111.4 months vs. 73.08.6 months , p<0.001 ) .
not surprisingly , non - complete resection group ( simpson 's grade iii - v ) demonstrated a shorter rfs compared to complete resection group ( mean value , 154.012.1 months vs. 114.021.9 months , p=0.002 ) .
the absence of postoperative complication ( mean value , 157.611.3 months vs. 70.412.4 months , p=0.001 ) and postoperative kps over 90 ( mean value , 163.212.0 months vs. 71.59.7 months , p<0.001 ) were significantly related with recurrence in a longer follow - up period . on multivariate analysis , pathologic grade , postoperative kps , peritumoral edema and resection degree were independent predictable factors for tumor recurrence .
benign pathology ( hr 0.109 , 95% ci 0.026 - 0.453 , p=0.002 ) , postoperative kps over 90 ( hr 0.078 , 95% ci 0.025 - 0.243 , p<0.001 ) , low peritumoral edema ( hr 0.134 , 95% ci 0.046 - 0.392 , p<0.001 ) , and complete resection ( hr 0.226 , 95% ci 0.077 - 0.669 , p=0.007 ) were significantly associated with longer rfs time .
the incidence of death rate was 5.0% over follow - up period ( 8/158 ) .
the surgery - related mortality which the death occurred within one month after resection was 3.16% in this study ( 5/158 ) .
the 5- , 10- , and 15-year survival rates were 96.2% , 94.9% , and 94.9% , respectively ( fig .
the results of analyses of the variables that could be correlated with survival time are shown in fig . 4 and table 4 .
on univariate analysis , pathology , location , size , postoperative complication and kps , and simpson 's grade showed statistical significance . the more aggressive pathology group ( who grade ii and iii ) showed a shorter survival time than the benign group ( mean value , 40.116.2 months vs. 227.46.2 months , p<0.001 ) .
the tumor location was important factor for survival time [ mean value , 167.16.7 months ( group i ) vs. 236.65.5 months ( group ii ) , 98.08.6 months ( group iii ) , p=0.009 ] .
the group located at skull base showed shorter survival time than the non - skull base group ( mean value , 98.08.6 months vs. 232.36.3 months , p=0.002 ) .
the size of tumor is also important variable in survival time [ mean value , 200.52.6 months ( group < 4 cm ) vs. 192.120.8 months ( 4 cm group < 6 cm ) , 152.711.2 months ( group 6 cm ) , p=0.023 ] . in larger - sized group
( 4 cm ) , the survival time was shorter compared that of small - size group ( mean value , 200.52.6 months vs. 200.815.9 months , p=0.008 ) .
interestingly , non - complete resection group ( simpson 's grade iii - v ) demonstrated a shorter survival time than the complete resection group ( mean value , 232.85.7 months vs. 139.117.2 months , p<0.001 ) .
with regard of permanent complication after surgical resection , the presence of complication was significantly related with shorter survival time ( mean value , 233.14.5 months vs. 85.912.9 months , p=0.001 ) .
the patient with low level of postoperative kps ( < 90 ) also showed shorter survival time , compared to the patient with higher score ( mean value , 239.42.8 months vs. 89.79.2 months , p<0.001 ) .
our study showed that the patient lesser than 90 in preoperative kps survived shorter than the patients of high level kps , with a marginal statistical significance ( mean value , 234.54.4 months vs. 132.910.2 months , p=0.051 ) .
on multivariate analysis , pathology , resection degree and postoperative kps were independent predictable factors for survival rate .
benign pathology ( hr 0.041 , 95% ci 0.005 - 0.343 , p=0.003 ) , complete resection ( hr 0.150 , 95% ci 0.029 - 0.769 , p=0.023 ) and postoperative kps over 90 ( hr 0.041 , 95% ci 0.005 - 0.351 , p=0.004 ) were significantly associated with a longer survival rate .
most common permanent complication is cranial nerve injury ( 42.9% ) followed by operation - related hemorrhage or infarction , motor weakness , hydrocephalus , and infection .
the results of analyses of the variables that could be correlated with permanent complications are shown in table 5 .
on univariate analysis , location , preoperative symptom , and preoperative kps showed statistical significance .
the tumor location was important factor for development of permanent complication ( 8.1% in group i vs. 2.3% in group ii , 28.0% in group iii , p=0.002 ) .
the group located at skull base showed higher possibility of permanent complication than the non - skull base group ( 28.0% vs. 6.0% , p=0.001 ) .
the patient with brain stem or cranial nerve sign showed higher possibility for postoperative complication , compared to the patient with other minor symptoms ( 19.0% vs. 7.4% , p=0.043 ) .
the patient with low level of postoperative kps ( < 90 ) was also significantly associated with permanent complication ( 37.1% vs. 3.5% , p<0.001 ) .
on multivariate analysis , location and postoperative kps were independent predictable factors for development of permanent complication .
non - skull base location ( hr 0.206 , 95% ci 0.058 - 0.727 , p=0.014 ) and postoperative kps over 90 ( hr 0.048 , 95% ci 0.012 - 0.197 , p<0.001 ) were significantly related with a higher complication rate .
a rising number of patients with intracranial meningiomas have been operated on in recent years and a few surgical series were reported in the literature22 ) . and ,
surgical results with infratentorial meningiomas have much improved during the last two decades , but radical removal continues producing a high morbidity rate and still occasional mortality19 ) . in intracranial meningioma resection , surgical outcome and its predictive factors were not fully identified .
some authors mentioned the presence of peritumoral edema as a predictor of poor outcome in elderly patients3,8,13 ) , whereas others did not find any relationship between edema and unfavorable outcome10,23 ) .
tumors size has been considered as a predictive factor for postoperative outcome by some authors3,8 ) . in other reports , however , tumor size did not have any significant influence on surgical morbidity10,15,24 ) .
some authors have pointed out that outcome is less favorable in elderly patients with meningiomas located at the base of the skull , especially the posterior fossa1,2,4,5,20 ) .
in consideration of previous studies , surgery for infratentorial meningioma is still associated with significant postoperative deficits , thus confirming that these lesions represent a great challenge even for contemporary neurosurgeons25 ) .
since the first classification of infratentorial meningiomas was proposed by cushing and eisenhardt in 1938 , castellano and ruggiero subdivided these tumors into five groups ; cerebellar convexity , tentorium , posterior petrous , clivus and foramen magnum meningiomas9 ) .
based on this classification , total 158 patients with infratentorial meningiomas underwent surgery during 20 years in out hospital ( 20.2% , in total 782 patients with intracranial meningiomas ) .
although a radical resection of these histologically benign tumors is the ideal objective of surgical therapy , this is not always possible25 ) . during surgical planning
, it should be kept in mind that meningiomas show a marked tendency to invade dura , nerves , and surrounding bone21 ) .
the dura surrounding the tumor should be resected and the bony invasion should be drilling until normal bone is seen27 ) . and vascular encasement , although representing an additional surgical problem , by itself did not generally prevent the pursuance of gross total removal25 ) .
in fact , as noted by sekhar et al.28 ) , blood vessels are surrounded by an arachnoid plane that can be carefully dissected by experienced surgeons .
subtotal resection carries a lower risk of morbidity than radical excision , but residual tumor may lead some patients to the initial clinical scenario sooner or later , and reoperation is usually less successful and more risky than initial surgery , particularly when the patient is given radiotherapy after the initial operation18,28 ) . at the present moment the majority of authors recommend subtotal resection for old patients or when there are factors defying complete removal7,12,17 ) .
the critical factors influencing the possibility of radical and safe resection of meningiomas are tumor - vascular relationships and the integrity of the arachnoid plane between the tumor and the brainstem19 ) . in our series ,
the recurrence rate of infratentorial meningiomas is particularly difficult to estimate because of differences in the reported series regarding the rates of radical excision , the methods of assessment of complete removal , the follow - up periods , the average age of the patients and the percentage of patients receiving postoperative radiotherapy19 ) .
some studies have shown that meningiomas may recur after an apparently radical excision , but it is clear that completeness of resection is the main factor preventing regrowth in all locations1,4,17 ) .
others indicated that frozen section analysis for intraoperative pathological sample is appropriate since a diagnosis of meningioma will direct that bone adjacent to the tumor site of origin be removed to reduce recurrence rate30 ) . in our series ,
non - benign pathology , non - complete resection , moderate or severe degree of peritumoral edema , and low postoperative kps ( < 90 ) were independent factors for short rfs in multivariate analysis .
it is not difficult to anticipate that meningioma with high pathological grade or non - complete resection frequently recurred after the surgery .
it means , in our opinion , that the group of postoperative kps under 80 tend to have subtotal resection because of intraoperative events , such as accidental injuries or poor dissection plane of cranial nerves , surrounding en - passing vessels , or brain stem , even though initial attempt for gross total resection .
therefore , these groups seem to have lower postoperative kps , have higher recurrence rate .
the more have edema , the more have recurrence rate . this is probably because the patients have moderate to severe edema tend to have high - grade pathology , large size , or poor dissection plane , leading to eventual recurrence of tumor . considering that the goal of surgery of meningiomas is gross total resection with minimal morbidity and low mortality14 ) , single - stage total removal should be attempted27 ) .
but the attempt for aggressive surgical resection continues producing a high morbidity rate and still occasional mortality19 ) .
the perioperative mortality rate in the surgical management of infratentorial meningiomas has varied from 0 - 15.7%25 ) .
in our series , the total death rate during the follow - up period was 5.0% ( 8/158 ) of case .
the postoperative mortality rate , as defined patients ware expired within 30 days after initial operation , was 3.16% ( 5/158 ) .
non - benign pathology , non - complete resection , and low postoperative kps ( < 90 ) were independent factors for short survival in multivariate analysis . in our study ,
as previously reported by several authors , the most common postoperative complication was found to be cranial nerve paresis or palsy2,11,20,26 ) . in our study , the permanent neurological deficits occurred in 12% ( 19/158 ) of case and the most common type is cranial nerve injury ( 47% , 9/19 ) . in multivariate analysis , skull base location and low postoperative kps were independent factors for the occurrence of permanent complication .
because of more difficult anatomical factor in petroclival , foramen magnum or jugular foramen , surgical resection for these lesions have high risk of permanent complication , even though experienced neurosurgeon .
although a radical resection of these histologically benign tumors is the ideal objective of surgical therapy , this is not always possible25 ) . during surgical planning
, it should be kept in mind that meningiomas show a marked tendency to invade dura , nerves , and surrounding bone21 ) .
the dura surrounding the tumor should be resected and the bony invasion should be drilling until normal bone is seen27 ) . and vascular encasement , although representing an additional surgical problem , by itself did not generally prevent the pursuance of gross total removal25 ) .
in fact , as noted by sekhar et al.28 ) , blood vessels are surrounded by an arachnoid plane that can be carefully dissected by experienced surgeons .
subtotal resection carries a lower risk of morbidity than radical excision , but residual tumor may lead some patients to the initial clinical scenario sooner or later , and reoperation is usually less successful and more risky than initial surgery , particularly when the patient is given radiotherapy after the initial operation18,28 ) . at the present moment the majority of authors recommend subtotal resection for old patients or when there are factors defying complete removal7,12,17 ) .
the critical factors influencing the possibility of radical and safe resection of meningiomas are tumor - vascular relationships and the integrity of the arachnoid plane between the tumor and the brainstem19 ) . in our series ,
the recurrence rate of infratentorial meningiomas is particularly difficult to estimate because of differences in the reported series regarding the rates of radical excision , the methods of assessment of complete removal , the follow - up periods , the average age of the patients and the percentage of patients receiving postoperative radiotherapy19 ) .
some studies have shown that meningiomas may recur after an apparently radical excision , but it is clear that completeness of resection is the main factor preventing regrowth in all locations1,4,17 ) .
others indicated that frozen section analysis for intraoperative pathological sample is appropriate since a diagnosis of meningioma will direct that bone adjacent to the tumor site of origin be removed to reduce recurrence rate30 ) . in our series ,
non - benign pathology , non - complete resection , moderate or severe degree of peritumoral edema , and low postoperative kps ( < 90 ) were independent factors for short rfs in multivariate analysis .
it is not difficult to anticipate that meningioma with high pathological grade or non - complete resection frequently recurred after the surgery .
it means , in our opinion , that the group of postoperative kps under 80 tend to have subtotal resection because of intraoperative events , such as accidental injuries or poor dissection plane of cranial nerves , surrounding en - passing vessels , or brain stem , even though initial attempt for gross total resection .
therefore , these groups seem to have lower postoperative kps , have higher recurrence rate .
this is probably because the patients have moderate to severe edema tend to have high - grade pathology , large size , or poor dissection plane , leading to eventual recurrence of tumor .
considering that the goal of surgery of meningiomas is gross total resection with minimal morbidity and low mortality14 ) , single - stage total removal should be attempted27 ) .
but the attempt for aggressive surgical resection continues producing a high morbidity rate and still occasional mortality19 ) .
the perioperative mortality rate in the surgical management of infratentorial meningiomas has varied from 0 - 15.7%25 ) .
in our series , the total death rate during the follow - up period was 5.0% ( 8/158 ) of case .
the postoperative mortality rate , as defined patients ware expired within 30 days after initial operation , was 3.16% ( 5/158 ) .
non - benign pathology , non - complete resection , and low postoperative kps ( < 90 ) were independent factors for short survival in multivariate analysis . in our study ,
patients with high postoperative kps represented lower complication rate and good postoperative condition . for this reason ,
as previously reported by several authors , the most common postoperative complication was found to be cranial nerve paresis or palsy2,11,20,26 ) . in our study , the permanent neurological deficits occurred in 12% ( 19/158 ) of case and the most common type is cranial nerve injury ( 47% , 9/19 ) . in multivariate analysis ,
skull base location and low postoperative kps were independent factors for the occurrence of permanent complication . because of more difficult anatomical factor in petroclival , foramen magnum or jugular foramen , surgical resection for these lesions have high risk of permanent complication , even though experienced neurosurgeon .
in this study , gross - total resection was achieved in 81.6% of the cases and related with non - skull base location .
the recurrence rate was 13.3% and longer rfs was associated with benign pathology , postoperative kps over than 90 , low peritumoral edema , and complete resection .
the 5- , 10- , and 15-year overall survival rates were 96.2% , 94.9% , and 94.9% , respectively .
benign pathology , postoperative kps over than 90 and complete resection were independent factor for a longer survival .
the permanent complication was developed in 13% of the patients and related with skull base location and postoperative kps less than 90 .
our results show relatively low morbidity and mortality rates , and good surgical resection and low recurrence rate , compare to the results of past , due to significant advances contemporary neurosurgical techniques , neuromonitoring and neuroanestehsia . however , infratentorial meningioma still has been a challenge for neurosurgeon because of their close to critical vascular and nerves structure . to achieve the goal that a little more lower morbidity and mortality , the surgeon need to consider of these factors and try to appropriate surgical planning of each case .
 objectivebased on surgical outcomes of patients with infratentorial meningiomas surgically treated at our institution , we analyzed the predictors for surgical resection , recurrence , complication , and survival.methodsof surgically treated 782 patients with intracranial meningioma , 158 ( 20.2% ) consecutive cases of infratentorial location operated on between april 1993 and may 2013 at out institute were reviewed retrospectively . 
 the patients had a median age of 57.1 years ( range , 16 - -77 years ) , a female predominance of 79.7% , and a mean follow - up duration of 48.4 months ( range , 0.8 - -242.2 months).resultsgross total resection ( simpson 's grade i & ii ) was achieved in 81.6% ( 129/158 ) of patients . 
 non - skull base location was an independent factor for complete resection . 
 the recurrence rate was 13.3% ( 21/158 ) and the 5- , 10- , and 15-year recurrence rates were 8.2% , 12.0% , and 13.3% , respectively . 
 benign pathology , postoperative kps over than 90 , low peritumoral edema , and complete resection were significantly associated with longer recurrence - free survival rate . 
 the 5- , 10- , and 15-year survival rates were 96.2% , 94.9% , and 94.9% , respectively . 
 benign pathology , postoperative kps over than 90 and complete resection were significantly associated with a longer survival rate . 
 the permanent complication rate was 13% ( 21/158 ) . 
 skull base location and postoperative kps less than 90 were independent factors for the occurrence of permanent complication.conclusionour experience shows that infratentorial meningiomas represent a continuing challenge for contemporary neurosurgeons . 
 various factors are related with resection degree , complications , recurrence and survival . 
INTRODUCTION
MATERIALS AND METHODS
Patients
Analysis variables
Statistical analysis
RESULTS
Resection
Recurrence
Overall survival
Complication
DISCUSSION
Resection
Recurrence
Survival and complication
CONCLUSION