the emergence of single - fraction stereotactic radiosurgery ( srs ) over the past two decades has greatly altered the management of acoustic neuromas ( an)/vestibular schwannomas by neurosurgeons , neuro - oncologists and radiation oncologists . multiple studies comparing srs with microsurgical excision have revealed that srs has less morbidity and is more cost effective , with similar efficacy to surgical resection in controlling tumor progression for an with an average diameter of less than 3  cm [ 14 ] . however , for large an ( mean diameter  >  3  cm ) , decreased efficacy along with increasing facial and trigeminal nerve morbidity and hearing loss following srs make it a less attractive treatment option in comparison with microsurgery [ 5 , 6 ] . fractionated stereotactic radiotherapy ( fsrt ) is a noninvasive alternative treatment modality for tumors of the skull base . although fsrt requires multiple irradiation sessions , recent reports have indicated that for an with an average diameter  <3  cm , fsrt provides comparable efficacy to srs with significantly reduced morbidity to adjacent structures , particularly the trigeminal nerve [ 710 ] . because of this lower morbidity , fsrt has been utilized for large ( > 3  cm ) an in a limited number of cases . to further enhance the existing knowledge regarding the safety and efficacy of fsrt for this patient population our patient was a 43-year - old man with a past medical history of stroke who presented with a 12 year history of worsening imbalance , along with new - onset bilateral tinnitus , vertigo , and right - sided hearing decline associated with vomiting and hydrocephalus . audiometric testing confirmed right sensorineural hearing loss , and magnetic resonance ( mr ) imaging revealed a large tumor in the area of the right cerebellopontine angle without definite invasion of the internal auditory canal but with compression of the fourth ventricle . the patient had no facial weakness or changes in facial sensation . due to his clinical and radiographic findings , he underwent successful placement of a right frontal ventriculoperitoneal shunt . following shunt placement , he was considered for microsurgery , srs , or fsrt for treatment of his cerebellopontine - angle lesion . although microsurgery was presented to the patient , he was reluctant to undergo surgery , and due to the large size of the tumor ( mean diameter  =  3.8  cm ; maximum diameter  =  4.1  cm ) , he chose fsrt over srs . all fsrt treatments were overseen by the neurosurgeon , radiation oncologist and medical physicist . following a standardized testing simulation after placement of a gill - thomas - cosman relocatable headframe for immobilization ( integra radionics , burlington , ma , usa ) , a computed tomography ( ct ) scan with contrast was obtained , with the area of tumor scanned by 2-mm slices and the remainder of the head by 4- and 8-mm slices . 1 ) was performed using the radionics x - knife 4.0 three - dimensional ( 3d ) planning system ( integra radionics ) as previously described . the size of the tumor was 4.1  cm    3.5  cm    3.7  cm ( mean diameter  =  3.8  cm ) , which was encompassed with two overlapping isocenters each measuring 4.5  cm in diameter . the patient received daily fractions of 1.8  gy until a total target dose of 54  gy was administered . the radiation was prescribed to the 90% isodose line using five rotational arcs and one stationary beam . a mean dose of 0.082  gy was delivered to the brainstem per daily fraction . thirty treatments were stereotactically delivered over 6 weeks using a dedicated varian 6/100 linear accelerator ( varian medical systems , inc . , the patient tolerated the procedure well , with no immediate or delayed posttreatment complications . 1anterior three - dimensional view on the x - knife planning software demonstrating the right cerebellopontine - angle acoustic neuroma ( blue ) , the five arcs used for treatment , and the 4.5-cm cone ( red ) used to encompass the lesion during treatment planning for fractionated stereotactic radiotherapy . the tumor is depicted in relation to the brainstem ( yellow ) , eyes ( green ) , and optic chiasm ( green ) . the measured size of the tumor was 4.1  cm    3.5  cm    3.7  cm anterior three - dimensional view on the x - knife planning software demonstrating the right cerebellopontine - angle acoustic neuroma ( blue ) , the five arcs used for treatment , and the 4.5-cm cone ( red ) used to encompass the lesion during treatment planning for fractionated stereotactic radiotherapy . the tumor is depicted in relation to the brainstem ( yellow ) , eyes ( green ) , and optic chiasm ( green ) . the measured size of the tumor was 4.1  cm    3.5  cm    3.7  cm following fsrt , the patient was serially evaluated with pre- and post - gadolinium - enhanced mr imaging and the gardner local tumor control ( defined as the absence of tumor progression ) was achieved and sustained . at his last follow - up examination , 63  months after treatment , he continued to demonstrate local tumor control , with no evidence of hearing compromise in comparison with his hearing function prior to fsrt . he experienced no signs or symptoms of trigeminal nerve morbidity , facial nerve morbidity , acute complications , or other signs of radiation injury following fsrt . our patient was a 43-year - old man with a past medical history of stroke who presented with a 12 year history of worsening imbalance , along with new - onset bilateral tinnitus , vertigo , and right - sided hearing decline associated with vomiting and hydrocephalus . audiometric testing confirmed right sensorineural hearing loss , and magnetic resonance ( mr ) imaging revealed a large tumor in the area of the right cerebellopontine angle without definite invasion of the internal auditory canal but with compression of the fourth ventricle . the patient had no facial weakness or changes in facial sensation . due to his clinical and radiographic findings , he underwent successful placement of a right frontal ventriculoperitoneal shunt . following shunt placement , he was considered for microsurgery , srs , or fsrt for treatment of his cerebellopontine - angle lesion . although microsurgery was presented to the patient , he was reluctant to undergo surgery , and due to the large size of the tumor ( mean diameter  =  3.8  cm ; maximum diameter  =  4.1  cm ) , he chose fsrt over srs . all fsrt treatments were overseen by the neurosurgeon , radiation oncologist and medical physicist . following a standardized testing simulation , the patient had fsrt treatment planning for his right an . after placement of a gill - thomas - cosman relocatable headframe for immobilization ( integra radionics , burlington , ma , usa ) , a computed tomography ( ct ) scan with contrast was obtained , with the area of tumor scanned by 2-mm slices and the remainder of the head by 4- and 8-mm slices . 1 ) was performed using the radionics x - knife 4.0 three - dimensional ( 3d ) planning system ( integra radionics ) as previously described . the size of the tumor was 4.1  cm    3.5  cm    3.7  cm ( mean diameter  =  3.8  cm ) , which was encompassed with two overlapping isocenters each measuring 4.5  cm in diameter . the patient received daily fractions of 1.8  gy until a total target dose of 54  gy was administered . the radiation was prescribed to the 90% isodose line using five rotational arcs and one stationary beam . a mean dose of 0.082  gy was delivered to the brainstem per daily fraction . thirty treatments were stereotactically delivered over 6 weeks using a dedicated varian 6/100 linear accelerator ( varian medical systems , inc . , the patient tolerated the procedure well , with no immediate or delayed posttreatment complications . 1anterior three - dimensional view on the x - knife planning software demonstrating the right cerebellopontine - angle acoustic neuroma ( blue ) , the five arcs used for treatment , and the 4.5-cm cone ( red ) used to encompass the lesion during treatment planning for fractionated stereotactic radiotherapy . the tumor is depicted in relation to the brainstem ( yellow ) , eyes ( green ) , and optic chiasm ( green ) . the measured size of the tumor was 4.1  cm    3.5  cm    3.7  cm anterior three - dimensional view on the x - knife planning software demonstrating the right cerebellopontine - angle acoustic neuroma ( blue ) , the five arcs used for treatment , and the 4.5-cm cone ( red ) used to encompass the lesion during treatment planning for fractionated stereotactic radiotherapy . the tumor is depicted in relation to the brainstem ( yellow ) , eyes ( green ) , and optic chiasm ( green ) . the measured size of the tumor was 4.1  cm    3.5  cm    3.7  cm following fsrt , the patient was serially evaluated with pre- and post - gadolinium - enhanced mr imaging and the gardner  robertson hearing classification system . local tumor control ( defined as the absence of tumor progression ) was achieved and sustained . at his last follow - up examination , 63  months after treatment , he continued to demonstrate local tumor control , with no evidence of hearing compromise in comparison with his hearing function prior to fsrt . he experienced no signs or symptoms of trigeminal nerve morbidity , facial nerve morbidity , acute complications , or other signs of radiation injury following fsrt . presenting typically with unilateral sensorineural hearing loss , hydrocephalus , tinnitus , and/or imbalance , large an ( mean diameter  > 3  cm ) tend to enlarge within 12  years from diagnosis , potentially resulting in significant morbidity due to brainstem compression and lower cranial nerve damage by these lesions [ 14 , 15 ] . the traditional standard of care for the treatment of large an has been microsurgical excision , which to date has proven to be the treatment modality with the most long - term efficacy compared with srs or observation alone [ 6 , 14 , 16 ] . however , with the recent advent of fsrt for small and medium - sized an demonstrating low morbidity and excellent clinical efficacy , it is possible that fsrt may represent an effective noninvasive alternative to microsurgery in patients with large an [ 7 , 10 ] . previously , a small subgroup ( five patients with tumors  > 3  cm ) of an extensive acoustic neuroma fsrt series was reported to have experienced adequate tumor control with minimal morbidity . to contribute to the existing knowledge regarding fsrt for large an , we detailed our experience in a single patient . following operative ventriculoperitoneal shunt placement for the treatment of our patient s symptomatic hydrocephalus , subsequent fsrt resulted in complete local tumor control . this long - term tumor control ( > 5  years ) came without subsequent return of hydrocephalus or compromises in hearing , trigeminal nerve function , or facial nerve function . these findings are comparable to reported results for alternative treatment modalities for an of diameter > 3  cm [ 6 , 14 , 17 , 18 ] . this report indicates that there may be a role for fsrt in the treatment of large an following appropriate management of more immediate associated symptomatology . although the findings of this report are encouraging , they must be tempered by the fact that this study involves a single case , thereby limiting the ability to conclude definitively that fsrt is comparable / superior to microsurgery or srs for asymptomatic large an . however , the fact that this study supports the positive findings of a previous report involving fsrt for five patients with large an lends strength to the hypothesis that fsrt may be a useful treatment modality for an  > 3  cm . future prospective randomized controlled studies involving asymptomatic large an managed by observation , microsurgery , srs , or fsrt will be required to make a definitive determination of the optimal treatment modality for this patient population . in our experience of treating a patient with a large an ( maximum diameter  =  4.1  cm ; mean diameter  =  3.8  cm ) , following fsrt , the patient experienced long - term local tumor control ( > 5  years ) with no trigeminal nerve , facial nerve , or hearing - related morbidity . these findings indicate that fsrt may be a viable noninvasive treatment modality for an that may be too large to be successfully treated with srs . subsequent prospective studies involving larger patient sizes will be needed to adequately address this issue .
the treatment of acoustic neuromas ( an ) usually involves surgical excision or stereotactic radiosurgery . 
 however , for large an ( mean diameter  >  3  cm ) , stereotactic radiosurgery is rarely used , leaving patients with limited noninvasive treatment options . 
 recently , the use of fractionated stereotactic radiotherapy ( fsrt ) has been effective in treating small to medium - sized an . 
 we present a patient with a large an treated with fsrt . 
 the patient was a 43-year - old man presenting with imbalance , tinnitus , vertigo , and right - sided hearing decline associated with vomiting and hydrocephalus . 
 magnetic resonance ( mr ) imaging revealed a large , 3.8-cm , right cerebellopontine - angle tumor compressing the fourth ventricle . 
 following right frontal ventriculoperitoneal shunt placement , the patient underwent fsrt for treatment of the tumor . using the radionics x - knife 4.0 3d treatment planning system , 
 a total of 54  gy was delivered in 1.8-gy daily fractions with the prescription isodose line of 90% . 
 treatments were delivered using a dedicated varian 6/100 linear accelerator , and head immobilization was achieved with the gill - thomas - cosman relocatable stereotactic frame . 
 the patient was subsequently evaluated with serial contrast - enhanced mr imaging . 
 following fsrt , local control ( defined as the absence of tumor progression ) was achieved , and treatment was well tolerated . 
 there was no hearing - related , trigeminal , or facial - nerve morbidity following fsrt at 63-month follow - up . treating a patient with a large 
 an with fsrt resulted in local tumor control , with no trigeminal nerve , facial nerve , or hearing - related morbidity . 
 these results support fsrt as a potential noninvasive treatment modality for an some would consider too large for single - fraction stereotactic radiosurgery ( srs ) .