nasopharyngeal carcinoma ( npc ) is a tumor arising from the epithelial cells that cover the surface and line of the nasopharynx . radiotherapy ( rt ) is by far the most primary treatment of npc . due to complex anatomy , exposure of adjacent and nontarget organs during irradiation of the nasopharynx areas is frequently unavoidable . ondrey et al .   studied the radiation exposure of otologic structures in head and neck cancer and implied that the temporal bone received a significant dose of radiation . consequently , with the increasing number of irradiated npc survivors , more and more patients are experiencing otologic and neurotologic complications , such as otitis media with effusion , sensorineural hearing loss ( snhl ) , dizziness / vertigo , and oscillopsia [ 25 ] . however , benign paroxysmal positional vertigo ( bppv ) in irradiated npc patients remains scarcely reported . bppv is a syndrome characterized by short - lived episodes of vertigo ( a sensation of instability , often with a sensation of rotation ) in association with rapid changes in head position . there are a number of aetiologies associated with bppv , such as vertebrobasilar ischaemia , labyrinthitis , ear surgery , head trauma , and vestibular neuritis . because the radiation portals for npc consist of the bilateral temporal bones , whether it is radiation damage to the inner ear that leads to bppv in irradiated npc patients remains unexplored . the purpose of this study is to investigate the possible causes of postirradiation bppv and to better understand this clinical entity via retrospectively reviewing postirradiated npc survivors with bppv . we think this paper presents our experience with radiotherapy - related bppv in patients with npc and may be helpful in the evaluation and treatment of similar patients . our hospital is a major referral center for npc patients who need radiotherapy , and 1205 patients have been treated and followed up at the department of radiation oncology since 2002 . when the otologic complications occurred in these npc patients , they are referred to our department of otolaryngology . during the study period we conducted a retrospective study of these patients in our institute . during the same period , 11 irradiated npc patients without bppv who were matched for tumor stage , age , and gender with the study group were randomly selected and enrolled as the control group . this study was approved by the institutional review board of the fifth affiliated hospital of sun yat - sen university . efforts were made to collect data on the radiotherapy time , dose , fractionation , and portal arrangements for all the patients . they received external beam radiotherapy with 6  mv linear accelerators at our hospital , using a 2  gy daily fraction , and the prescription dose was 7078  gy/3539  f. stage i and ii patients received rt alone . in those with stage iii or iv , two courses of concurrent chemotherapy were administered ( cisplatin 60  mg / m and 5-fluorouracil 600  mg / m ) at weeks 1 and 5 . they were diagnosed as having local tumor relapse if recurrent nasopharyngeal carcinoma was confirmed by biopsy . patients who were diagnosed with local tumor relapse all received second course rt in this study . all these treated patients had undergone otoscopic examination of the eardrums , local checkup of nose and nasopharynx field , neurologic examination , blood examination , audiometry , electronystagmography ( eng ) , and magnetic resonance imaging ( mri ) . the diagnosis of chronic otitis media ( com ) was made when patients had a perforated ear drum and purulent ear discharge . otitis media with effusion ( ome ) were diagnosed by clinical symptoms , otoscopic examination , and audiometry . snhl was defined as bone conduction threshold deterioration of more than 30  db in the pure tone average ( pta ) . the diagnosis criteria of bppv were ( 1 ) history of repeated brief episodes of vertigo with changes in head position ; ( 2 ) vertigo provoked by the dix - hallpike or the supine roll test ; ( 3 ) detectable nystagmus by naked - eye examination or eng , during and after the provoking maneuvers . patients with any clinical , laboratory , or imaging findings suggesting pathology of the central nervous system were excluded in our study . patients with positive dix - hallpike maneuver were diagnosed with posterior canal bppv and treated by epley 's maneuver or semont 's maneuver , whereas patients with positive supine roll test were diagnosed with horizontal canal bppv and treated by the lempert maneuver   or gufoni 's maneuver . in case of failure or incomplete remission of symptoms , the same maneuver was repeated every 3 to 5 days , until a maximum of 3 repetitions . assessment of the success of the treatment included both patients ' relief from vertigo and negative dix - hallpike or supine roll test for vertigo and nystagmus . because the total number of the patients was less than 40 , clinical characteristics were compared between the two groups by using fisher 's exact test . a value of p < 0.05 ( two - sided ) was considered statistically significant . clinical characteristics of these 11 patients with postirradiated bppv are shown in table 1 . the latency period between the final rt session and the occurrence of bppv ranged from 3 to 7 years ( mean : 5.2 years ) . of the 11 patients with bppv , 4 patients ( 4/11 , 36.4% ) had undergone rt once and the nasopharyngeal accumulated rt dose was 7078  gy . the rest 7 patients ( 7/11 , 63.6% ) had undergone rt twice and the rt dose was 120130  gy . otoscopic examination revealed that 4 patients ( 5 ears ) experienced chronic otitis media and 5 patients ( 7 ears ) had otitis media with effusion , for a total of 9 patients ( 9/11 , 81.8% ) with middle ear complications . audiometry revealed that sensorineural hearing loss occurred after rt in 8 patients ( 14 ears , 72.7% ) . all patients denied using ototoxic otic drops and previous ear trauma . at the time of this analysis , 3 of the 11 patients died and 8 patients survived . the cause of death for the 3 patients was bleeding in 1 and distant metastases in 2 . comparison of the clinical characteristics of 11 postirradiated npc patients with bppv and 11 postirradiated npc patients without bppv is shown in table 2 . the radiation dose in the 11 patients with bppv was 7078  gy in 4 patients and 120128  gy in 7 patients , indicating that the risk of bppv rises significantly when the patient undergoes rt twice and the threshold radiation dose is > 120  gy ( p = 0.027 ) . the occurrence of postirradiated bppv was significantly related to incidences of otitis media ( com or ome ) and sensorineural hearing loss ( p = 0.011 and 0.009 , resp . ) . although the incidences of neck fibrosis were higher in patients with bppv , there were no significant differences between the two groups ( p = 1.000 ) .   in 8 patients ( 72.7% ) , the unilateral posterior canal was involved , as evidenced by vertigo and torsional upbeating nystagmus provoked unilaterally during the dix - hallpike test . in 3 patients ( 27.3% ) , vertigo and geotropic / apogeotropic horizontal nystagmus were provoked during the supine roll test , implying involvement of the horizontal canal . all the patients responded well to repositioning maneuvers , with resolution of positional vertigo and nystagmus ( table 3 ) . although it has been reported that postirradiated npc patients are prone to vertigo , we found that there are few articles related to the clinical manifestation or prognosis of benign paroxysmal positional vertigo . no studies have identified the risk factors of this disease in these patients either . in our study , 11 postirradiated npc patients with bppv had been studied . radiation damage to the inner ear and radiation - induced vascular insufficiency have been proposed as the aetiology of postirradiated bppv . more than 50% of the total radiation dose is delivered to the inner ear during head - and - neck cancer rt . for example , conventional fractionated rt ( 2  gy per day with a total dose of 60  gy ) to the inner ear of guinea pigs induced atrophy and degeneration of stria vascularis , a reduced number of capillaries , degeneration of endotheliocyte in vessels , outer hair cell , and supporting cell of corti 's organ , and degeneration of vestibular hair cell and otolith seperated from the utricular macula . gabriele et al .   also reported that 44% of patients developed vestibular disorders when the inner ear received 2851.2  gy of radiation . in the current study , high radiation dose and a second course of radiation can increase the risk of postirradiated bppv , further supporting that radiation damage to the inner ear correlates with bppv .   in the present study , postirradiated otitis media are considered as a complication of radiotherapy , arising from impairment of the middle ear mucosa and dysfunction of the eustachian tube after irradiation . postirradiated snhl , another complication of radiotherapy , is due to the irradiation damage to corti 's organ and acoustic nerve and was found as a risk factor of bppv in our study . all these radiotherapy - induced ear injuries seem to be a predicting factor for development of postirradiated bppv . it is unlikely that hyperemia , edema , and desquamation of mucosa of the middle ear or corti 's organ after irradiation can cause postirradiated bppv , but development of postirradiated otitis media or snhl can just be another manifestation of radiation damage and indicates individual sensitivity to radiation . the presence of radiotherapy - induced ear complication would , thus , be evidence of radiation complication and points to an increased risk of damage to the vestibular apparatus and development of postirradiated bppv . postirradiated bppv , just like common bppv , is caused by debris in the semicircular canal of the ear that continues to move after the head has stopped moving . patients with this disorder complain of episodic vertigo of brief duration , provoked by head movements and accompanied by a characteristic paroxysmal positional nystagmus . the nystagmus is typically torsional - vertical or horizontal , depending on the semicircular canal involved , and is characterized by findings such as latency , crescendo and decrescendo , transience , reversibility , and fatigability . application of repositioning maneuvers , which intends to move particles from the semicircular canal into the vestibule , results in successful treatment of the disease in most patients rather than medication . some postirradiated npc survivors had marked neck fibrosis and it was difficult for them to perform the lempert maneuver , which involved rolling the patient 360 degrees in a series of steps to effect particle repositioning . this study showed that repositioning maneuvers could provide an effective treatment result in patients with postirradiated bppv . however , considering the low incidence of postirradiated bppv , the effectiveness of repositioning maneuvers for the treatment of this disease needs to be further studied in a larger group of patients . our results suggest that therapeutic benefits of a second course of rt are associated with the potential risk of radiation - induced bppv . postirradiated npc patients with otitis media or snhl are prone to have postirradiated bppv . in this study , the clinical manifestations of postirradiated bppv in npc patients varied , and repositioning maneuvers were safe and effective for relief of the vertiginous symptoms .
purpose . it has been assumed that postirradiated nasopharyngeal carcinoma ( npc ) patients are prone to benign paroxysmal positional vertigo ( bppv ) . 
 the purpose of this study was to better understand this clinical entity . 
 materials and methods . from september 2003 to june 2011 , we conducted a retrospective study of 11 irradiated npc patients with bppv in our institute . during the same period , 
 11 irradiated npc patients without bppv were randomly selected and enrolled as the control group . 
 all medical records of these patients were evaluated . 
 results . 
 the risk of bppv rises significantly when the patient undergoes radiotherapy ( rt ) twice and the threshold radiation dose is > 120  gy ( p = 0.027 ) . 
 the occurrence of postirradiated bppv was significantly related to incidences of otitis media and sensorineural hearing loss ( snhl ) ( p = 0.011 
 and 0.009 , resp . ) . 
 all the patients responded well to repositioning maneuvers . 
 conclusion . 
 a second course of rt , postirradiated otitis media , or snhl is associated with the potential risk of radiation - induced bppv . 
 repositioning maneuvers were safe and effective for relief of this disease .