the most common peripheral vestibulopathies diagnosed from positional vertigo may include benign paroxysmal positional vertigo ( bppv ) , labyrinthitis , and acute vestibular neuritis , and less commonly labyrinthine fistula or cerebellopontine angle tumors.1 ) labyrinthine fistula , in particular , is reported to rise from 3.6 to 13.9% of chronic otitis media with cholesteatoma , and known to affect the lateral semicircular canal most frequently.2,3 ) typical symptoms of labyrinthine fistula are positional vertigo , severe disequilibrium , and sensorineural hearing loss , collectively making it difficult to differentiate from bppv or meniere 's disease.4 ) confounding the distinction is the sensitivity of the fistula test , of which is reported to be between 30 to 60% at best . high resolution computed tomography of the temporal bone ( tbct ) may help diagnose fistulas with sensitivity of 90% , but this sensitivity is confined to the lesions of the lateral semicircular canal , and its accuracy has often been doubted.5 ) the authors have experienced a case of labyrinthine fistula complicating chronic otitis media with cholesteatoma , of which the initial nystagmus mimicked that of the lateral semicircular canal bppv , and thus report it a possible explanation for the mechanism underlying the nystagmus pattern . a 61-year - old female patient was admitted to the emergency unit with the complaint of 2 days ' dizziness of whirling nature accompanied by nausea and vomiting . brain diffusion weighted image ( dwi ) for the differential diagnosis of a central pathology was normal . on otoscopic examinations , normal right tympanic membrane was seen , but purulent ear discharge was filling the left external ear canal . the patient had been feeling a loss of hearing in her left ear for quite a long time and had been visiting a local otorhinolaryngologic clinic for several months diagnosed and treated for chronic external otitis in the left ear . the patient showed spontaneous , right - beating horizontal nystagmus ( 6.36 d / s ) . left - beating horizontal nystagmus ( 9.70 d / s ) was noted after head shaking . dix - hallpike test to either side provoked geotropic horizontal nystagmus , but the nystagmus was stronger on the left side ( 21.23 d / s on the left side compared to 15.00 d / s on the right ) and so was the degree of symptoms . geotropic direction - changing horizontal nystagmus was demonstrated on both sides during the supine roll test . the intensity of the nystagmus on both sides was comparable showing 17.71 d / s on the right side and 17.03 d / s on the left side . the latency and duration of positional nystagmus were 2 and 29 seconds , respectively on the right side , and 3 and 30 seconds , respectively on the left side . on the head bending nystagmus or lying - down nystagmus test , left - beating horizontal nystagmus ( 7.00 d / s ) on the head bending nystagmus test and right - beating horizontal nystagmus ( 14.93 d / s ) on the lying - down nystagmus test was demonstrated , respectively ( fig . 1 ) . the bithermal caloric test response demonstrated unilateral canal paresis of 29.98% on the left side . these findings collectively led to the initial impression of geotropic variant of the left lateral semicircular canal bppv on the left side combined with ipsilesional external otitis . the patient received the modified lempert maneuver for treatment of the presumptive bppv and was prescribed with empirical topical and oral antibiotics for management of the external otitis . she was discharged from the emergency unit for an our clinic visit scheduled for the following day . at the next follow - up visit , the patient still complained of a positional vertigo aggravated on a leftward head turn , despite the therapeutic maneuver . the patient was negative for positional nystagmus from the dix - hallpike test and supine roll test , but left - beating horizontal nystagmus on the head bending nystagmus test and right - beating horizontal nystagmus on the lying - down nystagmus test was demonstrated , respectively . from these atypical nystagmus patterns , a thorough examination of the ear was undertaken , where keratinous debris and inflammatory polyps were hidden behind the purulent material blocking the left external auditory canal . the keratinous debris was cleared and polypoid tissues were removed for tissue pathology , after which the patient was sent for the tbct . on the tbct , the left middle ear cavity was mostly occupied with soft tissue eroding all the ossicles as well as the bone overlying the lateral semicircular canal and the tegmen tympani ( fig . 2 ) . magnetic resonance imaging and brain dwi were taken but reported negative for intradural intracranial invasion . under the diagnosis of left cholesteatomatous chronic otitis media with the complication of labyrinthine fistula the patient was instructed an absolute bed rest in a 30 degree head elevated position . a brain - blood - barrier - penetrating intravenous antibiotic and osmotic laxative were prescribed . pure tone audiometry , taken on the day of admission , showed normal air - conduction threshold of 18 db hl for the right ear , and a mixed hearing loss with an air - conduction threshold of 78 db hl for the left ear ( fig . 3a ) . tissue pathology taken on the first clinic exam was reported as a cholesteatoma . after resolution of dizziness , canal wall - down tympanomastoidectomy was performed for complete removal of the cholesteatoma on the 7th day of admission . intraoperatively , dehiscence of the bony labyrinth of the lateral semicircular canal was observed without any leakage of perilymphatic fluid after the removal of the matrix . in the immediate postoperative period , the patient complained of dizziness , and a weak right - beating horizontal nystagmus was observed . otherwise , it was uneventful postoperatively , free from signs of facial palsy or cerebrospinal fluid leaks . one day after the surgery , dizziness was subsided and there was no evidence of spontaneous nystagmus . the patient was discharged from the hospital on the 8th postoperative day without any evidence of complications . on follow up 3 months postoperatively , the patient was free of dizziness and felt improved hearing , of which pure tone audiogram showed improved hearing thresholds ( left air - conduction threshold of 45 db and bone - conduction threshold of 23 db ) ( fig . labyrinthine fistula is an aberrant connection between the perilymph - filled inner ear and air - filled middle ear , of which the perilymph leak results in pathology of the vestibule and the cochlea.6 ) in most instances , bony labyrinth is involved up to but not involving the endosteum so that the endosteum is merely separating the perilymphatic space from the matrix.7 ) in more rare cases , the granulation or fibrous tissue may infiltrate the membranous labyrinth , thus some authors have described a three - stage classification of labyrinthine fistulas.8 ) in this case , we initially suspected the patient to have a central pathology because of the inverted head shaking nystagmus beating to the opposite direction from the spontaneous nystagmus . however , no central lesions were observed on the brain dwi . on both the dix - hallpike test and supine roll test in the emergency unit , head bending nystagmus was beating to the left , and lying - down nystagmus was to the right . these findings , collectively , added on the findings of purulent otorrhea with a history of recent treatment of external otitis , misled to an initial presumptive diagnosis of the left lateral semicircular canal bppv and external otitis . although the nystagmus was more intense on the right supine roll compared to the left , the difference was not significant , and the symptoms were similar between both sides . moreover , the head bending nystagmus was seen to beat to the left , leading to the impression of the lateral semicircular canal bppv on the left side rather than the right.9 ) however , in the follow up clinic visit the next day , the diagnosis was corrected to be a left labyrinthine fistula complicating a cholesteatoma on observing an atypical nystagmus pattern and clearing out the external ear of purulent and keratinous materials . the nature of the nystagmus pattern in this patient with labyrinthine fistula mimicking the typical positioning nystagmus of the left semicircular canal bppv requires some explanation . subtle movements of the cholesteatoma following positional changes of the head may affect pressure changes in the area of the fistula , which in turn influence the change in the direction of the endolymphatic flow . when the head was turned 90 degrees to the left during the initial examination in the emergency unit , the cholesteatoma might have leaned closer to the left semicircular canal creating a positive pressure on the membranous labyrinth . hence , a utriculopetal endolymphatic flow causing a utriculopetal deviation of the cupula in turn , leads to an excitatory stimuli creating a left - beating geotropic horizontal nystagmus in accordance with ewald 's second law ( fig . 4a).10 ) when there is a rightward 90 degrees head rotation , the cholesteatoma moves away from the lateral semicircular canal creating a space between the bony labyrinth and the cholesteatoma , within which a negative pressure is formed . this negative pressure creates utriculofugal endolymphatic flow and a resultant rightward geotropic horizontal nystagmus from utriculofugal cupula deviation and an inhibitory stimulus ( fig . pascal 's law may explain for the pressure changes and the directions of the endolymphatic flow.11 ) most acutely vertiginous patients are easily diagnosed with otologic pathologies such as bppv , meniere 's disease or acute vestibular neuritis based upon patient 's symptoms and simple audio - vestibular workups . but we experienced a misdiagnosed dizzy patient by paying less attention to physical findings and being presumptive on initial video - oculographic results . since the fistula test is of little value in the diagnosis of labyrinthine fistula , negative test results might have added to the missed initial diagnosis.12,13 ) moreover , fistula test may not be applied in cases where a perforated tympanic membrane with acute inflammation might be expected . our case is an example where clinical diagnosis of a dizzy patient may be misleading if made based only on presumptive judgments without a thorough otologic workup and thereby report the case with a possible explanation for the complexity and equivocality of the nystagmus study results throughout the course of diagnosis .
acute peripheral vestibulopathy , of which the chief complaint is positional vertigo , comprises benign paroxysmal positional vertigo ( bppv ) , labyrinthitis , labyrinthine fistula , and cerebellopontine angle tumors . 
 since the typical presentation of labyrinthine fistulas may be sensorineural hearing loss , positional vertigo , or disequilibrium , it is often difficult to distinguish from bppv or meniere 's disease . 
 herein we report a 61-year - old female patient with typical symptoms and signs attributable to geotropic type variant of the lateral semicircular canal bppv on the left side , who eventually was confirmed as having a labyrinthine fistula from chronic otitis media with cholesteatoma on the left side . 
 this is another case where , even in the presence of isolated vertigo showing typical findings of acute peripheral vestibulopathy , other otologic symptoms and signs must not be overlooked .