|Year : 2013 | Volume
| Issue : 2 | Page : 82-84
Audio-vestibular findings in Vestibular Paroxysmia
Niraj Kumar Singh, Preeta Singh, M Usha, M Akshay
Department of Audiology, All India Institute of Speech and Hearing, Manasagangothri, Mysore, India
|Date of Web Publication||15-Jun-2013|
Niraj Kumar Singh
Department of Audiology, All India Institute of Speech and Hearing, Manasagangothri, Mysore 570 006, Karnataka
Source of Support: None, Conflict of Interest: None
Vestibular paroxysmia (VP) is attributed to neurovascular cross-compression due to vascular loops around the Vestibulocochlear nerve. The exact audio-vestibular profile of individuals with VP is uncertainly reported in literature. Thus, the study was aimed at reporting the results of audio-vestibular test battery in VP. A 37 year-old-female and a 30 year-old-male with tinnitus, giddiness, and positional vertigo underwent routine audiological testing, oto-acoustic emissions, auditory brainstem response, vestibular evoked myogenic potentials, and chochlear hydrops analysis masking procedure which produced normal results. The Dix-Hallpike maneuver revealed positional vertigo and nystagmus while symptoms such as oscillopsia and giddiness were reported during central vestibular tests. The magnetic resonance imaging (MRI) report revealed labyrinthine artery loops around the VII and VIII cranial nerves. We conclude that subtle symptoms like oscillopsia, giddiness, or vomiting sensation on central vestibular tests should be carefully noted to enhance the identification of VP using audio-vestibular tests battery and MRI should be done for all cases presenting with symptoms of non-fatigable positional vertigo.
Keywords: Oscillopsia, Positional vertigo, Vascular loops, Vestibular paroxysmia
|How to cite this article:|
Singh NK, Singh P, Usha M, Akshay M. Audio-vestibular findings in Vestibular Paroxysmia. Indian J Otol 2013;19:82-4
| Introduction|| |
Vestibular Paroxysmia (VP), also referred to as Neurovascular cross-compression, results from vascular loops around the 8 th cranial nerve. It is characterized by 8 th nerve symptoms like tinnitus, hearing loss and episodic vertigo lasting from seconds to minutes, often triggered by atypical and inconsistent positional movements. It may also be associated with headache, visual disturbance or nausea.  The reports in current literature involving vascular loops have shown VP to be an incidental finding. 
Adequate information on incidence and prevalence is not available in literature as it is easily camouflaged by other vestibular disorders and marred by poor documentation. Various authors have attempted to probe into the clinical manifestations and symptomatology; nonetheless, a diagnostic gold standard remains elusive. Presently the clinical diagnosis of VP is mainly based on the exclusion criterion. A few sporadic studies , have reported about symptom complex and the audio-vestibular evaluation results in cases with VP. The incidence of vertigo attacks with position change or hyperventilation has been reported in 50% of patients, only at rest in 28%, and only with provocation in 22%.  In nearly 75% of the cases, unsteadiness of gait has been reported.  Along with vertigo, the presence of sensorineural hearing loss has been reported to range from 50% to 95%. ,,,,
The auditory brainstem response (ABR), electronystagmography (ENG), and magnetic resonance imaging (MRI) have also been investigated in cases with VP, however, the consensus regarding the findings has been lacking. ABR abnormality has been reported to range from 0% to 85%. ,,, The prolongation of I-III inter-peak latency difference has been the most frequently reported finding. ENG abnormalities have been found in 93% of the patient.  The existence of spontaneous nystagmus has been reported in 75-90% of the clients , whereas, presence of caloric weakness was reported in 90% patients. , The sensitivity of gadolinium enhanced MRI was found to be 95% in detecting surgically confirmed VP.
The above findings of literature appear to point towards a lack of consensus for specific features and test results. In addition, the existing literature is also deprived of published reports about the incidence of VP. Though, it has been described as a rare pathology, it is likely that it's high-level of camouflage due to overlap of lot of symptoms with other pathologies may have eluded the researchers or clinicians from identifying it. A larger pool of data is required to arrive at some conclusion in terms of its differential diagnosis using the frequently available tests. Case reports are positive steps in this direction and hence this study aimed at reporting the findings of audio-vestibular test battery in two cases of VP.
| Case Report|| |
Client A presented with symptoms of tinnitus (ringing and staccato type) and giddiness, more during the morning hours. Client B presented with identical symptoms except tinnitus. In addition, Client A also reported tolerance problem and burning sensation when exposed to loud sounds. Both the clients reported of no other otological symptoms, family history, and medical problems.
The routine audiological evaluation included audiometry and immittance evaluation. It revealed normal hearing sensitivity bilaterally and absence of middle ear problems. Tinnitus evaluation for Client A produced pitch match at 500 and 1500 Hz and intensity match at 30 and 35 dB HL for right and left ears respectively. Residual inhibition was non-existent.
The auditory evoked potentials included ABR, chochlear hydrops analysis masking procedure (CHAMP), and vestibular evoked myogenic potentials (VEMP) which were administered using the Biologic Navigator Pro evoked potential system (version 7.0.0) with default protocols. The click-evoked ABR, using the standard protocol for site of lesion testing, revealed normal absolute latencies, inter-peak and inter-aural latency differences and amplitude ratio. The results of CHAMP revealed a difference of 0.62 ms and 0.63 ms for left and right ears respectively between the "click alone" and "Click with 500 Hz high-pass masking noise" conditions in Client A and 0.56 ms and 0.50 ms in Client B. An asymmetry ratio of 3% and 60% was found on VEMP for Clients A and B respectively.
The Electronystagmography (ENG) test battery, involving gaze, optokinetic, positional, positioning, and Bithermal caloric tests, was administered using the Recorders and Medicare Systems Private Limited ENG instrument. Spontaneous nystagmus was apparent during the gaze testing, nystagmus was noticed on the ENG traces during Dix-Hallpike maneuver, and transient giddiness was reported. Perception of oscillopsia and multiple light beams was reported during optokinetic tests. The gaze and optokinetic traces were normal for Client A but abnormal for Client B. The Caloric test, using the standard protocol for bithermal water irrigation, revealed unilateral weakness towards right side in both the clients.
Subsequently, the clients underwent MRI scan (T2-weighted/Turbo spin echo, sagittal and coronal section). The MRI revealed labyrinthine artery loops around the 7 th and 8 th cranial nerves bilaterally in both clients [Figure 1].
|Figure 1: Magnetic resonance imaging images obtained from the two clients with vestibular paroxysmia|
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During a span of 1 year, 25 cases reported with positional vertigo as a part of the symptom complex. Of these only two cases underwent MRI and were both diagnosed with "VP". The other cases did not undergo MRI.
| Discussion|| |
Client A reported of "staccato tinnitus" and tolerance problem whereas Client B did not. Individuals with VP have been reported to exhibit "typewriter tinnitus" due to microvascular compression of the cochlear nerve.  The reports of Client A may be related to the "ephatic coupling" of nerve fibers that results from compression of nerve fibers over a prolonged period. ,,,, This causes the impulse to travel through several other neurons ("cross-talk" of fibers within a compressed cochlear nerve), thus resulting in hypersensitivity and tinnitus. The long standing cross compression may have resulted in "cross-talk," thereby increasing the loudness perception and tinnitus. The description of the "typewriter tinnitus" actually is same as the staccato description given by Client A. Further, the burning sensation may probably be related to the same phenomenon in the temporal branch of the Facial nerve that supplies to the external ear.
The findings of routine audiometry in the present study revealed hearing sensitivity to be within normal limits. However, incidence of sensorineural hearing loss has been reported in 50-100% of the individuals with VP. ,, Absence of sensorineural hearing loss in the present study may be attributed to the lower degree or lack of impingement on the cochlear branch. Further, the existence of vestibular symptoms could be an indicator of higher degree of impingement towards the vestibular branches of the nerve. An intricate relationship between the location and degree of impingement and the expressivity of related symptoms has been reported. 
The ABR results were normal in both participants. This is in agreement with Brookler et al.  However, others have reported prolongation of I-III interpeak latency difference.  The congruence with Brookler et al.  and dissonance with Moller  could again be attributed to lower degree of impingement of the vascular loop on the cochlear branch, as reasoned earlier. 
The results of the ENG test battery revealed unilateral caloric weakness, spontaneous nystagmus and positive results for positional vertigo on Dix-Halpike maneuver. Similar findings have been reported in literature. ,,,, The Dix-Halpike maneuver revealed positional vertigo which necessitated differential diagnosis from Benign Paroxysmal Positional Vertigo (BPPV). However, BPPV is not accompanied by abnormalities in Gaze and optokinetic testing,  which these clients demonstrated. The results of CHAMP revealed normal values which could rule out endolymphatic hydrops.  VEMP revealed reduced amplitude in one ear of Client B which was related to the inability of the client to turn to one side owing to a shoulder injury sustained in a recent accident. Though, VP is bilateral in both the clients, the presence of unilateral weakness could be attributed to higher degree of impingement on the weaker side compared to the relatively stronger side. 
The MRI findings of both the clients revealed presence of vascular loops around the 7 th and 8 th cranial nerve. MRI has been reported to have a sensitivity of 95% in cases with VP.  Out of a total of 25 continuous clients who showed symptoms of BPPV, only the clients of the present study underwent an MRI. This is suggestive of a high incidence of VP, which might be misdiagnosed as BPPV since the presenting symptoms of the two are alike and the results on Dix-Hallpike maneuver are similar.
This study highlights the importance of test protocol in the diagnosis of VP and the clinical findings of the cases with VP. Only audiological or vestibular assessment may not be sufficient for differential diagnosis of VP. They only help in excluding other similar vestibular disorders. MRI should be done for all the cases who present with the symptoms of non-fatigable positional vertigo which would improve the chances for diagnosis of VP. Features like oscillopsia, giddiness, and nausea during gaze and optokinetic testing along with a history of positional vertigo and positive results on Dix-Hallpike could be pivotal in its identification if MRI is not feasible.
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