Aim of the present study was to evaluate the effects of obstructive sleep apnoea syndrome (OSAS) on the peripheral and central vestibular
system, by means of a case series prospective study at the University referral centre of Otolaryngology Head and Neck Surgery; 45 consecutive
patients suffering from OSAS were compared with a control group of 30 volunteer subjects selected from among the department
employees. Severity of the disease was evaluated by means of cardio-respiratory function monitoring during sleep; the apnoea-hypopnoea
index was calculated. Both groups underwent: 1) head and neck examination; 2) fibre-optic examination; 3) pure tone audiometry; 4) evaluation
of eye movement disorders using oculomotility tests recorded with the help of video-nystagmography; 5) caloric vestibular responses
recorded with video-nystagmography; 6) auditory brainstem response. Results, when evaluating our data, showed that the peripheral vestibular
system may become asymmetric due to hypoxic damage while the central vestibular system corrects this disequilibrium

DISPENZA, F.

GALLINA, S.

KULAMARVA, G.

RIGGIO, F.

SPECIALE, R.

English

PubMed

GALLINA, Salvatore

SPECIALE, Riccardo

Dispenza, F

Kulamarva, G

Riggio, F

Archivio istituzionale della ricerca - Università di Palermo

281ACTA oTorhinolAryngologiCA iTAliCA 2010;30:281-284VestibologyObstructive sleep apnoea syndrome (OSAS): effects on the vestibular systemObstructive sleep apnoea syndrome (OSAS): effetti sul sistema vestibolareS. Gallina1, F. DiSpenza2, G. Kulamarva3, F. riGGio1, r. Speciale11 otorhinolaryngology unit, Biomedicine and neurosciences clinic Department, university of palermo;2 otorhinolaryngology unit, Surgical and oncological clinical Department, university of palermo;3 enT clinic, Kasaragod, indiaSummAryAim of the present study was to evaluate the effects of obstructive sleep apnoea syndrome (oSAS) on the peripheral and central vestibular system, by means of a case series prospective study at the university referral centre of otolaryngology head and neck Surgery; 45 con-secutive patients suffering from oSAS were compared with a control group of 30 volunteer subjects selected from among the department employees. Severity of the disease was evaluated by means of cardio-respiratory function monitoring during sleep; the apnoea-hypopnoea index was calculated. Both groups underwent: 1) head and neck examination; 2) fibre-optic examination; 3) pure tone audiometry; 4) evalu-ation of eye movement disorders using oculomotility tests recorded with the help of video-nystagmography; 5) caloric vestibular responses recorded with video-nystagmography; 6) auditory brainstem response. results, when evaluating our data, showed that the peripheral ves-tibular system may become asymmetric due to hypoxic damage while the central vestibular system corrects this disequilibrium.Key wordS: OSAS • Dizziness • Vertigo • Imbalance • DisequilibriumriASSunToObiettivo del presente studio è la valutazione degli effetti dell’OSAS sul sistema vestibolare periferico e centrale. A questo scopo è stato realizzato uno studio prospettico presso un centro di riferimento Universitario di Otorinolaringoiatria e Chirurgia della Testa e del Collo, basato sullo studio di un gruppo di 45 pazienti consecutive affetti da OSAS confrontati con un gruppo di controllo di 30 soggetti normali. La severità della malattia è stata valutata con monitoraggio cardio-respiratorio nel sonno con calcolo dell’indice apnea-ipopnea. Entrambi i gruppi sono stati esaminati con: visita completa ORL, esame endoscopico, audiometria, videonistagmografia, prove caloriche, ABR. I risultati dello studio hanno evidenziato che il sistema vestibolare periferico può diventare asimmetrico o iporeflessico a causa del danno ipossico, mentre il sistema vestibolare centrale ripristina il corretto equilibrio.PArOle chIAVe: OSAS • Vertigine • DisequilibrioActa Otorhinolaryngol Ital 2010;30:281-284IntroductionSeveral Authors in the last decade 1-3 have focused atten-tion on research into brainstem neurophysiology in respira-tory tract regulation and related disturbances during sleep. They used auditory brainstem response (ABr) as a means of measuring the effect of brainstem on the pathophysiol-ogy of obstructive sleep apnoea syndrome (OSAS). Various branches of medicine such as neurology, Pulmonology, otorhinolaryngology, and Cardiology have made efforts to find diagnostic procedures and treatment for oSAS. The role of the ear-nose-throat (enT) specialist became fun-damental in the diagnostic pathway, morphological obser-vations and classification of the anatomical anomalies of the upper respiratory tract, which are often associated with oSAS. The enT surgeon also plays an important role in the surgical correction of such problems.The cardiovascular problems and neurological distur-bances due to hypoxia of the oSAS are well known. But, the neurotological consequences are not so clearly iden-tified and, therefore, are subject of debate. There are no convincing studies yet, in the english literature, regarding this topic. we could only find some publications on the ef-fect of oSAS on hearing function. even these do not show any uniform results 1 3.The aim of this investigation is to verify the functional neurotological alterations in oSAS patients focusing in particular on the peripheral and central vestibular system. Based on the evidence that the vestibular nuclei are more sensitive to hypoxia than other cerebral nuclei, as dem-onstrated in animal experiments 4, our hypothesis is that the functional alteration of the vestibular nuclei may be an index of abnormal activity of the respiratory nuclei considering the anatomical contiguity of this centre. The S. gallina et al.282Table I. Apnoea Hypopnoea Index (AHI) of the two groups.AHI OSAS Group Control Group0-5 0 3010-30 29 –> 30 16 –All patients in the OSAS group were classified as moderate to severe disease. In the control group, no patients presented sleep snoring.hypoxic damage could also be the cause of a deficit of the peripheral vestibular system.Material and methodsThis prospective study was performed on 45 consecutive patients suffering from oSAS in the period 2004-2005. They were compared with a control group of 30 volun-teers selected from among the department employees. Case history and presenting symptoms were collected. The severity of the disease was evaluated by monitor-ing cardio-respiratory function during sleep in both the groups. The apnoea-hypopnoea index (Ahi) (event per hour of sleep) was calculated according to the American Academy recommendations 5.All of the patients in the oSAS group and subjects in the control group were evaluated as follows: 1) A detailed head and neck examination; 2) fibre-optic nasal, pharyn-geal and laryngeal examination; 3) pure tone audiometry (PTA) (recording the average of 0.5, 1, 2, 4 khz); 4) evalu-ation of eye movement disorders using oculomotility tests recorded by videonystagmography (VNG); 5) caloric ves-tibular responses with cold water stimulation and recorded by VNG; 6) auditory brainstem response (ABr).The oculomotility test evaluation included: a) voluntary saccadic eye movements: latency, maximal velocity, ac-curacy; b) smooth-pursuit movements: latency, gain, mor-phology; c) optokinetic nystagmus: slow-phase angular velocity, gain, symmetry; d) nystagmus during caloric vestibular tests: duration, frequency, slow-phase angular velocity with the classic Jongkees’ formula 6.Patients with previous diagnosis of neurotological disease (i.e., labyrinthine diseases, benign paroxysmal positional vertigo, etc.), cardiovascular diseases, pulmonary disorders or metabolic alterations were excluded from the study.informed consent was obtained, in each case, and our in-stitutional review Board approved the present study.ResultsThe oSAS group included 31 males and 14 females. mean age of the patients was 43.3 years (range 24-56 years). mean age of the Control group was 41 years (range 27-54 years) and the male/female ratio was 2:1. no differences in obesity grade, cardiovascular disease, diabetes or other cardiovas-cular diseases were observed between the two groups.Among the 45 oSAS patients evaluated, 29 patients suf-fered from low to moderate grade oSAS (Ahi 10-30) and 16 had severe grade oSAS (Ahi > 30) (Table i). none of the individuals in the control group suffered from oSAS (Ahi ≤ 4).Four patients (8.8%) in the oSAS group complained of one episode of dizziness or imbalance during the last year and were excluded from the evaluation. no patients in ei-ther group complained of any hearing loss.Audiological assessment of the oSAS patients revealed: normal hearing in 36 patients and high frequencies of bilateral sensorineural hearing loss in 5 patients with a down-sloping audiometric curve (mean PTA for 4 and 8 Khz of 45 dB).Auditory brainstem response examination showed an in-creased I-V wave interval in 36.5% of OSAS cases and in 4 subjects in the control group. All subjects with increased latency had normal hearing.in the control group, we discovered 2 patients with a bi-lateral sensorineural hearing loss at 4 Khz and 8 khz fre-quencies, with mean PTA of 35 dB, but the ABr in these 2 individuals was normal.Caloric vestibular tests in the oSAS group demonstrated abnormal findings in 27 patients and normal vestibular functions in the remaining 8 patients.of the 27 patients with an abnormal test result, 20 had bi-lateral vestibular hyporeflexia and 7 revealed a unilateral vestibular hyporeflexia. The saccadic eye movement study showed an increased latency (> 200 msec) in 4 cases. Five patients had a morphological alteration of smooth-pursuit movements. The optokinetic nystagmus was normal in all cases. The control group presented normal instrumen-tal vestibular tests in all cases but one that revealed an asymptomatic unilateral hyporeflexia.Stratification of the data according to the grade of oSAS did not show any significant difference between the inci-dence of bilateral or unilateral hyporeflexia (p > 0.23). All data are shown in Tables ii, iii.DiscussionThe recurrent apnoic episode, which is so characteristic of oSAS, results in a continuous reduction in the haemo-globin oxygen saturation. This causes, especially in the severe cases, a hypoxic condition during sleep. The ef-fects of this chronic hypoxia, during sleep, result in altera-tions in the normal physiology of several organ systems in the body.regardless of the cause of the oSAS, the central causa-tive pathology lies in the upper respiratory tract. Although there has been much research in the field of enT in treat-ing this condition, it is surprising to find that very little research has been performed looking into the effect that oSAS may have on the neighbouring anatomical struc-tures that are regularly dealt with on a day-to-day basis. effects of oSAS on vestibular system283As already mentioned, there are no studies in the english literature mentioning the effect of oSAS on the vestibular apparatus. urban et al. 1 did not find vestibular alterations in 83% of the series reported.however, there is some mention in two studies, one con-ducted by an italian group and the other by a Chinese group on a similar topic, although both were focused on the effect of oSAS on hearing function. only abstracts are available for these studies in the english literature 7 8.we conducted the present study in order to find out whether there were any possible effects on the vestibular labyrinth secondary to oSAS.The functional alteration of the vestibular nuclei may be an indication of abnormal activity of the respiratory nu-clei considering the anatomical contiguity of this centre. The vestibular nuclei damage could be revealed by an al-teration of the slow and rapid eye movements.The quantitative and qualitative evaluation of periph-eral and central vestibular function, by computed VNG, allowed us to acquire precise data about the alterations found in oSAS. The susceptibility of the posterior laby-rinth to a hypoxic state was proven by the high percent-age of vestibular reflex alterations observed during caloric stimulation. The test results were found to be worse in patients with a severe grade of oSAS.Sleep deprivation due to oSAS might affect postural sta-bility on account of a reduced adaptation ability and laps-es in attention 9. The right temporo-parietal cortex activity, an area also involved in VOr control, may be altered by sleep deprivation 10. A slight compromise of the central vestibular system is demonstrated by the low percentage of oculomotility test alterations in our series. These struc-tures, located in the brainstem and cerebellum, are thought to regulate the slow eye movements and ocular reflex.The results observed show an apparent incongruence be-tween the occurrence of subjective symptoms of vestibu-lar hypofunction such as giddiness or vertigo, that was seen in just four patients (4/35), as opposed to the objec-tive findings of VNG which showed variations in 27/35 patients.A possible explanation is that the caloric test, in such patients, could be influenced by a different factor such as mental alertness, drowsiness or lapse in attention due to oSAS with consequent suppression of the oc-currence of caloric nystagmus, resulting in bilateral hyporeflexia.A potential link between sleep disturbance and dizziness could possibly explain the difference between the incidence of symptoms and the otoneurological findings. The chronic idiopathic dizziness present in some OSAS patients may be related to sleep deprivation related to sleep apnoea 11.however, it is tempting to hypothesize that the chronic hypoxic state seen in oSAS results in the development of a progressive reduction in vestibular function. if the peripheral vestibular system becomes asymmetric due to hypoxic damage, the central vestibular system corrects this disequilibrium between the two sides. our results can also indicate that the central vestibular system is more re-sistant to the hypoxic state. Because of this, a unilateral peripheral vestibular deficit may be well compensated by the central vestibular system and the equilibrium may be restored.Table II. Clinical and instrumental findings in OSAS group.Clinical and Instrumental data Patients ControlsSymptoms Dizziness 4 * 0Subjective Hearing Loss 0 0Sensorineural Hearing Loss at Pure Tone Audiometry 5 (12.2%) 2 (6.6%)ABR (increased I-V wave interval) 15 (36.5%) 4 (13%)Caloric Test Hyporeflexia Bilateral 20 (48.7%) 0Hyporeflexia Unilateral 7 (17%) 1 (3.3%)SEM (latency > 200 msec.) 4 (9.7%) 0SPM (morphology alterations) 5 (12.2%) 0SEM: saccadic eye movements; SPM: smooth-pursuit movements; * patients excluded from final analysis.Table III. Stratification of Vestibular tests with Apnoea Hypopnoea Index (AHI) score.Bilateral hyporeflexia Unilateral hyporeflexia Morphological alteration of smooth pursuitAHI 10-30 (29 cases) 11 (37.9%) 4 (13.7%) 2 (6.8%)AHI > 30 (16 cases)   9 (56.2%) 3 (18.7%) 3 (18.7%)The percentage was calculated for each subgroup of AHI score. The χ2 test did not show a significant difference between grade of OSAS and incidence of hyporeflexia (p > 0.23).S. gallina et al.284Conclusionsevaluation of vestibular function, in oSAS patients, shows the effects of the sleep apnoea and its associated hypoxia on the peripheral, principally, and central ves-tibular systems. The peripheral vestibular system may become asymmetric or hypo-reflexic due to hypoxic damage while the central vestibular system corrects this disequilibrium. These findings may help to better iden-tify some of the vertiginous symptoms which oSAS pa-tients complain of and which are classified as idiopathic dizziness 11.References1 urban PP, Schlegel J, ellrich J, et al. Electrophysiological brainstem investigations in obstructive sleep apnoea syn-drome. J neurol 1996;243:171-4.2 Snyderman nl, Johnson JT, moller m, et al. Brainstem evoked potentials in adult sleep apnoea. Ann otol rhinol laryngol 1982;91:597-8.3 Peled r, Pratt h, Scharf B, et al. Auditory brainstem evoked potentials during sleep apnoea. neurology 1983;33:419-23.4 yoshida S, Sasa m, Takaori S. Different sensitivity to hypoxia in neuronal activities of lateral vestibular and spinal trigemi-nal nuclei. Stroke 1988;19:357-64.5 American Academy of Sleep medicine Task Force. Sleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research. The Report of an American Academy of Sleep Med-icine Task Force. Sleep 1999;22:667-89.6 Jongkees lB. Thermic test and electronystagmography. Acta otorhinolaryngol Belg 1965;19:455-64.7 Cimino A, Speciale r, gallina S, et al. Brain stem auditory evoked potentials in obstructive sleep apnoea syndrome. Ac-ta otorhinolaryngol ital 1995;15(Suppl):15-17.8 She wd, Zhang Q, Chen F, et al. Peri-uvulopalatopharyn-goplasty otoacoustic emissions in patients with obstructive sleep apnoea-hypopnea syndrome. Zhonghua er Bi yan hou Ke Za Zhi 2004;39:48-51.9 Gomez S, Patel M, Berg S, et al. Effects of proprioceptive vibratory stimulation on body movement at 24 and 36h of sleep deprivation. Clin neurophysiol 2008;119:617-25.10 Quarck G, Ventre J, etard O, et al. Total sleep depriva-tion can increase vestibulo-ocular responses. J Sleep res 2006;15:369-75.11 Sowerby lJ, rotenberg B, Brine m, et al. Sleep apnoea, day-time somnolence and idiopathic dizziness - A novel associa-tion. laryngoscope 2010;120:1274-8.received: march 10, 2010 - Accepted: July 27, 2010Address for correspondence: Dr. F. Dispenza, Via Oreto 339, 90124 Palermo, Italy. e-mail: francesco.dispenza@gmail.com

Obstructive sleep apnoea syndrome(OSAS):effects on the vestibular system

American Academy of Sleep medicine Task Force. Sleeprelated breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research. The Report of an American Academy of Sleep Medicine Task Force. Sleep

Auditory brainstem evoked potentials during sleep apnoea.

Brain stem auditory evoked potentials in obstructive sleep apnoea syndrome. Acta otorhinolaryngol ital 1995;15(Suppl):15-17.

Brainstem evoked potentials in adult sleep apnoea. Ann otol rhinol laryngol 1982;91:597-8.

Different sensitivity to hypoxia in neuronal activities of lateral vestibular and spinal trigeminal nuclei.

Effects of proprioceptive vibratory stimulation on body movement at 24 and 36h of sleep deprivation.

Electrophysiological brainstem investigations in obstructive sleep apnoea syndrome.

Peri-uvulopalatopharyngoplasty otoacoustic emissions in patients with obstructive sleep apnoea-hypopnea syndrome. Zhonghua er Bi yan hou Ke Za Zhi

Sleep apnoea, daytime somnolence and idiopathic dizziness - A novel association. laryngoscope 2010;120:1274-8. received: march 10,

Thermic test and electronystagmography.

Total sleep deprivation can increase vestibulo-ocular responses.

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3146317

Obstructive sleep apnoea syndrome (OSAS):
effects on the vestibular system

Obstructive sleep apnoea syndrome (OSAS): effects on the vestibular system

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Archivio istituzionale della ricerca - Università di Palermo