Central Annals of Otolaryngology and Rhinology

Cite this article: Giacomini P, Di Mauro R, Topazio D, Di Girolamo S (2015) Head Tilt Posturography: Clinical Value in Peripheral Labirinthine Disorders. Ann Otolaryngol Rhinol 2(12): 1073.

*Corresponding authorDavide Topazio, Department of Otolaryngology, University of Tor Vergata, Viale Bruno Rizzieri 200 H, 00173 Rome, Italy, Tel: 393-297-922094; Email:

Submitted: 16 September 2015

Accepted: 11 November 2015

Published: 13 November 2015

ISSN: 2379-948X

Copyright© 2015 Topazio et al.

OPEN ACCESS

Keywords•Acute vestibular injury•Postural stability•Head

Research Article

Head Tilt Posturography: Clinical Value in Peripheral Labirinthine DisordersPiergiorgio Giacomini, Roberta Di Mauro , Davide Topazio* and Stefano Di GirolamoDepartment of Otolaryngology, University of Tor Vergata, Italy

Abstract

Acute vestibular injury, such as vestibular neuritis (VN), can produce a profound alteration in balance manifested by perception disorder and impaired control of postural adjustment and execution of movements. Stabilometry assesses posture balance through the quantification of body oscillations from the orthostatic position in a force platform. It involves monitoring center of pressure (COP) displacement to the lateral direction (X) and anterior-posterior direction (Y). In our study we investigated the postural control of patients affected by VN. We analyzed 30 subjects: 15 patients constituted the case group affected by VN were compared with 15 healthy volunteers. A static posturography was made within 6-24 hours of symptoms onset. Our purpose was to assess the use of posturography Fourier Frequency analysis with head tilt for the detection of peripheral vertigo destabilization. Fourier spectral analysis of body sway reveals that, independently from visual control, patients exhibit a significantly higher level of low/middle frequency oscillations on the frontal plane. The macular stimulation by head tilt increases significantly the difference in all analyzed parameters: there are significant differences of body oscillation in the patients vs controls on X and Y planes, the latter evident only in head tilt tests. The head tilt seems to show an antero-posterior plane destabilization otherwise not evident.

INTRODUCTIONPostural stability can be defined as the ability to maintain

the body in equilibrium. Static postural control depends on information received by the central nervous system from three peripheral sources: eyes, somatosensory system, and vestibular receptors, followed by outputs to the musculoskeletal system. Acute vestibular injury such as vestibular neuritis (VN), can produce a profound alteration in balance manifested by perception disorder and impaired control of postural adjustment and execution of movements. In these disorders, erroneous information is conveyed to the central nervous system, generating a series of postural impairments [1]. VN is defined as the sudden unilateral, usually partial, loss of vestibular function. Is the second most common cause of peripheral vestibular vertigo [2]. The characteristic signs and symptoms include sudden and prolonged vertigo, nausea/vomiting, horizontal nystagmus toward the unaffected ear, and ipsilesional body tilt. The vertigo attack appears without hearing impairments or any signs of brainstem dysfunction. Caloric testing reveals reduced or absent responses in the ipsilateral ear [3]. Stabilometry assesses posture balance through the quantification of body oscillations from the orthostatic position in a force platform. It involves monitoring center of pressure (COP) displacement to the lateral

direction (X) and anterior-posterior direction (Y) [4]. In our study we investigated the postural control of patients affected by VN. We analyzed not only the vestibulo-spinal reflex by standard stabilometry, but also by otolithic stimulation (head lateral tilt) to explore how the macula may influence the postural performance. Our purpose was to assess the use of head tilt posturography for the follow-up of peripheral vertigo. In particular its utility to detect improvements of VST normally hard to be recorded.

MATERIALS AND METHODSThe study involved 30 subjects. Fifteen patients constituted

the case group affected by VN (7 left and 8 right) aged from 41 to 69 years (mean age 55±14), the control group comprised 15 healthy volunteers with a mean age of 27.5 ±2.5 years. Informed consent was obtained from the subjects before each test. All subjects underwent otoneurological examination in accordance with the following protocol: accurate anamnesis for otoneurological diseases, pure tone audiometry, evaluation of tonic segmentary deviations, video-oculography, static posturography within 6-24 hours of symptoms onset. Vestibular neuritis diagnostic criteria were: presence of acute vertigo and nausea, spontaneous horizontal nystagmus directed to the healthy side, enhanced by Head-Shaking test, dynamic and static ataxia, unilateral

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significant caloric vestibular deficit, normal hearing [5]. We excluded patients and/or controls with neurological, psychiatric or systemic diseases (alcoholism, thyroid dysfunction, lumbar radiculopathy), postural hypotension, visual acuity under 10/10, vestibular pathology (in healthy controls). Static posturography was performed using a normalized computerized static posturography platform (S.Ve.P. – Amplaid, Bologna, Italy). Detailed information about this device has already been published [6]. We applied the following test:

1. Upright head with open eyes for 30 seconds and ocular fixation target at 1,5cm (OE);

2. Upright head with closed eyes for 30 seconds (CE);

3. Right head tilt (Right HT) with open eyes for 30 seconds;

4. Left head tilt (Left HT) with open eyes for 30 seconds;

5. Right head tilt with closed eyes for 30 seconds;

6. Left head tilt with closed eyes for 30 seconds.

VN patients were tested during the acute phase (at the moment of symptom manifestation). All the results were matched with normal controls. Posturography parameters were calculated from the statokinesigram; we analyzed Fourier Fast Transformation (FFT) on both X and Y axes: FFT calculates the frequency composition of body sway by means of a mathematical model. A personal analysis of FFT was applied, details of the method have been published elsewhere [7].

Statistical analysis

Normal distribution of continuous variables was assessed by Shapiro-Francia test. Continuous variables were compared by Student’s t-test. Categorical variables were compared by the c2 test or Fisher exact test when required. Statistical analysis was performed using Stata 6.0 software (Texas Station University College).

RESULTSStabilometry shows that VN exhibit a pattern of body

oscillation which is different from controls in all the parameters analyzed. Fourier spectral analysis of body sway reveals that, independently from visual control, normal patients exhibit a significantly lower level of low/middle frequency oscillations (both on the lateral and the anteroposterior axes). During the acute phase, in the upright position, patients affected by VN shows a pattern of body oscillation of 24,06 (open eyes) and 28,46 (closed eyes) on low frequencies on X axis and of 25,02 (open eyes) and 27,16 (closed eyes) on Y axis. Instead, healthy patients exhibit a pattern of body oscillation of 20,54 with open eyes and 23,16 with closed eyes on X axis and of 21,47 with open eyes and 25,46 with closed eyes on the Y axis (Table 1, Table 2).

Furthermore, the macular stimulation by head tilt increases significantly the difference in all analyzed parameters. The differences between the two groups are significant only by the use of the head tilt test. VN patients body oscillations seem prevalent on the Y axis (Figure 1).

Analyzing results with open eyes and closed eyes, the body sway was worse with eyes closed in low and middle frequency

oscillations on both axis as expected for the peripheral aethiology of the vertigo.

DISCUSSIONMany clinical tests have been developed to asses and

quantify functional capacity related to balance and postural control. Posturography is a set of techniques that study posture and informs us about the vestibular-spinal function (VRS) and the compensation reached at this level by any damage to the balance system, regardless of what happens in other levels [8]. The relation between the results of the static posturography and the various specific clinical balance tests has been the subject of many studies in order to understand the value clinical of this test [9, 10]. Normally, the tests are applied under different protocols for the support base (feet together, separated, supported by one foot, etc.), surface (hard or foam) and vision (opened and closed eyes) [4]. As a result, a subject is stable when his/her center of mass (COM) is maintained over the supporting base. Under static conditions, muscular forces are generated in order to maintain the COM within the limits of stability, the vertical projection of these forces being the COP [11]. During the static position, the frequencies of the center of pressure displacement can be analyzed by the Fourier Transform (FFT), among the two asses (x, y). Even if there isn’t a common agreement about the importance and specificity of this index, the postural control seems to act in specific frequencies for any control system (visual, proprioceptive and vestibular). Static posturography can analyzes this oscillation frequency by registering the variation of the center of pressure elaborated by FFT during the time [7]. The evolution of VSR after acute labyrinthine pathology may be tracked by posturography applying the FFT analysis [12]. The development of compensation has also been studied:

Table 1: Results on X axis.

OE Right HT Left HT

VN (15) 24,06±5,30 23,20±4,09 17,85±2,97

Controls (15) 20,54±5,72 21,05±4,60 12,3±2,43

CE Right HT Left HT

VN (15) 28,46±3,98 25,67±3,89 20,14±3,43

Controls (15) 23,16±4,65 23,51±3,77 14,68±3,77

Table 2: Results on Y axis.

OE Right HT Left HT

VN (15) 25,02±6,21 26,45±7,09 20,16±4,43

Controls (15) 21,47±7,01 20,19±5,32 16,11±3,65

CE Right HT Left HT

VN (15) 27,16±2,78 29,58±4,08 22,26±3,07

Controls (15) 25,46±4,33 23,01±3,64 18,66±2,97

VN pre therapy and controls X axisp<0,05 RHT (mhx) p<0,01 OE, CE (mhx) p<0,001 LHT (lhx mhx)

VN pre therapy and controls Y axisp< 0,05 RHT (lhy), LHT (lhy)p<0,01 RHT (mhy)p<0,001 LHT (mhy)

Figure 1 Body oscillation in the patients vs controls.

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Narita et al. followed up 31 patients with vestibular dysfunction for about 260 days. They used measures of serial posture oscillation and the parameters of displacement and area. They found a correlation of clinical improvement and reduction of posture oscillations with time, confirming the usefulness of the test for follow up of patients with vestibular dysfunction. The stabilometric parameters chosen were useful to perform functional assessment of patients with dizziness. Because of the results of electronystagmography were normal, they suggest that there is a deficient compensation of VSR in relation to the compensation of VOR level. Even though this information is not enough for the diagnosis, it seems to be useful for management, follow up and vestibular rehabilitation [13]. In the present study, we performed a stabilometric analysis by the Fast Fourier Transform (FFT) of body sway of patients with VN and compared them with the groups of normal subjects. We confirmed that the patients presented instability in the orthostatic position. It is expected in subjects with vestibular dysfunction that they have more visual dependency due to the impaired vestibular input: in our cases worse stabilometric parameters were recorded when testing posture closing their eyes, which confirms the usefulness of static posturography frequency analysis by FFR in monitoring the VSR. In our study, we have introduced an additional parameter in the stabilometric examination: by lateral head tilt of the patients we cause stimulation of macular labyrinthine receptor aimed to sensitize the posturography testing. By this way we obtained statistical significant differences between the analyzed conditions, showing the usefulness of head tilting in detecting subtle alterations of postural pattern otherwise undetected. The proposed method of testing VSR seems therefore worth to be used in the clinical setting to increase the sensitivity of the exam. In our cases we have greater oscillations of the pressure center in all the head positions, compared to controls. However, the statistical significance of data is reached only with the head tilt. In conclusion, we suggest the use of head tilt frequency analysis posturography for the follow-up of peripheral vertigo patients after treatment to detect subtle improvements of VST otherwise hard to be recorded.

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Giacomini P, Di Mauro R, Topazio D, Di Girolamo S (2015) Head Tilt Posturography: Clinical Value in Peripheral Labirinthine Disorders. Ann Otolaryngol Rhinol 2(12): 1073.

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