The authors have no acknowledgements.

The study was approved by the ethical committee of the Medical University of Vienna and has been performed in accordance with the ethical standards found in the Declaration of Helsinki. An informed consent was signed by all patients and controls before the study.
1. Installation of the patient in the chair
<ol>
	<li>Perform the measurement binocularly. Install the patient in a stable chair with a backrest and a head fixation unit. The latter maintains the patient&#39;s head in a stable and d...

<ol>
	<li>Dieterich, M., Brandt, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perception+of+Verticality+and+Vestibular+Disorders+of+Balance+and+Falls.">Perception of Verticality and Vestibular Disorders of Balance and Falls.</a> Frontiers in Neurology. 10, 172 (2019).</li><li>Elwischger, K., Rommer, P., Prayer, D., Mueller, C., Auff, E., Wiest, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thalamic+astasia+from+isolated+centromedian+thalamic+infarction.">Thalamic astasia from isolated centromedian thalamic infarction.</a> Neurology. 78 (2), 146-147 (2012).</li><li>Wiest, G., Zimprich, F., Prayer, D., Czech, T., Serles, W., Baumgartner, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vestibular+processing+in+human+paramedian+precuneus+as+shown+by+electrical+cortical+stimulation.">Vestibular processing in human paramedian precuneus as shown by electrical cortical stimulation.</a> Neurology. 62 (3), 473-475 (2004).</li><li>Wiest, G., Tian, J. R., Baloh, R. W., Crane, B. T., Demer, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Otolith+function+in+cerebellar+ataxia+due+to+mutations+in+the+calcium+channel+gene+CACNA1A.">Otolith function in cerebellar ataxia due to mutations in the calcium channel gene CACNA1A.</a> Brain. 124, 2407-2416 (2001).</li><li>Dakin, C. J., Rosenberg, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gravity+estimation+and+verticality+perception.">Gravity estimation and verticality perception.</a> Handbook of Clinical Neurology. 159, 43-59 (2018).</li><li>Demer, J. L., Crane, B. T., Tian, J. R., Wiest, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+tests+of+vestibular+function.">New tests of vestibular function.</a> Annals of the New Yorc Academy of Science. 942, 428-445 (2001).</li><li>Clarke, A. H., Schonfeld, U., Helling, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unilateral+examination+of+utricle+and+saccule+function.">Unilateral examination of utricle and saccule function.</a> Journal of Vestibular Research. 13 (4-6), 215-225 (2003).</li><li>Kingma, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+testing+of+the+statolith-ocular+reflex.">Clinical testing of the statolith-ocular reflex.</a> ORL Journal for Otorhinolaryngology and its Related Specialties. 59 (4), 198-208 (1997).</li><li>Bisdorff, A. R., Wolsley, C. J., Anastasopoulus, D., Bronstein, A. M., Gresty, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+perception+of+body+verticality+(subjective+postural+vertical)+in+peripheral+and+central+vestibulardisorders.">The perception of body verticality (subjective postural vertical) in peripheral and central vestibulardisorders.</a> Brain. 199 (5), 1523-1534 (1996).</li><li>Welgampola, M. S., Colebatch, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+and+clinical+applications+of+vestibular-evoked+myogenic+potentials.">Characteristics and clinical applications of vestibular-evoked myogenic potentials.</a> Neurology. 64 (10), 1682-1688 (2005).</li><li>Kingma, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Function+tests+of+the+otolith+or+statolith+system.">Function tests of the otolith or statolith system.</a> Current Opinion in Neurology. 19 (1), 21-25 (2006).</li><li>Kheradmand, A., Winnick, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perception+of+Upright:+Multisensory+Convergence+and+the+Role+of+Temporo-Parietal+Cortex.">Perception of Upright: Multisensory Convergence and the Role of Temporo-Parietal Cortex.</a> Frontiers in Neurology. 8, 552 (2017).</li><li>Zwergal, A., Rettinger, N., Frenzel, C., Dieterich, M., Brandt, T., Strupp, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+bucket+of+static+vestibular+function.">A bucket of static vestibular function.</a> Neurology. 72 (19), 1689-1692 (2009).</li><li>Bronstein, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Interaction+of+Otolith+and+Proprioceptive+Information+in+the+Perception+of+Verticality:+The+Effects+of+Labyrinthine+and+CNS+Disease.">The Interaction of Otolith and Proprioceptive Information in the Perception of Verticality: The Effects of Labyrinthine and CNS Disease.</a> Annals of the New York Academy of Science. 871, 324-333 (1999).</li><li>Saeys, W., Herssens, N., Verwulgen, S., Truijen, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sensory+information+and+the+perception+of+verticality+in+post-stroke+patients.+Another+point+of+view+in+sensory+reweighting+strategies.">Sensory information and the perception of verticality in post-stroke patients. Another point of view in sensory reweighting strategies.</a> PLOS ONE. 13 (6), 0199098 (2018).</li><li>Baier, B., Th&#246;mke, F., Wilting, J., Heinze, C., Geber, C., Dieterich, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+pathway+in+the+brainstem+for+roll-tilt+of+the+subjective+visual+vertical:+evidence+from+a+lesion-behavior+mapping+study.">A pathway in the brainstem for roll-tilt of the subjective visual vertical: evidence from a lesion-behavior mapping study.</a> Journal of Neuroscience. 32 (43), 14854-14858 (2012).</li><li>Huh, Y. E., Kim, K., Chung, W., Youn, J., Kim, S., Cho, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pisa+Syndrome+in+Parkinson's+Disease:+Pathogenic+Roles+of+Verticality+Perception+Deficits.">Pisa Syndrome in Parkinson's Disease: Pathogenic Roles of Verticality Perception Deficits.</a> Science Reports. 8 (1), 1804 (2018).</li><li>Ogawa, Y., Otsuka, K., Shimizu, S., Inagaki, T., Kondo, T., Suzuki, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Subjective+visual+vertical+perception+in+patients+with+vestibular+neuritis+and+sudden+sensorineural+hearing+loss.">Subjective visual vertical perception in patients with vestibular neuritis and sudden sensorineural hearing loss.</a> Journal of Vestibular Research. 22 (4), 205-211 (2012).</li><li>Toupet, M., Van Nechel, C., Bozorg, A., Grayeli, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+body+laterality+on+recovery+from+subjective+visual+vertical+tilt+after+vestibular+neuritis.">Influence of body laterality on recovery from subjective visual vertical tilt after vestibular neuritis.</a> Audiology and Neurootology. 19 (4), 248-255 (2014).</li><li>Lopez, C., Lacour, M., Ahmadi, A. E., Magnan, J., Borel, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+of+visual+vertical+perception:+a+long-term+sign+of+unilateral+and+bilateral+vestibular+loss.">Changes of visual vertical perception: a long-term sign of unilateral and bilateral vestibular loss.</a> Neuropsychologia. 45 (9), 2025-2037 (2007).</li><li>Kitahara, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Idiopathic+benign+paroxysmal+positional+vertigo+with+persistent+vertigo/dizziness+sensation+is+associated+with+latent+canal+paresis,+endolymphatic+hydrops,+and+osteoporosis.">Idiopathic benign paroxysmal positional vertigo with persistent vertigo/dizziness sensation is associated with latent canal paresis, endolymphatic hydrops, and osteoporosis.</a> Auris Nasus Larynx. 46 (1), 27-33 (2019).</li><li>Platho-Elwischger, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasticity+of+static+graviceptive+function+in+patients+with+cervical+dystonia.">Plasticity of static graviceptive function in patients with cervical dystonia.</a> Journal of the Neurological Sciences. 373, 230-235 (2017).</li><li>Aranda-Moreno, C., J&#225;uregui-Renaud, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+subjective+visual+vertical+in+vestibular+disease.">The subjective visual vertical in vestibular disease.</a> Revista de Investigaci&#243;n Cl&#237;nica. 57 (1), 22-27 (2005).</li><li>Guerraz, M., Luyat, M., Poquin, D., Ohlmann, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+neck+afferents+in+subjective+orientation+in+the+visual+and+tactile+sensory+modalities.">The role of neck afferents in subjective orientation in the visual and tactile sensory modalities.</a> Acta Otolaryngologica. 120 (6), 735-738 (2000).</li><li>Luyat, M., No&#235;l, M., Thery, V., Gentaz, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gender+and+line+size+factors+modulate+the+deviations+of+the+subjective+visual+vertical+induced+by+head+tilt.">Gender and line size factors modulate the deviations of the subjective visual vertical induced by head tilt.</a> BMC Neuroscience. 13, 28 (2012).</li><li>Fraser, L. E., Makooie, B., Harris, L. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Subjective+Visual+Vertical+and+the+Subjective+Haptic+Vertical+Access+Different+Gravity+Estimates.">The Subjective Visual Vertical and the Subjective Haptic Vertical Access Different Gravity Estimates.</a> PLOS ONE. 10 (12), 0145528 (2015).</li><li>Otero-Millan, J., Kheradmand, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Upright+Perception+and+Ocular+Torsion+Change+Independently+during+Head+Tilt.">Upright Perception and Ocular Torsion Change Independently during Head Tilt.</a> Frontiers in Human Neuroscience. 10, 573 (2016).</li><li>Kim, S. H., Kim, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+Head+Position+on+Perception+of+Gravity+in+Vestibular+Neuritis+and+Lateral+Medullary+Infarction.">Effects of Head Position on Perception of Gravity in Vestibular Neuritis and Lateral Medullary Infarction.</a> Frontiers in Neurology. 9, 60 (2018).</li><li>Funk, J., Finke, K., M&#252;ller, H. J., Utz, K. S., Kerkhoff, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+lateral+head+inclination+on+multimodal+spatial+orientation+judgments+in+neglect:+Evidence+for+impaired+spatial+orientation+constancy.">Effects of lateral head inclination on multimodal spatial orientation judgments in neglect: Evidence for impaired spatial orientation constancy.</a> Neuropsychologia. 48 (6), 1616-1627 (2010).</li><li>Winnick, A., Sadeghpour, S., Otero-Millan, J., Chang, T. P., Kheradmand, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Errors+of+Upright+Perception+in+Patients+With+Vestibular+Migraine.">Errors of Upright Perception in Patients With Vestibular Migraine.</a> Frontiers in Neurololgy. 9, 892 (2018).</li><li>Deriu, F., Ginatempo, F., Manca, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancing+research+quality+of+studies+on+VEMP+in+central+neurological+disorders:+a+scoping+review.">Enhancing research quality of studies on VEMP in central neurological disorders: a scoping review.</a> Journal of Neurophysiology. 122 (3), 1186-1206 (2019).</li><li>Rosengren, S. M., Colebatch, J. G., Young, A. S., Govender, S., Welgampola, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vestibular+evoked+myogenic+potentials+in+practice:+Methods,+pitfalls+and+clinical+applications.">Vestibular evoked myogenic potentials in practice: Methods, pitfalls and clinical applications.</a> Clinical Neurophysiology Practice. 4, 47-68 (2019).</li></ol>

The authors have nothing to disclose.

SVV is a method to ensure the sense of verticality. It results from the integration of several information. The vestibular system being of paramount importance in this perception, it has been shown that a lesion at any level of vestibular information pathway leads to SVV errors.
The measurement of SVV in the head upright position is now regarded as the clinical standard method for recording otolith function. However, this method is hampered by low sensitivity as SVV-deviations in darkness in h...

Impairment of otolith function can be caused by peripheral as well as by central vestibular conditions1. Peripheral vestibular causes include Meniere&#39;s disease, labyrinth infarction, as well as superior or inferior vestibular neuritis. Central otolith dysfunction can occur in lesions of central otolithic pathways from brain stem via thalamus2 to the vestibular cortex3. In addition, diminished otolith reflexes are also found in cerebellar disorders4. While a number of standardized methods, such as caloric testing or video-head impulse test, are available for the assessment of semicircular canal function, no standardized clinical measurement method exists for gravity estimation and verticality perception5.
Since the otoliths are responsible for the perception of linear acceleration, otolith function can in principle be measured by linear acceleration by recording the so-called translational vestibulo-ocular reflex (t-VOR). However, this requires the use of special and complex equipment such as a parallel swing or linear sleds4,6. For the assessment of unilateral saccular and utricular function a specific off-center centrifugation test has been developed, which could be used clinically in balance laboratories with a specific rotational chair system7. When displacing the head by 3.5&#8211;4 cm from the rotation axis, the eccentrically positioned utricle is stimulated unilaterally by a resultant centrifugal force. In this paradigm otolith function can be determined either by measuring the resulting eye torsion or the subjective visual vertical (SVV). This procedure, however, also requires sophisticated equipment and the method still shows limited sensitivities for both SVV and eye torsion assessment7. Otolith function can further be quantified through eye movement recordings. Assessment can be done in horizontal or linear acceleration, but also during head- or body tilt in the roll plane with application of 3-D videooculography. The latter allows determination of ocular torsion. The clinical application of this method is also limited due to its low sensitivity8. The perception of body verticality (i.e., the sensation that I feel my body aligned with the true vertical) can be assessed by means of the so-called subjective postural vertical. In this experimental task, patients are seated in a chair in a motorized gimbal and asked to indicate when they entered and exited the upright position, while being tilted 15 &#176; in the pitch or roll plane. The disadvantage of this technique is not only its elaborate experimental approach, but also that it measures both otolith and body proprioceptive signals9. Whether vestibular evoked myogenic potentials (VEMPs) are useful clinical screening tools for otolith function in various clinical disorders is still controversial10,11.
Visual tasks are currently the most frequently used clinical methods for measuring graviceptive function, which can be assessed through measurement of the subjective visual vertical (SVV)12. Seen from a precise physiological perspective, SVV is not a direct test of the otolith function alone, as the SVV is the result of a weighting between several sources of information (gravity, proprioceptive and also visual when they are available). However, for rapid clinical use, an easy application of this SVV task, the so-called bucket test, has been developed13 especially for the emergency setting, enabling immediate detection of acute disturbances of graviceptive perception. The more precise and standardized procedure consists of letting an observer align a light bar or rod with the estimated vertical. Tested in darkness in healthy individuals in an upright position, deviations are limited to &#177; 2&#176; from the earth vertical14. Using the SVV task, graviceptive function has so far been assessed in a variety of neurological conditions such as stroke15,16 or Parkinson&#8217;s disease17. Furthermore, impaired SVV-perception has also been reported in unilateral18,19 or bilateral vestibular lesions20, as well as in patients with benign paroxysmal positional nystagmus21.
We here present a modified SVV assessment method, which measures SVV estimates not only in head-upright position but also at &#177; 15&#176; and &#177; 30&#176; head tilts in the roll plane. This paradigm increases the information content for the detection of graviceptive deficits and for systematic tilts of the SVV.

<table>
	<tbody>
		<tr>
			<td>Adjustable plastic goniometer board 7,87&#34; x 7,87&#34;, (marked tilt angles of 0&#176;, 15&#176; and 30&#176; )</td>
			<td>self-produced</td>
			<td>6</td>
			<td>for fixation at the backrest and for adjustment of neckrest along the given tilt angles (0&#176;,15&#176;,30&#176;)</td>
		</tr>
		<tr>
			<td>Elastic head band with adjustable screw on the back</td>
			<td>Micromedical Technologies Inc</td>
			<td>4</td>
			<td>modified with attached adhesive strap</td>
		</tr>
		<tr>
			<td>HD LCD display, 1366 x 768p resolution, 19&#34;</td>
			<td>Philips</td>
			<td>5</td>
			<td>for monitoring SVV-adjustments outside the cabin (infrared camera recording)</td>
		</tr>
		<tr>
			<td>Subjective Visual Vertical Set including infrared video camera (black/white, resolution 0,25&#176;)</td>
			<td>Micromedical Technologies Inc</td>
			<td>2</td>
			<td></td>
		</tr>
		<tr>
			<td>Sytem 2000 (Rotational Vestibular Chair System with Centrifuge)</td>
			<td>Micromedical Technologies Inc., 10 Kemp Dr., Chatham, IL 62629-9769 United States</td>
			<td>1</td>
			<td></td>
		</tr>
		<tr>
			<td>Tiltable headrest&#160;</td>
			<td>Micromedical Technologies Inc</td>
			<td>3</td>
			<td>modified with attached adhesive strap</td>
		</tr>
	</tbody>
</table>

assessment of static graviceptive perception in the roll-plane using the subjective visual vertical paradigm

Vestibular disorders are among the most common syndromes in medicine. In recent years, new vestibular diagnostic systems have been introduced that allow the examination of all semicircular canals in the clinical setting. Assessment methods of the otolithic system, which is responsible for the perception of linear acceleration and perception of gravity, are far less in clinical use. There are several experimental approaches for measuring the perception of gravity. The most frequently used method is the determination of the subjective visual vertical. This is usually measured with the head in an upright position. We present here an assessment method for testing otolith function in the roll plane. The subjective visual vertical is measured in the head upright position as well as with head inclination of &#177; 15&#176; and &#177; 30&#176; in the roll plane. This extended functional paradigm is an easy-to-perform clinical test of otolith function and ensures increased information content for the detection of impaired graviceptive perception.

SVV assessment was performed using a rotational chair system (Figure 1a) comprising a tiltable headrest and an adjustable LED light bar. The SVV adjustments were recorded via an infrared camera from a goniometer display on the back of the lightbar (Figure 1b). The devices used and the test protocol correspond exactly to the test methods presented here.
SVV measurement was performed in 13 healthy individuals at a mean age of 52.8 years...

Watch this Scientific Journal Video about Assessment of Static Graviceptive Perception in the Roll-Plane using the Subjective Visual Vertical Paradigm at JoVE.com

Assessment of Static Graviceptive Perception in the Roll-Plane using the Subjective Visual Vertical Paradigm

The perception of gravity is commonly determined by the subjective visual vertical in the head upright position. The additional assessment at head tilts of &#177; 15&#176; and &#177; 30&#176; in the roll plane ensures increased information content for the detection of impaired graviceptive perception.

Vestibular disorders are among the most common syndromes in medicine. In recent years, new vestibular diagnostic systems have been introduced that allow ...

Our technique of SVV assessment at certain angles of head tilt offers a standardized protocol to detect disturbances of the graviceptive function with higher redundancy compared to non-dynamic methods representing an easy-to-perform technique in clinical practice. The main advantage of this technique is its higher information content and its simple clinical applicability. As shown in our manuscript, this technique has already been applied for the detection of treatment response to botulinum toxin in patients with cervical dystonia.Basically this method can be used for the assessment of graviceptive dysfunction in a variety of diseases. The application of this method in patients with specific cortical lesions may help to localize cortical areas involved in graviceptive processing. Fixation of the patient's head at the desired angle is crucial for the method.To further avoid bias data, we recommend a randomized protocol considering tilt angle to avoid a learning effect. Install the patient in a stable chair with a backrest and a head-fixation unit. The fixation unit maintains the patient's head in a stable and defined position.It consists of an elastic headband and a U-shaped headrest which can be fixed to each other using an adhesive strap. The headrest can be adjusted in the desired inclination angle by aligning it along the scale of a goniometer, which is attached to the chair's backrest. At the beginning of the experiment, adjust the headrest at a zero-degree inclination at sub-occipital height.Place the elastic headband on the patient's head and fix it with a screw on the back. Connect the two adhesive straps on the headband and on the headrest with each other. Mount the SVV unit with the fixation device on the chair in front of the patient.Through a connected potentiometer, adjust the position of the light bar in the roll plane exactly opposite to the patient's head and at the same level as the patient's eyes. Connect the SVV unit to the electrical connection underneath the chair. Place the potentiometer in the patient's left hand and instruct them on how to perform the SVV setting.To calibrate, tilt the light bar 30 degrees to the right or left relative to the absolute vertical and ask the patient to adjust it to the vertical position under visual control. This serves to self-calibrate the patient and to check the visual motor ability of the patient. Open the examination protocol for simultaneous entry of the SVV estimates.Close the cabin door so that the patient is in complete darkness throughout the experiment. Ask the patient via the intercom system to tilt the light bar in the starting position 30 degrees to the right or to the left. After a waiting period of 15 seconds, instruct the patient to adjust the light bar from the starting position until it reaches the subjective vertical.The patient is not under time pressure and can still correct the set position at any time. The patient confirms the setting verbally via the intercom system. Enter the tilt angle shown on the display in degrees in the protocol.In total let the patient adjust the SVV in six passes with the starting position of 30 degrees randomized. Undo the initial head fixation by disconnecting the adhesive straps. Loosen the headrest and adapt the tilt position according to the protocol, 15 degrees or 30 degrees to the right or to the left.Fix the headrest in this position firmly. Fix the patient's head with the elastic headband to the headrest. Ensure that this head tilt is tolerable for the patient and adapt the height of the headrest if needed.Instruct the patient to maintain this head position during the trial. Close the cabin door and perform the trial as in the neutral head position. Upon completion of the trial, undo the head restraint and adjust the headrest according to the randomized head tilt position given by the protocol.Close the cabin door again and perform the same procedures until all SVV settings in all head tilts have been recorded. In this study, SVV measurement was performed in 13 healthy individuals at a mean age of 52.8 years. The absolute tilt of the SVV from the adult vertical at zero-degree head position showed an SVV median of 1.33.At a head tilt of 15 degrees, an SVV median of 1.66 was achieved and the measurements of the SVV at a head tilt of 30 degrees yielded an SVV median of 5.33. The method was also used to analyze SVV tilts in 32 patients suffering from cervical dystonia. Assessment of the SVV at the patient's habitual head posture revealed major deviations from the actual vertical with a median of 2.65 degrees.In comparison to healthy individuals at their habitual head posture, approximately zero-degree head tilt, the patients'response was significantly impaired with a median difference of negative 1.34 degrees. Three weeks after injection of botulinum toxin, the patients'SVV estimates in habitual head position and at 30-degree head tilt did not differ anymore from those of the controls. Exact positioning of the patient's head is crucial for the experiment.We highly recommend using a randomized protocol for the tilt angles in order to avoid a detection bias. We ourselves use this technique to evaluate the effects of botulinum toxin injection on the verticality perception in patients with cervical dystonia.

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5.6K Views.  Medical University Vienna, Austria. Our technique of SVV assessment at certain angles of head tilt offers a standardized protocol to detect disturbances of the graviceptive function with higher redundancy compared to non-dynamic methods representing an easy-to-perform technique in clinical practice. The main advantage of this technique is its higher information content and its simple clinical applicability. As shown in our manuscript, this technique has already been applied for the detection of treatment response to botulinum t...