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NedSVE/IBV v.5. New System for postural control assessment in patients with visual conflict

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Postural control is based on a complex system of neurologic signals from joints, muscular receptors and visual control. The relevance of the three systems: visual, propioceptive and vestibular is demonstrad'ted but the relationship between them is less known because their models always result non-linear or complex. It is generally accepted that visual information contributes greatly to the maintenance of balance, spatial orientation and self-perception of motion. Based on these reasons, the IBV has developed a new version of the balance assesment application NedSVE/IBV, including two tests to improve the value of the contribution of the visual system in maintaining balance.
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José María Baydal Bertomeu, Andrea Castelli, José David Garrido Jaén, Ignacio Bermejo
Bosh, Mª José Vivas Broseta, Mª Amparo Guerrero Alonso, Mª José Such Pérez,
Mª Francisca Peydro de Moya
Instituto de Biomecánica de Valencia
NedSVE/IBV v.5. A new system for
postural control assessment in patients
with visual conflict
Postural control is based on a
complex system of neurologic
signals from joints and muscular
receptors. The relevance of the
three systems: visual, propioceptive
and vestibular is demonstrated but
the relationship between them is
less known because their models
always result non-linear or complex.
It is generally accepted that visual
information contributes greatly to
the maintenance of balance, spatial
orientation and self-perception of
motion. Based on these reasons, the
IBV has developed a new version of
the balance assessment application
NedSVE/IBV, including two tests
to improve the value of the
contribution of the visual system in
maintaining balance.
INTRODUCTION
The ability to control our posture and our position in a given space is
derived from a complex interaction between the musculoskeletal sys-
tem and the nervous system which is known as the “postural control
system”. Postural control is based on a complex system of muscular
and articular responses which coordinates the information provided
by the visual, somatosensory and vestibular systems. The significance
of the role of these three systems has been clearly demonstrated.
However, the integration and processing of visual, proprioceptive and
vestibular information by the central nervous system is less well known.
Models have been developed which explain this integration of systems
but, given that the relationships between them are not linear, the
resulting models suffer from an excessive degree of complexity.
The visual system contributes to our sense of spatial orientation and
to our perception of our own movements. The most important visual
information is that which provides data concerning the three-dimensio-
nal structure of our environment, for which reason the lighting to which
it is subject, the complexity of its component parts and the degree of
adaptation are all important factors. Visual stimulation may be foveal
and voluntary (involving a process of slow monitoring) or retinal and
involuntary (involving the optokinetic system). Both systems activate
different neuronal mechanisms with the common aim of focusing vision.
In the bibliography, visual vertigo and visual dependence have been
described as malfunctions of the sense of balance caused by errors in
the processing of visual information. In the same way, patients suffe-
ring from malfunctions of the central nervous system or symptoms of
strabismus exhibit malfunctions in balance strategy when faced with
a visually conflictive environment. Nevertheless, the concept of visual
dependence in individuals with balance malfunctions has to date been
the subject of very little study or research.
Changes in the visual environment may cause balance malfunctions
and falls in patients with vestibular pathology. In the same way, the
symptoms of strabismus may themselves trigger off balance mal-
functions, so it can be seen that in order to assess postural control it
is necessary to have access to valid measurements which can useful
for quantifying therapeutic results during the process of vestibular
rehabilitation.
All these factors have led the IBV to perfect the NedSVE/IBV balance
assessment system so as to develop a method of assessing visual
dependence in the process of maintaining balance. The objectives fixed
for this project are as follows:
1. To develop a full protocol for the assessment of the contribution of
the visual system to an ability to maintain balance that is capable
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of distinguishing between patients with balance problems
associated with visual dependence and those with balance
problems associated with vestibular and somatosensory
deficits.
2.
To generate a database with reference values extracted
from variable proposals for a range of pathologies of
different degrees of severity. The database would make
it possible to obtain a solid corpus of knowledge and refe-
rence material with which to compare patients, so that,
depending on their functional state, treatment to bring
about their recovery can be modified as appropriate.
3.
To modify the NedSVE/IBV 4.0 system by including evi-
dence of visual conflict that can support the diagnosis of
patients with a high dependence of visual perception on
postural control and can include it in the new NedSEV/IBV
5.0 version.
The characteristics of the new 5.0 version of the NedSVE/IBV
system are described below.
DEVELOPMENT
Description of the Sample
In order to develop the database for the NedSVE/IBV 5.0
system, a study was carried out of the postural response of
a sample of healthy individuals between 20 and 79 years of
age, equally distributed by age group. None of the individuals
had a personal history associated with peripheral or cen-
tral vestibular pathology, traumatic brain injury or articular
impairment preventing normal mobility.
Description of the Measurement Equipment
A system to alter the visual perception of space must provide
full immersion in the environment through its video projec-
tion. To this end we added to the monitors of the NedSVE/
IBV system patients a pair of virtual reality goggles including
a mask so as to cover the full field of vision.
The virtual reality goggles used were the VUZIX VR920 model,
consisting of two 640x480 pixel screens which are the bino-
cular vision equivalent of a 62-inch screen viewed from a
distance of 3 meters.
The goggles include a head tracker which enables the system
to monitor head position, which provides for opportunities
to develop new evidence both in terms of assessment and of
rehabilitation (Figure 1).
The video developed in this version is designed to produce a
high level of instability in terms of visual references, affecting
the ability of the visual component to maintain balance. This
was achieved by projecting a video in which no static points
appear that could be used as a visual reference, combined
additionally with continuous mobility in the orientation of the
field of vision (Figure 2).
Description of the Measurement Protocol
The protocol followed for carrying out the tests was based on
the classic sensory assessment procedure, consisting of the
Romberg test, to which were added the two tests (RAV and
RGV) that produce visual conflict through the projection of a
video using virtual reality goggles. The duration of the tests
was pre-determined as 30 seconds. The measurements were
initially manual but were subsequently taken in automatic
mode.
RAV: A Romberg test with eyes open and visual conflict.
Patients are positioned on the platform barefoot, with the
soles of their feet placed so as to coincide with the foo-
tprints marked out on the platform surface and with their
arms in a relaxed position alongside their bodies, looking
toward a fixed point and standing as still as they can. Once
the patients are in position, they put on the virtual reality
goggles, which project a video film with the aim of altering
the visual information they receive.
RGV: A Romberg test on a foam rubber cushion with visual
conflict. For this test the same instructions are followed
as for the RAV test, except that the patient is placed on
Figure 1. Structure and goggles used.
Figure 2. Images of the
videos which generate
visual conflict.
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a somatosensory foam rubber cushion. The subject also
puts on virtual reality goggles to project the video so as to
modify the visual information received, the proprioceptive
information being already modified by the foam mattress.
Study Variables
The variables used when carrying out the study were as
follows: Maximum movements in an anterior-posterior
direction and in a medial-lateral direction. These varia-
bles indicate the postural movement along each of the axes
concerned. They are calculated from the differences between
the maximum and minimum values in each of these direc-
tions of movement.
These variables are those most frequently used by the main
researchers studying human balance. The analysis of the
maximum movements made in each direction of movement
provides a series of advantages which make such an analysis
advisable. Among the most important of these is the high
degree of sensitivity this gives for detecting pathological
patterns, giving a very faithful reflection of all the variations
of the statokinesiogram, both in a horizontal and a vertical
plane.
REsULTs
Table 1 shows the results obtained during the course of the
RAV test from the variables analyzed in each of the directions,
anterior-posterior (AP) and medial-lateral (ML). The results
are also segmented into 6 age groups. Table 2 shows the same
information for the RGV test. The following observations can
be made in relation to the tables:
1.
There are significant differences between the different age
groups. It can be seen in both the RAV and the RGV tests
that the older the groups are, the more the movements
increase.
2.
The RGV test shows higher values for the movements than
the RAV test in both directions of movement, i.e. both (AP)
and (ML).
3.
There are no differences in movements on the computerized
dynamic platform (CDP) between the groups of men and
of women.
Table 1. Maximum medial-lateral and anterior-posterior movements in the RAV
test, distributed by gender and age groups.
AGE
GROUP
Men Women
RAV (AP) RAV (ML) RAV (AP) RAV (ML)
20-29
19.88 (3.92) 20.12 (5.57) 19.37 (3.97) 21.25 (5.24)
30-39
21.74 (5.50) 21.46(6.53) 21.67(6.03) 21.61 (6.75)
40-49
22.01 (4.73) 21.74 (5.79) 22.05 (3.85) 21.49 (5.82)
50-59
21.79 (9.37) 22.80 (9.42) 23.06 (5.80) 22.64 (8.79)
60-69
26.42 (12.38) 25.37 (7.61) 25.38 (12.04) 23.35 (8.12)
70-79
28.75 (11.42) 27.88 (13.17) 27.78 (10.74) 26.98 (7.64)
(a) (b)
Figure 3. (a) ROMBERG test with visual alteration. (b) ROMBERG test with foam rubber cushion and visual alteration.
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Table 2. Maximum medial-lateral and anterior-posterior movements in the RGV
test, distributed by gender and age groups.
AGE
GROUP
Men Women
RGV (AP) RGV (ML) RGV (AP) RGV (ML)
20-29 55.84 (9.52) 56.40 (8.67) 56.16 (6.98) 57.22 (15.53)
30-39
54.27 (11.15) 56.07 (10.69) 56.79 (12.39) 59.99 (22.85)
40-49
56.21 (16.77) 52.25 (16.97) 55.55 (12.34) 58.00 (12.48)
50-59
70.10 (14.29) 70.73 (13.22) 63.97 (12.37) 65.86 (11.25)
60-69
80.59 (24.66) 80.91 (23.88) 72.56 (14.08) 68.49 (15.06)
70-79
85.92 (34.09) 87.47 (19.64) 79.84 (24.40) 83.22 (34.41)
CONCLUsIONs
Version 5 of the NedSVE/IBV application is an integrated sys-
tem for the functional assessment of balance, based on the
kinetics of its movements. The application combines static
posturography tests with dynamic tests based on an analysis
of walking, stability limits and monitoring of mobile targets
using the computerized dynamic platform (CDP). The tests
included in the application are as follows:
Sensory-Dynamic Assessment:
Romberg Test with Eyes Open (ROA)
Romberg Test with Eyes Closed (ROC)
Romberg Test with Visual Conflict (RAV)
Romberg Test with Eyes Open and Foam-
Rubber Cushion (RGA)
Romberg Test with Eyes Closed and Foam-
Rubber Cushion (RGC)
Romberg Test with Visual Conflict and Foam-
Rubber Cushion (RGV)
Human Walking Test (AMH)
Assessment of Skills and Control:
Calculation and assessment of Stability Limits
Anterior-Posterior Directional Rhythmical
Control
Medial-Lateral Directional Rhythmical Control
Tests defined by the user
Balance Rehabilitation Module
The tests which include visual conflict (RAV and RGV) are
segmented by age, so that the system determines a pattern
in accordance with the patient’s age.
The indications of this application in the field of rehabilitation
and assessment of body injuries are as follows:
Functional and evolutive diagnoses of balance malfunctions.
Assessment of otogenic diseases affecting any part of the
ear (Ménière’s disease, vestibular neuronitis) and clinically
exhibited in unstable conditions.
Assessment of neurological diseases affecting the CNS
(multiple sclerosis, traumatic brain injury, etc.).
Cervical lesions accompanied by instability and dizziness.
Application of biofeedback for interactive re-education of
the sense of balance.
Cervical musculoskeletal disorders accompanied by vertigo
syndrome.
·
AgrAdecimientos
A la Dra. María Elvira Santadreu Jiménez, Jefa del Servicio de Rehabilitación, Hospital Universitario
Insular de Gran Canarias.
Al Dr. Jesús J. Benítez del Rosario, Servicio de Otorrinolaringología del Hospital Universitario de
Gran Canaria y al Dr. Jesús Benitez Negrín, Profesor asociado de la Universidad de Las Palmas de
Gran Canaria.
... The RWS Test consists to follow a target reference that moves sinusoidally in the medial-lateral or anterior-posterior axis. This test is included in most commercial posturography platforms [14–16]. Used as a training, RWS exercises can generate several benefits as improved balance and reduced risk of falls. ...
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