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January2013 Vol.50 Issue:      1 Table of Contents
Full Text

Somatosensory and Motor Systems Affect Postural Stability in Parkinson’s Disease Patients

Moshera H. Darwish1, Mohammed S. El-Tamawy2, Sandra M. Ahmed2, Hager Rasmy3

Departments of Physical Therapy for Neuromuscular Disorders and its Surgery;

Faculty of Physical Therapy; Cairo University1; Misr University for Science and Technology3;

Neurology2, Faculty of Medicine; Cairo University; Egypt


Background: Postural instability refers to a multi-system dysfunction in Parkinson’s Disease (PD) patients. Posturography is an objective, non-invasive specialized clinical assessment technique to assess such problems. Objective: Evaluate and analyze objectively dynamic balance during functional activity performance in patients with Parkinson’s Disease (PD). Methods: Twenty Egyptian PD patients and 20 controls were included. Different tests were done using posturography; sensory organization, sit to stand, tandem walk and Step/quick test. Results: Comparison of both groups showed a statistically significant difference between both groups with PD patients showing signs of postural instability in all tests. Different testing protocols proved that this instability was due to deficit in many functional systems (somatosensory, visual, vestibular and motor) Conclusion: PD patients suffers of postural instability due to deficits in sensory and neuromuscular systems. [Egypt J Neurol Psychiat Neurosurg.  2013; 50(1): 1-4]

 Key Words: Postural stability, Parkinson’s disease, posturography.

Correspondence to Moshera Darwish, Department of Physical Therapy for Neuromuscular Disorders and Its surgery, Faculty of Physical therapy, Cairo University, Egypt. Email:



Idiopathic Parkinson's Disease (IPD) is a chronic neurodegenerative disease that has profound motor and non-motor symptoms and effects on quality of life, health care and personal costs1.

Postural stability refers to a multi-system function that works to keep the body upright while sitting, standing and during changing posture. Postural instability is commonly observed in severe cases of IPD2. A single, objective measure of this later finding is impossible due to the integrated nature of postural stability3.

In the year 2000 posturography was introduced as a tool for documentation of disability and impairment4. Computerized dynamic posturography (CDP) is an objective, non-invasive specialized clinical assessment technique5. Different examination protocols examine movement coordination and sensory organization of visual, somatosensory and vestibular information relevant to postural control6.

The aim of this study is to evaluate and analyze objectively dynamic balance during functional activity performance in patients with Parkinson’s Disease (PD).




This study is a case control study performed in the department of Neurology, Cairo University. It included 20 Egyptian patients with PD and 20 control healthy subjects. Both patients and control were matched for age, sex, height and weight (p>0.05). The mean age, weight and height in PD patients group were 51±7.42 yrs, 68.2±18.11 kg and 162.55±6.97cm respectively. Inclusion criteria were: Duration of disease from 5-8 years with no cognitive dysfunction (Mini Mental State Examination (MMSE) score mean value was 28.3±0.47) and patients who are able to walk without any assistive devices or physical assistance (disease severity ranged from stage 2.5-3 according to the modified Hoen and Yahr scale7.

Patients were excluded if they had cognitive dysfunction, peripheral neuropathy, ear problems, visual problems, cardiovascular disease that could affect locomotion, or require assistive device, physical assistance.

A computerized dynamic posturography (Smart balance master® and Balance master system®) was used. The testing protocols included: (1) Sensory organization test that measure the equilibrium score parameter; it evaluates the different sensory systems (somatosensory, visual and vestibular) on postural stability, (2) Sit to stand (STS) measured the weight transfer, rising index and center of gravity (COG) sway velocity parameters, (3) Tandem walk (TW) measures the step width, speed and end sway parameters, (4) Step/Quick turn (SQT) measures turn time and turn sway parameters.


Statistical Analysis

Descriptive data were presented as mean ± standard deviation (SD). The paired t-test was used to examine the difference between posturographic scores of both patients and controls. SPSS (version 12 windows) and graph Pad Instat (version 3.05) were used for data analysis. P value <0.05 was considered statistically significant and >0.05 was considered statistically non-significant.




A.           Sensory organization test (equilibrium score)

The equilibrium scores (ES) were measured during different situation corresponding to the six sensory conditions. Comparison of patients and control scores showed a statistically significant difference (p<0.01) in all tests as shown in Table (1)

B.           Sit to Stand test (STS)

Comparison of both groups showed highly significant statistical difference (p<0.01) in weight transfer time being higher in patients. A significant statistical difference also was found in rising index and COG sway being decreased in patients compared to control group as shown in Table (2).


C.           Tandem walk

There was a statistically significant increase in step width and end sway and statistically significant decrease in speed in patients compared to controls as shown in Table (3). The increase in step width was explained by patient lack of good dynamic balance control if the base of support (BOS) is narrow.


D.           Step and quick turn (SQT) test

Comparison of the turn time and turn sway to the left and right directions showed a significant increase in patient group compared to control group. This difference were more on turning to the right side as shown in Table (4)


Table 1. Comparison of mean values of equilibrium scores of the six sensory conditions.









Eye open, surrounding and platform stable





Eye closed, surrounding and platform stable





Eye open, sway referenced surrounding





Eye open, sway referenced platform





Eye closed, sway referenced platform





Eye open, sway referenced surrounding and platform





* Statistically significant at p<0.01


Table 2. Comparison of mean values of Sit to Stand (STS) test in patients and controls.





t value




Weight transfer(second)





Rising index %





Center of gravity (COG) sway velocity (degree/second)





*Statistically significant p<0.05             **Statistically significant p<0.01


Table 3. Comparison of mean values of tandem walk in patients and controls.





T value




Step width (centimeter)





Speed (centimeter/second)





End sway (degree/second)





*Statistically significant p<0.05             **Statistically significant p<0.01

Table 4. Comparison of mean values of step and quick turn (SQT) test in patients and controls.





T value




Turn time (second)

Left direction





Right direction





Turn sway (degree/second)

Left direction





Right direction





* Statistically significant p<0.05             ** Statistically significant p<0.01





The results of this study proved that there was a significant affection of postural stability in Parkinson Disease (PD) patients compared to age, sex, weight and height matched controls and this instability was due to abnormality of sensory system.

A deficit in the sensory organization tests was observed as it was previously demonstrated in different studies2,8. This reflects breakdown in the central hierarchy of postural control which can be explained by dysfunction of the basal ganglia (BG) as one of its function is somatosensory integration. Somatosensory deficit produce an abnormally constructed body scheme and explain stooped posture of PD patients9-11.

The result of the present study showed that there was an increase in postural sway when visual information was deprived which means that PD patients has a visual dependence for the regulation of postural control. This agrees with many studies (2, 8, 12) that postulate that presence of inaccurate visual information overrides the ability to reweigh sensory feedback sources and prioritize accurate information. Other studies rejected this finding like Beuter et al.13 and Roujier14, who stated eye closure was compensated by increase excitatory drive to postural muscles.

Also the role of basal ganglia (BG) in sensory organization was demonstrated when the PD patients postural instability became accentuated with moving surrounding experiments. This was explained as a difficult initial posture adjustment. This was proved by Vaugoyeau et al.15.

The study showed that patients were unable to use vestibular input in the presence of impaired visual and proprioceptive input to maintain balance which agree with Bronte-Stewart et al.2. Later this finding was disapproved by Nallegowda et al.12, but this is may be due to the fact that they measured only the vestibulospinal reflex.

Lack of proper rising of patients may be attributed to their rigidity and bradykinesia as well as restricted range of motions at the level of ankle, knee, hip and/or spine (extension).

In this study, the PD patients were unable to walk on a narrow base of support (BOS). This was explained by poor ability of patients to alter postural synergies for changes in initial stance posture to reduce ability to use proprioceptive information to select postural muscle activation patterns based on the specific pattern of displacements as a result of impaired proprioceptive guidance of movement16-18.

The patients were unable to turn around during functional activity of daily living. This agrees with many studies19-21, which attributed this finding to loss of intersegmental axial coordination which correspond to the well-known phenomenon of “en bloc” turning of Parkinson’s Disease.



The result of this study concludes that many functional systems are involved as a cause of the postural instability in PD patients (somatosensory, visual, vestibular and motor) and that posturography has an essential role in evaluation of such problems.


[Disclosure: Authors report no conflict of interest]




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21.    Baltadjieva R, Giladi N, Gruendlinger L, Peretz C, Hausdorff JM. Marked alterations in the gait timing and rhythmicity of patients with de novo Parkinson's disease. Eur J Neurosci. 2006; 24(6): 1815-20.



الملخص العربى


تأثير الجهاز الحسى والحركى على الاتزان الوضعى فى مرض باركنسون


يعانى المرضى المصابون بمرض باركنسون من خلل بالأجهزة الحسية والحركية مما يؤثر بشكل سلبى على الاتزان الوضعى. يقوم جهاز قياس الاتزان بوضع الجسم فى المواقف المختلفة التى تختبر على حده  كل الأجهزة فى الجسم التى تتداخل من أجل الحفاظ على اتزان الجسم (الحسى, المرئى, الحركى).

تهدف هذه الدراسة إلى تقييم الاتزان الوضعى فى مرضى الباركينسون والتعرف على أسباب عدم الاتزان لديهم.

الدراسة تضمنت عشرون مريض باركينسون وعشرون من الأصحاء. قامت المجموعتين باختبار الاتزان باستعمال جهاز الاتزان. الاختبارات تمت أثناء الوقوف, عند الجلوس والقيام, عند المشى وعند الاستدارة إلى الجهة اليمنى والشمال.

أوضحت الدراسة وجود فارق إحصائي ذو دلالة بين المجموعتين أثبتت وجود خلل بالاتزان فى جميع المواقف عند مرضى الباركينسون وأن هذا الخلل ناتج عن مشكلة بالأجهزة الحسية والحركية بالجسم والتفرقة بينهم ويوضح أهمية تقييم هؤلاء المرضى بجهاز قياس الاتزان.


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