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RehabMeasures Instrument

Sensory Organization Test

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Purpose

Sensory organization test is a form of posturography that is designed to assess quantitatively an individual`s ability to use visual, proprioceptive and vestibular cues to maintain postural stability in stance (Clendaniel, 2000).

Acronym SOT

Area of Assessment

Balance – Vestibular
Balance – Non-vestibular

Assessment Type

Performance Measure

Administration Mode

Computer

Cost

Not Free

Actual Cost

$80000.00

Cost Description

$80,000-$180,000

Diagnosis/Conditions

  • Vestibular Disorders

Key Descriptions

  • Subjects stand on dual-force plates in a 3 sided surround. The anterior-posterior sway is recorded.
     
    There are 6 independent sensory conditions tested, each condition consisting of three twenty second trials:
     
    The conditions are:

    1. Eyes open on firm surface
    2. Eyes closed on firm surface
    3. Eyes open with sway referenced visual surround
    4. Eyes open on sway referenced support surface
    5. Eyes closed on sway referenced support surface
    6. Eyes open on sway referenced support surface and surround 
     
    The outcome measures are:

    1. Equilibrium Score which is the average center of gravity sway for each trial for each condition
    2. The composite equilibrium score which is a weighted average of the six conditions. It is derived from the individual equilibrium scores
    3. The sensory analysis ratios which are computed averages to identify impairments of individual sensory systems
    4. Center of gravity (COG) Alignment which reflects the patient's COG position relative to the center of the base of support at the start of each trial of the SOT
    5. Strategy Analysis quantifies the relative amount of movement about the ankles (ankle strategy) and about the hips (hip strategy) the patient used to maintain balance during each trial
  • There are 6 independent sensory conditions tested, each condition consisting of three twenty second trials:
    1) Eyes open on firm surface
    2) Eyes closed on firm surface
    3) Eyes open with sway referenced visual surround
    4) Eyes open on sway referenced support surface
    5) Eyes closed on sway referenced support surface
    6) Eyes open on sway referenced support surface and surround 
  • The outcome measures are:
    1) Equilibrium Score which is the average center of gravity sway for each trial for each condition
    2) The composite equilibrium score which is a weighted average of the six conditions derived from the individual equilibrium scores
    3) The sensory analysis ratios which are computed averages to identify impairments of individual sensory systems
    4) Center of gravity (COG) Alignment which reflects the patient's COG position relative to the center of the base of support at the start of each trial of the SOT
    5) Strategy Analysis quantifies the relative amount of movement about the ankles (ankle strategy) and about the hips (hip strategy) the patient used to maintain balance during each trial
  • Sensory Organization Test (SOT) utilizes dynamic posturography (standing on a force plate) to objectively measure postural sway and center of pressure (COP) under the same testing conditions as the CTSIB , but with 20 (versus 30) second trials and with feet shoulder width apart.

Equipment Required

  • NeuroCom Balance Master
  • Equitest or Smart Equitest

Time to Administer

15 minutes

Required Training

Training Course

Age Ranges

Adult

18 - 64

years

Elderly Adult

65 +

years

Instrument Reviewers

Reviewed for the VestEDGE task force of the Neurology section of the APTA by Elizabeth Dannenbaum (MscPT)

ICF Domain

Activity

Measurement Domain

Motor
Sensory

Professional Association Recommendation

Recommendations for use of the instrument from the Neurology Section of the American Physical Therapy Association’s Multiple Sclerosis Taskforce (MSEDGE), Parkinson’s Taskforce (PD EDGE), Spinal Cord Injury Taskforce (PD EDGE), Stroke Taskforce (StrokEDGE), Traumatic Brain Injury Taskforce (TBI EDGE), and Vestibular Taskforce (Vestibular EDGE) are listed below. These recommendations were developed by a panel of research and clinical experts using a modified Delphi process.

 

For detailed information about how recommendations were made, please visit:  http://www.neuropt.org/go/healthcare-professionals/neurology-section-outcome-measures-recommendations

 

Abbreviations:

 

HR

Highly Recommend

R

Recommend

LS / UR

Reasonable to use, but limited study in target group  / Unable to Recommend

NR

Not Recommended

 

Recommendations for use based on acuity level of the patient:

 

Acute

(CVA < 2 months post)

(SCI < 1 month post) 

(Vestibular < 6 weeks post)

Subacute

(CVA 2 to 6 months)

(SCI 3 to 6 months)

Chronic

(> 6 months)

VEDGE

LS

LS

LS

 

Recommendations based on level of care in which the assessment is taken:

 

Acute Care

Inpatient Rehabilitation

Skilled Nursing Facility

Outpatient

Rehabilitation

Home Health

TBI EDGE

NR

NR

NR

LS

NR

 

Recommendations for use based on ambulatory status after brain injury:

 

Completely Independent

Mildly dependant

Moderately Dependant

Severely Dependant

TBI EDGE

LS

LS

LS

NR

 

Recommendations based on vestibular diagnosis

 

Peripheral

Central

Benign Paroxysmal Positional Vertigo (BPPV)

Other

VEDGE

LS

LS

LS

LS

  

 

Recommendations for entry-level physical therapy education and use in research:

 

Students should learn to administer this tool? (Y/N)

Students should be exposed to tool? (Y/N)

Appropriate for use in intervention research studies? (Y/N)

Is additional research warranted for this tool (Y/N)

TBI EDGE

No

Yes

Yes

Not reported

VEDGE

No

Yes

Yes

Yes

Considerations

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Vestibular Disorders

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Standard Error of Measurement (SEM)

Wrisley et al 2007 (n = 13 healthy young adults (mean age 24±4 years, 6 men) tested 2 days apart)

  • Composite Score: SEM (calculated) = 2.81

Minimal Detectable Change (MDC)

Wrisley et al 2007: a composite change of greater than 8 points  would indicate a change due to rehabilitation (n = repeated testing of 13 healthy young adults)

Cut-Off Scores

Whitney et al 2006 : SOT composite score of less than 38 increases the likelihood ratio (4.13) for identifying repeated fallers in the past 6 months (n =100 vestibulopathic individuals) (sensitivity 53%, specificity 87%)

Normative Data

The SOT composite score and condition 2-6 significantly decreases with increased age in healthy individuals: ANOVA on SOT equilibrium score showed a main effect of age F(3.90) = 23.24 and  test condition (F(5.90) = 355.91.

Test/Retest Reliability

Ford-Smith et al 1995 : Healthy non-institutionalized older adults (n = 40): Tested at a one week interval: Composite score: Good test-retest reliability (ICC 0.66, SOT average of three trials ranged from poor (Condition 3: ICC = 0.68) to fair test-retest reliability (condition 5: ICC = 0.68, condition 6: ICC = 0.64) 

 

Wrisley et al 2007

  • Adequate composite score reliability ICC = 0.67
  • Individual equilibrium scores ranged from poor to adequate ICC = 0.35 -0.79

Criterion Validity (Predictive/Concurrent)

Cohen et al 2008: SOT vestibular condition (condition 5/1) had moderately high sensitivity (85%) and specificity (77%) in identifying vestibulopathies (n = 40 adults, 40 adults with vestibular impairements) 

 

The review article by Di Fabio (1995) reports that many studies on sensitivity and specificity of using the SOT to identify people with vestibulopathy,  most studies found  low to moderate sensitivity and specificity. The responsiveness increases when the SOT is combined with rotary chair or caloric test results.  

 

Basta et al 2005 investigated the influence of pure otolith disorders on SOT scores in 33 adults with minor head injury with utrical or sacculo-utricalar disorders, finding SOT were abnormal in 76.9% of the people with combined sacular-utricular involvement, while the scores were only abnormal in 45% of utricular disorder group.

Construct Validity

Gill-Body et al 2000: SOT, Timed up and Go(TUG), Dizziness Handicap Inventory (DHI) scores of people with unilateral (n = 41) and bilateral (n = 44) vestibular hypofunction: bilateral vestibular hypofunction: Adequate correlation (-0.31) between DHI emotional score and  mean SOT sway in condition 3, and in unilateral vestibular hypofunction clients an adequate correlation (-0.35) was found between mean sway in condition 3 and the physical DHI score

TUG scores were not correlated to any SOT scores for both groups 

 

Whitney et al 2006: The composite score and self-reported falls history within the past 6 months were significantly related (F3 5.81, p < 0.01) (n = 100 vestibulopathic individuals)

 

(Whitney and Wrisley, 2004; n = 30; mean age = 63 (17); patients with balance and vestibular disorders, Balance and Vestibular Disorders)

  • Modified CTSIB and SOT (Sensory Organization Test) scores were slightly more correlated when participants completed the assessment with their feet together than when completed with feet apart.

Face Validity

Basta et al 2007: Sensitivity and Specificity of the SOT to detect otolith disorders (as measured by VEMP and Subjective Visual Vertical tests (n = 22 patients and controls): Sensitivity = solely in condition 3,5 and 6 is it higher than 50%)              

Specificity = decreases with increasing difficulty of the condition

Parkinson's Disease

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Criterion Validity (Predictive/Concurrent)

(Landers MR et al, 2008) 

  • SOT was not found to be a sensitive means of differentiating fallers from non-fallers; AUC – 62.6 with cut off score of 68.5; sensitivity = .60, specificity = .625, +LR = 1.60, -LR = .64, odds ratio = 2.5 (0.80 -7.9) 

(Rossi et al, 2009; n = 45 with PD (26 men, 19 women); mean age = 70.4 years (range = 46-82 years); Average time since diagnosis = 4.53 (2.9) years; H&Y I = 0; H&Y II = 17; H&Y III = 20; H&Y IV = 8. Controls were 20 healthy volunteers mean age 68.7 (range 60-84) years; 10 men, 10 women) 

  • Individuals with PD performed significantly worse on the SOT than controls; condition 3 (= 0.022), condition 4 (= 0.014), condition 5 (= 0.002), condition 6 (= 0.002). Sensory Analysis individuals with PD had significantly worse performance on average balance (= 0.001), visual input (= 0.014), and vestibular input (= 0.002). 

  • Pathological balance scores (<68) were found in 24 of 45 individuals (6 in H&Y II, 12 in H&Y III, 6 in H&Y IV). 

(Franklach et al, 2009; 102 subjects with PD (25 women, 77 men), mean age 60.2 (9.3) years; There was a subgroup of 18 individuals who had UPDRS III score < 20 and never had medication and 25 control subjects (18 women, 7 men) mean age 56.9 (8.4) years. 

  • No statistical difference between PD patients with UPDRS < 20 and controls on any SOT condition 

  • PD patients with UPDRS III scores > 20 and controls differed significantly (< 0.01) in all 6 SOT conditions 

  • The equilibrium score for each SOT condition correlated with the UPDRS III score; Spearman rank correlation, SOT 1, 4, 5 (< 0.0001); SOT 2 (< 0.02); SOT 3, 6 (< 0.001). 

(Colnat-Coulbois et al 2011, 24 subjects in late stage PD (10 women, 14 men), mean age 60.0 (14) years. 48 control subjects (20 women, 28 men), mean age 62.0 (11.0) years. Median disease duration for the PD group was 11 years, all were in H&Y stage IV) 

  • Individuals in late stage PD had significantly lower scores on SOT indicating poorer equilibrium (z = -5.93, < 0.001) and lower strategy scores (= -3.67, < 0.001) than healthy controls 

  • The PD group had more difficulty controlling balance sways in more complex sensory conflict situations: in which visual information is the main reliable cue (= -2.98, = 0.003); vestibular information was the main reliable cue (= -4.80, < 0.001); proprioceptive information is disrupted (= -4.77, < 0.001). 

(Chong R et al. 1999, 15 individuals with PD (8 females, 7 males), mean age 60 (9) years. 11 subjects with Alzheimers disease (5 females, 6 males), mean age 73 (10) years. 17 healthy controls (8 females, 9 males), mean age 65 (6) years.) 

  • Individuals with PD had more falls during the SOT than the control group x2(1) = 6.4, < 0.05) but were equivalent to those with Alzheimers. 

  • In condition 6 in which both visual and proprioceptive information is incongruent 53% of the PD subjects fell in the first trial, 100% of AD subjects lost their balance and 59% of the healthy controls. Both healthy controls and PD subjects improved performance in trials 2 and 3 while subjects with AD did not improve. 

(Lee JM et al. 2012, 31 individuals with early stage PD (H&Y 1 to 2.5), (16 women, 15 men) mean age 68.1 (7.28) years; 20 healthy control subjects (10 women, 10 men) mean age 66.6 (7.8) years. 

  • No difference in equilibrium control between early stage PD and control subjects.

 

SOT condition (%)a

Group I H-Y 1 (n = 10)

Group II H-Y 2 and 2.5 (n = 21)

Controls (n = 20)

p-value

SOT 1

91.48(1.77)

93.21(2.78)

93.29(3.02)

0.196

SOT 2

88.53 (2.38)

88.85(5.46)

89.82(5.74)

0.758

SOT 3

85.88(7.57)

87.85(5.89)

88.38(6.92)

0.621

SOT 4

73.53(7.23)

73.36(9.78)

76.03(7.30)

0.559

SOT 5

58.08(8.01)

47.26(23.74)

58.54(10.52)

0.082

SOT 6

53.78(14.23)

43.95(30.05)

54.60(14.95)

0.275

a= Kruskal-Wallis test

 

Floor/Ceiling Effects

Parkinson Disease: 

(Colnat-Coulbois et al. 2011) 

  • 24 individuals in H&Y stage IV were able to successfully complete the test indicating no floor effect for ambulatory individuals with PD.

Bibliography

Basta, D., Clarke, A., et al. (2007). "Stance performance under different sensorimotor conditions in patients with post-traumatic otolith disorders." Journal of Vestibular Research 17(1): 25-31. 

Basta, D., Todt, I., et al. (2005). "Postural control in otolith disorders." Human movement science 24(2): 268-279. 

Chong, R. K., Horak, F. B., et al. (1999). "Sensory organization for balance: specific deficits in Alzheimer's but not in Parkinson's disease." The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 54(3): M122-M128. 

Clendaniel, R. A. (2000). "Outcome measures for assessment of treatment of the dizzy and balance disorder patient." Otolaryngologic Clinics of North America 33(3): 519-533. 

Cohen, H., Heaton, L. G., et al. (1996). "Changes in sensory organization test scores with age." Age Ageing 25(1): 39-44. Find it on PubMed

Cohen, H. S. and Kimball, K. T. (2008). "Usefulness of some current balance tests for identifying individuals with disequilibrium due to vestibular impairments." Journal of Vestibular Research 18(5): 295-303. 

Colnat-Coulbois, S., Gauchard, G., et al. (2011). "Management of postural sensory conflict and dynamic balance control in late-stage Parkinson's disease." Neuroscience 193: 363-369.

Di Fabio, R. P. (1995). "Sensitivity and specificity of platform posturography for identifying patients with vestibular dysfunction." Physical Therapy 75(4): 290-305. 

Ford-Smith, C. D., Wyman, J. F., et al. (1995). "Test-retest reliability of the sensory organization test in noninstitutionalized older adults." Arch Phys Med Rehabil 76(1): 77-81. Find it on PubMed

Frenklach, A., Louie, S., et al. (2009). "Excessive postural sway and the risk of falls at different stages of Parkinson's disease." Movement Disorders 24(3): 377-385.

Gill-Body, K. M., Beninato, M., et al. (2000). "Relationship among balance impairments, functional performance, and disability in people with peripheral vestibular hypofunction." Physical Therapy 80(8): 748-758. 

Landers, M. R., Backlund, A., et al. (2008). "Postural instability in idiopathic Parkinson's disease: discriminating fallers from nonfallers based on standardized clinical measures." Journal of Neurologic Physical Therapy 32(2): 56-61. 

Lee JM, Koh SB, Chae SW, Seo WK, Kwon DY, Kim JH, et al. Postural Instability and Cognitive Dysfunction in Early Parkinson's Disease. Can J Neurol Sci. 2012;39(4):473–482. [PubMed]

Pedalini, M. E., Cruz, O. L., et al. (2009). "Sensory organization test in elderly patients with and without vestibular dysfunction." Acta Otolaryngol 129(9): 962-965. Find it on PubMed 

Rossi, M., Soto, A., et al. (2009). "A prospective study of alterations in balance among patients with Parkinson’s disease." European Neurology 61(3): 171-176. 

Whitney, S. L., Marchetti, G. F., et al. (2006). "The relationship between falls history and computerized dynamic posturography in persons with balance and vestibular disorders." Archives of physical medicine and rehabilitation 87(3): 402-407. 

Wrisley, D. M., Stephens, M. J., et al. (2007). "Learning effects of repetitive administrations of the sensory organization test in healthy young adults." Arch Phys Med Rehabil 88(8): 1049-1054. Find it on PubMed

 

Wrisley, D. and Whitney, S. (2004). "The effect of foot position on the modified clinical test of sensory interaction and balance." Archives of physical medicine and rehabilitation 85(2): 335-338. Find it on PubMed 

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