Postural Stability Deficiencies in Asymptomatic Individuals With HIV
Condition: HIV; Balance; Vestibular Disorder; Somatosensory Disorders; Postural Stability
MeSH terms: Vestibular Diseases; Somatosensory Disorders
Study type: Interventional

Summary: 
      Persons with HIV can present vestibular system impairments, affecting postural stability.
      There is scarce literature related to the contribution of the visual and somatosensory
      systems in maintaining postural stability in persons with HIV. The purpose of this study is
      to describe the sensory systems used to maintain postural stability and how the sources of
      sensory information contributes to postural stability in asymptomatic persons with HIV.
      Postural stability was measured in 20 asymptomatic persons with HIV (11 male, 9 female, aged
      43 ± 8 years). Static postural stability was evaluated during eight conditions that perturbed
      the visual, somatosensory and vestibular inputs. A paired-samples t-test was conducted to
      compare center of pressure (COP), antero-posterior displacement (APD) and right-left
      displacement (RLD) on stable and unstable surface and to characterize each balance sensory
      system. There was a significant difference in the COP and APD of eyes open condition compared
      to the remaining conditions on stable surface. Furthermore, there was a significant
      difference in the COP, APD and RLD for the eyes open on a foam surface compared to the
      remaining conditions on an unstable surface. Postural instability can be detected in
      asymptomatic persons with HIV under challenging conditions, previous to the evident
      appearance of balance impairments.
    

Detailed description: 
      The institutional review boards (IRB) of the University of Puerto Rico Medical Science
      Campus, reviewed and approved this study before any data collection was initiated. An
      informed consent was provided to each subject to access their medical records, HIV status,
      CD4+ cell count and as a requirement to participate in the study.

      The subjects were recruited from La Perla de Gran Precio (Community wellness center that
      specializes in individuals with HIV) localized in San Juan, Puerto Rico. Each subject was
      evaluated by interview and review of their medical record for the inclusion and exclusion
      criteria assessment. Different tests were performed as a screening tool to identify
      additional limitations or impairments in the different sensory systems. To rule out severe
      neuropathy, the subject had to be able to detect a Semmes- Weinstein Monofilament of 5.07 or
      less in more than two areas of the foot.12,13 The visual system was screened using Snellen
      chart and the subject had to obtain at least 20/40 of visual acuity. To rule out severe
      balance impairments, the Romberg Test and Fukuda's Stepping Test were used. For Romberg Test,
      subjects had to maintain standing position for 30 seconds and Fukuda's Stepping Test required
      that the subject did not rotate more than 30° from the initial position or deviate more than
      0.5 meters from the center of the circle. Functional strength of lower extremities was
      screened using a Five Times Sit to Stand test, where the subject had to complete the test in
      10 seconds or less. Severe proprioception impairments were assessed using a Proprioceptive
      Awareness test, where the subject was asked to replicate the initial position performed by
      the evaluator in the contralateral ankle joint in three trials. After the screening of the
      inclusion and exclusion criteria, a total of 20 subjects were able to participate in the
      study.

      Each subject was instructed to stand in a static bipedal posture on the MatScan® pressure mat
      and performed eight balance tasks. Data of center of pressure, antero-posterior sways and
      medial-lateral sways were collected in each of the conditions. Each task took 30 seconds to
      be performed. The first four tasks were performed with the mat on the hard surface of the
      floor. These four tasks are as follows:1) eyes open looking at a fixed point to evaluate all
      systems (EO); 2) eyes closed (with head fixed approximately 90˚) to eliminate visual input
      (EC); 3) eyes open looking at a fixed point and actively moving head upward and downward to
      alter vestibular inputs (EO+HUD). The subject was instructed to maintain a movement frequency
      of 60bpm and amplitude of approximately 45 degrees in each direction: neck flexion and
      extension; 4) eyes closed (with head fixed approximately 90˚) to eliminate visual input and
      the head actively moves upward and downward to alter vestibular inputs (EC+HUD). The subject
      is instructed to maintain the movement frequency and amplitude as described in task 3.

      The subjects were asked to perform four more tasks while standing on a thick piece of balance
      foam that was placed on top of the MatScan®, creating an unstable surface. The remaining four
      tasks (tasks 5-8) are as follows: 5) eyes open looking at a fixed point while standing on the
      balance foam to alter somatosensory inputs (EO+BF); 6) eyes closed with head fixed
      approximately 90˚ while standing on the balance foam to alter somatosensory inputs and
      eliminate visual inputs (EC+BF); 7) eyes open looking at a fixed point and actively moving
      the head upward and downward while standing on the balance foam to alter somatosensory and
      vestibular inputs (EO+HUD+BF). The subject was instructed to maintain the movement frequency
      and amplitude as described in task 3; 8) eyes closed with head fixed approximately 90˚ and
      actively move head upward and downward while standing on the balance foam to eliminate visual
      inputs and alter somatosensory and vestibular inputs (EC+HUD+BF). The subject is instructed
      to maintain the movement frequency and amplitude as described in task 3.

      Data of postural stability was obtained using the MatScan® pressure mat (TekScan, Boston,
      MA). The data collected from the pressure mat was analyzed with Tekscan Sway Analysis Module™
      (SAM) software (TekScan, Boston, MA) designed for this purpose. Mean and standard deviation
      were used to describe data. The statistical software used was SPSS-20 to perform a
      Paired-Samples t-test and compare the center of pressure, antero-posterior and right-left
      body sways displacement. P values <0.05 were accepted as statistically significant.
    

Intervention name(s): Postural Stability Testing
Intervention type(s): Other
Intervention description(s): Each subject was instructed to stand in a static bipedal posture on the MatScan® pressure mat and performed 8 balance tasks. Data of center of pressure, antero-posterior sways and medial-lateral sways were collected in each of the conditions. Each task took 30 seconds to be performed. The first 4 tasks were performed with the mat on the hard surface of the floor. These 4 tasks are as follows: standing with eyes open, standing with eyes closed, standing with eyes open looking and actively moving head upward and downward, and standing with eyes closed and the head actively moving upward and downward. The subjects were asked to perform four more tasks while standing on a thick piece of balance foam that was placed on top of the MatScan®. The remaining 4 tasks are as follows: standing with eyes open, standing with eyes closed, standing with eyes open looking and actively moving the head upward and downward, and standing with eyes closed with head actively moving upward and downward.
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Screening
Keywords: HIV; Balance; Vestibular; Somatosensory; postural stability; center of pressure