Assessment of Postural Orientation and Equilibrium In Early Amyotrophic Lateral Sclerosis (ALS)
Condition: Amyotrophic Lateral Sclerosis
MeSH terms: Motor Neuron Disease; Amyotrophic Lateral Sclerosis; Sclerosis
Study type: Observational

Summary: 
      The purpose of this pilot study is to characterize changes in postural orientation and
      equilibrium in early diagnosed ALS patient. The investigators plan to cross validate the use
      of a standardized test of equilibrium (EquiTest, Computerized Dynamic Posturography - CDP) in
      early diagnosed ALS patients.
    

Detailed description: 
      ALS is a progressive neurodegenerative disorder involving primarily upper and lower motor
      neurons. The progressive loss in motor neurons leads to weakness, fatigue, spasticity, and
      loss of balance. Falls are reported in 30-35% of ALS patients prior to enrolment to ALS
      clinic. This early loss of balance may not be detected by the classical neurological exam, or
      the standard clinical balance scales. Understanding the impairments in the balance control
      system which leads to fall during the course of ALS is a prerequisite for the clinical
      decision-making process in order to develop a proper balance rehabilitation program and fall
      prevention strategies for these patients.

      Patients and control subjects will undergo balance system evaluation consisting of the
      following testing:

        1. Sensory Organization Test Protocol

           Standardized EquiTest assessment protocol:

           Sensory Organization Test (SOT) - will be used to measure change how well participants
           maintain balance under progressively more difficult test conditions, which either
           disrupt or remove visual and proprioceptive feedback. Visual and proprioceptive
           environments will be altered systematically for fixed support and sway-referenced
           support and surround conditions, and under normal (eyes open), absent (eyes closed), and
           sway-referenced vision (eyes sway-referenced). Under sway-referenced conditions, the
           platform on which the subject stands and/or the visual surround also move proportionally
           to their AP sway. During SRC the floor and visual surround are controlled by a
           servomechanism (Gain=1.0) to follow movements of the subjects' center of gravity.
           Sway-referencing eliminates accurate somatosensory and/or visual information used to
           orient the body. Performance under sway-referenced visual conditions shows the
           participant's ability to suppress conflicting visual inputs and to rely on alternative
           systems for maintaining equilibrium (table 1).

           Participants are carefully positioned on the platform by aligning the lateral malleoli
           with the axis of rotation of the platform and visual surround. Participants wear a
           harness during all testing, which protects participants from falling. As an additional
           safety measure, the technician stands behind the participant. There are three trials per
           condition with each trial lasting 20 seconds. When a participant takes a step, touches
           the surround panels, or needs assistance from the technician, that trial is marked as a
           fall and the participant receives an equilibrium score of zero for that trial.

           In addition to the ES, movement strategy scores (MSS) will be measured by horizontal
           shear forces. Movement strategy scores reflect the relative use of movement about the
           ankle, hips and upper body to maintain balance during the SOT. Scores around 100 reflect
           a predominant use of ankle strategy to maintain balance, whereas low scores are
           indicative of the use of hip strategies to restore stability.

        2. Motor Control Test Protocol The Motor Control Test (MCT), using the same apparatus will
           be performed to examine postural responses to external perturbations. During the MCT,
           subjects will receive perturbation from the force platform. Perturbations are expressed
           as translation movement (medium horizontal anterior to posterior movements of less than
           1 sec. duration) or as rotation movements (at 6.0 degrees per second, which cause ankle
           dorsiflexion or plantarflexion). Six forward and six backward translations are
           generated. Five toes up and five toes down rotations are generated. The computer assures
           random delays of 1.5 to 2.5 seconds between translation trials and 3.0 to 5.0 seconds
           between rotation trials. During each perturbation, the computer monitors the subjects
           sway responses, measuring forces exerted against the dual force plate. These forces are
           expressed as weight symmetry and strength symmetry. Weight symmetry measures the
           distribution of total body weight over each leg, independent of other response strength
           and strength symmetry measures. Weight symmetry scores near 100 indicate a symmetrical
           weight distribution (EquiTest manual, 1991).

      Outcome variables:

      i. Sensory Organization Test (SOT) scores on conditions 1-6. ii. Movement Strategy Score on
      conditions 1-6 iii. Weight Symmetry Score on conditions 1-6
    

Observational model: Other
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients diagnosed with Amyotrophic Lateral Sclerosis
      
Keywords: fall; balance