Assessment of Postural Orientation and Equilibrium In Early Amyotrophic Lateral Sclerosis (ALS)

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

Inclusion Criteria:

Inclusion Criteria for subjects with early ALS:

- Probable or definite ALS according to World Federation of Neurology diagnostic
criteria4.

- Early stage ALS defined as presence of:

1. Normal lower extremities muscle strength (≥ 4/5 in manual muscle strength or ≥
80% in the computerized dynamometer quantitative muscle strength);

2. ALSFRS score of ≥ than 30;

3. FVC of ≥75% predicted;

4. Ambulatory without the use of any assistive device.

- 18 - 75 years of age.

- Able to provide informed consent.

Inclusion Criteria for control subjects:

- Healthy 18 - 75 years of age without significant medical condition as defined by the
investigator.

- Able to provide informed consent.

- Not having any of the exclusion criteria listed below.

Exclusion Criteria:

- Age < 18 or > 75 years.

- History of falls (2 or more in the last year), history of fainting, history of
cerebrovascular accident (CVA) or myocardial infarction (MI), history of lower limb
joint replacement.

- History of neuromuscular dysfunction "except diagnosis of ALS for individuals with
ALS".

- Post-traumatic, septic, inflammatory, or neuropathic arthritis.

- Lower extremity injury/surgery that may effect balance.

- Vestibular pathology (i.e., inner ear problems, vertigo, meniere's).

- Peripheral neuropathy.

- Parkinson's Disease.

- Currently taking anti-convulsive medications (e.g., clonazepam, diazepam,
lorazepam,phenytoin, zonegran, carbamazepine, depakote, gabapentin, lamotrigine,
lamotrigine, oxcarbazepine, tiagabine, topiramate)

- Diabetes Mellitus.

- No history of neurological or medical condition that may interfere with balance as
defined by investigators.