Balance and Posture in Adults With Cerebral Palsy

Individuals with Cerebral Palsy (CP) present with considerable functional heterogeneity, and
demonstrate a marked decrease in functional status with age due to the development of
disturbances in somatosensory function, secondary neuromuscular impairments, and poor
control over the trunk muscles. These factors promote balance instability, result in an
increased fall risk, and contribute to lost functional capabilities. Little is known about
the progression of neuromotor and somatosensory impairments as individuals with CP age, thus
a knowledge gap exists concerning postural control and balance in the adult with CP,
particularly which those associated with aging (primary) and those associated with
compensatory behaviors. The objective of this proposal is to explore mechanisms behind
abnormal motor response in postural control in the adult with CP. We HYPOTHESIZE that
somatosensory reliance, as well as muscle passive and active properties, change with aging
and functional adaptation. In order to address our central hypothesis, we propose the
following specific aims: SPECIFIC AIM 1: To examine the central disturbances of sensory
processing and sensorimotor integration that contribute to abnormal postural control in
young adults with CP. We will: a) determine the effect of visual dependence on postural
control in the adult with CP as directly measured with a test for visual dependence; and
b)relate the presence of visual dependence to the effect of disturbances of the visual flow
field on the center of mass (CoM) and center of pressure (CoP) responses in the adult with
CP; and c) determine the relationship between central disturbances of sensory processing and
sensorimotor integration on functional balance as measured by standardized clinical
assessments of balance and fall risk. SPECIFIC AIM 2: To examine the peripheral alterations
in passive muscle-tendon properties that could contribute to abnormal postural control in
young adults with CP. We will determine the effects of a disturbance of the base of support,
a disturbance to the visual flow field, and a combined disturbance of the two on joint
kinematics,CoP, and CoM responses in the adult with CP using functional principal component
(time-series) analyses. SPECIFIC AIM 3: To examine the impaired muscle activation and loss
of selectivity over muscle control that contributes to abnormal postural control in young
adults with CP. We will determine the effects of a disturbance of the base of support, a
disturbance to the visual flow field, and a combined disturbance of the two on the surface
electromyographic (sEMG) activity of lower limb and trunk muscles using wavelet analyses. At
the conclusion of this study, we will have characterized postural control strategies
employed by adults with CP in the presence of somatosensory and biomechanical perturbations.
The combination of our innovative methodology to challenge all aspects of the sensorimotor
system, with our analytical approach of both time series and wavelet analysis of the data,
will allow us to separate the primary dynamic postural deficits from compensatory actions, a
critical distinction for optimizing treatment interventions.

Inclusion Criteria:

- Individuals with spastic diplegic or quadriplegic CP with the ability to stand for a
period of 2 minutes

- Cognitive/communication skills sufficient to follow multiple step commands and to
attend to tasks associated with data collection

- The control group will consist of age matched adults with no known neurological or
somatosensory impairments.

- Subjects in all groups cannot have a reported sensitivity to motion sickness or
visual field deficits or visual problems (lower than 20/40) not corrected by glasses.

Exclusion Criteria:

- Abnormal score for vestibular integrity as tested with the Dynamic Illegible 'E'-test

- Abnormal sensation to light touch and kinesthesia in the foot and ankle as assessed
using the monofilament test.