Download Problems with the timely activation of postural responses

Abnormal postural control
Learning objectives
• Following the completion of this chapter, the
student must be able to
1. Summarize fall rates and risk factors for falls
among persons with neurologic pathology
2. Give examples of sequencing and timing
problems that affect the coordination of
postural motor responses.
3. Discuss two deficits affecting the ability to
modify postural motor responses to changing
task and environmental conditions
Learning objectives continued
4. Describe the effect of impaired anticipatory
postural control on voluntary movement –
which neural pathologies are likely to result in
these types of problems
Introduction
• Balance is critical to independence in daily living
activities.
• Impairments in postural control producing loss
of stability have a profound impact on the daily
life of individuals with neurologic pathology.
• The consequences of impaired stability include
loss of functional independence, increased
prevalence of disability and falls.
Falls following neurologic pathology
• Falls are a major problem among persons with
neurologic pathology.
• Among individuals who had a stroke, falls are four
times more likely to result in a hip fracture, because
of increased rates of osteoporosis in their paretic
side.
• Falls are also a significant problem in Parkinson’s
disease (PD), with falls rates ranging from 40% –
68%
• Falls were one of the most common reasons for
emergency hospital admissions among people with
PD.
Falls following neurological pathology
continued...
• Fall rates are high among people with multiple
sclerosis
• As was true for older adults, the majority of falls
in persons with neurologic pathology are
associated with mobility, occuring during
walking, transfers, and stair climbing.
Risk factors for falls in neurologic
population
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Lower balance score (< 30 on Berg balance test)
Presence of apraxia
Cognitive deficits
Lower Functional Independence Measure (FIM)
score
Factors predicting falls in persons with
Parkinson’s disease
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Multiple medications
Increased physical disability
Dementia
Depression
Increased severity
Marked response to levadopa
Dyskinesia
Impaired balance and gait
Reduced stability when performing concurrent
tasks
3 Variables predicting falls in persons
with multiple sclerosis
• Balance
• Walking ability
• Use of cane
Problems in the motor components of
postural control
• Motor components include neuromuscular
(coordinating multiple muscles into postural
muscle synergies) systems and
musculoskeletal systems
Motor coordination problems
• Sequencing problems – delayed recruitment of
synergistic muscles, co activation of antagonist
muscles resulting in stiffness
• Problems with the timely activation of postural
responses.
• Problems adapting postural activity to changing
task and environment demands.
Musculoskeletal contributions to
coordination problems
• In a person with a central nervous system lesion,
musculoskeletal disorders develop most often
secondary to immobility and restricted
movement.
• Alignment – refers to the relationship of body
segments to one another as well as to the
position of the body with reference to gravity
and the base of support. Alignment determines
movement strategies that will be effective in
controlling posture.
Musculoskeletal contributions to
coordination problems continued
Alignment continued
• Children with CP – restricted ROM,
contractures, atypical postures
• Unilateral neural lesion – change in the position
of the body with reference to gravity and the
base of support. Weight displaced to non
involved side, wide base of support.
• Neurological deficit – center of mass displaced
either forwards or backwards
Musculoskeletal contributions to
coordination problems continued
• Changes in alignment can be viewed as either a
musculoskeletal impairment or as a strategy
compensating for other impairments.
Musculoskeletal contributions to
coordination problems continued
• Constraining movement at a joint
• Example: AFO’s (ankle foot orthoses)
• The type of device we use to contol position and
motion at the ankles can have a significant impact
on the sequencing and timing of muscles used to
recover balance.
• AFOs that restrict motion at the ankle will reduce
the participation of ankle joint muscles in the
control of stability. This will result in an increase in
the use of hip and trunk muscles for balance control.
Loss of anticipatory postural control
• The inability to adapt how we move in response
to changing task and environmental conditions
can be a source of instability in many persons
with instability.
• Another source of postural dyscontrol is, is the
loss of anticipatory processes that activate
postural adjustments in advance of potentially
destabilizing voluntary movements.
• Anticipatory postural activity is heavily
dependent on previous experience and learning
Sensory disorders
• Normal postural control requires (1) the
organisation of sensory information from visual,
somatosensory and vestibular systems that provide
information about the body’s position and
movement with respect to the environment, and (2)
the coordination of sensory information with motor
actions.
• Sensory problems can disrupt postural control by (1)
affecting a person’s ability to adapt sensory inputs to
change in task and environmental demands, and (2)
preventing the development of accurate internal
models of the body for postural control
Impaired postural stability under dual
task conditions
• Inability to maintain balance while performing
multiple tasks have been found in persons with
various types of neurologic pathology.
Postural control in persons with
Dementia
• The relationship between impairments in
cognitive function and postural control are being
studied by many researchers, in part because of
the high fall rates of falls reported in persons
with various types of dementia, including
Alzheimer’s disease
Impaired seated postural control
• Postural control underlying the ability to sit
independently is a critical part of functional
independence in ADL. Impaired sitting balance is a
frequent occurence in both children and adults with
neurologic pathology.
• Acquisition of sitting balance in both children with
neurologic pathology has been shown to be a good
predictor of functional outcomes
• Sitting balance has been shown to be a good
prognostic indicator of outcome for persons who
have had a stroke and traumatic brain injury.
Summary
• An enormous range of problems can contribute
to postural dyscontrol in individuals with a
neurologic deficit.
• Coordination problems that manifest within
postural movement strategies include: (a)
sequencing problems; (b) problems with the
timely activation of muscle response synergies;
(c) disorders related to the scaling of postural
muscle activity and (d) problems adapting motor
responses to changing task conditions
• Musculoskeletal disorders present in individuals
with neurologic deficits develop most often
secondary to the neurologic lesion. Yet,
musculoskeletal problems can be a major
limitation to normal postural function in the
neurologically impaired patient.