Assessment Task 2_THIEL

Assessment Task 2 – Balance and stroke
Alexander Thiel
Read this article (de Oliveira, de Medeiros, Frota, Greters & Conforto, 2008) about stroke and
balance (yellow titles) and clarify how these important resources required for postural control
change after stroke. In the article is also presented commonly used balance scales. Which tests are
familiar to you? The length of the summary should be 1-2 pages.
For postural control, three sensory modalities are mainly needed: somatosensory, visual and
vestibular afferents. The information of all these systems is essential for adequate postural control.
70 percent of the information required for postural control comes from somatosensory afferents, 20
percent from vestibular afferents and about 10 percent from visual input. That means that
nondisabled adults mostly tend to use somatosensory information from their feet in contact with the
surface while standing in a controlled environment with a firm base of support (BS).
Nondisabled persons use an important ability to choose and rely on the appropriate sensory input for
each condition and situation. This ability is called sensory reweighting. For example, if someone is
standing on an unstable surface, the central nervous system (CNS) increases sensory weighting to
vestibular and visual information and decreases the dependence of somatosensory inputs of the
surface. On the other hand, in darkness, somatosensory and vestibular feedback is much more
important than visual feedback. The ability to analyse, compare and select the right sensory
information for each situation can be impaired in hemiparetic stroke patients and can increase the
risk of falling. That means that abnormal interactions between those three sensory systems can lead
to abnormal postural reaction as well as just relying on a single system.
Some definitions are required for understanding balance:
Base of support - the area beneath an object or person that includes every point of contact
that the object or person makes with the supporting surface
Center of mass - the center of mass is the mean location of a distribution of mass in space
(mean point of mass in a person/object)
Line of gravity – line which is projected vertically underneath the center of mass
The quality and size of the BS is one of the most important parts of balance. Postural stability can be
understood as the ability to keep the center of mass (Cm) within the BS. In hemiparetic patients,
weakness, impaired muscle control, decreased range of motion and pain can lead to changes in the
BS. Studies investigated a positive correlation between balance impairments and decreased lower
limb strength.
Strategies and solutions for postural control include the ankle, hip and step strategy. The ankle
strategy is more effective at keeping the trunk in a stable and vertical position during small
movements, which occur from distal to proximal. It depends more on accurate somatosensory input.
The hip strategy is superb for faster and larger movements of the CM. This strategy requires
adequate vestibular information. The step strategy represents a completely different kind of strategy
as the BS adapts to the CM in movement. The balance control can be reactive or anticipatory.
Patients with stroke mostly use compensating strategies, like holding objects or using the step
strategy more often than nondisabled persons. Also the hip strategy is predominantly used instead of
the ankle strategy. Nevertheless, all strategies are often not efficient enough for good stability and
can cause falls in patients with stroke.
Also the perception of verticality may be abnormal, especially in the presence of neglect. “Pushersyndrome” is characterized as a tendency to lean towards the affected side because of fear of falling
to the nonparalyzed side. Altered perception of the body posture is the reason for this phenomenon.
The patients experience their body as vertically correct when it is actually tilted to the paralyzed side.
Studies found out that patients with pusher syndrome show no disturbed processing of visual and
vestibular inputs determining visual vertical.
Conclusions about possible effects of the lesion side could not be proved by now.
Familiar tests for me, which are mentioned in the article, are:
Berg Balance Scale (BBS) – I used it in neurological rehabilitation
Timed Get Up & Go (TUG) – I mostly used it in geriatric departments
Tinetti Balance Test - I mostly used it in geriatric departments
Functional Reach Test (FR) – I used it as a part of BBS
Balance Subscale of Fugl-Meyer Test (FM-B) – I didn’t use it often
Tests, which I am not familiar with, are:
Postural Assessment Scale for Stroke Patients (PASS)
Dynamic Gait Index (DGI)
Multi-Directional Reach Test (MDRT)
Activities-Specific Balance Confidence Scale (ABC)