Musculoskeletal Assessment

This portion of the balance evaluation includes the following things: strength, range of motion (ROM), pain, posture, and abnormal tone. Strength is typically measured by asking the patient to perform movement against resistance, while the response is rated. The limitation of this test is that it tests muscles in isolation. For this reason functional tests are usually preferred. An example of this type of test would be to have the patient perform a semi-squat, which tests several muscle groups and balance at the same time.

Strength    Range of motion    Pain    Posture    Tone

A decrease in range of motion can affect balance, especially if the decrease leads to a compensation in their posture that affects their ability to react quickly to losses in balance.

Pain can disrupt normal function and cause movement changes that can have an adverse effect on balance by causing limping or the shifting of body weight to the unaffected side.

The presence of abnormal tone is another area that can affect the body’s ability to react quickly to a loss of balance. Flaccid or spastic muscles can lead to a loss of sensation, strength timing or cause the weight to be shifted to the other side where the musculature is stronger.

 

New wearable devices to classify fall risk are currently under investigation with initial investigations showing 97% specificity and 98% sensitivity when compared with varying fall-risk Tinetti Scores. [Giansanti D, Macellari V, Maccioni G. New neural network classifier of fall-risk based on the Mahalanobis distance and kinematic parameters assessed by a wearable device. Phsiol Meas. 2008;29(3):N11-N19.

 

Sensory Systems

The sensory system’s contribution to balance can be somewhat confusing. The sensory system consists of several important organs and senses like the eyes, ears, inner ear, taste, smell, and the somatosensory system (including touch and proprioception--the ability to sense stimuli arising within the body. Even if you are blindfolded, you know through proprioception if your arm is above your head or hanging by your side). The use of these senses in combination is what gives us the ability to balance in different surroundings and with multiple stimuli barraging us. The use of these systems in combination also allows us to learn new movements quickly and to fine tune and repeat movements easily.

 

 

Vision is perhaps the most critical part of our balance system. We use vision to determine where we are in relation to our surroundings, and to see where the various parts of our bodies are (think of when you shake hands). However, vision information can sometimes be wrong, like when you are in a stationary train and the train next to yours begins to move—you feel that you are moving, and so the other systems come into play.

The vestibular system is responsible for taking this information and making sense of it—and determining if the information is correct. This system processes the information about movement with respect to gravity. This system works in conjunction with the visual system to help maintain posture during walking and to stabilize the eyes.

Somatosensory input consists of touch and proprioception. This system provides information to the central nervous system regarding our position in space, and how that changes given alterations in terrain and body positioning.

Disruptions in sensory input in visual, somatosensory or vestibular systems can affect balance adversely. How balance is affected depends on several factors, including the extent of the damage to the nervous system, how much sensory loss there is, and if there are other senses that compensate for the loss, like a visually impaired person developing a more acute sense of hearing. In the case of a patient that has had diabetes or stroke, several systems could be impaired.

Sensory loss can also lead to improper sensory weighting. For instance, someone with a balance impairment may rely too heavily on vision for help with walking. Patients watching their feet as they walk is a classic example of this. They are relying on their vision to keep their balance, as opposed to their other senses. Retraining this individual would include improving their somatosensory and vestibular input in an effort to reduce their reliance on vision for balance.

Once the central nervous system detects a loss of input from one of its systems, it goes to work trying to compensate for the recent changes. Whether the injury involves neurologic changes, weakness or loss of function, the nervous system does not always choose the best way to compensate. Its immediate goal is to develop a strategy that minimizes musculoskeletal damage and maximize function.