MOTOR CONTROL TEST (MCT)
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The MCT assesses the ability of the automatic motor system to quickly recover following an unexpected external disturbance. Sequences of small, medium or large platform translations (scaled to the patient's height) in forward and backward directions elicit automatic postural responses.
Translation of the surface in one horizontal direction results in displacement of the COG away from center in the opposite direction relative to the base of support. To restore normal balance, a quick movement of the COG back to the center position is required.
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MCT Comprehensive Report
- Weight Symmetry quantifies the relative distribution of weight on each leg. Accurate interpretation of the latency and amplitude scaling measures requires weight-bearing symmetry within the normal limits (automatic responses may be suppressed in a leg not carrying weight).
- Latency quantifies the time between translation (stimulus) onset and initiation of the patient's active response (force response in each leg). The composite latency score is an average of the individual scores for the two legs. Latency scores are displayed only for the medium and large translations. Latencies for large translations are typically shorter than for medium translations in normal subjects.
- Amplitude Scaling quantifies the strength of responses for both legs and for the three translation sizes. Strengths are typically similar for both legs and increase with increasing translation size.
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Automatic postural responses are the first line of defense against a fall following unexpected external disturbances to balance. To be effective in this capacity, responses must be timely and well coordinated between the two legs. As response latencies increase and/or amplitudes decrease outside normal ranges, effectiveness is reduced and patients tend to sway farther in response to disturbances. Patients with abnormally strong responses tend to over-correct and oscillate back and forth. When responses are asymmetrical between the two legs, patients are at increased risk for instability during tasks such as walking and reaching when the less effective leg is the primary means of postural support.
When combined with the Sensory Organization Test (SOT), the MCT results are very useful in differentiating among normal responses, true pathological conditions, and exaggerated sway responses. Because they are not under conscious control, automatic responses are initiated very rapidly and are highly repeatable across trials. Exaggerated responses are volitional, take longer to initiate, and tend to vary widely from one trial to the next. Thus, automatic and (exaggerated) volitional responses can be readily distinguished within the MCT data set.
Automatic response latency information is also of significance in the diagnostic process. Prolonged latencies are strong evidence of musculoskeletal/biomechanical problems and/or pathology within the long loop pathways including the peripheral nerves, ascending and descending spinal pathways, and brain structures. When prolonged latencies are documented by the MCT, the EMG component is useful in further localizing the deficit within the peripheral nerves or central pathways.
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