of Motor Function
is motor function controlled?
movement requires the transmission of a message from the motor strip of
the cerebral cortex (upper motor neuron) to the appropriate muscle on the
opposite side of the body. Thus, injury to the cerebral cortex causes
decreased muscle function contralaterally (on the side of the body opposite
to the brain injury). While the ability to tell the muscle to move
is a function of the cerebral cortex, the ability to make the movement
smooth and coordinated requires the cerebellum. Shaky or uncoordinated
movements may be the result of cerebellar dysfunction. The cerebellum
controls smoothness of movement on the same side (the message to move the
left leg comes from the right cerebral cortex, but is coordinated and made
smooth by the left hemisphere of the cerebellum).
is motor function "rated"?
motor function is intact, muscles can be moved to command. Symmetrical
movement and strength is one of the most important assessment findings.
Reduced motor function can occur as a result of injury to the cerebral
cortex, motor pathway, peripheral nerve or muscle. While it takes
a certain level of function to move a muscle to command, increased innervation
and muscle strength is required to overcome gravity. Even greater
strength is required to overcome resistance by an examiner. Assessment
of motor function can be graded as follows (right compared to left):
= normal strength (normal strength, able to maintain the muscle contraction
against examiner resistance)
= mild weakness ( weakly or briefly able to overcome examiner resistance)
= able to support the limb against resistance but unable to overcome examiner
= can move the limb, but unable to lift against gravity
= flicker but no movement
= no movement
is a quick way to assess motor function in a conscious patient?
an intensive evaluation can be performed for each muscle groups, a quick
way to identify motor weakness is the assessment for limb drift.
the patient hold arms out horizontally, palms up, with eyes closed.
If there is upper limb weakness, the affected side will "drift" or pronate
within 30 seconds.
the patient lying in a supine position, bend the knees to 30 degrees.
If there is weakness in the lower extremities, the affected leg will drift
downward within 30 seconds.
patient in supine position, flex both knees and support under one of examiners
arms. Allow one heel to rest on the bed. Extend the other leg
at the knee and allow it to drop gently to the bed. Compare the speed
of drop for both legs.
is a quick way to assess motor function in an unconscious patient?
both patient's arms together. While protecting the limbs from injury,
release both arms together. A paralysed arm will fall more rapidly.
patient supine. Flex the knees with both feet on the bed. Release
the knees simultaneously. A paralysed leg will fall to an extended
position and the hip will rotate externally. The normal leg will
stay flexed for a few seconds and gradually assume the previous position.
other assessments can be made of an unconscious patient?
the patient as they make spontaneous movements. Note the symmetry
of movement. If the individual does not respond to command,
but makes purposeful movements such as pulling at lines or tubes, the response
is referred to as localizing. This is an appropriate response
that requires functional motor pathways.
no spontaneous movement is noted, provide central pain stimulation.
Central pain can be tested by rubbing the sternum, squeezing the the tissue
in the axilla, squeezing the trapezius muscle at the angle of the neck
and shoulder or by applying supraorbital pressure (avoid if facial fractures
present). Interchange technique to avoid bruising or injury to tissues.
If response is obtained to central pain, peripheral stimulation is not
needed. Peripheral pain may produce a spinal reflex, and is therefore,
not an effective test of upper motor neuron function.
can be described by the presence of normal flexion in response to pain.
Pulling away without flexing the wrist is one way to differentiate
normal flexion from abnormal flexion. Rigid flexion is considered
flexion. Rigid extension is referred to as abnormal extension.
Absence of movement or tone is referred to as flacid
other assessments evaluate motor function?
addition to the assessment of strength described above, muscles should
be inspected and palpated. Inspect for asymmetrical movement or abnormal
limb rotation. Palpatate the muscle for decreased (flacid) or increased
(spasticity). Decreased tone may represent early upper motor neuron
or peripheral nerve injury. Increased tone is associated with upper
motor neuron injury.
Brenda Morgan, Clinical Educator
November 19, 1999
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