Testing of Upper Extremity Cerebellar Function
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Testing of Upper Extremity Cerebellar Function
function is to look for evidence of a lesion involving the cerebellar
hemispheres or the cerebellar pathways.
upper extremity cerebellar function, should be performed on all
patients as part of a standard neurologic examination. Other tests of
upper extremity cerebellar function, such as rapid alternating
movements or testing for rebound, don’t need to be performed routinely.
These additional tests of cerebellar function should be performed when
the possibility of cerebellar dysfunction is suggested by the history
or you need to look for additional confirmation of cerebellar
dysfunction when an abnormality is suggested on the finger-to-nose test.
Approach to the Cerebellar Examination. The left cerebellar hemisphere
coordinates the left arm (and leg), and the right cerebellar hemisphere
coordinates the right arm (and leg). Table 33-1 summarizes the lesions within the cerebellum or its pathways that may cause incoordination on examination.
Ask the patient to “make a pointer” with his or her index finger.
Ask the patient to touch his or her nose with that index finger.
Hold your index finger directly in front
of the patient, at nearly an arm’s length away from him or her, and ask
the patient to touch your index finger.
Ask the patient to repeat the process
back and forth a few times, moving his or her index finger between the
tip of the patient’s nose and your index finger, as smoothly as
Repeat the same process with the patient’s other arm.
Show the patient what you will be asking
him or her to do by holding one of your hands stationary with its palm
up, then rapidly clap your other
on the stationary hand, alternately turning the moving hand palm side
up or palm side down (i.e., alternating pronation and supination),
alternating between each clap.
Ask the patient to perform this maneuver
on one side while you watch for a few seconds. If you suspect that the
patient might be ataxic on a particular side, it is probably best to
have the patient begin the test by moving the good side and holding the
other (potentially ataxic) arm stationary.
Then ask the patient to perform the same
maneuver with the opposite hands (i.e., keeping the other hand
stationary) while you observe for a few seconds.
Ask the patient to hold both arms directly in front of him or her, palm side down.
Tell the patient to try to keep the arms
in the same position without moving and specifically to resist your
attempt to push the arms down.
Using both of your hands, press down on
the dorsum of both of your patient’s hands while the patient resists
that force, and then let go.
Observe the response of the patient’s arms after you let go of them.
finger-to-nose maneuver smoothly and accurately with each arm, and
there should be no significant asymmetry between the two arms.
hand on the other, alternating supination and pronation of the moving
hand, fairly smoothly and accurately on each side. Some neurologically
normal patients, however, perform this maneuver slightly less smoothly
when the nondominant hand is the moving hand.
upward when you release your downward pressure on them. This slight
rebound should be symmetric, however, and the patient’s arms should
rapidly return to their straight, forward position.
Clumsiness of an arm during the
finger-to-nose maneuver is abnormal. Clumsiness due to cerebellar
dysfunction usually manifests as side-to-side wavering of the arm
(including movements at the shoulder) throughout its attempt to reach
its target; this is referred to as dysmetria or appendicular ataxia (or simply ataxia). See Chapter 33, Approach to the Cerebellar Examination, for a discussion of the terminology describing cerebellar dysfunction.
Assuming the patient’s arm is strong
(cerebellar hemisphere lesions do not cause weakness), clumsiness
during the finger-to-nose maneuver on one side suggests cerebellar
hemisphere dysfunction ipsilateral to the side of the clumsy extremity.
When patients with mild weakness in an
extremity also have what appears to be significant cerebellar dysmetria
in the same extremity (and the subtle weakness doesn’t seem to be
severe enough to explain the dysmetria), the lesion may be in the
contralateral posterior limb of the internal capsule or the pons. This
is called an ataxic-hemiparesis (see Table 33-1).
Inability to rapidly, smoothly, and
accurately perform rapid alternating movements in the upper extremities
is abnormal and is called dysdiadochokinesia.
As noted in the section Normal Finding, however, a mild asymmetry in
ability to perform this test (worse in the nondominant hand) may not be
In the absence of any weakness, a
significant problem performing rapid alternating movements on one side
(dysdiadochokinesia) is suggestive of cerebellar hemisphere dysfunction
ipsilateral to the side of the clumsy extremity.
This test can be particularly affected by
weakness, so in the presence of any weakness in an extremity,
difficulty with rapid alternating movements can be a nonspecific
mechanism when you release your downward pressure on the patient’s arm,
is abnormal. The abnormal side rebounds significantly upward and then
bounces down and up several times, as if it is held by a loose spring,
before finally settling back to the straight, forward position. The
finding of rebound, like the finding of dysmetria or
dysdiadochokinesia, is ipsilateral to the abnormal cerebellar
The patient’s eyes should be open
throughout the cerebellar examination, including during the
finger-to-nose maneuver. No additional information regarding cerebellar
function is learned by having the patient’s eyes closed.
During the finger-to-nose maneuver, it is
usually not necessary to give the patient a variable target by moving
your finger to different positions, but occasionally this is helpful to
bring out dysmetria that was not otherwise evident (or to further prove
that the patient’s coordination is good). To do this, move your finger
to a different position—always at approximately the same distance from
the patient (i.e., slightly less than an arm’s length away)—when the
patient brings his or her finger to his or her nose, and then keep your
finger stationary in the new position until the patient brings his or
her finger to yours.
The bounciness of an arm on the side of
cerebellar dysfunction, as seen on the test for rebound, may
occasionally be suggested earlier in the examination when the patient
brings the arms into position when testing drift.