Approach to the Cerebellar Examination

By admin On Dec 13, 2024

Ovid: Field Guide to the Neurologic Examination

Authors: Lewis, Steven L.

Title: Field Guide to the Neurologic Examination, 1st Edition

> Table of Contents > Section 2
– Neurologic Examination > Cerebellar Examination > Chapter 33 –
Approach to the Cerebellar Examination

Chapter 33

Approach to the Cerebellar Examination

PURPOSE

The purpose of testing cerebellar function is to look
for evidence of a lesion involving the cerebellum or the cerebellar
pathways.

WHEN TO PERFORM THE CEREBELLAR EXAMINATION

Cerebellar function should be examined in all patients
as part of a standard neurologic examination. This should include the
finger-to-nose maneuver (see Chapter 34, Testing of Upper Extremity Cerebellar Function) and observation of gait (see Chapter 39,
Examination of Gait). Other tests of cerebellar function, such as rapid
alternating movements or testing for rebound, should be performed when
there is a clinical suspicion for a cerebellar abnormality and are
discussed in Chapter 34, Testing of Upper Extremity Cerebellar Function, and Chapter 35, Testing of Lower Extremity Cerebellar Function.

NEUROANATOMY OF THE CEREBELLUM

The function of the cerebellum is to coordinate
movements. The midline of the cerebellum (the vermis) is primarily
involved in truncal balance and gait. The lateral parts of the
cerebellum (the two cerebellar hemispheres) coordinate the movements of
the ipsilateral extremities. In other words, the left cerebellar
hemisphere coordinates the left arm and leg, and the right cerebellar
hemisphere coordinates the right arm and leg.

There are also pathways to and from the cerebellum that
travel through the cerebral hemispheres and the brainstem; these
cerebellar pathways in the internal capsule and the base of the pons
coordinate the contralateral extremities. In other words, the
cerebellar-destined fibers located within the left internal capsule or
left pons are involved in coordination of the right arm and right leg.

EQUIPMENT NEEDED TO EXAMINE CEREBELLAR FUNCTION

None.

HOW TO EXAMINE CEREBELLAR FUNCTION

Examination of upper extremity cerebellar function,
including testing finger-to-nose, rapid alternating movements, and
rebound, is described in Chapter 34

P.110

, Testing of Upper Extremity Cerebellar Function. Examination of lower
extremity cerebellar function, including heel-to-shin testing, is
described in Chapter 35, Testing of Lower Extremity Cerebellar Function. The examination of gait and tandem gait is described in Chapter 39, Examination of Gait.

NORMAL FINDINGS

Patients whose motor and sensory functions are intact
are able to smoothly and accurately perform the finger-to-nose and
heel-to-shin maneuvers, are able to rapidly and accurately perform
alternating movements in the hands, and have a stable and narrow-based
gait.

ABNORMAL FINDINGS

Abnormal findings on cerebellar testing can be generally
divided into the cerebellar abnormalities seen on examination of gait
and the abnormalities seen on examination of the extremities.

Gait

The abnormal finding on examination of gait due to cerebellar dysfunction is called gait ataxia,
which is characterized by a wide-based, unsteady gait (sometimes with
inability to walk at all because of the severe unsteadiness) and
inability to perform tandem gait (see Chapter 39, Examination of Gait).
Gait ataxia can be seen due to any lesion
of the cerebellum in the midline (vermis) or in the hemispheres.
Cerebellar vermis lesions tend to produce gait ataxia without
significant extremity findings. Cerebellar hemisphere lesions, on the
other hand, typically produce extremity findings (see Extremities) as
well as gait ataxia. When patients with an ataxic gait tend to veer or
fall consistently toward one side, the side that they veer toward is
likely the side of the cerebellar hemisphere lesion.

Extremities

The main type of abnormality seen on
examination of the extremities due to cerebellar dysfunction is
incoordination of the extremity.
On the finger-to-nose or the heel-to-shin
tests, findings of cerebellar dysfunction manifest as clumsiness in
performance of the maneuver, usually with some side-to-side wavering of
the extremity (including movements at the shoulder or hip) throughout
its attempt to reach its target. This is cerebellar ataxia, which is
probably better referred to as appendicular ataxia to distinguish it from the finding of gait ataxia described in Gait.
There are many other names for the clumsiness seen in the extremities due to cerebellar disease, including dysmetria.
Although dysmetria probably more accurately refers to the overshoot or
undershoot of the target seen in cerebellar disease, in practice the
term dysmetria is used as a generic term
synonymous with appendicular ataxia to describe any cere-bellar-type
clumsiness during the finger-to-nose or the heel-to-shin tests. In
fact, dysmetria seems to be the preferred
term by most clinicians to describe any clumsiness seen during the
finger-to-nose or the heel-to-shin tests attributed to cerebellar
dysfunction.
Asymmetric or unilateral dysmetria (i.e.,
appendicular ataxia) in the arm or leg, or both, in the absence of any
weakness suggests a cerebellar hemisphere lesion ipsilateral to the
side of the clumsiest extremities.

P.111

Other abnormal findings in the
extremities that may be seen on cerebellar testing include difficulty
performing rapid, alternating movements (dysdiadochokinesia) and rebound
in the arms. These findings, which also occur ipsilateral to the
cerebellar hemispheric lesion, are described in further detail in Chapter 34, Testing of Upper Extremity Cerebellar Function.
Weakness does not occur due to
dysfunction of the cerebellum, whether in the cerebellar hemispheres or
the vermis. Sometimes, however, patients with mild weakness in an
extremity also have what appears to be cerebellar dysmetria in the same
extremity (i.e., the mild weakness doesn’t seem to be severe enough to
explain the dysmetria). In such cases (called ataxic-hemiparesis), the lesion may be in the contralateral posterior limb of the internal capsule or the pons.
Table 33-1 summarizes the effect of lesions within the cerebellum or its pathways that may cause incoordination on cerebellar testing.
Cerebellar disease may also cause tremor. The term intention tremor,
however, is sometimes used to describe cerebellar dysmetria, which is
not really a tremor at all, but rather, as described previously, is
clumsiness and wavering in an attempt to reach a target. True tremors
due to cerebellar pathway disease are, however, usually worse with
action and may be coarse. A rhythmic tremor of the head or trunk, or
both, can also occur due to cerebellar disease and is known as titubation.

TABLE 33-1 Summary of the Lesions within the Cerebellum or Its Pathways That May Cause Incoordination on Examination

Location of Lesion	Area of Body Where Coordination Is Affected
Vermis (midline)	Trunk (gait)
Left cerebellar hemisphere	Left extremities
Right cerebellar hemisphere	Right extremities
Left posterior limb of internal capsule or the left base of pons	Right extremities; also with mild right-sided weakness (ataxic-hemiparesis)
Right posterior limb of internal capsule or the right base of pons	Left extremities; also with mild left-sided weakness (ataxic-hemiparesis)

ADDITIONAL POINTS

Much of the terminology used to describe cerebellar findings on examination is vague and ambiguous. Try to avoid the term intention tremor
to describe clumsiness during the finger-to-nose and heel-to-shin
maneuvers, as this term can be confused with other true tremors of
cerebellar or noncerebellar (see Chapter 46,
Examination of the Patient with a Movement Disorder) etiologies.
Sticking to the terminology recommended here (e.g., dysmetria,
appendicular ataxia) is less confusing.