Authors: Lewis, Steven L.
Title: Field Guide to the Neurologic Examination, 1st Edition
Copyright ©2004 Lippincott Williams & Wilkins
> Table of Contents > Section 2
– Neurologic Examination > Sensory Examination > Chapter 31 –
Examination of Cortical Sensation
– Neurologic Examination > Sensory Examination > Chapter 31 –
Examination of Cortical Sensation
Chapter 31
Examination of Cortical Sensation
PURPOSE
The purpose of the examination of cortical sensation is
mainly to see if there is evidence for a lesion involving the
nondominant (usually the right) parietal cortex.
mainly to see if there is evidence for a lesion involving the
nondominant (usually the right) parietal cortex.
WHEN TO EXAMINE CORTICAL SENSATION
Cortical sensation does not need to be assessed
routinely. Examination of cortical sensation may be helpful, however,
in situations in which there is a question of whether a patient’s
symptoms are due to a right hemisphere (cortical) process as opposed to
a spinal cord or peripheral process. The finding of cortical sensory
abnormalities in these situations, in the absence of significant gross
loss to the primary sensory modalities, would be further evidence of a
hemispheric (cortical) localization.
routinely. Examination of cortical sensation may be helpful, however,
in situations in which there is a question of whether a patient’s
symptoms are due to a right hemisphere (cortical) process as opposed to
a spinal cord or peripheral process. The finding of cortical sensory
abnormalities in these situations, in the absence of significant gross
loss to the primary sensory modalities, would be further evidence of a
hemispheric (cortical) localization.
NEUROANATOMY OF CORTICAL SENSATION
Cortical sensation refers to
sensation that requires some processing by the cortex to discriminate
one stimulus from another. The cortical sensory modalities (described
in sections below) include graphesthesia, stereognosis, and the ability
to perceive the presence of bilateral simultaneous sensory stimuli.
These cortical sensory functions are in contrast to the primary sensory
modalities (such as pinprick and vibration) for which there are
specific peripheral receptors and that don’t require much further
cortical integration.
sensation that requires some processing by the cortex to discriminate
one stimulus from another. The cortical sensory modalities (described
in sections below) include graphesthesia, stereognosis, and the ability
to perceive the presence of bilateral simultaneous sensory stimuli.
These cortical sensory functions are in contrast to the primary sensory
modalities (such as pinprick and vibration) for which there are
specific peripheral receptors and that don’t require much further
cortical integration.
EQUIPMENT NEEDED TO TEST CORTICAL SENSATION
-
For graphesthesia: none
-
For stereognosis: a few coins of different denominations
-
For testing bilateral simultaneous stimulation: none
HOW TO EXAMINE CORTICAL SENSATION
Graphesthesia
-
Ask the patient to close his eyes and tell him you’ll be writing a number on his hand and he should tell you what the number is.
-
Write any one-digit number on the palm of
the patient’s hand using your finger or a dull object like the cap of a
pen and ask the patient what number it is. This may be repeated using a
different number to confirm the accuracy of the patient’s responses.
It’s helpful to “erase” the previous stimulus by rubbing the patient’s
palm with your hand between stimuli. -
Repeat the same on the other hand.
Stereognosis
-
Ask the patient to close her eyes and
tell her you’ll be placing an object into her hand and she should try
to tell you what it is. -
Place a coin of any denomination in the
patient’s hand and ask her to identify it. Inform the patient that she
can manipulate the object in her hand but should only use the one hand.
If necessary, repeat this using a different (or even the same) coin to
better assess the accuracy of the response. -
Repeat the same on the other hand.
P.105
Bilateral Simultaneous Stimulation
Testing for extinction on double simultaneous
stimulation can be performed with any sensory stimulus, as long as the
same stimuli are used on both sides. The most common sensory modalities
used to test for extinction are visual fields and gross touch.
stimulation can be performed with any sensory stimulus, as long as the
same stimuli are used on both sides. The most common sensory modalities
used to test for extinction are visual fields and gross touch.
To test bilateral simultaneous visual stimulation:
-
Begin as you would normally to check visual fields (see Chapter 13, Visual Field Examination): Stand directly across from the patient and ask the patient to look directly at your eyes.
-
Hold your left hand up so that you have
one, two, or five fingers in the patient’s right visual field and ask
the patient to tell you how many fingers you’re holding up (while he or
she is still looking only at your eyes). Put your left hand down when
you’re done. -
Then test the patient’s left visual field
alone by holding up your right hand with one, two, or five fingers. Put
your right hand down when you’re done. -
Last, hold both hands up so that you’re
testing the patient’s right and left visual fields at the same time
(still with the patient looking only at your eyes). It’s probably best
to hold one finger up with one of your hands and two fingers up with
your other hand. Ask the patient how many fingers you’re holding up.
To test bilateral simultaneous touch:
-
Ask the patient to close his eyes and
tell him you’ll be touching him with your hands and that he should
indicate which side you touch: left, right, or both. -
Touch the patient’s right arm with your left hand and listen for the patient’s response.
-
Touch the patient’s left arm with your right hand and listen for the response.
-
Finally, touch both of the patient’s arms simultaneously with both of your hands and listen for the patient’s response.
NORMAL FINDINGS
In the absence of significant cutaneous loss to the
primary sensory modalities, patients should normally be able to
identify a number drawn on each palm (graphesthesia), identify the
denomination of individual coins in their hands (stereognosis), and
recognize that the right and left extremities are being touched
simultaneously. In the absence of a visual field deficit (hemianopsia),
patients should normally be able to count fingers in both the right and
the left visual fields simultaneously.
primary sensory modalities, patients should normally be able to
identify a number drawn on each palm (graphesthesia), identify the
denomination of individual coins in their hands (stereognosis), and
recognize that the right and left extremities are being touched
simultaneously. In the absence of a visual field deficit (hemianopsia),
patients should normally be able to count fingers in both the right and
the left visual fields simultaneously.
ABNORMAL FINDINGS
Graphesthesia
If there is normal cutaneous sensation to the primary
sensory modalities, the inability to correctly identify a number drawn
on the palm with the eyes closed is abnormal (agraphesthesia). An
abnormality on this test is most likely
sensory modalities, the inability to correctly identify a number drawn
on the palm with the eyes closed is abnormal (agraphesthesia). An
abnormality on this test is most likely
P.106
to
be of clinical significance when there is unilateral dysfunction,
especially on the left hand; in this situation, the finding is
suggestive of contralateral (i.e., right, nondominant) parietal
cortical dysfunction.
Stereognosis
If there is normal cutaneous sensation to the primary
sensory modalities, the inability to correctly identify the
denomination of individual coins in the hand is abnormal
(astereognosis). Similar to the test for graphesthesia, an abnormality
on this test is most likely to be of significance when there is
unilateral dysfunction on the left hand, suggestive of right parietal
cortical dysfunction.
sensory modalities, the inability to correctly identify the
denomination of individual coins in the hand is abnormal
(astereognosis). Similar to the test for graphesthesia, an abnormality
on this test is most likely to be of significance when there is
unilateral dysfunction on the left hand, suggestive of right parietal
cortical dysfunction.
Bilateral Simultaneous Stimulation
In the absence of a hemianopsia, the inability to count
fingers on one side when the examiner is holding fingers in both fields
simultaneously is abnormal. In the absence of significant cutaneous
loss to the primary sensory modalities, feeling that only one side of
the body is being touched when in fact both sides are being touched is
also abnormal. In either of these situations, the patient is said to
have extinction of the stimulus on the
side that he or she doesn’t recognize. This would be reported as,
“There was extinction on double simultaneous visual [or tactile]
stimulation.” Similar to the other cortical sensory tests, extinction
is most commonly seen due to right (nondominant) parietal cortical
dysfunction, in which the finding would be extinction of the left-sided
stimulus.
fingers on one side when the examiner is holding fingers in both fields
simultaneously is abnormal. In the absence of significant cutaneous
loss to the primary sensory modalities, feeling that only one side of
the body is being touched when in fact both sides are being touched is
also abnormal. In either of these situations, the patient is said to
have extinction of the stimulus on the
side that he or she doesn’t recognize. This would be reported as,
“There was extinction on double simultaneous visual [or tactile]
stimulation.” Similar to the other cortical sensory tests, extinction
is most commonly seen due to right (nondominant) parietal cortical
dysfunction, in which the finding would be extinction of the left-sided
stimulus.
ADDITIONAL POINTS
-
There’s no reason to test cortical
sensation when the examination has already disclosed significant
sensory dysfunction on one side, because any abnormal findings could be
explained by the loss of primary sensation. -
When testing graphesthesia, even patients
without cortical dysfunction sometimes have difficulty correctly
identifying the number “4,” probably because there are different ways
to write it.