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 > Cranial Nerve Examination > Chapter 23
– Examination of Smell
– Neurologic Examination > Cranial Nerve Examination > Chapter 23
– Examination of Smell
Chapter 23
Examination of Smell
PURPOSE
The purpose of testing smell is to assess for dysfunction of the olfactory (first) cranial nerves.
WHEN TO EXAMINE SMELL
Testing the sense of smell does not need to be performed
routinely; in fact, this test rarely needs to be done. Smell should be
tested, however, in patients who have a complaint of a diminished sense
of smell, in patients in whom a frontal lobe lesion is suspected or
known, or in patients with a history of closed head injury or skull
fracture.
routinely; in fact, this test rarely needs to be done. Smell should be
tested, however, in patients who have a complaint of a diminished sense
of smell, in patients in whom a frontal lobe lesion is suspected or
known, or in patients with a history of closed head injury or skull
fracture.
NEUROANATOMY OF SMELL
Smell receptors in the nasal mucosa send their axons
through the cribriform plate to the ipsilateral olfactory bulb, which
then sends its axons to the olfactory cortex.
through the cribriform plate to the ipsilateral olfactory bulb, which
then sends its axons to the olfactory cortex.
EQUIPMENT NEEDED TO TEST SMELL
Coffee grounds (or other substance with a nonnoxious, recognizable odor).
HOW TO EXAMINE SMELL
-
Put some coffee grounds in a paper cup outside of the patient’s view.
-
Ask the patient to close his or her eyes
and to cover one nostril. Tell the patient that you will be placing a
substance under the open nostril and asking him or her to identify the
substance by smell. Inform the patient that it will not be an
unpleasant smell. -
Test the patient’s ability to smell the coffee through one nostril and then the other.
-
If the sense of smell is abnormal, confirm that the patient can breathe through each nostril.
NORMAL FINDINGS
Normally, the patient should be able to identify the smell of coffee grounds through each (unobstructed) nostril.
ABNORMAL FINDINGS
-
Unilateral absence of smell in the
setting of an intact nasal passageway suggests the possibility of
ipsilateral olfactory bulb dysfunction, such as can occur as a result
of trauma from a basilar skull fracture or compression from an inferior
frontal mass. -
Bilateral absence of smell suggests
bilateral olfactory nerve dysfunction, which can also be due to
traumatic or compressive dysfunction of these nerves but could also be
caused by a primary disorder of smell.
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ADDITIONAL POINTS
Despite being conveyed by the first cranial nerve, this
test is relegated to the last chapter of the cranial nerve section of
this book because of how infrequently it needs to be performed. In the
appropriate clinical scenarios, however, useful and important
information can be learned from this test.
test is relegated to the last chapter of the cranial nerve section of
this book because of how infrequently it needs to be performed. In the
appropriate clinical scenarios, however, useful and important
information can be learned from this test.