Download olfaction

Smell aka Olfaction (Latin olfacere)
1
-
Smell is the least understood of our senses.
one of the chemical senses
This results partly from the fact that the sense of smell is a
subjective phenomenon that cannot be studied with ease in
lower animals.
-
Another complicating problem is that the sense of smell is
poorly developed in human beings (Microsmatic) in
comparison with the sense of smell in many lower animals
(Macrosmatic).
-
Important for pleasure and for enjoying the taste of food.
Chemical detection without the danger of ingesting poison
-
alert us to potential dangers, e.g. smoke
2
In humans
• Strong link to sense of taste
• Strong link to emotional states
• Exploited by commercials/marketing
• Used for identification of gender
•Dangers and hazards
• Pheromones - signal sexual arousal or
a readiness for mating
3
-
lies in the superior part of each nostril
-
Located 7 cm inside the nasal cavity
-
In each nostril, the olfactory membrane has a
surface area of about 2.4 square centimeters
The human olfactory epithelium covers an area of roughly 1 cm2 on each side
-
Olfactory Cells - The receptor cells for the smell
sensation - bipolar nerve cells derived originally
from the CNS
about 10 million of these cells in the olfactory
epithelium interspersed among sustentacular
cells--rabbit  have approximately 50 million olfactory axons, whereas
humans  have only 6 million bilaterally
4
Olfactory mucous membrane is the place in body where NS is closest to
-
The mucosal end of the olfactory cell forms a knob
from which 4 to 25 olfactory hairs (also called
olfactory cilia), project into the mucus that coats
the inner surface of the nasal cavity
-
cilia react to odors in the air and stimulate the
olfactory cells
-
Spaced among the olfactory cells - Bowman’s
glands that secrete mucus onto the surface of the
olfactory membrane.
-
Olfactory cells are constantly being replaced with
a half-time of a few weeks 5
6
7
The olfactory
mucosa
Olfactory Receptor Cells have cilia
Cilia are bathed in mucous
Mucous contains Odorant binding
proteins (OBP)
OBP transmits the odorant
molecules from the air to receptor
sites on the cilia
-Each neuron has a thick dendrite
with an expanded end called
olfactory knob
-From rods cilia project to the
mucous surface
-Each receptor neuron has 10-20 cilia
-Axons of olfactory receptor neurons pierce cribriform plate of ethmoid bone and
enter olfactory bulbs
9
-Olfactory neurons have half-time of few weeks- Live for 5- 8 weeks & then die
10
11
12
*
-
The portion of each olfactory cell that responds to the
olfactory chemical stimuli is the olfactory cilia.
-
The odorant substance, on coming in contact with the
olfactory membrane surface, first diffuses into the
mucus that covers the cilia.
-
Then it binds with receptor proteins in the membrane
of each cilium - OBP
-
Receptor protein – G protein – cAMP pathway – opening
of Na channels – action potential – exciting the olfactory
neuron - olfactory nerve – CNS
13
*
-
Only volatile substances that can be sniffed into
the nostrils can be smelled
-
Substance must be at least slightly water soluble
so that it can pass through the mucus to reach the
olfactory cilia.
-
substance to be at least slightly lipid soluble,
presumably because lipid constituents of the cilium
itself are a weak barrier to non-lipid-soluble
odorants.
-
Sniffing is a semi-reflex response that usually
14
occurs when a new odor attracts
attention.
*
*Because only 5% of our nostril is
covered with the olfactory
epithelium, we sniff to
maximize the coverage of the
air intake over this portion of
our nose as seen in the diagram
to the left.
*Cool huh?
Odor pathways
➜ Orthonasal Pathway
➜ Retronasal pathway
16
- The
olfactory receptors adapt about 50
per cent in the first second or so after
stimulation.
- Thereafter,
they adapt very little and
very slowly.
- our
own experience that smell sensations
adapt almost to extinction within a
minute or so after entering a strongly
odorous atmosphere.
17
*
-
Because this psychological adaptation is far
greater than the degree of adaptation of the
receptors themselves
-
most of the additional adaptation occurs
within the CNS
-
Large numbers of nerve fibers pass from the
olfactory regions of the brain backward along
the olfactory tract and terminate on special
inhibitory cells in the olfactory bulb, the
granule cells.
-
cross-adaptation
18
*
-
1. Camphoraceous
-
100 primary sensations of smell
2. Musky
3. Floral
4. Pepperminty
5. Ethereal
6. Pungent
7. Putrid
19
*
- affective
quality of either pleasantness or
unpleasantness.
- smell
is probably even more important
than taste for the selection of food
-a
person who has previously eaten food
that disagreed with him or her is often
nauseated by the smell of that same
food on a second occasion
20
Very little known
*
• No odorotopic map found.
• All cells fire for all odors but form different patterns
different odors => Population code.
• Other complications: Change in intensity leads
to increase in the firing rate of neurons but triggers
changes in the perceived quality of the odorant.
Rats are 8 to 50 times more sensitive to odors than humans
Dogs are 300 to 10,000 times more sensitive
The difference lies in the number of receptors they each have
Humans have 10 million and dogs have 1
billion olfactory receptors
21
*
-
the minute quantity of stimulating agent in the
air can elicit a smell sensation.
-
the substance methylmercaptan can be
smelled when only one 25 trillionth of a gram is
present in each milliliter of air.
-
Because of this very low threshold, this
substance is mixed with natural gas to give the
gas an odor that can be detected when even
small amounts of gas leak from a cylinder.
22
*
Odor (as well as taste) are much more phenomenological
than vision or audition.
• Odor Detection
• Very good: Mercaptan 1 part per 50 billion parts of air.
• Varies greatly from odor to odor (molecular properties)
• Varies with a variety of other factors
• Time of day, Age and Gender
Smoking is injurious to odor detection!
• Odor Identification
• Much worse
• Shows context dependence
• Varies once again with age and gender
Humans can discriminate among 100,000 odors but they cannot label
them accurately
This appears to be caused by an inability to retrieve the name from memory,
23
from a lack of sensitivity
*
Olfactory receptors
respond only to substances
in contact with olfactory
epithelium and need to be
dissolved in mucus
Methyl marcaptan one of
the substances in garlic
can be smelled at very low
concentration showing the
remarkable sensitivity of
olfactory receptors
Humans can recognize
more than 10.000
different odors
However determination of
intensity of odor is poor
Substance
mg/L of Air
Ethyl ether
5.83
Chloroform
3.30
Pyridine
0.03
Oil of peppermint
0.02
Iodoform
0.02
Butyric acid
0.009
Propyl mercaptan
0.006
Artificial musk
0.00004
Methyl mercaptan
0.0000004
24
*
• Determined by Gender
•Women vastly superior
• Can be improved with practice
• - benefits both genders
• Stimulus Saliency
• Infants and mothers can recognize each other by
smell alone
• Infants hedonic reactions to smell develops with age
• Odor Familiarity - Seen in elderly people
Smoking is injurious to odor identification!
25
*
• Odor Constancy
• Natural sniffs lead to constant odor perception
but artificial blowing of air does not
• Common Chemical Sense
• Odors judged pleasant at moderate
concentrations are judged unpleasant at high
concentrations
• Related to the action of free nerve endings –
stimulated in an indiscriminate manner
• Warning system for the organism
• Adaptation - Adapt to a particular odor
• Cross Adaptation: Adapt to a different odor
• Could have led to odor categorization but turns
out that cross-adaptation is not symmetric!
26
Researchers have found it difficult to map perceptual
experience onto physical attributes of odorants.
Linking chemical structure to types of smells
Some molecules with similar shapes had very
different smells
Some similar smells came from molecules with
different shapes
1,000 different receptor types - about 1% of your DNA
codes for olfactory receptors making it the largest single
gene family
27
Perception of Smell
*We can distinguish between about 10,000
different smells
Different threshold levels for different smells
*Two thresholds for each smell -low threshold
for the existence of a chemical, somewhat
higher threshold to discriminate one smell
from another
28
*
-
Olfactory bulb - olfactory tract – olfactory nerve – 1st
cranial nerve
-
both the tract and the bulb are an anterior outgrowth
of brain tissue from the base of the brain
-
olfactory bulb lies over the cribriform plate, separating
the brain cavity from the upper nasal cavity
-
The cribriform plate has multiple small perforations
through which an equal number of small nerves pass
upward from the olfactory membrane in the nasal
cavity to enter the olfactory bulb in the cranial cavity
29
30
*
Olfactory bulb - organ which houses all the nerves which receive
inputs from the olfactory receptors
-Axons of receptors contact
the primary dendrites of
mitral cells and tufted cells.
-Forming complex globular
synapses called olfactory
glomeruli.
-Periglomerular cells are
inhibitory neurons connecting
one glomerulus to another
31
Olfactory Bulb
32
*
 There are approximately 20 olfactory foramina on either side of
the nose in the cribiform plate of the ethmoid bone passes 40 or
so bundles of axons form right and left olfactory nerves
 They terminate in the olfactory bulbs – below the frontal lobes of
the cerebrum
 Axons of the olfactory bulbs form the olfactory tract which
projects to the primary olfactory area of the cerebral cortex.
 Some project into the limbic system and hypothalamus
(emotional and memory evoked responses).
 Olfactory sensations are the only sensations that reach the
cerebral cortex without first synapsing in the thalamus.
 The primary olfactory area has axons that extend to the orbit
frontal area (frontal lobe) – region for odor identification.
33
Olfactory
pathway
34
-Granule cells have
no axons and make
reciprocal synapses
with lateral
dendrites of tufted
and mitral cells
-Mitral and Tufted –
excite granule
releasing glutamate
and granule cell in
turn inhibits both by
releasing GABA
*
36
*
37
38
*
-
short axons from the olfactory cells terminating in multiple
globular structures within the olfactory bulb called glomeruli
-
Each glomerulus is the terminus for dendrites from about 25
large mitral cells and about 60 smaller tufted cells, the cell
bodies of which lie in the olfactory bulb superior to the
glomeruli – granule cells - Periglomerular cells
-
mitral and tufted cells send axons through the olfactory
tract to transmit olfactory signals to higher levels in the CNS
-
Mucus – cilia - Axons of olfactory cells – glomeruli in bulb –
dendrites of mitral, tufted cells in bulb – axons of mitral,
tufted cells in tract - CNS
39
40
*
-
Olfactory tract divides into
-
other passing laterally into the lateral olfactory area
(stria) - a newer & less old system
-
The Medial Olfactory Area (very old) – septal nuclei –
hypothalamus – limbic system – removal – not much
effect
-
The Less Old Lateral Olfactory Area - prepyriform and
pyriform cortex plus portion of the amygdaloid nuclei –
limbic system (hippocampus) – learning & aversion
medially into the medial olfactory area (stria) of the
brain stem – very old olfactory system
41
*
-
lateral olfactory area - anteromedial portion of the
temporal lobe (cerebral cortex)
-
*This is the only area of the entire cerebral cortex where
sensory signals pass directly to the cortex without
passing first through the thalamus
-
The Newer Pathway - passes through the thalamus,
passing to the dorsomedial thalamic nucleus orbitofrontal cortex
-
conscious analysis of odor
-
Granule cells, Periglomerular cells – lateral inhibition
42
*Mitral cell axons form the lateral olfactory tract.
*Projects to accessory olfactory nuclei, olfactory
tubercule, entorhinal cortex, amygdala,
pyriform cortex
*Pyriform cortex axons project to thalamus,
hippothalamus, hippocampus, amygdala.
*
Lateral olfactory tract projects directly to the piriform cortex (= primary olfactory cortex =
paleocortex) adjacent to lateral olfactory tract in temporal lobe. This is only sense that does
not have relay in thalamus on way from receptors to cerebral cortex. From piriform cortex
there are projections to hypothalamus, the thalamus, amygdala, entorhinal cortex. From
thalamus there is a projection to orbitofrontal cortex where odor perception and
discrimination takes place. Electrical stimulation of piriform cortex causes olfactory
sensations. People with lesions of orbitofrontal cortex are unable to discriminate odors.
Pathways through amygdala and hypothalamus mediate emotional, motivational and many
physiological effects of odors.
*
45
*
*Signals are
sent to
* Primary
olfactory
(piriform)
cortex in the
temporal lobe
* Secondary
olfactory
(orbitofrontal
) cortex in the
frontal lobe
* Amygdala
deep in the
cortex
ch 15
46
47
48
*
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
Anthony J Greene
50
*
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
Anthony J Greene
51
*
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
Anthony J Greene
52
*
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
Anthony J Greene
53
*
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
Anthony J Greene
54
*
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
Anthony J Greene
55
*
-
In rodents and various other mammals, the nasal
cavity contains another patch of olfactory mucous
membrane located along the nasal septum in a welldeveloped vomeronasal organ.
-
This structure is concerned with the perception of
odors that act as pheromones.
-
Its receptors project to the accessory olfactory
bulb and from there primarily to areas in the
amygdala and hypothalamus that are concerned
with reproduction
-
56
The organ is not well developed
in humans.
*
Organ is not well developed
in humans very well
developed in rodents
This organ is concerned with
perception of odors that act
as pheromones
There is evidence of
pheromones in humans and a
close relationship between
smell and sexual function
57
*
-
Evidence for the existence of pheromones in
humans ???
-
close relationship between smell and sexual
function - The perfume ads
-
The sense of smell is said to be more acute in
women than in men, and in women it is most
acute at the time of ovulation.
-
Smell and, to a lesser extent, taste have a
unique ability to trigger 58long-term memories
Species specific odorants.
Some pheromones stimulate the vomeronasal organ
VNO--> accessory olfactory bulb-->hypothalamus.
(Found in 8% of human adults), VNO receptors are
pseudogenes in humans
*➜ Kairomone Attracts individuals of other species
*➜ Allomone Repels individuals of other species
*➜ Pheromone Affects individuals of the same species
*➜ Primer pheromone
*Triggers a long-lasting physiological change in the target
animal
*➜ Releaser pheromone
*Triggers an immediate behavioral response in the target
animal
*
Powerful effects on behavior, specifically sexual behavior, territorial
behavior and identification of kin
Mammals
*Most mammals only become sexually aroused in the
presence of pheromones
*Increased likelihood of pregnancy
*Synchronization of estrus cycles
*Mutual recognition of mother and offspring
*Territory marking (e.g. dogs)
*Releasers - trigger a specific behavioral response
*Primers - trigger a hormone response which increases the
60
likelihood of certain types of behaviors
*Pheromones:
Humans
Humans
*infants can correctly identify their own mother's
milk and are much more likely to nurse when its
their own mother
*female menstrual cycles can be altered by
pheromones - the sorority effect
*male and female behavior is highly influenced by
pheromones
t-shirt experiment - musky versus sweet -
*the musky odor is rated by males and females as
unpleasant and is thought to serve as a territorial
61
marker among males
Pheromones: Alpha Androstenol
alpha androstenol (predominantly secreted by females)
1.
2.
Increase sexual arousal in males
Increases male perception of female attractiveness
•
women in photographs were rated as significantly more sexually
attractive when judges were first exposed to alpha androstenol
3.
Increases willingness of females to initiate social
contact with males
•
females exposed to alpha androstenol were much more
receptive to male-initiated contact
• more likely to seek out male company
Anthony J Greene
62
• less likely to seek female company
*
-
Pain Fibers in the Nose - Naked endings of many trigeminal
pain fibers are found in the olfactory mucous membrane stimulated by irritating substances
-
peppermint, menthol and chlorine - sneezing, lacrimation,
respiratory inhibition
-
anosmia (absence of the sense of smell), hyposmia
(diminished olfactory sensitivity), and dysosmia (distorted
sense of smell).
-
Olfactory thresholds increase with advancing age, and
more than 75% of humans over the age of 80 have an
impaired ability to identify smells.
-
Anosmia + Hypogonadism (Kallmann's syndrome)
63
*
Many trigeminal pain
fibers are found in
olfactory membrane
They are stimulated
by irritating
substances
Are responsible for
initiating sneezing,
lacrimation and other
reflex responses.
64
*
*Measuring the detection threshold
* Yes/no procedure - participants are given trials with odors along
with “blank” trials
*They respond by saying yes or no
* Forced-choice - two trials are given, one with odorant and one
without
*Participant indicates which smells strongest
*Measuring the difference threshold
* Measure the smallest difference that can be detected between two
samples
ch 15
65
Olfactory Testing
Essential for multiple factors:
Validate patient’s complaint
Characterize specific nature of the problem
Monitor changes in function over time
Detect malingering
Establish compensation for permanent
disability
Many patients complaining of anosmia or
hyposmia have normal function relative to age
and gender
90% of patients with idiopathic Parkinson’s
Disease have demonstrable smell loss, yet less
66
than 15% are aware of their problem
Olfactory Testing
Asking a patient to sniff odors is like testing
vision by shining a light in each eye and asking
whether the patient can see the light
No current testing that can distinguish central
and peripheral deficits
Unilateral testing is often warranted
Sealing contralateral naris using Microfoam tape
and having the patient sniff naturally and exhale
through the mouth to prevent retronasal
67
stimulation
Medical/Legal Considerations with Ansomia
 Common in head injury and often the only residual
neurologic impairment
 Claims of accidental and iatrogenic smell disturbance
often results in substantial financial awards
 Veterans Administration awards a 10% whole-body
disability for total anosmia
 Occupation should be taken into account in disability
issues
68
Olfactory Testing
Psychophysical Testing
Electrophysiologic Testing
Neuropsychologic Testing
69
Psychophysical Testing
UPSIT or Smell Identificiation Test
Can be administered in 10 to 15 minutes by most
patients
4 booklets of 10 odorants apiece
Stimuli embedded into 10- to 50-μm diameter
microencapsulated crystals
Multiple choice questions with four response
alternatives
Test is forced-choice, required to choose an answer
even if none seems appropriate
Chance performance is 10 out of 40 , lower scores can
represent avoidance
Norms available based on administration to 4,000
people
70
Individuals are ranked relative
to age and gender
UPSIT (continued)
Test can classify individual’s function into 6
categories:
Normosmia
Mild microsmia
Moderate microsmia
Severe microsmia
Anosmia
Probable malingering
Very high reliability, test-retest Pearson r = 0.94
71
Medical/Legal Considerations with Anosmia
UPSIT score sensitive to malingering
Theoretical probability of true anosmic to
score UPSIT 5 or less: 0.05%
Theoretical probability of true anosmic
scoring 0 on UPSIT:0.00001
72
Electrophysiologic Testing
2 procedures are available but
application largely experimental
Odor event-related potentials(OERPs)
Electro-olfactogram (EOG)
73
Odor Event-Related Potentials
(OERPs)
Discerning synchronized brain EEG activity
recorded on the scalp from overall EEG activity
following presentations of odorants
Stimuli presented in precise manner using
equipment that produces stimuli embedded in warm,
humidified air stream
Unable to perform necessary trials and test
reliability is suspect
No inference can be made regarding location of a
lesion or deficit
Can be usefully in detecting malingering
74
OERP
75
Electro-olfactogram (EOG)
Measures electrode placed on the surface of the
olfactory epithelium
Few patients amenable to recordings
Must place electrode under endoscopic guidance
without local anesthesia
Can be quite unpleasant and sneezing/mucous
discharge common
Cannot reliably record in many subjects
Presence of robust EOG does not always represent
olfactory functioning
Anosmic patients with Kallmann syndrome and
hyposmic patients with schizophrenia have large EOG
responses
76
Neuropsychologic Testing
Strong association between Alzheimer’s,
Parkinson’s, and olfactory dysfunction
Brief neuropsychologic testing warranted in
some cases to determine presence of dementia
Mini-Mental State Examination- brief screening
tool for dementia and can be quickly administered
in a few minutes for further referral as necessary
77
Neuroimaging
Olfactory dysfunction of idiopathic etiology
warrants CT imaging
High-resolution CT is most useful and costeffective screening tool
MRI: useful in evaluating olfactory bulbs,
olfactory tract, and intracranial structures
MRI can detect decrements associated with
anosmia and patients with schizophrenia
Olfactory Biopsy
Small amount of superior septal tissue
removed by experienced rhinologist
Multiple biopsies needed78 to obtain true
neuroepithelium
The tools of the psychophysical trade: an informed, consenting human subject and
an odor source. Odorants are supplied by a variety of means: squeeze
bottles, ‘rip-and-sniff’ packets, glass vials (as depicted here), or sophisticated
computer-controlled olfactometers that deliver odors in a stream of warm and
79
humidified air directly into the nose
Threshold olfactory tests
 A dilutional series of a stimulus odor
 Uses an ascending concentration trial
 Must answer ‘yes’ or ‘no’
The UPSIT
 Commercial
 Most used
 Self-administered in 10-15 minutes
 Scored in < 1 minute by non-med person
 Available in various languages
 40 “scratch & sniff “ patches
 Pt. chooses from 4 answers & must choose 1
 Can detect malingering
http://www.smelltest.ir/
82
‫چرخ و فلک بوها یک تست بویایی بسیار ساده‬
‫است که به صورت بازی طراحی شده است‪ .‬در‬
‫این تست ‪ 9‬بوی استاندارد قرار داده شدهاند و در‬
‫کنار هر یک از آنها‪ ،‬چهار گزینه به صورت مصور‬
‫وجود دارد‪ .‬از کودک خواسته میشود که پس از‬
‫بو کشیدن هر یک از بوها‪ ،‬بر اساس بویی که‬
‫تشخیص داده‪ ،‬یکی از چهار گزینهی مجاور آن را‬
‫انتخاب نماید‪ .‬بر اساس تعداد پاسخهای صحیح‪،‬‬
‫مشخص میشود که حس بویایی کودک نرمال‬
‫است یا اینکه دچار اختالل بویایی میباشد‪.‬‬
‫کودکان از مشکالت بویایی خود خبر ندارند‪ .‬وجود‬
‫اختالالت بویایی در کودکان بسیار خطرناک است‪،‬‬
‫زیرا تشخیص بسیاری از مخاطرات مانند‬
‫آتشسوزی‪ ،‬نشت گاز و غذای فاسد‪ ،‬تنها از بوی‬
‫آنها امکانپذیر است‪ .‬از طرفی‪ ،‬کودکان دچار‬
‫اختالالت بویایی عموماً مشکالت تغذیهای نیز‬
‫دارند‪.‬‬
‫چرخ و فلک بوها‪ ،‬در وحلهی اول یک تست پزشکی برای تشخیص اختالل بویایی در کودکان ‪ 3‬تا ‪ 11‬سال است‪.‬‬
‫با انجام این تست میتوان از سالمت بویایی کودک اطمینان حاصل نمود‪.‬‬
‫انجام این تست مزایایی دیگری نیز دارد که عبارتند از‪:‬‬
‫ تجربه بوهای مختلف و شناخت بهتر دنیای پیرامون‬‫ تقویت ادراک حسی کودک‬‫ آشنایی کودک با توانمندیهای جسمی خود و افزایش اعتماد به نفس‬‫ سنجش و تقویت تمرکز در کودکان‬‫چرخ و فلک بوها برای استفاده در منازل‪ ،‬مهد کودکها‪ ،‬پیش دبستانیها‪ ،‬دبستانها‪ ،‬مراکز درمانی‪،‬‬
‫تحقیقاتی‪ ،‬آموزشی و توانبخشی مناسب است‪.‬‬
‫«آزمون تشخیص بویایی ایران» اولین‬
‫روش استاندارد ارزیابی حس بویایی به‬
‫صورت ک ّ‬
‫می در ایران است‪ .‬این تست‪،‬‬
‫نسخهی ایرانی تست تشخیص بویایی‬
‫دانشگاه پنسیلوانیا ()‪UPSIT‬است که در‬
‫آن از بوهای آشنا با فرهنگ مردم ایران‬
‫استفاده شده است‪.‬‬
‫«آزمون تشخیص بویایی ایران» به‬
‫صورت یک کیت حاوی ‪ 24‬نوع بوی‬
‫مختلف در هشت دستهی عطری‪ ،‬میوه‪-‬‬
‫ای‪ ،‬نعنایی‪ ،‬تند‪ ،‬شیرین‪ ،‬ترش‪ ،‬چوبی و‬
‫زننده میباشد و با استفاده از آن می‪-‬‬
‫توان توانایی افراد در افتراق بوهای‬
‫مختلف را ارزیابی نمود‪.‬‬
‫نتیجهی تست به صورت یک عدد از صفر تا ‪ 24‬گزارش میشود و عملکرد حس بویایی‬
‫را در محدوده نرموسمی‪ ،‬آنوسمی‪ ،‬هیپوسمی (میکروسمی) شدید و خفیف مشخص‬
‫مینماید‪.‬‬
‫«آزمون تشخیص بویایی ایران» برای مردم ایران استانداردسازی شده است و‬
‫محدودهی نرمال آن برای سنین ‪ 20‬تا ‪ 50‬سال‪ 19-24 ،‬میباشد‪ .‬این محدوده برای‬
‫افراد با رنج سنی کمتر از ‪ 20‬و بیشتر از ‪ 50‬سال کمی افت دارد‪.‬‬
‫انجام این تست بسیار ساده است و به صورت خودآزمون نیز قابل انجام است‪ .‬مدت‬
‫زمان انجام تست برای کاربر غیرحرفهای ‪84‬‬
‫کمتر از ‪ 12‬دقیقه است‪.‬‬
‫آزمون تشخیص بویایی ایران‬
‫ویژهی پزشکی قانونی‬
‫‪Iran smell Identification Test‬‬
‫)‪(Iran-SIT‬‬
‫‪For forensics medicine‬‬
‫·شامل کیت و نرمافزار ویژهی تشخیص‬
‫تمارض‬
‫تشخیص تمارض به از دست دادن حس‬
‫·‬
‫بویایی ( )‪Malingering‬به روش‬
‫کالمی ()‪Subjective‬‬
‫·بررسی ‪ 6‬معیار تشخیص تمارض‬
‫دقت تشخیص بیش از ‪%90‬‬
‫·‬
‫مدت زمان انجام تست کمتر از ‪ 20‬دقیقه‬
‫·‬
‫مناسب برای استفاده در مراکز معتمد‬
‫·‬
‫پزشکی قانونی‬
‫‪85‬‬
‫‪http://www.smelltest.ir/‬‬
‫آزمون تشخیص بویایی ایران‬
‫«تست سریع»‬
‫روش ساده‪ ،‬سریع و کم هزینه برای ارزیابی اولیهی عملکرد حس بویایی‬
‫طراحیشده به صورت یک کیت با ‪ 6‬بوی مختلف‬
‫تشخیص نرموسمی‪ ،‬آنوسمی و یا وجود اختالل بویایی‬
‫مدت زمان انجام تست کمتر از ‪ 3‬دقیقه‬
‫مناسب برای استفاده در مطبها و کلینیکهای گوش و حلق و بینی‬
‫تست کاربردی در تحقیقات پزشکی با حجم نمونه باال و غربالگریها‬
‫‪86‬‬
‫تست آستانه بویایی‬
‫‪Smell Threshold Test‬‬
‫شامل یک سری محلول فنیل بوتیل الکل با غلظتهای مختلف از ‪ 10-2‬تا ‪10-9‬‬
‫تعیین حد آستانهی بویایی افراد (کمترین غلظتی از بو که فرد میتواند شناسایی‬
‫کند)‬
‫تشخیص اختالالت هایپوسمی و هایپروسمی‬
‫مناسب برای کاربردهای تحقیقاتی و کلینیکی‬
‫·‬
‫‪87‬‬
Sniff Magnitude Test
‫تست حجم بویایی‬
SMT
88
‫دستگاه )‪SMT (Sniff Magnitude Test‬وسیلهای برای ارزیابی عملکرد ک ّ‬
‫می بویایی به‬
‫صورت غیرکالمی است‪ .‬این دستگاه شامل سنسورهای حساس و دقیقی است که‬
‫توانایی بویایی افراد را ارزیابی میکنند و همچنین با بهرهگیری از یک نرمافزار‪ ،‬دادهها‬
‫را تحلیل کرده و نتیجه را با دقت باالیی ارائه مینماید‪.‬‬
‫ویژگیهای کلّی ‪SMT:‬‬
‫دارای کمترین وابستگی به زبان‪ ،‬تواناییهای شناختی‪ ،‬حافظه و توانایی نام بردن‬
‫بوها‬
‫قابلیت تشخیص اختالالتی که به علت نقص در ورودی حسی اولیه ایجاد میشوند را‬
‫از اختالالتی که به علت نقص در ورودی حسی اولیه ایجاد میشوند را از اختالالتی که‬
‫به علت پردازش در سطح باالتر در اثر بیماریهایی مانند تروپوسمی‪ ،‬فانتوسمی و‬
‫اگنوزی بویایی‬
‫عدم تأثیر کم شدن حافظه یا دقت افراد کهنسال روی نتیجهی تست‬
‫اندازهگیری عملکرد حس بویایی به صورت ک ّ‬
‫می‬
‫مشخصات فنّی ‪SMT:‬‬
‫این دستگاه دارای یک یونیت کنترل‪ ،‬یک کانوال‪ 4 ،‬قوطی فلزی حاوی بوهای مختلف‪،‬‬
‫نرم افزار مخصوص و سیمهای اتصال است‪.‬‬
‫استفاده از این دستگاه مستلزم بهکارگیری هم زمان یک کامپیوتر و پرینتر میباشد‪.‬‬
‫دستگاه دارای استاندارد ‪ISO 9001:2000‬و ‪ISO 13485:2003‬است‪.‬‬
‫‪89‬‬
‫روش کار ‪SMT:‬‬
‫ابتدا کانوال به بینی بیمار متصل میشود‪ ،‬سپس با‬
‫قرار گرفتن قوطیهای مخصوص در مقابل بینی‪ ،‬از‬
‫وی خواسته میشود که محتویات قوطی را بو بکشد‪.‬‬
‫در این حالت‪ ،‬نرم افزار مخصوص دستگاه به طور هم‬
‫زمان نمودار بویایی فرد را رسمکرده و وضعیت اختالل‬
‫وی را مشخص مینماید‪.‬‬
‫موارد استفاده از ‪SMT:‬‬
‫برای تشخیص تمارض به از دست دادن حس بویایی‬
‫در کاربردهای پزشکی قانونی‬
‫تشخیص بیماری های آلزایمر‪ ،‬پارکینسون‪ ،‬ام اس و‬
‫بسیاری از بیماری های اعصاب مرکزی‬
‫تشخیص آسیب مغزی در اثر تروما‬
‫تشخیص هر بیماری یا وضعیتی که به عصب یکم‬
‫جمجمه ای آسیب وارد کند‪.‬‬
‫‪90‬‬
‫درمان اختالالت بویایی‪ ،‬وابستگی زیادی به علّت زمینهای ایجاد اختالل دارد‪ .‬اختالالت مرتبط با‬
‫انسداد مسیر بویایی معموال ً با درمانهای متداول برطرف میشوند‪ ،‬در حالی که درمان اختالالت‬
‫ّ‬
‫حسی در بسیاری از موارد بینتیجه میماند‪ .‬در شماری از آسیبهای سیستم بویایی‪،‬‬
‫نورونهای گیرندهی بویایی با گذشت زمان ترمیم و بازسازی میشوند‪ ،‬اما به دلیل نداشتن نظم‬
‫و جهتگیری صحیح‪ ،‬توانایی بویایی فرد بهبود نمییابد‪ .‬تمرین بویایی ( )‪Olfactory Training‬‬
‫یک روش جدید برای توانبخشی حس بویایی است که در آن نورونهای بازسازی شده با‬
‫قرارگیری در معرض بوهای خاص جهتگیری مینمایند‪ .‬تحقیقات نشان میدهند که نورونهای‬
‫گیرندهی بویایی انسان توانایی ترمیم و بهبود دارند و قرارگیری در معرض برخی بوها به صورت‬
‫مداوم میتواند به بازیابی حس بویایی کمک کند‪ .‬در این روش فرد به صورت مداوم و کوتاه مدت‬
‫در معرض بوهای خاص در یک دوره زمانی قرار میگیرد‪ .‬به این ترتیب وقتی که نورونهای‬
‫گیرندهی بویایی ترمیم و بازسازی میشوند‪ ،‬بوها میتوانند جهت گیری مناسب را در آنها ایجاد‬
‫نمایند‪.‬‬
‫اولفکتِرین‪ ،‬یک کیت درمان اختالالت بویایی به روش تمرین بویایی ( )‪Olfactory Training‬است که‬
‫در آن چهار ماده معطر که سررده هرم بویایی میباشند‪ ،‬قرار داده شدهاند‪.‬‬
‫تحقیقات نشان دادهاند که استفاده ار این کیت‬
‫دوبار در روز و به مدت ‪ 12‬هفته باعث بهبود‬
‫عملکرد بویایی در افراد دچار اختالل پس از‬
‫عفونت ( )‪Postinfection‬یا ضربه به سر ( ‪Post‬‬
‫)‪Trauma‬و یا کسانی که حس بویایی خود را به‬
‫دالیل نانشاخته ( ایدیوپاتیک) از دست‬
‫دادهاند‪ ،‬میگردد‪.‬‬
‫توصیه میشود قبل از شروع درمان‪ ،‬حس‬
‫بویایی بیمار با استفاده از «تست بویایی کامل»‬
‫مورد ارزیابی قرار گیرد و پس از اتمام دوره درمان‬
‫(‪ 12‬هفته)‪ ،‬مجدداً تست بویایی انجام شود تا ‪91‬‬
‫میزان بهبود بویایی بیمار مشخص شود‪.‬‬
*
Classification
Conductive loss
Obstruction of nasal passages
E.g., chronic nasal inflammation, polyposis
Sensorineural loss
Damage to neuroepithelium
E.g., viral infection, airborne toxin
Central olfactory neural loss
CNS damage
E.g., tumors, neurodegenerative disorders
Anosmia or “Odor Blindness” can be Temporary since ORCs can regenerate
• Sometimes can be total but in that case is 92
specific to certain odors, e.g. sweat,urine
• Anosmia can have serious consequences such as loss
of apetite and weight
Disorders of Olfaction
Obstructive Nasal and Sinus Disease
Upper Respiratory Infection
Head Trauma
Aging
Congenital Dysfunction
Toxic Exposure
Neoplasms
HIV
Epilepsy and Psychiatric Disorders
Medications
Surgery
Idiopathic Loss
93
Causes of Smell Disorders
*Age
*Decreased smell occurs in the normal
elderly
*The greatest correlation with olfactory
decline
*More severe in men than women (Any
conjecture on why?)
*Multifactorial causes
Upper Respiratory Infections
*Most Common cause of permanent smell
problems
*Damage olfactory epithelium & possibly
central structures
*Common cold, hepatitis, influenza, HSV,
rabies and a bunch I’ve never heard of &
thus don’t care about
*
Toxins
*Herbicides
*Pesticides
*Solvents
*Heavy Metals, esp cadmium, nickel,
chromium & manganese
*Damage olfactory epithelium
*Enter brain, esp. cadmium, gold &
manganese
Epilepsy
*Right-sided foci > left-sided
*Anti-seizure meds can correct
problems
Neurodegenerative Diseases
*Alzheimers & Parkinson’s :
*Usually ASX, but present
in 85-90% of pts
*Doesn’t respond to
meds
*Magnitude not assoc
with disease stage
Neurodegenerative Diseases
*Down’s Syndrome
*Huntington’s Disease
*Multiple Sclerosis
*Jacob-Creutzfeld
Head Trauma
*About 20% of all chemosensory
disorders
*Directly related to degree of trauma
*Also related to strong deceleration
injury
*Occipital and side injury more than
frontal
*If recovery, occurs within 1st year of
injury
Other Disorders
*Cerebellar Degeneration
*Schizophrenia
*Migraine
*Hyperemesis gravidarum &
hyperosmia
*A number of systemic diseases
*Some Medicines
*Congenital anosmia