Olfactory System

Dr Vasanthika Sanjeewanie ThuduvageSenior Lecturer/ Consultant ENT and

Head &Neck Surgeon

Olfactory Epithelium

Olfactory Epithelium 3 cell types, basal, supporting, and olfactory receptor

cells. Basal cells are stem cells that give rise to the

olfactory receptor cells.

Receptor cells are actually bipolar neurons.

Olfactory Receptors

Figure 16.3a, b

Olfactory EpitheliumOlfactory Epithelium

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Table 14.3 (1 of 12)

Olfactory Nerve

olfactory nerve (I)

Olfactory bulb

Olfactory tractOptic nerve (II)Optic chiasma

Optic tractOculomotor nerve (III)

Trochlear nerve (IV)

Trigeminal nerve (V)

Abducens nerve (VI)

CerebellumMedulla

Clinical examination

• Loss of smell sensation –patient miss olfactory danger signals.

• olfactory deficits - two types 1-conductive 2-sensorineural• 1-interfernce of an odour in contact• 2-dysfunction of receptor/central connections•

evaluation

• University of Pennsylvania Smell Identification Test [UPSIT; known commercially as the Smell Identification Test

• the side that might be abnormal should be examined first

• perception of an odour –continuty of olfactory pathway

• identification of an odour – intact cortical functions

• Anosmia - Absence of smell sensation • Hyposmia - Decreased sensation • Dysosmia - Defect in sense of smell • Cacosmia - Sensation of a bad or foul smell • Parosmia - Sensation of smell in the absence

of appropriate stimulus

some causes of loss of smell

• URTI• Head trauma• Nasal and sinus disease• Idiopathic

– These Four are most Common Causes

Others- Olfactory groove meningiomaFrontal Lobe tumorSellar /Parasellar tumorVitamin deficiency (B6,B12,A)

Parkinsons DiseaseKallmans SynddromePsychiatric conditionsCadmium ToxicityCocaine Abuse

Olfactory dysfunction

• Kallmann syndrome (ie, hypogonadism with anosmia)

• Foster Kennedy syndrome (ie, papilledema, unilateral anosmia, and optic atrophy usually associated with an olfactory groove meningioma).

• Cranio cerebral Trauma – Results in damage of olfactory nerve at the cribriform plate of ethmoid

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