Anosmia etiology
Anosmia after anterior communicating artery aneurysm surgery
Abrupt onset of anosmia
a) severe upper respiratory infection with damage to the neuroepithelium: the most common cause
b) head trauma: second most common cause. Anosmia occurs in 7–15% of patients with significant head trauma.
Anosmia after traumatic brain injury
Gradual onset of anosmia
a) allergic rhinitis and sinus disease 1):
third most common cause of anosmia (anosmia in this setting may be intermittent)
b) intracranial neoplasms: olfactory groove meningioma, see Foster Kennedy syndrome ,esthesioneuroblastoma
c) may also be associated with Alzheimer’s disease
d) olfactory sense diminishes with age: ≈ 50% of patients 65–85 years of age have some loss of sense of smell
e) metabolic abnormalities: vitamin deficiency
f) physical blockage of nasal passages: nasal polyps…
g) endocrine abnormalities: diabetes…
h) chemical: alcohol abuse, exposure to solvents, 2) cocaine (ischemic infarction of olfactory mucosa from vasoconstriction)
3. congenital anosmia: Kallmann syndrome (anosmia with hypogonadotropic hypogonadism 3))
Anosmia is due to a number of factors, including an inflammation of the nasal mucosa, blockage of nasal passages or a destruction of one temporal lobe. Inflammation is due to chronic mucosa changes in the paranasal sinus lining and the middle and superior turbinates. Since anosmia causes inflammatory changes in the nasal passageways, it is treated by simply reducing the presence of inflammation.
It can be caused by chronic meningitis and neurosyphilis that would increase intracranial pressure over a long period of time, and in some cases by ciliopathy including ciliopathy due to primary ciliary dyskinesia (Kartagener syndrome, Afzelius' syndrome or Siewert's syndrome).