Anosmia is loss of the sense of smell.
Most cases of anosmia are bilateral.
- upper respiratory tract infection (commonest)
- increasing age
- nasal polyps
- ethmoid tumours
- basal skull fracture or frontal fracture, or after pituitary surgery
- congenital- eg Kallmann syndrome (hypogonadotrophic hypogonadism), cleft palate
- meningioma of the olfactory groove and other tumours of the floor of the anterior cranial fossa
- following meningitis
The main unilateral causes
- head trauma without a fracture
- early meningioma of the olfactory groove