cranial nerve I palsy
A change in smell sensation due to a olfactory nerve palsy can be uni- or bilateral in nature. Lesions are most likely to cause anosmia and a bilateral lesion is more likely to be detected by routine enquiries about an individual's sense of smell.
Most causes of anosmia are bilateral.
Causes of bilateral anosmia include:
- upper respiratory tract infection - most common
- ethmoid tumour
- meningioma of the olfactory groove
- trauma, e.g. basal skull fracture, frontal fracture, after pituitary surgery
- congenital, e.g. Kallman's syndrome
- conductive, e.g. nasal polyps, enlarged turbinates
Causes of unilateral anosmia include:
- head trauma without a fracture
- early meningioma of the olfactory groove
Last reviewed 01/2018