First Cranial/ Olfactory Nerve:
It is a sensory nerve. The central processes from olfactory epithelium passes to olfactory area of cerebral cortex (the uncus of the parahippocampal gyrus).
To test the ability to identify familiar aromatic odours with one nostril at a time with eyes closed.
Vials of aromatic substances e.g fresh instant coffee, orange extract, peppermint extract, oil of cloves.
Before starting to check the sense of olfaction the examiner should ensure that both nasal passages are patent. Ask the subject to close one nostril, inhale and then exhale. The eyes of the subject should be closed. For testing the sense of smell, the examiner should have three small bottles, one containing some oil of clove, second oil of peppermint, and in the third some tincture of asafoetida. First of all use the least irritating substance. After closing one nostril and open vial of the volatile substance is put close to the nostril and the subject is asked to inhale and identify the odour. he same procedure is repeated in the other nostril. Before starting with the other odour allow the patient to rest for a minute. Subject should be able to discriminate between different odours.
Common bedside substances such as soup, fruit or garlic may also be used. Irritating substances such as ammonia should not be used to test separately. In anosmia the sense of smell is abolished. Hyposmia is reduction of sense of smell. Prevention of sense of smell is called parosmia.