Cranial Nerve I, The Olfactory Nerve
The olfactory nerve is not commonly tested during a screening physical exam but can be performed if damage secondary to trauma or intracranial mass is suspected. Each nostril should first be evaluated for patency by compressing one nostril and having the patient breath through the opposite. Each nostril should then be tested separately with a volatile, non-irritating substance such as cloves, coffee or vanilla. The patient should close his eyes, occlude one nostril and identify the substance placed under the open nostril.
New onset, unilateral loss of smell (anosmia) is concerning for pathology while chronic bilateral anosmia is normally congenital.