Anosmia is the loss of the sense of smell caused by damage to the first cranial nerve and parts of the fifth cranial nerve. The first cranial nerve is responsible for qualitative odor sensations like flowers or fresh cut grass.
The fifth cranial nerve controls the overtones of smell like warmth, coolness, sharpness, and irritation. An onion or ammonia will not only smell strong but they will also cause a body response. Smell an onion and tears will form.
Damage to the parts of the fifth cranial nerve that connects to the tongue is rare. Anosmia will still let you distinguish stinging, burning, cooling and sharpness through the nerve endings in your tongue.
Complete loss of taste and smell is called ageusia.
Your sense of smell is what controls your concept of the more delicate qualities of taste. When you have anosmia, you can still distinguish the five basic taste categories: salty, sweet, bitter, sour, and umami. This flavor comes from the buds located on your tongue.
When you lose your sense of smell, you lose the ability to enjoy the nuances of flavor. Eat chocolate ice cream with your eyes closed. A person with anosmia will tell you it’s cold, it’s sweet, it’s soft and creamy, but they won’t be able to tell you it’s chocolate.
Updated: December 15, 2017
Sources: Superficial siderosis is a rare neurologic disease characterized by progressive sensorineural hearing loss, cerebellar ataxia, pyramidal signs, and neuroimaging findings revealing hemosiderin deposits in the spinal and cranial leptomeninges and subpial layer. The disease progresses slowly, and patients may present with mild cognitive impairment, nystagmus, dysmetria, spasticity, dysdiadochokinesia, dysarthria, hyperreflexia, and Babinski signs. Additional features reported include dementia, urinary incontinence, anosmia, ageusia, and anisocoria. Superficial siderosis MedGen UID: 831707 •Concept ID: CN226971 •Finding Orphanet: ORPHA247245