Smell Loss

Smell Loss

Many conditions can cause smell loss. This loss could be temporary or lasting. Lasting smell loss can be a risk factor for brain disease, including Parkinson’s.

The Michael J. Fox Foundation notes that following a diagnosis, some people with Parkinson’s report losing their sense of smell years or even decades earlier.  This condition is called hyposmia. Lost sense of smell can impact quality of life — affecting taste and, in some cases, leading to weight loss.

Scientists do not know why smell loss occurs in Parkinson’s. One popular theory is that the Parkinson’s process may start in the olfactory bulb. This part of the brain controls sense of smell. Some researchers believe clumps of the protein alpha-synuclein (a hallmark of Parkinson’s disease) may form in the olfactory bulb before migrating to other parts of the brain.

Loss of sense of smell may occur years before motor symptoms or a Parkinson’s diagnosis.

An often overlooked symptom of Parkinson’s disease

While most people with a reduced sense of smell will not develop Parkinson’s, the majority of Parkinson’s disease patients do have reduced sense of smell. Loss of sense of smell is often overlooked by diagnosing physicians as an early sign of PD. Fight Parkinson’s notes that most people with a reduced sense of smell will not develop Parkinson’s. It may be due to a lack of the mineral zinc, sinus problems, age, or the result of a previous injury.

However, for newly diagnosed people with Parkinson’s, 96% will have lost some ability to smell.

If you believe that you may have trouble with smell, consult your doctor.

Why am I losing my sense of smell?

Little is confirmed about what causes the early, pre-motor symptoms of Parkinson’s, such as hyposmia, this loss of smell. But one prevalent theory in Parkinson’s research about disease progression has to do with the protein alpha-synuclein, whose clumping is found in all people with the disease.

This theory, based on the research of Heiko Braak, MD suggests that the disease may start not in the substantia nigra (the region of the brain where loss of nerve cells leads to the dopamine deficit experienced by people with PD) but in the gastrointestinal system and the olfactory bulb, the part of the brain that controls sense of smell. Researchers have hypothesized that the alpha-synuclein clumps found in all people with Parkinson’s may form in these parts of the body first, before migrating to other parts of the brain. Should this turn out to be true, and if researchers can find the clumps and break them up before they reach the brain, it may become possible to treat Parkinson’s before major neurological damage occurs.