Silent symptom of Parkinson’s that appears years before other symptoms

In a magical scene at the end of the 2007 film RatatouilleNotoriously harsh food critic Anton Ego is instantly transported back in time, his childhood memories revived by a spoonful of the film’s eponymous dish. No pictures were needed – just the taste and aroma of the food.

Smell is one of our quietest senses, but also one of the most powerful. In fact, it may even open up memories we thought long forgotten.

It’s also the most personal and subjective meaning, which makes it so difficult for people to agree on what smells good. However, a consensus seems to be emerging on the world’s worst smell.

In 1889, in a German laboratory, a chemical reaction involving a compound called thioacetone produced a stench so terrible that it caused people up to half a kilometer away to vomit and faint, leading to the partial evacuation of the city of Freiburg.

We still don’t know what caused this reaction to the stink, but it seems no one is in a hurry to find out.

But what happens when we start losing our sense of smell? And what if loss of smell is more than a common symptom?

A shortcut to our emotions

Smell is an evolutionary advantage: it warns us of invisible dangers and alerts us. Scent can also influence our decisions, and big brands are well aware of this, they scent their stores with scents that appeal to our emotions and invite us to stop by.

Smell has the ability to evoke memories and intense emotions and the olfactory bulb is responsible for this. This small area of ​​the forebrain, located very close to the nose, receives olfactory signals and sends them directly to the areas of the brain that manage our memory and emotions.

Despite its importance, smell is the least understood of the senses and is often underestimated. When it fades, it usually goes unnoticed, but we don’t realize how important it is until we lose it.

Such was the case with Michele Crippa, a famous Italian “super taster” who lost his sense of smell during the pandemic. Although she regained it a few weeks later, her personal nightmare had just begun, as when her sense of smell returned, it was disfigured. The oranges smelled like burnt plastic, the peaches smelled like basil, and the vanilla made her feel sick. This probably happened because the neurons of his olfactory bulb were damaged.

Although any loss of smell is unpleasant, it may have greater significance: a warning signal from deep within our brain.

The common cold, or Parkinson’s?

Most of us have lost our sense of smell at some point, usually due to a cold or flu. However, this symptom can also be an early symptom of neurodegenerative diseases such as Alzheimer’s or Parkinson’s. This has been known for a long time, but the surprising thing is that the ability to smell is lost many years before the symptoms of these diseases appear.

So, what can be used to predict loss of smell? parkinson’s diseaseThe answer, however unhelpful it may be, is: it depends.

an early warning

A major problem with neurodegenerative diseases is that by the time they can be diagnosed the damage has already progressed. in the matter of parkinson’s diseaseWhen the first symptoms (stiffness, tremors, and so on) appear, more than half of the neurons that produce dopamine, the neurotransmitter that controls movement, have already been lost.

Identifying early symptoms such as loss of smell – which affects 90% of patients – could serve as a biomarker, alerting us to the presence of the disease. This will allow us to diagnose it much earlier and provide access to more effective treatments.

The problem is that this symptom is not exclusive to Parkinson’s: it can also appear with aging, stress, or other conditions. This means that we underestimate its importance.

We still don’t know for sure why neurodegenerative diseases cause smell loss, although we have some clues. In some Parkinson’s patients, the disease may begin in the olfactory bulb long before it spreads to areas that control movement. This is because some viruses, pesticides or toxins that we inhale can damage it and cause changes in the area.

In the case of Alzheimer’s disease, damage may begin in a small blue area of ​​the brain stem called the locus coeruleus, a recent study has revealed. This “alert button” keeps us awake and focused, and its connection to the olfactory bulb connects smell to emotions. When that connection is broken, problems with smell begin to occur long before the first symptoms of dementia emerge.

In short, loss of the ability to smell would not be a symptom of the disease, but a warning sign that the degenerative process has begun.

diagnosis by smell

When a patient comes to the clinic, it is not always easy to distinguish between Parkinson’s disease and other similar movement disorders. Loss of smell, combined with other tests and indicators, can help confirm the diagnosis. It can also help us predict disease progression, as it correlates with more severe forms of the disease.

Furthermore, loss of smell in Parkinson’s disease is selective. Patients perceive pleasant odors such as chocolate without problem, but have difficulty detecting neutral or unpleasant odors such as soap, smoke or rubber.

Other patients, especially women, experience something even stranger: olfactory hallucinations. This means they perceive a “phantom” smell, such as tobacco or burning wood, that is not actually there.

Although it may seem incredible, Parkinson’s disease also has its own smell, which has been described as woody and musky. We know this because of Joy Milne, a Scottish woman who has a great sense of smell – she was able to recognize this particular smell of her husband’s 12 years before he was diagnosed with the disease.

Loss of smell may seem to be limited to the nose, but it is actually a window into the brain. This allows researchers to peer inside the brain to understand its secrets and gather valuable information that will help us care for people suffering from neurodegenerative diseases and improve their quality of life.