Olfactory hallucination are nothing to be sniffed at
Have you ever found yourself commenting on the sudden smell of burnt toast, much to the bewilderment of your family? Or were sure you could smell something foul, yet others around you were baffled and unable to detect anything? Well, you may well have been experiencing phantosmia.
Phantosmia is the name for olfactory hallucination – in other words, when you detect smells that aren’t actually there. And it is a symptom sometimes reported by people with multiple sclerosis (MS).
The smells detected can vary hugely from person to person, and they can be extremely pleasant, or completely foul. The odours can come and go, or someone may be able to smell them all of the time.
So far, science knows that phantosmia can be caused by a number of things. These include inflamed sinuses, brain tumours, temporal lobe seizures, head injury, upper respiratory infections and Parkinson’s disease.
Smell and MS
The sense of smell has long been used in sensory evoked potential testing to monitor the progression of MS, even though some doctors feel this option is not as reliable as visual evoked potential testing.
Smell is regulated by a network that includes the olfactory nerve and other areas of the brain. The nerve doesn’t have much myelin, and scientists previously thought the sense of smell was relatively untouched by MS. But research has since shown that olfaction is often damaged in the early stages of neurodegenerative disease, such as Alzheimer’s and Parkinson’s.
One three-year study, which looked at 20 people with MS, found that around half of people with the condition have a reduced sense of smell, and that olfactory impairment may be a marker for disease progression.
Consult your doctor if you are experiencing phantosmia, so that other conditions can be ruled out.
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