Anosmia [loss of sense of smell]

Category: Illness or disabilaties

Type

Involuntary

Introduction and description

Anosmia is the technical name for not being able to smell things -  “an inability to perceive odours”. It may be either temporary or permanent. Loss of the sense of smell can also be partial or total, decreased ability to smell has the technical name, hyposmia.

It can be  a very depressing illness, for which there is rarely a cure.  Food becomes less appetising if not wholly tasteless, because the sense of taste is dependent to a large degree on the sense of smell.  If you can’t smell you can’t taste anything much more than sweet and sour and salt.  Life becomes a bit more dangerous because you are unaware of gas leaks or fire or bad food.  And you lose links to memories.  Few people realise how many memories are triggered by smells – hay, violets, the smell of babies when they are new, pine woods, books, the sea, fresh winds, roses, fresh mint, joints of meat cooking in the oven, loved people, wet dogs, after-shave, perfume ….

You feel somehow more detached from the world as if you were watching a television programme.  And of course no one can see you have lost your sense of smell, so they are rarely very understanding. Go to a restaurant and friends will rarely understand that it makes not a jot of difference what you order it will all taste like wool.  There is the tendency to over eat ironically because you are desperate for the taste of anything and feeling full [or drunk] makes you feel less miserable.

The common view of anosmia as ‘trivial’, means that once you have had the tests that confirm you have lost your smell, that is it.  You are on your own.  People with anosmia are rarely given CT scans or MRI imaging tests to see what has gone wrong.  It is far more difficult for a person to receive the same types of medical aid as someone who has lost other senses, such as hearing or sight.

As you can see, I know, because I am one of them.

And people with anosmia can get ‘phantom smells’,  - olfactory hallucinations  - very real reminders of what a smell like coffee or baby poo was like, a sudden brief but wonderful reminder of both what they have lost, but also a sudden gift to lift their spirits.

The principle cause of loss of the sense of smell is damage to the olfactory organs

• death of the olfactory receptor neurons in the nose
• brain injury in which there is damage to the olfactory nerve
• damage to brain areas that process smell

The fact that some of the causes can relate to brain damage make it that bit more worrying that doctors rarely do any more tests, as the brain damage could be due to a tumour or some degenerative disease.  So it is now worth asking what caused this?

Causes

There are a very large number of things that can cause this damage. 

Nasal sprays 

One serious, common cause of  permanent loss is damage to olfactory receptor neurons because of the use of certain types of nasal spray.   So few people are aware of this link that there have been calls for these sorts of nasal sprays to be banned.  If you detect a note of bitterness here, you are right because I think that is what got me.  There are any number of these nasal sprays available over the counter from chemists.  If you get a seriously blocked nose from hay fever or allergic reactions to dust, dogs, cats, diesel fumes and so on, chemists sometimes recommend them.  They work by temporarily shrinking the nasal lining covering your turbinates (turbinates are large scrolls of bone on the side walls of your nose). The turbinate bone is covered with a sensitive pink nasal lining with many large blood vessels. The nasal sprays temporarily shrink the blood vessels in your turbinates, so you can breathe better through your nose.  But of course the relief is only temporary and occasionally  the turbinates swell up and are worse than before.  And by depriving your receptor cells of oxygen, you can kill them off – and you lose your sense of smell.

Other causes

Other causes are as follows.  The following list is derived from the information provided on PubMed

Viruses 

The difference here may be that one set of people used nasal sprays and the other did not - and as such it was not the virus that caused the damage but the pharmaceutical. 

Toxins, fungal spores, bacteria and other pathogens [possibly leading to Asthma and other allergic reactions ]

All sorts of pathogens - pollen, smoke, fungal spores, bacteria, household product fumes and so on can damage the very sensitive olfactory organ. 

Toxins such as acrylates, methacrylates and cadmium have been directly linked with loss of smell.  There are also links with heavy metal poisoning of all sorts. 

The symptoms can then display as an allergic reaction - sneezing, wheezing and even asthma.  The 'cause' is not the asthma, the cause is the pathogen, it is simply that asthma and allergies become 'co-morbidities'. 

For example, Nasal polyps are most commonly thought to be caused by allergy, but of course this is not a cause it is a symptom.  The cause is the allergen.  The polyps form around the allergen or toxic substance acting a bit like a cyst and thus blocking the nose and damaging the sensitive olfactory organ.

To repeat, it is not asthma or allergic reaction that is the cause, but an allergen - a toxic or pathogenic substance which has irritated the olfactory organ so much it has damaged it.  

For more help here, please see the entry on Nose diseases.

Brain damage

In some cases - like those above, the loss of smell is caused by the death of the olfactory receptor neurons in the nose.  But some cases of anosmia are caused by:

• brain injury in which there is damage to the olfactory nerve
• damage to brain areas that process smell

There may be nothing that can be done if the damage was done by a fall or a blow on the head, but other cases of brain damage need urgent investigation.  Thus included within this very general grouping we have for example

• Head trauma and damage to the ethmoid bone as well as concussion 
• Dementia and Alzheimers - Dementia with Lewy bodies and Alzheimer's disease and also simply old age
• Parkinson's disease - there are links here with both the brain damage caused and the medication used to treat the disease
• Brain tumours - including Kennedy's syndrome -  tumors of the frontal lobe and Tumours of the olfactory nerve
• Idiopathic intracranial hypertension - a neurological disorder that is characterized by increased intracranial pressure (pressure around the brain) in the absence of a tumour or other diseases. The main symptoms are headache, nausea, and vomiting, as well as pulsatile tinnitus, double vision and other visual symptoms
• Meningiomas  - which are a diverse set of tumors arising from the meninges, the membranous layers surrounding the central nervous system 

Yet again, the CAUSE of each of these conditions needs to be investigated.  So, for example, a person who has Parkinson's disease may lose their sense of smell.  But 'Parkinson's disease' is not the cause.  The true cause may be heavy metals or again the pharmaceuticals used to treat the Parkinson's disease.

Surgery

It should be clear that any surgery involving the brain runs the risk of damaging the olfactory organ or the parts of  the brain processing smell.  What is also not widely known is that transplants and other types of surgery can also indirectly result in anosmia.

In some cases it is due to what is called Postperfusion syndrome.   "Postperfusion syndrome is defined as asystoli or a decrease in mean arterial pressure of more than 30%, which occurred in the first 5 min of reperfusion and continued for 1 min."

 In other words, during surgery, blood presure plummets and the brain is starved of oxygen by the sudden drop in blood pressure; during this starvation, cells die - and some of those cells may be related to the sense of smell.

One type of surgery with a record of causing anosmia is  Laryngectomy  -  the removal of the larynx and separation of the airway from the mouth, nose and esophagus. In a total laryngectomy the entire larynx is removed and in a partial laryngectomy only a portion is taken out. The laryngectomee breathes through an opening in the neck.

Nutritional deprivation

All types of nutritional deprivation - vitamin imbalance, amino acid imbalance and so on can cause cells in the brain and the nose to die, but it is noticeable that Mineral deficiency - especially zinc deficiency   has a very noticeable effect.

Pharmaceuticals

Nasal sprays have been mentionned above, they are a major cause of anosmia.  There are other pharmaceuticals implicated, however. 

The eHealthme site collects the Adverse Drug reports submitted by doctors to the FDA and SEDA in the USA.  It then summarises them for ease of use.  We originally provided a direct link to the Anosmia entry listed on this site and the pharmaceuticals that can cause it, but the eHealthme website designers frequently reorganise the site and thus break the links.  Thus in order to find out which pharmaceuticals are implicated in Anosmia

• Follow the LINK to the eHealthme website
• Using the ‘All conditions’ index find the appropriate entry.  At the time of writing the site was being restructured and they had entries for Loss of smell and anosmia
• Now scroll down until you get to the section marked ‘Drugs that could cause ”

The list shows you all the drugs implicated in CAUSING Anosmia as well as the number of people who have made a complaint to their doctor and had their case reported by him.  Note that it is up to the doctor whether he reports or not.

There are some odd drug classes in this list - statins inevitably figure quite prominantly, but there are drugs for treating erectile dysfunction (ED) [eg Tadalafil, Cialis,], vitamin supplements, a drug used in the treatment of Gaucher's disease, diuretics, and anti-depressants. 

Antibiotics are also in the list - which may, by destroying the intestinal flora, result in pathogens entering the blood stream and thus causing brain damage.  There are antihistamines in the list as well, often a component of nasal sprays. 

Another drug implicated is Bupivacaine, marketed under the brand name Marcaine or Sensorcaine among others, a medication used to decrease feeling in a specific area.  In other words a local anaesthetic.  It is used by dentists in potentially painful dental work.  It is injected into the area, around a nerve that supplies the area.  One can only hypothesise that the injection damaged other nerves as well.

According to wikipedia it is known that Adrenergic agonists or withdrawal from alpha blockers (vasoconstriction) cause anosmia.

Treatment

Find the cause and correct it!  There are no medicines or plants, food or similar that can act directly on damaged nasal cells or the brain, you need to track down why it happened.

In time, as long as you don't damage the cells further, people have been known to regain their smell, but it is never quite as good as it was before the damage.

How it works

Why do people get olfactory hallucinations when they have lost their sense of smell?

Sensory deprivation. 

Only one sensory input has gone, but just as blindness serves to open the door to the composer to provide images, it would appear that anosmia opens the door for the composer to bring us smells, possibly from our perceptions possibly from ‘elsewhere’ …..

see also Perfumes.

Related observations

Healing observations

• The Healing Power of Sleep 026790

Hallucination

• Blithe spirit - The hallucination that saved us 014736
• Bonnie Blodgett and smell 003220
• Hallucinations from welding the San Francisco Bridge 006900
• Oliver Sacks - Herpes simplex damage 001368
• Oliver Sacks - Man suffering acute sense of loss 000468
• Oliver Sacks - Smell mix causes problems 001353
• Prevalence and phenomenology of olfactory hallucinations in Parkinson's disease 014727
• Rare effects of stroke – Stroke Association November 2012 012624