Is there hope when I lose my sense of smell?

I was asked at short notice to write this article but agreed as I knew I was going to be taking a break from my busy clinical schedule to go sailing for 5 days. This was however no luxury cruise but part of my reservist training with the Navy. Knowing this, the person requesting this article jokingly wished me inspiration with the sun and surf! After being stuck with my team of 57 men at sea living in cramped quarters in triple deckers with a single change of uniform, the aroma was unable to inspire me. The inspiration finally came as the highly qualified medical specialist officers were helping our medical orderlies clear the rubbish after 5 days at sea. Our noses, used to the highly sanitised hospital environment, were a little unused to the overwhelming flavours as we formed a human chain to clear the mountain of trash bags accumulated by ourselves and the rest of the ship crew! I decided then that losing our sense of smell might not be a bad thing!

 

Seriously, however, we often underestimate the importance of smell to our well-being. In the case of bad smells, our olfactory systems act as advance warning devices, detecting signals over long distances to alert us of potential dangers to avoid. When we know the reason for the bad smell, our brains are thankfully smart enough to turn off the signals to ignore the warning if we have no choice but to remain in that smelly environment (a phenomenon called accommodation). This innate ability to detect bad, averse smells has been demonstrated even in one day old babies who make funny faces when exposed to pungent odours.

 

But do our noses do more than giving us warnings? Of course! With the festive season around the corner, we would find all the delicious food tasteless because 75% of taste actually comes from our sense of smell. It has been estimated that our sense of smell is 10,000 times more sensitive than our sense of taste. Most of the subtle flavours we appreciate in fine gourmet dining and wine appreciation actually come from the aroma. That’s why we swirl our wine to release the aroma and use tapered glasses to trap the aroma in the glass. Our quality of life is severely affected when we lose our sense of smell and some anosmics (someone who has lost their sense of smell) suffer from depression as a result. Think of the last time you had a bad cold when everything was tasteless, bland and depressing – then think of that sensation for the rest of your life….

 

Smell also helps with recognition. We all have a unique smell (some more pleasant than others from recent personal experience!) except perhaps identical twins. It has been shown that dogs can distinguish between the smell of T-shirts worn by non-identical twins (but not identical ones). Babies recognize their mothers’ smell and vice versa. Emotion can be communicated by smell and it is well known that dogs and horses can “smell” fear in humans. A recent study showed that a panel of women could discriminate between armpit swabs from people watching happy versus sad movies. (Not surprisingly, the men were not very good at it!) Smell can influence our mood, memory, emotions and perhaps even the choice of our mate! An interesting study published in October 2005 showed that genetically modified mice that don’t smell don’t mate! Smell researchers actually won the Nobel Prize for Medicine in 2004! This perhaps reflects the shift in developed nations from focusing on basic critical medicine to quality of life issues. Much research in the past has focused on our vital senses, like vision and hearing and we are only beginning to understand a less crucial but important sense, like smell.

 

Admittedly, there is currently still very little we can do to help sensori-neural smell loss. Nerve damage can sometimes happen after an upper respiratory infection. In the US, the commonest cause is due to head injury. I once treated a local actress who lost her sense of smell from a head injury after a fall during stunt rehearsals for a charity program (for those who belittle their efforts, especially after the NKF debacle!) The prognosis is usually poor because the short nerve fibres get detached during the accident. Loss of smell can also be seen in some central nervous system disorders. It is one the first signs of Alzheimer’s disease and can also be seen in Parkinson’s disease. Rarely, it may be due to a frontal lobe tumour, so it is still important to investigate even when prognosis is poor.

 

More importantly, a large group of patients suffer from a conductive loss of smell and this is imminently treatable. In this group of patients, odour molecules cannot reach the olfactory system because of physical obstruction. It can happen in severe allergic rhinitis but more commonly in patients suffering from nasal polyps and chronic sinusitis. There can also be structural problems causing obstruction which can be easily treated surgically. I remember a young girl who finally acquiesced to surgery because she needed to smell during her chemistry practical examinations for her GCE ‘O’ levels! Patients suffering from conductive loss of smell need not continue to suffer from it with adequate medical treatment, and in some cases, surgery.

 

A visit to the otolaryngologist (Ear, nose and throat specialist) will help to diagnose treatable causes and exclude serious ones. Besides a thorough history and physical examination, endoscopy is crucial to exclude obstructive causes. Smell testing can be done by checking for the olfactory threshold using sniff bottles. The University of Pennsylvania Smell Identification Test (UPSIT) is a self administered test with scoring based on 40 microencapsulated odours. Sometimes, CT scans are ordered to exclude sinus disease or even MRI scans to exclude frontal lobe tumours.

 

If no obvious cause is detected on the first visit, patients are usually started on a trial of oral steroids to look for possible conductive loss. Steroids help reduce swelling and therefore improve the passage of odour molecules to the olfactory nerve fibres. It is often amazingly gratifying to see the smiling faces on patients who regain their sense of smell after years of unnecessary forbearance! If the sense of smell returns, we usually try to maintain it with topical steroids as these can be used for prolonged periods with little or no side effects. After a period of time, even these can be stopped with good long term results. We usually consider CT scans, if we can’t maintain the sense of smell with topical steroids and often find evidence of chronic sinus disease. The advent of minimally invasive endoscopic sinus surgery has dramatically improved the results in this group of patients. We can achieve cure in 80 to 90% of patients and improve medical control in the remaining group. Unfortunately, patients with sensori-neural loss of smell will not respond to steroids at all. However, as previously mentioned, we still need to perform an MRI scan is to exclude a frontal lobe tumour in these patients.

 

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