Loss of Sense of Smell: Causes, Diagnosis and Coping Mechanisms

Loss of sense of smell, medically known as anosmia, is an often-underestimated condition that affects our olfactory system—the complex mechanism responsible for detecting and processing scents. 

Olfaction, or our sense of smell, is one of the five primary senses that help us interpret and navigate our surroundings. Not only is it crucial for detecting dangers such as gas leaks or spoilt food, but it also plays an integral role in our experiences of pleasure, nostalgia, and social interactions, through scents and tastes that evoke memories or emotions.

The Science of Smelling

The phenomenon of smell, while seemingly simple, is a sophisticated process intricately connected to the essence of our human experiences, including the distressing experience of the loss of sense of smell. The olfactory system, responsible for this sense, has several key components collaborating to allow us to perceive and interpret various odours.

  • Mucus Membranes

Situated in the nasal cavity, these membranes contain special olfactory receptor cells. These cells capture and identify odour molecules when we breathe. 

  • Olfactory Nerve

Once the olfactory receptors in the mucus membranes detect an odour, the sensation is relayed via the olfactory nerve. 

  • Olfactory Cortex

The transmitted signals from the olfactory nerve are then processed in the olfactory cortex, a specific region of the brain dedicated to interpreting smells. 

In the event of a loss of sense of smell, all these connections and processes can be disrupted, affecting the perception of odours and the intricate web of associated emotions and memories.

Neurodegenerative Diseases and Sense of Smell

A diminished or loss of sense of smell is not merely a standalone symptom. Dr Martin Owens mentions, “The nose is like a window to the brain. When it’s foggy, there might be storms inside.” This section explores how this sensory loss intertwines with some of the most notable neurodegenerative disorders.

  1. Parkinson’s Disease

One of the earliest signs of Parkinson’s Disease, often occurring before motor symptoms manifest, is the loss of smell. While not everyone with anosmia will develop Parkinson’s, a significant portion of those diagnosed with the disease report this sensory decline.

  1. Alzheimer’s Disease

Alzheimer’s, a condition severely affecting memory, has also shown correlations with olfactory dysfunction. According to the Alzheimer’s Association, “Our ability to remember the smell of fresh baked cookies or a seaside breeze is deeply connected to memory centres impacted by Alzheimer’s.”

  1. Huntington’s Disease

This genetic disorder, characterised by the progressive breakdown of nerve cells in the brain, has been associated with several sensory deficits. Among these, the loss of sense of smell can manifest, further pointing to the broad impact of neurodegenerative diseases on the olfactory system.

  1. Multiple Sclerosis (MS)

Multiple Sclerosis affects the central nervous system, causing various symptoms. Among the potential sensory disturbances in MS, the diminished ability to smell can be observed, although it is less common than other sensory symptoms.

  1. Mild Cognitive Impairment (MCI)

Before more severe forms of dementia set in, some individuals experience MCI, a condition characterised by a noticeable cognitive decline that doesn’t interfere significantly with daily life. 

  1. Stroke Effects

Depending on the affected brain region, strokes can lead to many neurological issues. In some cases, if the areas connected to the olfactory system are impacted, it can result in a sudden loss of sense of smell.

Other Causes of Loss of Sense of Smell

The complex world of olfaction, with its deep-rooted connections to our daily experiences, can be severely affected by various factors. While we’ve explored the intimate connection between the loss of sense of smell and neurodegenerative diseases, it’s essential to understand that several other causes can lead to anosmia (complete loss) and hyposmia (partial loss). Delving into these causes provides a comprehensive insight into how intricate and vulnerable our loss of sense of smell can be.

  1. Head Injury

Trauma to the head can disrupt the olfactory nerve or the brain parts crucial for scent processing, leading to a potential loss of sense of smell.

  1. Viral Infections

Some viruses, particularly those targeting the respiratory system, might cause a temporary or permanent loss of sense of smell.

  1. Alzheimer’s

The association between Alzheimer’s disease and a decline in olfactory abilities further emphasises the multifaceted reasons behind the loss of sense of smell.

  1. Medications

Several medicines have potential side effects that can impede the olfactory system, leading to the unwelcome loss of sense of smell. These side effects might be temporary, with the sense of smell returning after discontinuation of the medication, or they might cause lasting damage in some cases. Common culprits include:

  • Antibiotics

Some types can affect the sense of smell, especially if taken over prolonged periods.

  • Antihypertensive Drugs

Used for high blood pressure, these can sometimes cause olfactory disturbances.

  • Antidepressants

Some individuals report changing their sense of smell when on specific antidepressants.

  1. Nasal Polyps

Nasal polyps are soft, painless, noncancerous growths on the nasal passages or sinus lining. These noncancerous growths on nasal or sinus linings can obstruct airflow, consequently causing a loss of sense of smell.

  1. Tumours

Both benign and malignant growths in the nasal or sinus region can impede the olfactory sense. A tumour could exert pressure on the olfactory nerve or hinder airflow, leading to the undesirable loss of sense of smell.

  1. Allergies

Chronic allergies can lead to persistent inflammation in the nasal passages. This inflammation can obstruct airflow and impede the function of olfactory receptors.

In addition to viral infections:

  • Sinus Infections

Chronic or acute sinusitis can cause inflammation of the sinuses, leading to a decreased sense of smell due to mucus buildup and blockage.

  • Respiratory Infections

Certain infections that affect the respiratory tract can temporarily or permanently damage the olfactory system.

Evaluation and Diagnosis

Any sudden or gradual change in the sense of smell warrants a consultation. Immediate consultation is crucial if the loss of smell accompanies other symptoms like pain and facial trauma or if it’s linked with starting new medications. Those with persistent anosmia without a clear cause, such as a cold or flu, should also seek medical advice.

Physical Examination Process:

The doctor will thoroughly evaluate the patient’s medical history, focusing on when the symptoms started and any accompanying issues. This is followed by examining the nasal passages to check for obstructions or abnormalities. Factors like nasal congestion, polyps, or other obstructions can be identified this way.

Specific Tests for Anosmia:

  • Scratch and Sniff Tests

This is a common test wherein the patient is presented with a set of odours to identify. The inability or difficulty in recognising these odours can indicate olfactory dysfunction.

  • Dilution-Based Tests

A specific odour is presented at varying concentrations in these tests. The patient’s ability to detect the odour at different dilutions helps assess the extent of the olfactory dysfunction.

Imaging Tests (CT or MRI) for Detecting Structural Abnormalities

When physical examination and initial tests don’t provide conclusive results, or if there’s suspicion of deeper structural issues like tumours, imaging tests become essential. Dr David Warner, a radiologist, states, “Advanced imaging often gives us the ‘big picture’ of what’s happening inside the nasal and brain structures when smell is impaired.”

  • CT Scans

Computed Tomography scans provide detailed images of the internal structures, especially bones. This can help identify obstructions or abnormalities in the nasal and sinus regions.

  • MRI

Magnetic Resonance Imaging offers a more detailed view of soft tissues, making it ideal for spotting tumours or abnormalities in the brain or olfactory nerve.

Coping Strategies for Those with Anosmia

Coming to terms with the loss of sense of smell can be an emotionally draining experience. It affects the person suffering from the condition and their loved ones. Here are some coping mechanisms and strategies for those dealing with anosmia:

  1. Enhanced Food Experience

Use strong herbs, spices, and varied textures to compensate for the reduced ability to detect aroma, allowing for a richer food experience.

  1. Reliance on Temperature and Texture

Focus on foods’ warmth, coldness, crunchiness, or creaminess for alternative sensory pleasure.

  1. Smoke and Carbon Monoxide Alarms

With an inability to detect smoke or gas, installing and regularly checking these alarms becomes crucial.

  1. Regularly Checking Expiry Dates

Habitually check expiration dates on foods to avoid consumption of spoilt items.

  1. Memory Aids

Develop new habits like setting timers or reminders for tasks that once relied on smell, such as turning off the oven.

  1. Join Support Groups

Connecting with others who’ve experienced a loss of sense of smell can be therapeutic. Support groups, online communities, and counselling sessions can offer solace and practical advice.

Fragrance of Progress

Though often overlooked, the loss of sense of smell can significantly alter one’s life, emphasising the importance of understanding, diagnosing, and addressing its causes. If you happen to experience it, consulting your physician and undergoing tests is still the best step forward.