Smell Loss: A Stroke's Impact On Olfactory Function

A stroke occurs when the blood supply to the brain is cut off, resulting in the death of brain cells. This can cause changes to any of the five senses, including vision, hearing, touch, taste, and smell. While changes in the sense of smell are not a primary indicator of a stroke, it is also not impossible. In fact, a study in BMC Neurology found that nearly a third of 78 participants who had strokes experienced a reduced ability to smell, and 15% had lost their sense of smell completely in the year following their strokes.

The senses of taste and smell are closely connected, and a disruption in one can impact the other. This is because flavour is determined by both the sense of taste and the sense of smell. Therefore, a stroke can cause changes in the sense of taste as well as smell.

Anosmia: the complete loss of smell

Anosmia is the medical term for the partial or total loss of the sense of smell. It can be caused by various factors, including certain medications, infections, and brain injuries such as strokes.

Causes of Anosmia

A stroke occurs when the blood supply to a part of the brain is cut off, resulting in the death of brain cells. If the stroke damages the areas of the brain responsible for interpreting smell information from the nose, it can lead to anosmia. However, the specific effect of a stroke depends on the size and location of the damaged area in the brain.

Other causes of anosmia include:

• Infections in the nose or sinuses
• Tooth or gum infections
• Allergies
• Inflamed sinuses
• Nasal polyps
• Brain tumours
• Head trauma
• Exposure to neurotoxins
• Temporal lobe seizures
• Epilepsy
• Parkinson's disease
• Ageing
• COVID-19

Impact of Anosmia

The loss of smell can have a significant impact on an individual's quality of life. It can affect their ability to detect potential dangers, such as smoke, gas, or chemicals, and may also impact their sense of taste, leading to a reduced appetite and nutritional deficiencies. Anosmia can also have emotional and social consequences, as smells are closely connected to our feelings and memories.

Treatment of Anosmia

Treatment options for anosmia depend on the underlying cause. In some cases, anosmia may improve over time, especially if it is caused by a stroke or infection. Good oral and nasal hygiene can also help prevent and treat anosmia. In severe cases, surgery may be considered to remove the olfactory mucosa, the area of the nasal cavity containing smell receptors. However, this surgery carries risks, including bleeding and damage to surrounding structures.

Hyposmia: a diminished sense of smell

Hyposmia is a reduced ability to smell. It is one of several types of smell problems that can occur after a stroke, along with:

• Anosmia: being unable to smell anything.
• Dysosmia: a distorted sense of smell.
• Phantosmia: smelling something that isn't there.
• Hyperosmia: being oversensitive to smells.

A stroke occurs when the blood supply to part of the brain is cut off, killing brain cells. If a stroke damages the parts of the brain that interpret information from the nose about smell, it can cause changes to your sense of smell.

A study in BMC Neurology looked at 78 participants who had strokes and found that nearly a third of them had a reduced ability to smell, and 15% had lost their sense of smell altogether during the year following their strokes.

Shifts in smell can have a ripple effect on other areas of life, including taste, nutrition, and mental health. Olfactory issues can affect taste, putting stroke survivors at risk of malnutrition and depression.

If you are experiencing hyposmia after a stroke, it's important to seek advice from a medical professional. A GP or stroke nurse can advise on the next steps and refer you to a specialist for further support.

Hyperosmia: increased sensitivity to smells

A stroke occurs when the blood supply to the brain is cut off, killing brain cells. This can cause changes to any of the senses, including vision, hearing, touch, taste, and smell. Changes to one's sense of smell are not a primary red flag for stroke, but that doesn't mean there's no connection at all. A stroke can affect the brain and its functions, and smell perception is one of them.

Hyperosmia is a condition where one becomes extremely sensitive to smells. It is one of the types of smell problems that can occur after a stroke. Other types include:

• Anosmia, which is the inability to smell anything.
• Dysosmia, a distorted sense of smell, which has two forms: Parosmia and Phantosmia.
• Hyposmia, a reduced ability to smell.

According to a study in BMC Neurology, which looked at 78 participants who had strokes, almost a third of them had a reduced ability to smell, and 15% had lost their sense of smell altogether in the year following their strokes.

If you are experiencing any changes in your sense of smell or taste, it is important to consult a doctor or a stroke nurse to determine the underlying cause and receive appropriate treatment and support.

Phantosmia: smelling something that isn't there

Phantosmia is a condition where a person perceives odours that aren't actually present in their environment. It is a type of olfactory hallucination, where the organs related to the sense of smell sense something that isn't there. The smells can vary from pleasant to foul, but most people with phantosmia tend to detect bad smells, such as "burned", "foul", "sewage", or "chemical". These phantom smells usually come and go and are not constant.

Phantosmia can be caused by a number of factors, including:

• Upper respiratory infection
• Seizures in the temporal lobe of the brain
• Brain tumours
• Migraines
• Neuropsychiatric disorders
• Sinusitis
• Parkinson's disease
• Alzheimer's disease
• Schizophrenia
• Traumatic brain injury
• Nasal mucosal abnormalities

If you experience phantosmia, it is important to consult a doctor, who may perform a physical exam and review your medical history to rule out any underlying causes, such as a brain tumour. Treatment options for phantosmia are limited and typically depend on the underlying cause. In some cases, medication or surgery may be recommended, but there is a risk of losing the sense of smell completely, so surgery is often a last resort.

Parosmia: distorted sense of smell

A stroke occurs when the blood supply to a person's brain is cut off, resulting in the death of brain cells. A stroke can cause changes to any of the five senses, including vision, hearing, touch, taste, and smell. If a stroke damages the parts of the brain that interpret information about taste and smell from the nose and tongue, it can lead to changes in these senses.

While not a classic sign, a stroke can sometimes affect an individual's sense of smell. Olfactory function may change as a result of a stroke rather than as a warning sign. For example, a study in BMC Neurology found that nearly a third of participants who had strokes experienced a reduced ability to smell, and 15% had a complete loss of smell during the year after their strokes.

One specific type of distorted sense of smell is parosmia, also known as troposmia. With parosmia, your brain changes how something smells. For instance, you might smell burnt toast when, in reality, you are smelling freshly brewed coffee. Parosmia differs from phantosmia, where people smell something that isn't there.

Parosmia can happen after a stroke, especially if the frontal lobe of the brain is affected. The frontal lobe is responsible for how odours are perceived and processed. A stroke that impacts the frontal lobe may result in distorted smells.

If you are experiencing changes in your sense of smell or taste after a stroke, it is important to seek medical advice. A doctor or stroke nurse can help determine the cause and provide treatment or referrals to specialists, such as an ear, nose, and throat doctor or a dietitian.

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