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Anosmia After Head Trauma: Causes, Complications, and Treatment

woman struggling to smell orange slice because she has anosmia after head trauma

Anosmia refers to a loss of the sense of smell. It can be caused by a brain injury, amongst other causes. This problem is commonly overlooked by doctors during treatment, but it can seriously impact a person’s quality of life.

You’re about to learn the different causes of anosmia after head trauma plus some treatments that can help you cope.

Cause of Anosmia After Head Trauma

Anosmia, also known as smell blindness, is caused by damage to the parts of the brain that control your sense of smell. These include:

  • The orbitofrontal cortex, located above and behind the eyes.
  • The insula, which lies beneath the ears.
  • The piriform cortex, located between the other two.

Besides these three areas, there are smaller brain regions that also play a part in smell. These are collectively called the olfactory regions.

Finally, if the skull’s cribriform plate (the piece of bone directly behind the nose) is shattered, this could sever the olfactory nerves that connect to the nose. This will lead to smell blindness.

Other Disorders of Smell After Brain Injury

woman holding nose and grimacing because she smells something bad

Sometimes, head trauma can lead to other smell disorders that don’t make you lose your sense of smell.

Disorders of smell besides anosmia include:

  • Hyposmia: Partial loss of smell
  • Hyperosmia: Enhanced sense of smell
  • Phantosmia: False or imaginary smells
  • Dysosmia: Distortion of smells

When a person suffers from dysosmia, for example, sour milk might smell fresh to them, or fresh flowers might smell rotten and dead. This can lead to loss of appetite and weight loss.

Complications of Anosmia After Head Trauma

Anosmia can have a severe impact on daily life in ways most people do not realize. Some complications of losing your sense of smell include:

  • Loss of taste. Taste and smell are intimately connected. Unfortunately, this means that anosmia can impair your sense of taste as well. Most people with anosmia can only taste very spicy or very salty foods.
  • Weight loss. Lack of taste can cause a decrease in appetite, which can lead to unhealthy weight loss.
  • Food poisoning. The inability to smell spoiled food can cause an increased risk of food poisoning.
  • Memory impairments. The olfactory bulb, located behind the eyes, connects to the amygdala, the part of the brain in charge of emotions and personal memories. Without smell, therefore, the brain cannot encode as many memories.
  • Fire hazards. Anosmia can impair a person’s ability to detect smoke and other harmful chemicals. This increases a person’s risk of injury.
  • Depression. Losing the ability to taste and smell good food can cause a lack of interest in social gatherings and lead to depression.

Diagnosing Anosmia

doctor examining patient's nose to see what is causing her anosmia after head trauma

Anosmia is often overlooked after a brain injury because most doctors are focused on treating the most life-threatening injuries first. In addition, some patients do not even realize they can no longer smell until several weeks later, when they can finally focus on something besides their injury.

Despite the fact that anosmia can be easily missed, research suggests that around 20% of traumatic brain injury patients suffer from some type of olfactory disorder.

Therefore, it’s important to diagnose anosmia as soon as possible.

The most widely used diagnostic test for anosmia is the University of Pennsylvania Smell Identification Test (UPSIT). This test evaluates a person’s ability to distinguish smells by using 40 scratch-and-sniff cards. The test is scored in the following way:

  1. Normosmia: normal smell function
  2. Mild Microsmia: mild smell impairment
  3. Moderate Microsmia: moderate smell impairment
  4. Severe Microsmia: severe smell impairment
  5. Anosmia: no smell function

Now that we’ve discussed the different types and complications of anosmia, let’s look at some treatments.

Treating Anosmia After Brain Injury

For people with a distorted sense of smell, some medications such as Gabapentin can help.

Unfortunately, there are not many treatments available to reverse full anosmia after head trauma. But a new therapy called olfactory training seems to hold promise.  

Olfactory training involves smelling strong scents such as roses, eucalyptus, and lemon. This stimulates the olfactory nerves in the nose in the hopes of retraining the brain to detect smells. However, it only has about a 30 percent success rate for people with brain injuries.

Otherwise, all you can do is wait to see if the olfactory regions of your brain heal on their own. If they do, you should recover your sense of smell within six months after your brain injury.

Coping with Loss of Smell After TBI

If your sense of smell never returns, you will need to learn how to live without smelling or tasting. This process will be difficult, though not impossible.

Here are a few ideas to help you cope with the loss of smell after a head injury.

  • Use seeds and nuts to add texture. While these won’t restore your sense of taste or smell, they can help your meals seem a little less bland. This might increase your appetite and help you gain back lost weight.
  • Try ice cube stimulation. If anosmia impaired your sense of taste, ice cube stimulation might help. Some patients report that sucking on an ice cube for one minute before a meal helped improve their sense of taste. In particular, it restored their ability to taste sweet foods. While more studies are needed to understand why this happens, it might be something worth trying.
  • Throw out expired food. It’s important to throw out food as soon as it hits the expiration date since you won’t be able to tell when it goes bad.
  • Install smoke and gas detectors. This is crucial, especially if you live alone.

While living with anosmia can be frustrating, these methods should make things a bit more manageable.

Anosmia After Head Trauma: Key Points

Anosmia is caused by damage to the parts of the brain in charge of smell. Besides impairing smell, anosmia can cause a person to lose their sense of taste as well.

While there are currently no proven treatments for anosmia caused by head trauma, olfactory training may prove useful. Talk to your doctor for more information on treating anosmia. New therapies are on the rise, and your doctor might know of some that may help.

It’s also possible that your anosmia will heal on its own. If that does not occur, however, some coping strategies can help make life without smell a little more bearable.

Featured Image: ©iStock/microgen/AaronAmat/yacobchuk

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