Anosmia

What Causes Anosmia?

Anosmia can be triggered by a broad range of causes, including infections, neurological conditions, and other medical disorders.

Respiratory Causes

Respiratory infections and conditions can lead to anosmia. Some of the most common include:

• Colds
• Influenza (flu)
• Allergies
• Sinus infections
• COVID-19

Neurological and Medical Causes

Many medical conditions can disrupt communication between the nose and the brain, leading to a loss of smell. Some of these conditions include:

• Alzheimer’s disease
• Advanced age
• Aneurysm
• Cancer
• Diabetes
• Huntington’s disease
• Multiple sclerosis
• Multiple system atrophy (MSA)
• Nasal polyps
• Paget’s disease
• Parkinson’s disease
• Pick’s disease
• Schizophrenia
• Traumatic brain injury

Other Causes

Environmental and physical factors can also cause anosmia, including:

• Exposure to toxins or pollutants
• Radiation therapy
• Brain surgery
• Cosmetic surgery
• Side effects of medications
• Smoking

Is Anosmia Hereditary?

Most of the time, anosmia is not inherited. Even in the case of congenital anosmia, most cases are sporadic, meaning the person has no family history of the condition. However, some genetic diseases associated with anosmia, such as Kallmann syndrome, are sometimes inherited. In these cases, the pattern of inheritance depends on the underlying disorder.

How Is Anosmia Detected?

Early signs of anosmia include:

• Changes in familiar smells
• Inability to detect strong odors
• Changes in the sense of taste

How Is Anosmia Diagnosed?

Diagnosis of anosmia focuses on identifying the underlying problem causing the loss of smell. The diagnostic process may include a series of exams and tests as your doctor works to rule out possible causes and zero in on the condition responsible for the anosmia.

Diagnostic steps may include:

• A physical exam, including examination of the inside of the nose
• Smell testing
• Blood and laboratory tests
• Computerized tomography (CT) or magnetic resonance imaging (MRI) to look for possible neurological causes
• Tests of olfactory nerve function

PLEASE CONSULT A PHYSICIAN FOR MORE INFORMATION.

How Is Anosmia Treated?

Treatment of anosmia targets the underlying condition causing the loss of smell, and typical treatment varies depending on the cause. In some cases, the cause can’t be determined, limiting the options for treatment. No treatment is available in other cases, such as those caused by age or degenerative diseases such as Alzheimer’s.

Some cases of anosmia resolve by themselves without treatment. This is often true of anosmia caused by respiratory infections.

How Does Anosmia Progress?

Anosmia that continues over a long period can lead to complications that are seriously detrimental to the health, safety, and quality of life of the affected person. Possible long-term complications include:

• Depression
• Malnutrition
• Weight loss
• Consumption of spoiled food
• High blood pressure caused by over-salting foods
• Exposure to harmful toxins due to the inability to detect warning odors
• Fire danger because of the inability to smell smoke

How Is Anosmia Prevented?

There is no known way to prevent anosmia.

Anosmia Caregiver Tips

If you’re caring for someone with anosmia, keep these tips in mind:

• Accept the reality of the condition. Although anosmia is invisible to others, its symptoms and impacts on the sufferer are very real. Be patient, understanding, and supportive of your loved one.
• Understand the seriousness of the disorder. Loss of smell has significant effects, and it can seriously diminish the sufferer’s quality of life.
• Keep safety in mind. Help protect your loved one from potential dangers such as spoiled food, toxic substances, and smoke.

Many people with anosmia also suffer from other brain and mental health-related issues, a condition called co-morbidity. Here are a few of the disorders commonly associated with anosmia:

• People with anosmia are at increased risk of depression and anxiety .
• Anosmia has been associated with increased rates of somatic symptom disorder.

Anosmia Brain Science

As the COVID-19 pandemic has progressed, scientists have worked to understand how the viral infection causes loss of smell. Anosmia has emerged as one of the most reliable early signs of the disease and the primary neurological symptom of COVID. However, scientists have not fully understood how the virus interferes with the sense of smell.

A recent study may offer important new insights. Until recently, researchers assumed that COVID-19, like many other respiratory infections, caused anosmia by infecting and damaging nerve cells in the nose responsible for detecting odors and sending smell-related signals to the brain. However, the new study suggests that COVID-19 may affect smell by infecting other types of cells in the nose rather than nerve cells. These other cells are important in detecting odors, but they aren’t responsible for transmitting smell signals directly to the brain.

These findings may be good news for COVID patients suffering from anosmia. Loss of smell caused by COVID typically resolves faster than anosmia caused by other respiratory infections. Also, because olfactory nerve cells don’t seem to be damaged by COVID, permanent loss of smell is unlikely.

Anosmia Research

Title: Treatment of Pediatric Patients That Lost Sense of Smell Due to COVID-19

Stage: Recruiting

Principal investigator: Amanda L. Stapleton, MD

University of Pittsburgh

Pittsburgh, PA

This research study is a randomized controlled trial in pediatric and young adult patients who have lost their sense of smell due to COVID-19 viral infection. The goals are to learn more about the effects of smell retraining therapy on smell loss following COVID-19 and to determine if budesonide-saline irrigations make smell retraining therapy more effective.

Title: Longitudinal At Home Smell Testing to Detect Infection by SARS-CoV-2

Stage: Not Yet Recruiting

Principal investigator: Mark W. Albers, MD PhD

Massachusetts General Hospital

Boston, MA

The purpose of this study is to learn more about how to identify better people who have been infected with the SARS-CoV-2 virus (which causes COVID-19). Most people exposed to the virus develop changes in their sense of smell (olfaction). We are interested in measuring smell function objectively via smell cards that test odor intensity, identification, and discrimination. The impact of smell testing to identify people at risk for SARS-CoV-2 will be maximized if objective and precise olfactory testing can be performed in the convenience of one’s home. We will use results from this test to better understand the relationship between SARS-CoV-2 and olfactory function and to learn whether the AROMHA longitudinal smell test is a reliable screening tool to detect smell loss in the context of possible COVID exposure.

Title: Smell in Covid-19 and Efficacy of Nasal Theophylline (SCENT2)

Stage: Recruiting

Principal Investigator: Jay F. Piccirillo, MD, FACS

Washington University School of Medicine

Saint Louis, MO

Evidence of COVID-19 related to anosmia and dysgeusia continues to accumulate daily.

Currently, up to 80% of patients report subjective olfactory dysfunction (OD), and prevalence using objective olfactory testing could be even higher.

We propose a phase II single-site, double-blinded, placebo-controlled randomized clinical trial to determine the efficacy and safety of intranasal theophylline, a known phosphodiesterase inhibitor in the treatment of asthma, as a possible treatment for COVID-19 related OD. Theophylline has shown benefit in similar clinical trials for post-viral OD.

Post-viral olfactory dysfunction has numerous known adverse effects, such as loss of cortical gray matter and decreased quality of life. COVID-19 related olfactory dysfunction has already been shown to be correlated with depression and decreased quality of life, so finding an effective treatment is imperative.

Intranasal and oral corticosteroids and olfactory training are currently used to treat post-viral OD; however, they have demonstrated limited efficacy, and there is no current gold standard of care. There is no current consensus on the pathogenesis of COVID-19 related anosmia; however, evidence for post-viral olfactory dysfunction suggests sensory axonal regeneration and olfactory signaling may rely on elevated levels of secondary messengers cAMP and cGMP, a known effect of theophylline. In this phase II treatment trial, patients will be allocated 1:1 to receive either intranasal theophylline irrigation or placebo for six weeks. Various smell surveys and scratch-and-sniff tests will be utilized to capture changes in smell ability.

Due to COVID-19, this study will be conducted virtually, except for the first ten enrolled patients who will undergo one serum theophylline test. Therefore, this study is limited to patients living in Missouri or Illinois.