Scent and Sensibility
Tuesday, June 5th, 2012, 8:30 am
"I get no respect, I tell ya"
As far as the 5 senses go, smell doesn’t get any respect.
Often when we are kids we argue about which would we rather be, blind or deaf. You never hear anyone debating on whether they would rather be blind, deaf, or lose their sense of smell. In fact, most people don’t even know that the medical term for loss of smell is Anosmia.
Anosmia (pronounced /æn??zmi?/) is a lack of functioning olfaction, or in other words, an inability to perceive odors.
Olfactory bulb – sends nerve fibers across the skull base to smell receptors that line the roof of the nasal cavity
Just like there are degrees of hearing loss and degrees of visual loss, there are also some patients who have decreased sense of smell. This is referred to as hyposmia.
Anosmia can be caused by a variety of problems such as
Often multiple items on this list cause the anosmia. For instance often we see patients with a deviated septum that prevents airflow to the smell receptors, but also has nasal allergies or smokes which further inflames the nasal mucosa and narrows the nasal passages further.
These causes can be categorized into three different types.
Problems with the conduction of the actual odors to the receptors in the nose
- Sinus infections
- Nasal Polyps
- Nasal masses
- Deviated nasal septum
- Upper respiratory infections
- Cigarette Smoke
Problems with the nerve receptors themselves
- Head Trauma
- Cigarette Smoke
- Intranasal drug use
- Post Laryngectomy patients
Problems with the brain that interfere with the brain registering the smells.
- Head Trauma
- Parkinson’s Disease
- Alzheimer’s Disease
- Brain tumors
Head trauma patients who sustain head trauma, especially from high-speed car crashes, can suffer from anosmia.
The brain sloshes back and forth from the sudden stop and shears the nerves (that are fixed to the bone in the skull base) that go to the smell receptors.
Often this type of anosmia can be permanent
This one case demonstrates how nasal masses or lesions can cause decreased sense of smell.
70 y.o. female who presents with 10 year history of decreased sense of smell and decreased taste. Symptoms began gradually many years ago has not changed in years. Did not have any workup for this until she came in with a different complaint. Had some mild nasal congestion. She uses nasal steroids, which helps her congestion some but has no impact on her sense of smell.
Flexible nasal endoscopy was performed that demonstrated bilateral masses that blocked air from getting to the smell receptors.
CT scan was performed to better visualize the nasal masses. In these series of scans, the first scan is the actual CT scan, and the second is the same CT scan but the nasal mass has been highlighted in red.
The patient recently underwent surgery and the pathology demonstrated a rare but benign nasal lesion called Respiratory epithelial adenomatoid hamartomas. Hopefully removing these will help her anosmia.
Anosmia can cause health concerns that many people are not aware of. Natural gas is actually odorless, but the smell that we associate with natural gas is actually added so that we can smell gas leaks. Without a sense of smell, you would not be able to detect gas leaks or fires as quickly. It also protects us from eating or drinking spoiled food. It is not uncommon for patients with anosmia to get food poisoning from drinking expired milk or other foods. Also, smell plays an important role in taste and people with anosmia frequently notice that their food doesn’t taste as good.
If anosmia is caused by the odors not getting to the smell receptors, often it can be reversed. If the problem is due to a deviated nasal septum, enlarged nasal turbinates, nasal masses, nasal polyps or chronic sinusitis, surgical intervention often can correct the problem.
If nasal allergies are cause, treatment of this often help decrease edema in the nasal cavity and increases nasal airflow to the roof of the nose where the smell receptors are located. These can be controlled with oral antihistamines, nasal steroids, nasal antihistamines, allergy shots, and avoidance of known allergic triggers. Some also advocate nasal saline irrigation to help wash allergens and pollution off of the nasal mucosa as well.
If the patient is a smoker, quitting can help the sense of smell return. The tobacco products can cause nasal congestion, which causes anosmia, but also can be toxic to the smell receptors. These receptors can regenerate but it can take months after a patient quits smoking for this to occur.
Increased attention has been given to anosmia in recent years as it is frequently seen in Alzheimer’s and Parkinson’s disease. Some studies have even suggested that detection of anosmia (not from nasal masses as the patient above), may be a predictor of developing either of these diseases.
If the problem is caused by problems with the smell receptors or the way the brain processes the smell, often nothing can be done.
So what should a person do they think they have anosmia? Evaluation by an otolaryngologist is a first step. The evaluation looks into causes and possible treatments based on the suspected cause. The workup can vary based on the individual patients symptoms and physical findings. In cases where it is permanent, the person should take safety measures to protect themselves. Gas leak detectors are available for these patients that detect natural gas that are similar to carbon monoxide detectors.
References:
Eloy J, Friedel ME, Eloy J, Mirani NM, Liu JK. Bilateral olfactory fossa respiratory epithelial adenomatoid hamartomas. Arch Otolaryngol Head Neck Surg. 2011;137(8):820-822. doi:10.1001/archotol.137.8.820.
Tags: anosmia, head trauma, hyposmia, nasal mass, nasal polyps, nose, olfaction, olfactory, sense of smell, smell
Category: General Medical, Interesting Stuff, Nose