Nasal Turbinates or Nasal Conchae

Anatomically speaking, nasal concha is a narrow, arched, and elongated bony ridge projecting into the nasal cavity. Sometimes referred to as nasal turbinates, it occupies the nasal cavities’ superior or upper chambers. Their presence enhances the cavities’ surface area, facilitating rapid humidification and warming of inhaled air absorbed by the lungs.

In Which species Do we Find Nasal Conchae?

Specific groups of vertebrates including birds, reptiles, mammals, and amphibians have highly developed olfactory epithelium lining the upper section of the nasal cavities. This specialization equips them with a sharper and more perceptive sense of smell. However, the nasal conchae in humans tend to be less pronounced in comparison to dogs, dingoes, wolves, coyotes, and jackals. Consequently, the human race has evolved depending more on the bodily senses like balance, touch, taste, and sight, and less on the sense of smell.

Position & Shape

These curled and extended bones get their name from the Latin term, ‘concha’ meaning a spiral-shaped seashell or conch shell. There are two turbinate bones, each positioned on either side of the nasal cavity separated into two distinct airways by the septum. The nasal conchae, in human beings, segregate the airways into four rut-like channels. The segregation facilitates the flowing of inhaled air in a smooth and consistent pattern all around the nasal mucous membrane.

Nasal Conchae

Anatomical Structure

Nasal turbinates comprise layers of ciliated respiratory epithelium and pseudostratified columnar cells superimposed with a layer of vascular tissue. Anatomical review of the turbinate bone reveals three distinct:

  • Superior or upper turbinates: They link to the medial turbinates via nerve-endings and are the smallest of all turbinate segments. Their endpoints face the posterior ethmoidal air cells. The primary function is to safeguard the olfactory bulb located in the forebrain which is responsible for olfaction.
  • Medial or middle turbinates: This section is smaller than the lower turbinate but larger than the superior turbinate. It protrudes downwards, facing the orifices of the middle ethmoid, anterior ethmoid, and maxillary sinuses. It cushions the sinuses from the pressurized airflow in the nasal passages.
  • Inferior or lower turbinates: It is the lower turbinates that play the most crucial role in filtering, heating, humidifying, and channelizing the inhaled air. Largest amongst all the three turbinate divisions, their size is comparable to a human being’s index finger.

Functions

Comprising the major section of the nasal mucosal membrane, Nasal Conchae plays a key role in respiration. The different segments facilitate the respiratory process, fine-tuning olfaction, and boosting up immunity. All significant functions of the turbinate bones are listed below:

  • Protects the Airways: Cilia, small hair-like projections, lining the turbinates, traps the incoming contaminants and dust particles passing through the airways. The mucus containing the contagions, first make their way to the posterior of the nose, and then towards the front. The mucus is eventually ejected through the nostrils or imbibed via the throat wherefrom it reaches the stomach. The gastric secretions detoxify the mucus.
  • Regulates Nasal Airflow: The pressurized airflow activates the erectile tissues in the inferior turbinate’s frontal part which in turn helps to regulate nasal airflow. The erectile tissues inside the turbinates allegedly play a significant role in promoting the nasal cycle, when both nostrils get congested and decongested alternately.
  • Prevents Infections: The cilia also create a conducive environment for white blood cells to combat pathogens, and thereby prevent infections.
  • Protects the Neural Axons: The upper turbinate completely sheathes the neural axons transmitting via the foramina of the ethmoid bone’s cribriform plate to reach the nose.
  • Reinforces the Sense of Smell: The medial turbinates reinforce the sense of smell as the olfactory nerve transmits stimuli to some of its sections.
  • Stimulates Turbinates: Pain and temperature-sensitive neural receptors stimulate the turbinates.
  • Acts as a filter: Nasal concha humidifies the inhaled air, heats it up to a temperature varying from 32°C-34°C, and then filters it.
  • Enhance the nasal surface area: This way it deflects and directs airflow to the upper region of nasal passages.

Immunological Role

The respiratory epithelium overlaying the turbinates’ ‘lamina propria’ or erectile tissues (a slim layer of connective tissues) offering an immunological defense to the body. This ciliated epithelium is partly composed of goblet cells (prismatic or cylindrical epithelial cells) that generate mucus. The mucus inside the nasal airways screens dust particles and microorganisms bigger than 2-3 microns.

This thin, outer tissue layer also serves as the gateway to the lymphatic system that safeguards the body from pathogenic bacteria or viruses.

Olfactory Role

The olfactory epithelium which keeps the olfactory receptors active and healthy is a delicate tissue layer. Constant humidification of this lamina is imperative for maintaining its delicacy, or else it will dry up and stop functioning. If the dryness persists far too long, then chronic anosmia or permanent loss of the sense of smell, results. It is the nasal turbinates that maintain the humidity of the olfactory epithelium at all times.

Does nasal turbinate check occurrence of the common cold?

One catches a common cold mainly during the winter season as the viruses responsible for the condition are more active. During the cold season, the majority of people stay indoors where poor or insufficient ventilation helps spread the viruses. Additionally, the relative humidity and reduced sunlight have a depressive effect which in turn impedes the smooth functioning of the immune system.

Nevertheless, a good proportion of the populace in cold climes does not catch a cold. The turbinate bones in these people stimulate the cilia to become hyperactive which filters off microbes in the inhaled air.

Clinical Significance

Inflammation and enlargement of turbinate bones, a condition called turbinate hypertrophy could cause the turbinates to dysfunction. Swelling leads to obstruction of airways whereby the affected individual experiences difficulty in breathing often accompanied by nosebleed. Nasal polyps, cold, allergies, flu, hormonal imbalances, and nasal septum deformity are possible causes of nasal concha hypertrophy.

Nasal Turbinates Dysfunction

Turbinate dysfunction occurs due to swelling which enlarges the bone causing nasal congestion and impairing the respiratory process. The intensity of the signs and symptom would depend on the severity of the syndrome. Nasal decongestants, steroids, and antihistamines can help deal with the disorder, but overuse of such medication might aggravate the condition. For diagnosing and treating turbinate hypertrophy, it is crucial to identify and understand the causative factors.

Incidences

The etiologies in more than 90% of the cases are attributable to infections and inflammations. It is worthwhile to note that almost everybody experiences the disorder to an extent at some stage in life. Nearly 50% of the populace suffers from chronic turbinate hypertrophy and dysfunction.

Symptoms

  • Nasal congestion
  • Discomfiture
  • Splitting headaches in the middle of the face
  • Facial pain
  • Rhinorrhea or a runny nose
  • Pressure in the nasal region, especially in the medial canthus (when the inflamed or bulged turbinates touches the lateral nasal wall)
  • Sporadic or irregular clogging of either side of the nasal passage

Positional Congestion (nasal blockage on airways)

A change in posture while sitting or lying in supine position decreases the nasal cross-sectional area available for breathing in individuals exhibiting rhinitis symptoms. Nasal obstruction intensifies and they may demonstrate symptoms of acute chronic rhinosinusitis when their medial turbinates bend. It badly affects the osteomeatal complex functioning and causes mucus accumulation.

Nasal polyps, deformed nasal septum, and viral infection are some common causes of the condition. It largely affects the middle-aged and young people but is not uncommon in children. It is a grave disorder where the sinuses stay inflamed for nothing less than 12 weeks even after the affected individual undergoes conventional treatment modes. A chronic rhinosinusitis patient displays the following symptoms:

  • Difficulty breathing
  • Experiences postnasal drainage
  • Facial pain
  • Earache
  • Nausea
  • Fatigue
  • Sore throat
  • Persistent coughs
  • Pain in the upper jaw (maxilla)

Surgical resection of the entire middle turbinate or a part of it (segmental resection or segmentectomy) might be necessary if all other treatment options fail. As there are many factors behind nasal turbinate hypertrophy, it is extremely necessary to establish the exact cause.

Causes

Allergens

Stimuli present in the environment called ‘irritants’ as well as allergens may cause soreness and hypertrophy of the turbinates. Certain drugs either imbibed in isolation or taken in combination (leading to drug interactions) could also hinder its functioning.

Deformed Nasal Septum

Sometimes, a deformed or deviated nasal septum is behind its bulginess, making it dysfunction. Blockade of the airways is the most prevalent symptom of nasal concha’s compromised functioning. Nevertheless, there are a host of other factors that might be responsible for its inflammation.

Dysfunction of PNS

The turbinates endowed with a large volume of blood vessels have a copious amount of blood circulating through them. At the same time, the parasympathetic nervous system plays a crucial role in maintaining the healthy functioning of turbinate bones. The PNS as part of the autonomic nervous system (ANS) helps maintain homeostasis inside the nasal airways.

The ANS supplies nerves to the submucosal membrane lining and the vascular system of the lower turbinates. The innervations enable the nasal turbinates to control major functions including maintenance of humidification and warmth, nasal secretions, and patency. So, it is obvious that if either the circulatory or the nervous system involved with them, somehow dysfunctions, then the discrepancy affects their normal functioning.

Disorders or infections hindering the operation of the ANS or Circulatory System
  • Vasomotor rhinitis: Vasomotor rhinitis is a non-allergenic form of nasal inflammation that could impede their functioning. The vasomotor neural axons regulate the contraction or dilation of blood vessels within the nasal membranes. Vasomotor rhinitis occurs when the nerve cells of the vasomotor nerves become inflamed. The main causes are disuse rhinitis, body temperature variations, erratic secretion of female hormones, and intake of cardiovascular and antihypertensive medications.
  • Allergic rhinitis: It is chiefly responsible for impairment or dysfunction of the nasal Environmental allergens and contaminants absorbed with the inhaled air lodge themselves on nasal membranes, inflaming the turbinates. Inflammation triggers an enhanced outflow of mucus through the nose (rhinorrhea), or it trickles down the throat. Persistent postnasal drip eventually causes congestion of the nose.
  • Disuse rhinitis: Disuse rhinitis mostly affects individuals who underwent laryngectomy or use nasal decongestants excessively. The infection could prevent or obstruct normal airflow within the nasal passages.
  • Condensation rhinitis: It is a condition where nasal membranes of skiers, snowboarders, and mountaineers physiologically respond to wintry environments which could also interfere with turbinate function.

Treatments

There are numerous treatment options and methods for dealing with turbinate hypertrophy. Carefully reviewing the patient’s medical history and conducting allergy assays usually comprise the first-line of medical therapy. There’s no gainsaying the fact accurate diagnosis is indispensable for recommending the relevant treatment option or mode.

Nasal and Oral Decongestants

Oral and topical nasal decongestants can be particularly effective in relieving and clearing turbinate concha congestion. Unless the physician so recommends, one should refrain from the extended use of topical sprays as doing so could cause rebound congestion.

It is better not to use topical sprays for more than 4-5 days at a stretch. Oral decongestants can also help in dealing with nasal congestion without any rebound effects even after prolonged use. Nevertheless, continued use of oral decongestants causes tolerance as airways blockage remains even after taking the medications. Doctors prescribe antihistamines, particularly for allergic rhinitis patients.

Antihistamines

When used in combination with phenylephrine and pseudoephedrine (oral decongestants), it offers relief from rhinorrhea and congestion. Overuse of some classes of antihistamines could cause drowsiness and inordinate dehydration as well as adversely affect cognitive functions. Antihistamines could also lead to drug interactions, particularly if taken together with sedatives, painkillers and muscle relaxants.

Nasal Steroids

Nasal steroids or intranasal corticosteroids, available chiefly as aerosols, come in perfectly handy for allergic rhinitis management. However, one has to continuously use steroid-based intranasal sprays for long to reap the medications’ beneficial effects. These steroids, apart from helping deal with allergic rhinitis symptoms also help check turbinate concha inflammation. Long-term use of intranasal corticosteroids has not been known to bring about drug intolerance.

Surgery

Surgical intervention is resorted to as a last resort when all conventional modes of treatment come to naught. Alternatively, surgery is the only option for individuals (diagnosed with turbinate hypertrophy) who’ve demonstrated contraindications to traditional medical management.

Methods
  • Turbinate reduction surgery:  Adopted very meticulously as total resection or removal of even a sizable section could hamper turbinate function. Excessive or complete reduction of inferior turbinate usually causes nasal dryness (known as ‘empty nose syndrome’) and crustiness. The otolaryngologist carries out a battery of diagnostic tests to establish whether the enlargement is mucosal or bony or both. Depending upon the nature or type of turbinate hypertrophy, the otolaryngology surgeon carries out cauterization, somnoplasty (bipolar radiofrequency reduction), partial resection or microdebrider resection surgery.
  • Submucosal Resection: The most commonly used surgical technique is ‘submucosal resection’ that leaves the mucosa intact which is crucial for maintaining respiration. Performing this type of surgery minimizes the occurrence and aggravation of atrophic rhinitis. Turbinate trimming is another effective surgical mode which facilitates accurate ablation of mucosa and bone.

Concha Bullosa

When any one of the three turbinate pairs fills up with an air pocket, the resulting condition is called concha bullosa. Ordinarily, turbinate pneumatization which affects nearly 50% of the populace does not impede respiration. But sometimes the bullosa or air-filled cavity could expand and obstruct the smooth airflow. There are some discomfiture and pain in the sinuses especially due to development of an air pocket within the medial turbinates. The level of discomfort or pain depends upon the size of the air-filled cavity, so the larger the pocket, the greater the discomfiture.

Signs & Symptoms 

Correctly diagnosing concha bullosa could be misleading as the symptoms of this disorder are somewhat similar to sinusitis. Nevertheless, concha bullosa does not cause any mucus drainage, otalgia or jaw pain. The usual symptoms associated with the syndrome include:

  • Sinusoidal pain or pressure along with pain around the ocular region
  • The feeling of obstruction within the nostrils
  • Difficulty in breathing

Sometimes, a large air pocket stimulates bulging of turbinate to the extent that hinders opening up of a juxtaposed sinus, ultimately causing chronic sinusitis.

Causes

Etiology of concha bullosa remains unclear. However, numerous researches and studies have established a close correlation between nasal septum deviation and concha bullosa. Deviation of the septum (to the left or right) obviously blocks one of the nasal passages, making it difficult to respire.

Diagnosis 

An imaging test or CT scan can easily help to confirm the presence of a turbinate air pocket or air-filled cavities. Even an MRI examination of the nose and the turbinate concha can reveal bullosa that more or less appear like dark circles. If the bullosa is asymptomatic and does not disrupt the individual’s lifestyle, medicines or surgery may not be essential.

Treatments

  • Turbinoplasty: Restructures the tissues and bones surrounding the concha bullosa to restore normal airflow.
  • Turbinate resection: Removes the bullosa entirely or partially.
  • Crushing: Compresses the air pocket forcing the air out of the cavity.

More often, a protruding turbinate or a divergent septum, the cause behind concha bullosa, is corrected via septoplasty.

References

  1. https://www.healthline.com/health/concha-bullosa#causes
  2. https://www.britannica.com/science/nasal-concha
  3. https://www.sinomarin.com/nose_1.htm
  4. https://www.myvmc.com/medical-centres/lungs-breathing/anatomy-and-physiology-of-the-nasal-cavity-inner-nose-and-mucosa/
  5. http://care.american-rhinologic.org/empty_nose_syndrome?print
  6. http://www.scielo.br/scielo.php?pid=S0034-72992005000400014&script=sci_arttext&tlng=en
  7. https://www.mayoclinic.org/diseases-conditions/chronic-sinusitis/symptoms-causes/syc-20351661
  8. https://open.bu.edu/bitstream/handle/2144/19467/Smith_bu_0017N_12309.pdf?sequence=1
  9. https://emedicine.medscape.com/article/877872-treatment
  10. http://care.american-rhinologic.org/septoplasty_turbinates

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