Sinusitis

Topic Highlights

●    Sinusitis is an inflammation of the paranasal sinuses caused by infections, bacterial, viral, fungal, or by allergens.

●    This visual presentation is a concise study of the anatomy of sinuses, causes of sinusitis, symptoms, risk factors, diagnosis, and treatment for sinusitis.

Transcript

Sinusitis, an inflammation of the paranasal sinuses, is a common cause of morbidity affecting mainly adults. It is caused by viral, bacterial or fungal infections or by allergens. While acute sinusitis can resolve with self-care and appropriate medications, in certain cases, particularly those with chronic sinusitis that remains unresolved despite medical treatment, surgical interventions may be the only recourse.

Sinusitis is the inflammation of mucous membranes of the paranasal sinuses that occurs due to various conditions that cause ostial obstructions or changes in the mucociliary transport mechanism.

Clinically, the condition may be classified as acute, subacute or chronic. Allergic reactions or viral, bacterial or fungal infections of the upper respiratory tract can result in sinusitis. Acute stages of the disease are mostly caused by viral or bacterial infections. The most common bacteria involved in the condition are streptococci, staphylococci, pneumococci and Haemophilus influenzae and the condition is usually preceded by an upper respiratory tract viral infection.

Chronic sinusitis is associated with Gram negative and anaerobic bacteria. It may also be secondary to dental infections. About 14% of adults or nearly 37 million people suffer from sinusitis in the United States where it is among the top 10 causes of morbidity. Approximately 200,000 patients undergo surgery because of non-resolving chronic sinusitis that persists despite medication. Lower socioeconomic status, smoking, allergies and asthma are the most common predisposing factors of the condition.

The condition is usually caused either by viral, bacterial or fungal infections or as a result of allergic reactions. It is usually preceded by an upper respiratory tract viral infection. It is also a common occurrence in immunocompromised patients as a result of opportunistic infections. The common viruses that are responsible for the condition include rhinovirus, coronavirus, respiratory syncytial virus and influenza. Bacteria that are associated with the disease include streptococci, staphylococci and pneumococci. Fungal infections include aspergillosis or candidiasis.

Nosocomial sinusitis occurs in critically ill patients especially those requiring nasal intubation. This type of sinusitis is usually bacterial, and is commonly due to staphylococci, Pseudomonas, Klebsiella or enterobacter species.

Allergic rhinitis may be caused by exposure to environmental factors such as pollen, dust mites or molds. Allergic rhinitis may be a predisposing factor to chronic or recurrent sinusitis because of changes in the mucociliary mechanism, reduction in the mucus drainage or congestion in the sinus tracts due to mucus.

Chronic sinusitis refers to symptoms that persist for three months or more, or to sinusitis that responds to therapy and then recurs periodically. Chronic sinusitis is associated with non typeable H. influenzae along with staphylococci, gram-negative bacteria and anaerobes and is more likely to be polymicrobial.

Paranasal sinuses comprise four paired cavities designated frontal, sphenoidal, maxillary, and ethmoidal sinuses. These sinuses are located in the bones of the face and lined by a mucous membrane continuous with that of the nasal cavity. The function of the paranasal sinuses is to reduce the bony mass and weight of the skull and participate in warming and humidification of inspired air.

The maxillary sinus is a pyramid shaped structure with the nasal wall at the base and the peak pointing toward the zygomatic process. The walls of the sinus are exceedingly thin. The nasal, orbital, anterior, and infratemporal surfaces of the body of the maxillary bone form the boundaries of the sinus. The maxillary sinus communicates with the nasal cavity through a large, irregular aperture present in the base. The posterior wall of the sinus consists of the alveolar canals that transmit the posterior superior alveolar vessels and nerves to the molar teeth. The floor is formed by the alveolar process of the maxilla and may have several projections that correspond to the roots of the first and second molar teeth. Infraorbital, lateral branches of the sphenopalatine, greater palatine, and the alveolar arteries supply this sinus.

Frontal air sinuses are two irregular cavities present in front of the ethmoidal notch, on either side of the frontal spine. They extend backward, upward, and laterally for a variable distance between the two tables of the skull and are separated from one another by a thin bony septum. Each of the sinuses communicates with the corresponding nasal cavity by means of a passage called the frontonasal duct. The frontal sinus is supplied by the ophthalmic artery.

Sphenoidal air sinuses are large, irregular cavities hollowed out of the interior of the body of the sphenoid bone, and are separated from each other by a bony septum. They vary considerably in form and size and are often partially subdivided by irregular bony laminae. A round opening is present at the upper part of each sinus by which it communicates with the upper and back part of the nasal cavity and occasionally with the posterior ethmoidal air cells. The posterior ethmoid artery supplies the roof of the sphenoid sinus while the rest of the sinus is supplied by the sphenopalatine artery.

The ethmoidal cells that form the ethmoidal sinuses are a number of thin-walled cellular cavities arranged in three groups, anterior, middle, and posterior. These cells are interposed between a lateral plate that forms a part of the orbit and a medial plate, which is a part of the corresponding nasal cavity. The ethmoidal cells are closed, except where they open into the nasal cavity. The ethmoid sinuses are supplied by the branches originating from both the external and internal carotid arteries.

When individuals have upper respiratory tract virus infections, there is swelling of the nasal mucous membrane. This obstructs the ostium of the paranasal sinus and reversible sinus cavity and abnormalities occur. The infundibulum gets occluded and the osteomeatal complex gets congested. This is worsened by a highly viscous exudate derived from mucous membrane glands rich in Goblet cells.

The oxygen in the sinus gets absorbed into the blood vessels of the mucous membranes, which results in development of a negative pressure within the sinus. As a result, a transudate accumulates in the sinus and acts as a medium for bacteria. This in turn stimulates the formation of an intense inflammatory exudate causing positive pressure to develop in the obstructed sinus. The mucous membrane becomes hyperemic and edematous. In some cases, bleeding and clot formation increase the viscosity of the sinus cavity exudates. The mucociliary apparatus within the sinus fails to transport the exudate to the ostium. This failure plays an important role in development of acute sinusitis.

Many characteristic histopathologic changes are seen within the lamina propria including oedema, infiltration of neutrophils, an increase in the number of lymphocytes and plasma cells, microabscesses and in some cases, thrombosed blood vessels and necrotic foci.

Most of the signs and symptoms resemble those of a common cold. The common symptoms seen are nasal discharge, sneezing, nasal obstruction, facial pressure, tenderness and swelling over the affected sinus and headache. The patient may also experience cough, generalized malaise, fever and chills. Hyposmia may sometimes be present. When the sinusitis complicates a dental infection, tooth pain and halitosis may also occur.

In maxillary sinusitis, the pain is over the maxillary sinus area along with headache and toothache (if etiology is of molar origin). With frontal sinusitis, the pain is in the frontal area along with frontal headache. In cases of severe frontal sinusitis there may be accumulation of pus below the periosteum of the frontal bone, which causes inflammation and edema of the forehead and is referred to as Pott's puffy tumor.

In ethmoidal sinusitis, the pain is localized behind and between the eyes along with a splitting frontal headache. When the sphenoidal sinus is involved, severe frontal, temporal or retro-orbital headache occurs, radiating to the occipital region. The nasal mucous membrane is inflamed and turgid. The nasal discharge is colored and often purulent. Seropurulent or mucopurulent exudates may be found in the middle meatus in maxillary, anterior ethmoidal and frontal sinusitis and in the area medial to the middle turbinate with posterior or sphenoidal sinusitis.

The diagnosis of sinusitis is made on the basis of medical history, physical examination and certain diagnostic tests. In general, the diagnosis of both acute bacterial and chronic sinusitis is made on the basis of clinical criteria. A detailed history has to be obtained and features such as facial pain/pressure, nasal obstruction/blockage, nasal discharge/purulence, headache and fever should be looked for.

Information should be obtained about coryzal and influenzal illnesses, respiratory allergies, toothache, and other dental complaints. Physical examination should include examination of the pharynx, nose, ears, sinuses, teeth, and chest. The majority of viral colds improve within seven days of onset. Previous or current toothache and other dental complaints are important features of the history as dental infection as a cause of sinusitis may go undiagnosed.

Taking a culture of the sinus aspirate or purulent discharge is the best way to distinguish from viral-bacterial or bacterial infections. Other tests such as white blood cell and differential counts are not useful because of lack of sensitivity and specificity. Sinus imaging is generally reserved for cases of unusual severity or those with suspected CNS or orbital extension.

Plain sinus radiograph is advised in many clinics and hospitals; however CT scanning has surpassed conventional radiography as the imaging method of choice because of its superior sensitivity. MRI is usually preferred in patients with suspected intracranial extension of infection including epidural abscess or cavernous sinus thrombosis. Dental X-ray may be advised to check for tooth abscesses in case of patients who complain of concomitant dental pain.

The therapy of sinusitis involves administration of medications in acute cases and surgical remedies in chronic cases. Adjuvants that include saline irrigations or steam inhalations, topical and systemic decongestants, topical and systemic steroids, and mucoevacuants are also advised in appropriate cases along with medications. Medical treatment in general, is intended to restore normal mucociliary function and drainage, eradicate bacteria, and provide analgesia.

If antibiotics are used, the choice is based on the expected pathogens and a 7-10 day course of amoxicillin is appropriate in uncomplicated, nonrecurrent cases of acute sinusitis. Broader-spectrum antibiotics which include the newer macrolides, quinolones, augmented penicillins, and cephalosporins are preferred in cases of recurrence or if the severity of the infection increases.

In refractory cases the type of antibiotic to be chosen depends on the sensitivity tests. Chronic cases may require administration of topical and systemic steroids. The steroids may improve drainage in cases of chronic sinusitis by decreasing mucosal edema. Patients with recurrent episodes of inflammation despite medical treatment and with CT scan evidence of persistent disease should be considered for surgical drainage.

Modern endoscopic surgery is often advised in such patients to correct abnormalities such as severe septal deviation, Haller cells, or concha bullosa and to widen sinus drainage sites. This process can also effectively be used to remove obstructive polyps and hypertrophied mucosa. Although endoscopic surgery does not offer a cure for the disease, it significantly improves the symptoms and quality of life.

Short-term courses of antimicrobials during periods of unusually severe exacerbation combined with daily nasal irrigations and removal of crusts when necessary may be advised in recurrent cases.