Sinusitis, also referred to as rhinosinusitis, is defined as the symptomatic inflammation of paranasal sinuses and nasal cavity mucosa. This inflammation can be from a multitude of sources including viruses, bacteria, fungi, and allergens. Criteria for the diagnosis of rhinosinusitis was most recently established in 1997 by the Rhinosinusitis Task Force and broke symptomatology into both major and minor criteria, with a diagnosis requiring either two major factors or one major plus two minor factors:
- Purulence on Nasal Examination
- Nasal Obstruction/Blockage
- Nasal Discharge/purulence/discolored posterior drainage
- Facial Pain/Pressure
- Facial Congestion/Fullness
- Ear pain/pressure/fullness
- Dental Pain
This was further classified by the duration of symptoms into acute, recurrent acute, subacute, and chronic rhinosinusitis. Acute rhinosinusitis lasts less than 4 weeks compared with subacute, which lasts between 4 to 12 weeks, and chronic which lasts longer than 12 weeks. Recurrent acute rhinosinusitis (RARS) is diagnosed when patients have 4 or more episodes of acute rhinosinusitis per year, lasting at least 7-10 days, without persistent symptoms in between these distinct episodes. This article will focus mostly on RARS specifically and include information on patient presentation, diagnosis, and intervention. 
The most common etiologies for RARS mirrors the other subtypes of sinusitis. Viral upper respiratory tract infections are the most common source of sinusitis but otherwise tend to be self-limiting. With viral inoculation, the mucosa of the nasal cavity and paranasal sinus become irritated and inflamed, which reduces the size of sinus ostia (sinus opening) and obstruct clearance of nasal flora, mucus, and inhaled particles. With this inflammation come alterations in the frequency of ciliary movement as well as mucous stasis, which predisposes the sinuses to bacterial infection. The most common bacterial pathogens are Streptococcus pneumoniae, Haemophilus influenzae, other Streptococcus species, Moraxella catarrhalis, or Staphylococcus aureus. Methicillin-resistant Staphylococcus aureus (MRSA) can also be found in the nares, which can lead to recurrent sinusitis, especially in patients already receiving multiple antibiotic courses.
There also tends to be some etiological overlap between RARS and chronic rhinosinusitis. Non-invasive fungal pathogens like Aspergillus fumigatus can be seen in these patients. Anatomic obstructive abnormalities including turbinate hypertrophy, conchae bullosa, stenosed sinus ostia, Haller cells, nasal polyposis, nasal masses, and septal spurs/deviation, can also predispose the nasal cavity and sinuses to infection. These lend themselves to correction with endoscopic surgical techniques. Other genetic factors that affect nasociliary motion or mucous production have been postulated to play a role in patients suffering from this disease. Environmental factors such as tobacco smoke, chronically inhaled irritants, or nasal packing have also been evaluated.
Sinusitis is one of the most common causes for seeking medical attention. As of 2015, 30 million cases were diagnosed in the United States alone. Among all antibiotics prescribed for any disease, one-fifth of them are used in the treatment of sinusitis. The direct cost of treatment of sinusitis is more than $11 billion in the United States, with $3 billion spent on acute and $8.3 billion spent on chronic sinusitis. In 2012, almost 1 in 8 adults were diagnosed with rhinosinusitis within the prior 12 months.
In regards to RARS, one study, which reviewed a medical claims database of 13.1 million people, noted the prevalence of RARS as 0.035% from 2003-2008, equivalent to 4588 patients. This population was mostly female (72.1%) with a mean age of 43.5 years old. Between medication costs and provider visits, the yearly cost burden to these patients was approximately $1091. Patients' annual average number of health care visits was 5.6 and the average yearly prescriptions filled was 9.4. 
The pathogenesis of rhinosinusitis is a result of the dysfunction of sinus ostia, the ciliary apparatus, and viscous sinus secretions. Viral upper respiratory infection or allergens can result in mucosal edema, which narrows the sinus ostia causing a direct mechanical obstruction. When there is an obstruction of the sinus ostium, there is a transient increase in pressure within the sinus cavity. As air is depleted in this small space, the pressure in the sinus becomes negative relative to atmospheric air pressure. This negative pressure allows nasal bacteria into the sinuses with normal physiologic maneuvers (sniffing or nose blowing). When the sinus ostium is obstructed, secretion of mucous by mucosa continues, resulting in fluid accumulation in the sinus. During mucosal inflammation of nasal ostia and mucosal membranes, both the structure and the function of the mucociliary apparatus are impaired. The quality and characteristics of sinus secretions also determine the pathogenesis of sinusitis. Cilia can beat only in a fluid. The mucous blanket in the respiratory tract is made up of two layers. The periciliary liquid phase is a thin, low-viscosity layer that surrounds the shaft of the cilia and allows the cilia to beat freely. The gel phase is a more viscous layer and rides on top of the periciliary liquid. Alterations in the mucous layer, which occur in the presence of inflammatory debris, as in an inflamed sinus, may further impair ciliary movement. Similarly, mucociliary dysfunction may occur due to frequent irrigation of the nasal cavity.
History and Physical
Patients will generally present with less than 4 weeks of a variety of complaints. These can include anterior or posterior nasal purulence, obstruction, hyposmia, anosmia, fever, facial pain or pressure, dental pain, fatigue, halitosis, and headache among other complaints. In accordance with the definition of RARS they will have at least 4 of these episodes within the last year, and likely will have undergone multiple treatment regimens with nasal sprays, steroids, and/or antibiotics.
On physical exam, an otolaryngologist could note anterior or posterior purulent rhinorrhea, turbinate hypertrophy, mucosal congestion or erythema on anterior rhinoscopy. There may be external tenderness to palpation of the frontal, ethmoid, or maxillary sinuses. The patient may be febrile or even tachycardic due to generalized facial pain. Orbital complications ranging from preseptal cellulitis to cavernous sinus thrombosis can be seen in these patients so cranial nerve testing, as well as inspection of the orbit, is also necessary.
Patients suffering from RARS tend to note similar symptoms to acute sinusitis. In an acute episode of sinusitis, viral sinusitis should be presumed if the patient reports persistent symptoms for less than 10 days. Acute bacterial rhinosinusitis is presumed when the symptoms last more than 10 days or worsen within 2 days after initial improvement, also known as double sickening. Despite the nature of viral or bacterial pathogens, most of the acute sinusitis resolve within 10 to 14 days.
History and physical examination are key to making a diagnosis of recurrent acute rhinosinusitis. Using the major and minor diagnostic criteria set forth by the American Academy of Otolaryngology-Head and Neck Surgery, as well as the timing of symptoms, a physician is able to make the proper diagnosis of RARS.
Nasal endoscopy is recommended if there is suspicion of resistant bacterial infection, allergic fungal sinusitis, nasal polyposis, or nasal masses. After initial diagnosis of RARS, nasal endoscopy has been performed in 2.4% of patients within 1 year and 9.2% within 3 years.
Radiological imaging, either x-rays, computed tomography (CT), or magnetic resonance imaging (MRI) are not recommended to make the diagnosis of uncomplicated recurrent acute sinusitis. A non-contrast CT scan of sinuses is generally only indicated in cases of chronic rhinosinusitis, suspicion of orbital complications, suspected anatomic abnormalities, or in presurgical planning for either balloon sinuplasty or functional endoscopic sinus surgery (FESS). Unfortunately, it has been noted that 11.4% of patients with uncomplciated RARS have had a CT scan within 1 year of diagnosis and 39.9% of patients within 4 years.
In cases of persistent or chronic sinusitis, cultures obtained from sinus aspirates or endoscopy may be needed to identify any resistant bacterial or fungal pathogen. The most frequent pathogens involved in recurrent acute rhinosinusitis are similar to that of acute sinusitis: Streptococcus pneumoniae, Haemophilus influenzae, other Streptococcus species, Moraxella catarrhalis, or Staphylococcus aureus. 
- Allergic Rhinosinusitis
- Acute Rhinosinusitis
- Chronic Rhinosinusitis with Nasal Polyposis (CRSwNP)
- Chronic Rhinosinusitis without Nasal Polyposis (CRSsNP)
- Subacute Rhinosinusitis
- Viral Rhinosinusitis
- Cerebrospinal fluid (CSF) Rhinorrhea
- Non-Invasive Fungal Rhinosinusitis
- Invasive Fungal Rhinosinusitis
Recurrent acute rhinosinusitis has an overall positive prognosis. Patients typically improve with medical management and more specifically topical nasal sprays and oral antibiotics. Of the subset of patients requiring surgical intervention, the procedures themselves can be minimally invasive or done in the office or in an outpatient setting. Rarely, patients will require a hospital stay for closer monitoring with intravenous antibiotics (IV) and or surgical intervention for orbital complications.
Although rare, notable complications can include but are not limited to the following: 
- Preseptal Cellulitis
- Orbital Cellulitis
- Subperiosteal Abscess
- Orbital Abscess
- Cavernous Sinus Thrombosis
Ophthalmology may be needed for further evaluation of orbital complicaitons.
Deterrence and Patient Education
Patients need to be educated on the proper diagnostic criteria and timeframe of their symptoms. Providing them with information can allow for earlier recognition of RARS versus other causes like viral rhinosinusitis and prevent the overuse of antibiotics and the high costs of medical or even surgical management. Discussion of proper medication dosing, as well as awareness of allergies or side effects, is crucial to provide better outcomes for patients.
Pearls and Other Issues
Points to remember:
- Recurrent sinusitis is a clinical diagnosis defined by 4 or more episodes of symptoms of sinusitis per year without any symptoms in between.
- Diagnostic imaging is not recommended for uncomplicated acute recurrent sinusitis, but a non-contrast CT scan showing anatomical obstruction could be useful in the diagnosis of recurrent acute sinusitis.
- Symptomatic treatment with a trial of decongestant nasal spray, daily intranasal irrigation, and/or corticosteroid nasal spray is the mainstay of treatment for the first ten days of symptoms.
- A variety of antibiotics are the choice of treatment for suspected bacterial sinusitis, based on local antibiograms, patient risk factors, allergies, and co-morbidities. Consider nasal bacterial drug resistance in refractory cases.
- While medical therapy has been the recommended treatment, many studies have shown that surgical intervention for recurrent acute sinusitis has similar positive effects as experienced in the surgical treatment of chronic rhinosinusitis. Specifically, in cases of proven turbinate hypertrophy, conchae bullosa, stenosed sinus ostia, frontal sinus cells, Onodi cells, Haller cells, and septal spurs. These lend themselves to correction with endoscopic surgical techniques.
- With the introduction of balloon sinus dilation, another method of treating recurrent acute sinusitis has emerged. This minimally invasive, endoscopic approach is a useful tool in the arsenal of otolaryngologists that has shown efficacy in these patients, although further FDA approval is pending.
- Orbital complications have been reported in the literature ranging from preseptal cellulitis to cavernous sinus thrombosis. Physicians must be on the lookout for orbital involvement or cranial nerve deficits and provide immediate treatment to these patients.
Enhancing Healthcare Team Outcomes
Recurrent sinusitis is best managed by an interprofessional team that can include a general otolaryngologist, a rhinologist, a pharmacist or any other midlevel providers. There is no one treatment that works in all patients as responses to treatments do vary. Physicians are necessary to make the proper diagnosis and prescribe the most optimal treatment. Pharmacists are necessary to provide proper dosing based on patient background and comorbidities. Nurses are critical to improving communication with the patient and physician. Finally, the operating room staff would be critical if these patients require surgery. However, this is a chronic condition that can lead to poor quality of life.