What is fungal sinusitis?
Fungal sinusitis is either an infection by fungi or an allergic reaction to fungi in the paranasal sinuses. Overall infectious fungal sinusitis is uncommon in the general population and is more likely to occur in people with weakened immune systems. An allergic reaction to the presence of the fungi in the paranasal sinuses are more common and is believed to be a significant cause of chronic rhinosinusitis (nose and sinus inflammation).
Types of Fungal Sinusitis
Fungal sinusitis can be divided into two types – invasive and non-invasive. Each type may have different subtypes.
The invasive types is where the fungi invade the tissue lining the paranasal sinuses. It is essentially a fungal infection. Fungi usually do not invade living tissue within the body as the immune defenses quickly eradicate these pathogens. However, in a person with a compromised immune system, fungi are able to establish itself within the sinus cavity and invade the tissue thereby leading to inflammation. Some fungi may cause acute, chronic or granulomatous infections. The acute infections are particularly dangerous as the fungi can spread throughout to the brain and lead to death.
The non-invasive forms of fungal sinusitis are where the fungi are present within the sinus cavity but do not infect it. Instead the fungi grow within the cavity and may elicit an allergic reaction due to its presence or irritate the sinus lining and block the cavity without infecting it. Polyps may also form. These reactions tend to cause profuse mucus discharge and combined with the action of the fungus, the discharge may be thick and profuse. A combination of a mucus plug, polyps and the fungal components can cause an obstruction of the sinus outlets. Most patients with non-invasive fungal sinusitis are not immune compromised (immunocomputent).
Non-Invasive Fungal Sinusitis
An allergic reaction to the presence of fungi within the paranasal sinuses (allergic fungal sinusitis) is more common than invasive types in the general population. These patients usually have a healthy immune system in that it is able to defend the body against invasion by microorganisms. However, patients who tend to suffer with allergic fungal sinusitis may have a history of allergic disorders like allergic asthma .
There may be excessive mucus discharge and prolonged inflammation can lead to polyp formation. Both the mucus collection and polyp can obstruct the sinus as well increase the pressure within the sinus. The raised pressure can cause erosion of the skull bone that forms the sinus walls. In this way the fungi may enter the orbit (bone housing the eyeball) or cranial cavity (where the brain is housed).
Another type of non-invasive fungal sinusitis that does not cause an infection, nor trigger an allergic reaction, is a sinus mycetoma. These fungi form “fungal balls” in the sinus, and tend to occur only on one side (unilateral) of the maxillary sinuses. Despite causing significant discomfort in the affected sinus, mycetoma fungal sinusitis does not usually trigger significant inflammation within the affected sinus.
Invasive Fungal Sinusitis
In this type of invasive fungal sinusitis, the infection spreads rapidly. The fungi invade and destroys the sinus lining and even the bony walls of the sinus cavity. By eroding the bony wall or entering local blood vessels and traveling through the bloodstream, the fungi can reach the central nervous system (CNS). This is referred to as acute fulminant sinusitis and can cause death. Overall acute fulminant sinusitis is rare except in patients who are immunocompromised – those patient living with AIDS or diabetics with prolonged poorly controlled diabetes mellitus.
In chronic invasive fungal sinusitis, the infection occurs over long periods of time and is usually not as severe as acute fulminant cases. These chronic cases are more frequently seen in diabetic patients and it is a slowly progressing infection.
This is a rarely seen form of invasive fungal sinusitis. Here the body attempts to wall off the infection leading to the collection of immune cells in a mass known as a granuloma.
Signs and Symptoms
Although the signs and symptoms of fungal sinusitis may vary among the different types, there are several common symptoms of all types of fungal sinusitis.
- Congestion of the nasal passages.
- Nasal discharge, sometimes bloody.
- Sinus pressure.
- Tenderness over the congested sinus.
More specific symptoms that may depend on the type of fungal sinusitis includes :
- Thick, sticky and granular nasal discharge (green to brown in color) – allergic fungal sinusitis.
- Yellow to brown ‘creamy’ discharge with granules – sinus mycetoma.
- Fever – acute invasive fungal sinusitis.
- Changes in mental status – acute fungal sinusitis.
- Ulceration on the nasal septum, turbinate bones and sometimes even the palate – acute invasive fungal sinusitis.
- Eye and eyelid symptoms with or without visual disturbances – allergic fungal sinusitis, acute and chronic invasive sinusitis.
Causes of Fungal Sinusitis
Different fungal species may be responsible for each type of fungal sinusitis. These fungi gain entry into the paranasal sinuses through the nasal cavity. The Aspergillus and Mucor species are by far the most common in fungal sinusitis.
- Allergic fungal sinusitis
– Aspergillus fumigatus
– Bipolaris species
– Curvularia lunata
– Drechslera species
- Mycetoma fungal sinusitis
– Aspergillus fumigatus
– Dematiaceous fungi
- Acute invasive fungal sinusitis
– Absidia species
– Apophysomyces species
– Cunninghamella species
– Mortierella species
– Mucor species
– Rhizopus species
– Rhizomucor species
– Saksenaea species
- Chronic invasive fungal sinusitis
– Aspergillus fumigatus
- Granulomatous fungal sinusitis
– Aspergillus flavus
Tests and Diagnosis
Specific types of antibodies (IgE) formed against the fungi may be detectable in the bloodstream. Other blood tests may indicate an infection in invasive fungal sinusitis. Imaging studies like a computed tomography (CT) scan and magnetic resonance imaging (MRI) are also useful diagnostic tools for fungal sinusitis, and for evaluating the spread to the orbit and central nervous system. Fungal cultures are conclusive ways of diagnosing the exact species responsible.
Surgery is preferred for the treatment of all types of fungal sinusitis. Corticosteroids may be used for non-invasive types and in particular allergic fungal sinusitis. This reduces inflammation and should be commenced after surgery if necessary. Antifungal drugs are only of use in invasive fungal sinusitis and surgery is still necessary. The preferred antifungals for acute or chronic invasive fungal sinusitis include :
- Amphotericin B
Surgery is indicated for all types of fungal sinusitis. Endoscopic surgery is preferred these days. Surgical debridement involves the removal of dead tissue and fungal material in the sinus cavity. Mucus plugs and polyps that may form in allergic fungal sinusitis also need to be removed. Following clearing of the sinus cavity and dead tissue in invasive fungal sinusitis, the surgeon ensures that the sinuses can drain effectively and be well ventilated. Surgery is effective and carries little risk, especially if the bony sinus walls are intact. Complications are more likely in acute invasive fungal sinusitis, particularly when the bony walls of the sinus have been compromised.
Recurrences is uncommon is complete removal of allergic mucin (allergic fungal sinusitis), complete debridement of necrotic tissue (invasive fungal sinusitis) and removal of fungal material. Antifungal drugs commenced after surgery in invasive fungal sinusitis ensures that the fungal infection does not recur in the short term thereafter. Overall, recurrence is uncommon.