Case 3

The most common causes of sinusitis are the same as for otitis media: 

• Streptococcus pneumoniae (40%)
• Hemophilus influenzae (30%)
• Moraxella catarrhalis (15%). 

Staphylococcus aureus and anaerobes are seen in chronic sinusitis and are often the pathogens seen in intracranial extension of infection. 

Since Hemophilus influenzae causing sinusitis is nontypable (does not react with available capsular antisera), the vaccine for Hemophilus influenzae type b now routinely given to children has had no impact upon the prevalence of sinusitis.

2. How are these organisms acquired by the host? 

•  These organisms colonize the upper respiratory tract, and may create an infection in the normally sterile sinus cavities when normal host mechanisms to prevent sinus infection are disrupted (see Pathogenesis ).
  
  

3. What is known about the pathogenesis of the infection? Describe the anatomy of the sinuses. Sinusitis in which sinus most often spreads to the orbit? Why is maxillary sinusitis so common? 

• Three factors are important in the normal functioning of the sinuses, to keep these cavities sterile: the ostia (through which the sinus drains into the nose) must be patent, the cilia must be functioning properly, and the secretions of the mucosa must be thin and not very copious. 
• An upper respiratory infection or a allergy may alter all of these factors: ostia may become occluded by mucosal inflammation and swelling, cilia may not function properly in the presence of inflamed mucosal tissue, and the secretions may become thick and copious, overpowering the ability of the cilia to direct the secretions toward the ostia and into the nose.
• It has been estimated that 5- 10 % of upper respiratory infections in early childhood are complicated by acute sinusitis. 
• Since children average 6-8 colds per year, sinusitis is a very common problem in pediatrics. 
• Adults also get sinus infections, with risk factors being allergy, cystic fibrosis, immunodeficiency disease anatomical problem, or ciliary dysfunction.

An understanding of the anatomy of the sinuses clarifies several important points:

• 1) Ethmoid and maxillary sinuses are formed in utero and are present at birth.
• 2) Frontal sinuses are not present until age 5-6 years.
• 3) The ostia or outflow tract of the maxillary sinus is high on its medial wall; this positioning creates a situation where drainage is against gravity-this explains part of the reason why maxillary sinuses are so commonly infected.
• 4) The ethmoid sinus is separated from the orbit by the paper-thin, fenestrated lamina paprycea bone. It is very easy for pus to get from the ethmoid sinus into the orbit. Therefore, sinusitis in the ethmoid is most likely to lead to orbital cellulitis and abscess.

4. How could the physician determine which bacterial agent is present in the sinus? 

• Nasal cultures are of no use in determining the bacterial agent because of the large number of bacteria which colonize the nose. 
• Sinus aspiration is occasionally performed, but generally therapy is aimed at covering the most likely pathogens, similar to otitis media.
•  Immunocompromised patients may require a diagnostic procedure, as they may develop sinusitis with a variety of unusual organisms including fungi.
  
  

5. What antimicrobial agents are effective for the treatment of acute sinusitis? Is there a drug of choice? 

•  Since the pathogens of acute otitis media and sinusitis are similar, the antimicrobial agent used are also similar. 
• Amoxicillin remains the drug of choice for uncomplicated sinusitis. Immediate use of a second-line agent (intravenously, in the hospital) would be appropriate if complications of sinusitis (eg orbital disease) are present.
  
  

6. What are the complications and long-term consequences of the infection?

•  The most common complication of sinusitis is orbital extension, usually from the ethmoid but occasionally from the frontal sinus. Intracranial extension of infection may occur and is manifested by subdural or epidural abscess, or brain abscess.