Aerosinusitis: Description, Causes and Risk Factors
Aerosinusitis is an inflammation of the mucous membrane of the paranasal sinuses caused by pressure difference within the sinus relative to ambient pressure, secondary to obstruction of the sinus ostium and occurring during descent in altitude.
Most cases occur in scuba divers and fliers and is easily diagnosed when presented to physicians immediately after exposure. On the other hand, the problem may remain undiagnosed when the history fails to relate the symptoms to exposure to environmental pressure changes or if the focus is on other etiologies.
Typically, aerosinusitis is preceded by an upper respiratory tract infection or allergy. The affected person suffers a sudden sharp facial pain or a headache during descent, which increases as the aircraft approaches ground level. The pain can ultimately become disabling unless the ambient pressure is reversed.
The pressure difference causes the mucosal lining of the sinuses to become swollen and submucosal bleeding follows with further difficulties ventilating the sinus, especially if the orifices are involved. Ultimately fluid or blood will fill the space.
The middle ear spaces and paranasal sinuses, two body cavities that communicate with ambient air, must compensate for rapid equilibration of air pressure during aviation and underwater activities such as self-contained underwater breathing apparatus diving. The pressure-volume relationship of air in enclosed body cavities is described by the Boyle's law, which states that the volume of a gas is inversely proportional to the pressure on it, when the temperature is constant. Inability to equilibrate from blocking of sinus ostia from preexisting inflammation or polyps may result in rapid changes in the pressure inside sinuses relative to the surrounding spaces such as cranial cavity. Aerosinusitis can occur during either ascent or descent. Although descent barotrauma or “squeeze” is more common by a ratio of at least 2:1, ascent barotrauma or “reverse squeeze” has more severe sequelae. Rapid ascent in diving or aviation leads to a buildup of positive pressures in the obstructed sinuses. Inability to rapidly equilibrate air pressures may lead to traumatic movement of air to adjacent cavities which offer the least resistance leading to injuries such as pneumocephalus, meningitis, and orbital emphysema.
The major identifiable preflight risk factors for civilian aerosinusitis include active upper respiratory infection and allergic rhinitis. In addition, a history of recurrent sinus barotrauma which is generally restricted to military aircrew, but conceivably exists in civilian patients with nasal polyps predisposes to aerosinusitis.
In most cases of aerosinusitis, localized pain to the frontal area is the predominant symptom. This is due to pain originating from the frontal sinus, it being above the brow bones. Less common is pain referred to the temporal, occipital, or retrobulbar region. Epistaxis or serosanguineous secretion from the nose may occur. Neurological symptoms may affect the adjacent fifth cranial nerve and especially the infraorbital nerve.
Weissman defined III grades of aerosinusitisaccording to symptomatology.
Grade I includes cases with mild transient sinus discomfort without changes visible on X-ray.
- Grade II is characterized by severe pain for up to 24 h, with some mucosal thickening on X-ray.
- Patients with grade III have severe pain lasting for more than 24 h and X-ray shows severe mucosal thickening or opacification of the affected sinus; epistaxis or subsequent sinusitis may be observed.
Radiologic assessment is usually necessary to establish the diagnosis but may help to indicate location and to search for underlying causes.
Plain films are useful to isolate location. The usual finding is mucosal edema, which can range from slight thickening to total opacification of one or more sinuses. There may be air-fluid (i.e., blood) levels. Hematoma formations, usually in the frontal sinus, are smooth and oval; they may be small or may nearly fill the sinus.
CT scans are considered the criterion standard for imaging assessment of aerosinusitis. Obtain coronal and axial views. CT scanning accurately defines involved sinuses, extent of any hematoma, and mucosal thickening. The study can suggest predisposing factors (e.g., septal deviation, middle meatus and turbinate abnormalities, nasal polyposis, underlying mass). CT scanning is an excellent tool for surgical planning.
MRI is similar to CT scanning in predicting involved sinuses, but it does not provide bony detail. MRI is better than CT scanning in differentiating paranasal sinus masses, although it is not as useful as CT scanning in surgical planning and can be more time consuming to obtain.
Other tests (e.g., ultrasound) are atypically used to aid in diagnosis or treatment. Transillumination of the sinuses may provide some additional information on location of barotrauma, but it is unreliable and does not change treatment.
Management of this condition is based on the Weissman stage. Stage I or II lesions are generally treated conservatively with a 1-week course of topical sprays, analgesics, a tapering course of steroids, and oral decongestants. Use of antibiotics is reserved for those cases initiated by bacterial sinusitis. Additionally, antihistamines are reserved for cases where allergies were the inciting cause. Stage III lesions are rarely seen in civilian air travelers due to the relatively low fluctuations in ambient air pressure. Air-crew that suffer Stage III aerosinusitis are at risk for recurrent sinus barotrauma that may require an expertly performed functional endoscopic sinus surgery to successfully manage it.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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