History of the Procedure
The sphenoid sinus has been described as the forgotten sinus or neglected sinus because of its anatomical location and the difficulty in diagnosing disease there. Diseases of the sphenoid often were determined only when complications arose. With the advent of modern imaging techniques and a higher index of suspicion, diseases of the sphenoid are much more easily found and treated. Modern imaging, antibiotic, and surgical options have changed the presentation and, often, the treatment of acute sphenoid sinusitis.
Problem
According to the American Academy of Otolaryngology—Head and Neck Surgery (AAO-HNS) task force on rhinosinusitis, sinusitis is defined as an inflammatory response involving mucous membranes of the nasal cavity and paranasal sinuses, fluids within these cavities, and/or bone. The condition is classified as acute if it persists for 4 weeks or fewer. In contrast, a subacute infection is defined as lasting 4-12 weeks, and a chronic infection persists for more than 12 weeks.
When this inflammatory response occurs in the sphenoid sinus, the result is sphenoid sinusitis or sphenoiditis. The disease may be limited to the sphenoid sinus or, more commonly, may involve multiple sinuses or pansinusitis.
Frequency
Sphenoid sinusitis often occurs in the context of pansinusitis. In the preantibiotic era, Teed reported an incidence of sphenoid involvement of 33% in patients with pansinusitis. A 1977 study by Wisberger and Dedo suggested that in the antibiotic era, incidence decreased to 8%. Isolated sphenoid sinusitis is much less common. Lew reported a 2.7% incidence in patients hospitalized for sinusitis in a 12-year period. Of these incidences, only one half had acute disease. Hnatuk et al suggest that the incidence is actually much lower, and that sphenoid sinusitis represents fewer than 1% of all cases of sinusitis.
Etiology
The microbiology of acute sphenoid sinusitis differs from that of uncomplicated maxillary sinusitis. Whereas maxillary sinusitis is caused predominantly by Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, sphenoid sinusitis has a different profile. Gram-positive organisms predominate, with Staphylococcus aureus most common, followed by Streptococcus pneumoniae. Chronic sphenoid sinusitis can be caused by both gram-negative and gram-positive organisms, anaerobes, and mixed flora, which are more common. Fungal disease also must be considered, especially in the context of a patient who is immunocompromised.
Pathophysiology
The pathophysiology of sphenoid sinusitis involves blockage of sinus ostia and impaired mucociliary clearance leading to stasis and secondary bacterial infection. Several predisposing factors have been implicated. Anatomic differences include variations in the position of the intersinus septum and small or abnormally placed ostia. Blunt, penetrating, or surgical trauma can alter drainage patterns as well as allow entry of pathogenic organisms. Swimming or diving with forceful water entry through the nose also has been implicated in causing disease. Immunosuppression due to long-term steroids, diabetes, or radiotherapy can predispose patients to this disease, as can obstruction of sinus ostia by polyps or tumor.
Clinical
Patients with acute sphenoid sinusitis often present with vague nonlocalizing symptoms. Headache is the most common symptom; almost all patients in various studies complain of headache. Although the vertex headache is classic, the pain also can be retroorbital, parietooccipital, or frontal. In general, the headache is described as severe, interfering with sleep, and not relieved by narcotics. Fever and purulent rhinorrhea often are noted, and hypoesthesia of the trigeminal nerve may be present in select cases. Neurologic and ophthalmologic findings suggest impending complications. Decreased mental status, lethargy, and seizures point to intracranial extension or meningitis. Ophthalmologic findings may include abducens nerve palsy or hypoesthesia of V1 and/or V2. Chemosis, proptosis, ptosis, diplopia, or decreased visual acuity and ophthalmoplegia may be noted.
Maintain a high index of suspicion for sphenoid sinusitis. A review by Hnatuk et al reported that 78% of cases of sphenoid sinusitis were initially misdiagnosed. Evaluate patients with severe progressive headache, with or without fever, for sphenoid sinusitis. Thoroughly investigate signs of orbital or neurologic complications.
Disease in the sphenoid sinus is not always inflammatory in nature. Consider a broad differential diagnosis in a patient with clinical suggestion of sphenoid disease and imaging studies consistent with sphenoid opacification. Isolated sphenoid lesions, for example, merit special consideration. In his review of 132 cases of isolated sphenoid disease, Lawson found that, while inflammatory disease predominates, neoplasms, fibroosseous disease, and other entities were significant.
In addition to acute and chronic sinusitis, inflammatory diseases included mucoceles, polyps, retention cysts, and fungal disease. Neoplasms included benign tumors, such as inverting papilloma, myxofibroma, plasmocytoma, and schwannoma. Salivary gland malignancies, such as adenoid cystic carcinoma and epidermoid carcinoma, were present, as well as malignancies including squamous cell, melanoma, and hemangiopericytoma.
Extension from adjacent sites, such as the nasopharynx and pituitary, was noted, as was metastatic disease from the prostate, kidney, and tonsil. Several cases of fibrous dysplasia and ossifying fibroma were observed.
Miscellaneous entities including foreign bodies, encephaloceles, and even an internal carotid aneurysm were also included. In general, although many clinical cases of sphenoid disease may be inflammatory in nature, consider other entities.