Ethmoid sinusitis is a term describing infection of the ethmoid sinus and is one of the variants of sinusitis. Having in mind its anatomical location, eye-related symptoms such as retroorbital pain and swelling are used as a distinguishing feature. The diagnosis is made primarily on clinical grounds supported by imaging studies, mainly in the form of computed tomography.
After the maxillary sinus, the ethmoid sinus is most commonly affected by infectious pathogens (including bacteria but also viruses and fungi), but it is not uncommon for more than one sinus to be involved  . The ethmoid sinus lines the medial wall of the orbit and drains into the middle nasal meatus, which is why typical features of sinusitis - nasal obstruction, rhinorrhea (either serous or purulent), malaise and fever in more severe cases - are often present in patients suffering from ethmoid sinusitis  . In many individuals, a preexisting infection of the upper respiratory tract is frequently reported, with symptoms of cough, a sore throat, rhinorrhea and a posterior pharyngeal drip . Having in mind the anatomical proximity of the ethmoid sinus to the eye apparatus, the distinguishing feature of this condition is the concomitant presence of pain between the orbits (or behind the eyes), as well as swelling and tenderness in that area  . Headaches are also a common manifestation of sinusitis. Symptoms may last from days to weeks, or even months, depending on the type of sinusitis and is an important clinical finding that can determine the course of treatment. Based on the duration of symptoms, acute (< 30 days), subacute (30-90 days) chronic (> 90 days) or recurrent (multiple episodes during the year) forms of sinusitis are described  . Although more severe complications of sinusitis are rare, most notable in terms of ethmoid sinusitis are preseptal or orbital cellulitis, osteomyelitis, subperiosteal orbital abscess and dissemination of microorganisms into the central nervous system (CNS), as well as pseudodacryocystitis and nasolacrimal duct obstruction  .
A meticulous patient history and a thorough physical examination are mandatory steps in achieving a diagnosis of ethmoid sinusitis, principally because clinical criteria are most important when it comes to infection of the paranasal sinuses    . Identifying the onset and type of symptoms is detrimental in assessing which sinus is affected, although signs of rhinorrhea, cough, pain and headaches are sufficient to make a presumptive diagnosis of a paranasal infection. Physical findings include dullness (or absence) of light on transillumination exam, whereas detection of serous or mucopurulent discharge is also a notable observation  . Clinical suspicion should be supported by imaging studies, which are necessary to confirm ethmoid sinusitis, with plain radiography often employed as the initial method. The occipitomental view is favored for visualization of the ethmoid cells, and an air-fluid level is considered as a diagnostic hallmark  . Computed tomography (CT), however, is superior compared to plain X-rays, and is recommended whenever possible   . A detailed microbiological investigation is also a mandatory step in the workup. Cultivation of secretions obtained through nasal swabs is detrimental in confirming bacterial etiology, causative agents predominantly being haemophilus influenza, streptococcus pneumoniae, and gram-negative bacilli . On the other hand, rhinovirus, influenza virus, and parainfluenza virus are notable viral agents .