The nose and paranasal sinuses comprise an integral whole, both anatomically and functionally. Infections of the upper respiratory tract are the most frequent disorders of childhood. The term rhinosinusitis has recently been used in clinical practice. The possibility of limitation of this type of infection in children at a developmental age is relatively poor. Rhinitis is usually associated with inflammation of the mucosa which lines the paranasal sinuses.

For a proper understanding of the processes leading to sinusitis, particularly ethmoiditis, it is necessary to summarise our knowledge of the anatomy and development of sinusitis.

The ethmoid sinuses are binate, and consist of groups of small, comunicating, air-filled cavities separated with thin walls. We can divide the ethmoid cells into two groups, anterior and posterior, on the basis of the location of drainage. The anterior ethmoid cells have their ostium at the ethmoid infundibulum in the middle nasal meatus, under the middle nasal concha, whilst the posterior ethmoid cells drain into the superior or supreme meatus. The number of cavities in the ethmoid sinus varies from individual to individual (1).

All sinuses develop by facial bone resorption, and an ingrowth of respiratory mucosa from the nose into these cavities. The ethmoid sinuses are the best-developed at birth, but their walls are not ossified. In clinical practice, it is very important to have a knowledge of adjacent structures. Laterally, the ethmoid cavities are connected with the orbit, separated only by the lamina papyracea. This lamina is not ossified in young children, and may have congenital dehiscences. These factors can promote the spread of infection into the orbital tissues. Ossification of the lamina papyracea begins at 2 years of age, and continues to age 6. The upper border of the ethmoid sinus is marked by the lamina cribosa and the anterior cranial fossa. Between the ethmoid bulla (the largest air cell) and the uncinate process there is a semilunar ostium, that of the ethmoid infundibulum. The maxillary and frontal sinuses drain into the same area (1). This region is known as the ostio-meatal complex, and is of fundamental importance in the development of sinusitis. All pathologies, ostio-meatal unit both functional and anatomical, which impair patency of the ostio-meatal complex may lead to disorders of the whole anterior group of ethmoid cells.

The mucous layer of the paranasal sinuses is a continuation of that of the nasal cavity, but is thinner and has fewer mucus glands and goblet cells. It is covered by stratified ciliated columnar epithelium (1). This, with the mucous layer, is responsible for muco-ciliary transport, one of the main protective mechanisms of the sinus. The active transport of the mucus is from the ethmoid cavity towards the ostium, and then into the nasal cavity. Any anatomical modification of the lateral nasal wall (concha bullosa, Haller´s cells, variations of the uncinate, processus and nasal septum deviation), or disturbance of the ciliary function (congenital, such as Kartegener´s Syndrome, or acquired due to bacterial or viral toxins, allergy, oedema, or locally applied drugs) can impair this transport mechanism (2).

This leads to accumulation of secretions, followed by further damage to the cilia. Lack of drainage and ventilation of the sinuses lead to a progress of the pathological condition. Therefore, a necessary step in the treatment of sinusitis is to open the passages, pharmacologically or surgically. Blood from the ethmoid sinus flows through the anterior and posterior ethmoidal veins to the superior ophthalmic vein, and on to the cavernous sinuses, these being situated on both sides of the sphenoid bone. These veins, like other veins of the face, are valveless. This allows the possibility of direct propagation of an infection from the ethmoid sinus and the orbits to the central nervous system.

The exact time of onset of a complaint in a child is sometimes difficult to estimate. Consequently the crucial criterion of infection is not based on the morphological condition of the mucus in the sinuses. Thus we can distinguish acute sinusitis, acute recurrent sinusitis (after medical treatment, secondary changes are not seen in the mucus), and protrected prolonged sinusitis (in which morphological changes in the mucus develop, and further surgical treatment may be necessary) (2, 3). Generally, acute sinusitis is the result of acute rhinitis. Acute ethmoiditis can be recognised even at an age of a few months, and the ethmoid sinuses are the most commonly infected sinuses in children, due to the fact that these are the most developed and air-filled after birth. Ethmoiditis may have a more severe course than in adults, and may quickly lead to life- -threatening orbital or intracranial complications. This results from the anatomical and functional conditions described earlier. Thus, early recognition of complications is very important, to begin appropriate treatment, or surgery.

The diagnosis of sinusitis is based on the medical history. ENT examination and blood tests are done, and X-rays are taken in justifiable cases. We must stress that X-rays are not the main tool in the recognition of sinusitis in children. The most important factor is clinical evaluation. Acute sinusitis is usually preceeded by prolonged rhinitis. Despite medical treatment, discharge from the nose and an elevated body temperature persist. Older children may complain of headache, which is localised between the eyes at the middle canthus of the eye, or in the temporal region. On examination by anterior rhinoscopy, we can find a muco-purulent secretion in the nasal cavities, especially in the middle nasal meatus, as well as oedema and erythematous mucus. These occur in company with a post-nasal discharge, and impairment of the patency of the nose. A lack of pathological secretion in the nose does not preclude sinusitis, because oedema may totally obstruct the sinus openings, and stop drainage of the purulent secretion. On examination, there are usually signs of pharyngitis or otitis.

The aetiology of acute sinusitis is similar to those of other acute infections of the upper respiratory tract. In 90% of cases, sinusitis is caused by bacteria (20-30% Streptococcus pneumoniae, 20-30% Haemophilus influenzae, 10-20% Moxarella catarrhalis, and 10-20% others. These latter include Streptococcus pyogenes, Staphylococcus aureus, and both anaerobic and gram-negative bacteria). In children with cystic fibrosis or with immunodeficiency, the common pathogen is Pseudomonas aeruginosa. Sinusitis may also be caused by viruses – influenzae, parainfluenzae, or rhinoviruses. In cases of immunodeficiency, we must also remember mycotic infection, the commonest pathogen being Aspergillus fumigatus. Recommended antibiotics for the initial treatment of children include amoxycillin with clavulonic acid, 2^nd generation cephalosporin, and clindamycin. The antibiotic therapy should last for from 10 to 14 days (3). Besides antibacterial therapy, we must restore proper ventilation and drainage of secretions from the sinuses, thus stopping any increase in pathological processes associated with the inflammation, to ensure the greatest chance of successful treatment. We apply topical decongestants (best applied on a cotton-tip applicator placed exactly on the opening of the sinuses), and a mucolytic, which produces liquefaction of the mucus membrare. We must bear in mind the proper hydration of the patient, and humidification to prevent any drying of the secretion. In children, we must also remember that there is a limited time for the use of topical decongestant drops (e.g: oxymetazolin), because they may damage the cilia. For the same reason, oleiferous drops are not recommended.

In the age of antibiotics, the number of complications associated with sinusitis has decreased markedly. Improperly treated complications may lead to persistent loss of health, and even to death, so each child suspected of having complications must be admitted to hospital. This allows us to initiate aggressive treatment, including surgery and neurosurgery. Orbital complications develop most often in ethmoiditis. The inflammation may spread directly into the tissues of the orbit through the thin lamina papyracea, or a heamatogenous spread may occur (10). In practice, it is important to distinguish preseptal complications (e.g: the tissue of the eye before the orbital septum is affect-ed) from postseptal complications (12). The orbital septum is a thin connective tissue in the eyelid, which is connected posteriorly to the periosteum of the orbit, and is a natural barrier preventing the spread of infection. The first group of complications include inflammatory oedema of the eyelid, and the second group include more serious conditions, such as inflammation of the soft tissue of the orbit (cellulitis orbitae), subperiosteal abscess, orbital abscess, and thrombosis of the cavernous sinus (4, 9, 10). Inflammatory oedema of the eyelids due to ethmoiditis typically begins from the medial canthus of the eye, and may be uni- or bilateral, often asymmetric. In addition to other signs characteristic for the sinusitis we notice the chemosis. The patient may emit tears because the opening of the naso-lacrimal duct, under the inferior nasal meatus, is closed by oedema. Oedema of the eyelids must be differentiated from oedema caused by allergic reactions (e.g: after an insect bite), by trauma in this area, by acute conjunctivitis, or by a low serum protein level due to general disease (nephropathy). In this case, the oedema is pale and symmetric.

In infants and younger children, inflammation of the maxilla and infiltration of the buccal tissue may develop due to sepsis. This condition must be differentiated from orbital complications resulting from sinusitis (2). Every child suspected of having orbital complications needs an immediate ophthalmological examination, which must be repeated to assess the progress of changes. The ophthalmological examination must include the position of the eyeball (proptosis), its mobility, visual acuity, and an estimatas of the pupillary reflexes and the fundus of the eye. In cases of orbital inflammation, we can observe limited mobility and proptosis of the eyeball. The child may complain of pain in the orbit, and diplopia. The eyeball is displaced laterally, with limited medial mobility, when a subperiosteal abscess develops on the medial wall of the orbit. An abscess of the orbit may develop in any part of the orbit, as a consequence of tissue inflammation, or can be secondary to a pre-existing subperiosteal abscess. Orbital complications are related to a risk of blindness. A few mechanisms may lead to damage to the optic nerve, and visual loss: compression of the nerve by oedematous tissues of the orbit, inflammation of the nerve, or thrombosis of the central artery of the retina (7). Sometimes a complete ophthalmological examination cannot be performed, due to poor co-operation from the child, or severe oedema of the eyelids. Diminished visual acuity is evidence of a severe condition.

In cases of orbital complications we should carry out computer tomography of the paranasal sinuses and orbit (12). A CT scan shows the degree of change in the affected sinuses, oedema of the orbital tissues (characteristic oedema of the medial rectus muscle), proptosis, and subperiosteal or orbital abscesses. Cavernous sinus thrombosis is the most serious life-threatening complication. The child is in generally poor condition, toxic, with high fever. It performs massive bilateral eyelid oedema, impaired visual acuity, and fixation of the eyeball. Neurological signs in the II, III, IV, V, V₁, and V₂ nerves may be seen. Intracranial complications are sometimes seen in children with immunodeficiency, or when the history includes a trauma to the head with bone fracture. The most frequent intracranial complication is meningitis, and others include: dural sinus thrombophlebitis, epidural and subdural abscess, and abscess of the brain. In the case of a general deterioration of the child, it must be examined neurologically, a CT scan of the brain sometimes being indicated (11). Indications for surgical treatment of acute ethmoiditis are based on clinical status and CT scans. When proptosis, limited mobility of the eyeball, loss of visual acuity or neurological signs are not seen, intensive medical treatment is started (intravenous antibiotic therapy, mucolytics, local decongestant drugs applied many times a day – every 3 to 4 hours at the outset – anti-febrile and analgesic drugs, and compresses on the eyelids). In the case of worsening, an increase of orbital signs, evidence of severe postseptal inflammation, or when neurological signs occur despite previous medical treatment, the patient requires urgent surgical intervention (8, 12). Although an intranasal approach and endoscopic drainage is described (4), we recommend an external ethmoidectomy in cases of ethmoiditis with complications. This is an operation performed through an external approach, via an incision near the canthus of the eye. In this way we obtain a good view into the ethmoid cavity, the possibility of precise evacuation of secretions, and can evacuate a subperiosteal abscess. These procedures should be performed by an experienced paediatric otorhinolaryngologist. In the case of recurrence of acute sinusitis, or prolonging of inflammation, and if modifications of the lateral nasal wall with stenosis of the ostio-meatal complex are seen at CT scan, functional endoscopic sinus surgery (FESS) is performed.

Ethmoiditis is a condition which is most commonly first recognised by the GP. Complications of ethmoiditis may be very dramatic, so a knowledge of the pathomechanisms of sinusitis in childhood should be known to the doctor who treats children. Early and proper diagnosis allows the opportunity for appropriate treatment.