Nowhere is there a greater discrepancy between paediatricians and ophthalmologists than in differentiating between periorbital and orbital cellulitis in children. The former tends to be overdiagnosed while the latter is often undertreated. Try the true and false self-assessment questions in Table 1 before reading further. TABLE 1 Self-assessment questions The key to understanding these two completely different conditions is awareness of the orbital septum, which is an extension of the periosteum of the frontal bone (Figure 1). It inserts into the tarsal plate of the upper lid, and infection does not penetrate from front to back or vice versa through this tough structure, unless it is breached by a sharp object. Infection in front of the orbital septum causes preseptal or periorbital cellulitis, while disease processes posterior to the orbital septum cause post septal or orbital cellulitis. Therefore, the etiology and treatment of these two conditions is completely different. Figure 1) Insertion of the orbital septum into the tarsal plate of the upper lid Periorbital cellulitis usually has an obvious local cause such as a sty or chalazion, spreading conjunctivitis or dacryocystitis. The cellulitis may result from a break in the skin such as those caused by superficial trauma, animal bites or local infections. Patients generally will show no systemic signs (Figure 2). There is no leukocytosis or fever, and they appear otherwise well. There is no pain on eye movement, vision is not impaired and there is usually no x-ray or computed tomography evidence of sinusitis. The extent of the infection does not respect the orbital septum because it is anterior to this structure and runs freely above or below the orbital rim. Treatment is directed toward the local cause of the infection (ie, treatment of conjunctivitis, chalazion or herpetic blepharitis). On rare occasions, systemic antibiotics are indicated for a particularly severe inflammation, but they generally are not required. Figure 2) Periorbital cellulitis secondary to infected chicken pox Patients with orbital cellulitis are irritable, toxic and have a fever. They have erythema and induration of one or both lids, often respecting the orbital septum with significant pain on pressure over the lid. The globe may be injected and there may be pain on eye movement. Late signs include limitation of extraocular movement, proptosis, decreased visual acuity and papilledema. An increased white blood cell count and x-ray and computed tomography evidence of unilateral or bilateral sinusitis, particularly involving the adjacent sinus, are likely to be present (Figure 3). Figure 3) Ethmoid sinusitis (arrow) The etiology of orbital cellulitis is related to the ethmoid bone (lamina papyracea), which is paper thin, separating the sinus from the orbit. Infection spreads from the sinus into the adjacent orbit but lies under the periosteum where it may collect as a subperiosteal abscess, causing exotropia, proptosis and restriction of eye movement nasally (Figure 4). All these signs occur late and are not helpful in distinguishing orbital from periorbital cellulitis early on. Figure 4) Exotropia and proptosis secondary to subperiosteal abscess Treatment of orbital cellulitis consists of admission to the hospital and intravenous antibiotics, currently cefuroxime axetil and clindamycin hydrocloride. These drugs take effect in 12 h to 36 h; therefore, worsening of the condition on day 1 is not a source of concern. Subperiosteal abscesses usually respond to intravenous antibiotics, but if it is large, it may need to be drained surgically. Subperiosteal abscesses located superior to the globe must always be drained surgically. After recovery, oral antibiotics such as Keflex (Biocraft Laboratories Inc, USA) are indicated for 10 to 14 days to clear any residual sinusitis. Nasal decongestants and follow-up with an otolaryngologist to ensure resolution of the sinusitis are indicated. In summary, consider the four factors differentiating periorbital from orbital sinusitis in Table 2. TABLE 2 Factors differentiating periorbital from orbital sinusitis
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Jun 17, 2014
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