Orbital cellulitis involves the tissues posterior to the orbital septum. It is most commonly associated with ethmoid or frontal sinusitis but can also occur following penetrating injuries of the orbit.
Most young children with orbital cellulitis have infections caused by a single aerobic pathogen. In the neonate, S aureus and gram-negative bacilli are most common. In older children and adults, S aureus, Streptococcus pyogenes, and S pneumoniae are common etiologic agents. Concurrent infections with multiple pathogens, including gram-negative and anaerobic organisms, can occur in older or immunosuppressed patients.
Early signs and symptoms of orbital cellulitis include lethargy, fever, eyelid edema, rhinorrhea, headache, orbital pain, and tenderness on palpation. The nasal mucosa becomes hyperemic, with a purulent nasal discharge. Increased venous congestion may cause elevated intraocular pressure. Proptosis, chemosis, and limited ocular movement suggest orbital involvement.
The differential diagnosis of orbital cellulitis includes nonspecific orbital inflammation, benign orbital tumors such as lymphatic malformation and hemangioma, and malignant tumors such as rhabdomyosarcoma, leukemia, and metastases.
Paranasal sinusitis is the most common cause of bacterial orbital cellulitis (Fig 18-11). In children younger than 10 years, the ethmoid sinuses are most frequently involved. If orbital cellulitis is suspected, orbital imaging is indicated to confirm orbital involvement, to document the presence and extent of sinusitis and a subperiosteal abscess (Fig 18-12), and to rule out a foreign body in a patient with a history of trauma.
Figure 18-11 Bacterial orbital cellulitis with proptosis (A) secondary to sinusitis (B).
(Courtesy of Jane Edmond, MD.)
Figure 18-12 Axial computed tomography (CT) image showing a medial subperiosteal abscess (arrow) of the left orbit associated with ethmoid sinusitis.
(Courtesy of Jane Edmond, MD.)
It is crucial to distinguish orbital cellulitis from preseptal cellulitis because the former requires hospital admission and treatment with IV broad-spectrum antibiotics. Choice of IV antibiotic is based on the most likely pathogens until results from cultures are known. If associated sinusitis or subperiosteal abscess is present, pediatric otolaryngologists should be consulted. The patient should be observed closely for signs of visual compromise. Many subperiosteal abscesses in children younger than 9 years resolve with medical management. Emergency drainage of a subperiosteal abscess is indicated for a patient of any age with either of the following:
evidence of optic nerve compromise (decreasing vision, relative afferent pupillary defect) and an enlarging subperiosteal abscess
an abscess that does not resolve within 48–72 hours of administration of antibiotics
Intraconal orbital abscesses are much less common than subperiosteal abscesses in children and require urgent surgical drainage.
Complications of orbital cellulitis include cavernous sinus thrombosis and intracranial extension (subdural or brain abscesses, meningitis, periosteal abscess), which may result in death. Cavernous sinus thrombosis can be difficult to distinguish from simple orbital cellulitis. Paralysis of eye movement in cavernous sinus thrombosis is often out of proportion to the degree of proptosis. Pain on motion and tenderness on palpation are absent. Decreased sensation along the maxillary division of cranial nerve V (trigeminal) supports the diagnosis. Bilateral involvement is virtually diagnostic of cavernous sinus thrombosis.
Other complications of orbital cellulitis include corneal exposure with secondary ulcerative keratitis, neurotrophic keratitis, secondary glaucoma, septic uveitis or retinitis, exudative retinal detachment, optic nerve edema, inflammatory neuritis, infectious neuritis, central retinal artery occlusion, and panophthalmitis.
Fungal orbital cellulitis (mucormycosis) occurs most frequently in patients with ketoacidosis or severe immunosuppression. The infection causes thrombosing vasculitis with ischemic necrosis of involved tissue (Fig 18-13). Cranial nerves often are involved, and extension into the central nervous system is common. Smears and biopsy of the involved tissues reveal the fungal organisms. Treatment includes debridement and systemic administration of antifungal medication. Allergic fungal sinusitis is a less fulminant condition that frequently presents with orbital signs, including proptosis from remodeling of the bony orbit. See BCSC Section 7, Oculofacial Plastic and Orbital Surgery, for further discussion.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.