Orbital cellulitis should be suspected in any patient with facial, sinus or dental infection with associated lid edema, orbital pain, proptosis, and limitation of ocular motility.
Conditions to consider in the differential diagnosis of orbital cellulitis include: trauma, allergies, hordeolum, meibomian gland abscess, dacrocystitis and dacroadenitis, blepharitis, conjunctivitis, endocrine dysfunction, idiopathic inflammation and neoplasm with inflammation.
Laboratory evaluation will often include a complete blood count, blood cultures and culture and gram stain of any purulent material. Please note that needle aspiration of the orbit is contraindicated.
Imaging: CT of the orbit with axial and coronal. Views should include narrow cuts of the frontal lobes to rule out peridural and parenchymal brain abscess formation. Coronal views are helpful in determining the presence and extent of any subperiosteal abscesses. MRI may be helpful in defining orbital abscesses and in evaluating the possibility of cavernous sinus disease.
This axial contrast enhanced CT of the orbits with left proptosis shows periorbital edema (white arrow) and a medial subperiosteal abscess (black arrow). Post-septal orbital cellulitis is usually a complication of adjacent sinusitis as seen in this case (with the blue arrow denoting opacified ethmoid air cells).
The orbit is surrounded by sinuses on three sides and is susceptible to contiguous spread of infection from these sinuses. This is more accentuated in children, because of their thinner bony septa and sinus wall, greater porosity of bones, open suture lines, and larger vascular foramina. Sinusitis is responsible for a least 75% of cases, and orbital complication may be the first and only presenting sign of sinusitis.
Orbital complications have been categorized by Chandler et al. into five separate stages according to severity.
1. Periorbital (pre-septal) cellulitis presents with lid edema with no proptosis and no changes in vision or limitations in ocular movement. Patients generally have signs and symptoms of sinusitis associated with edema and erythema of the eyelids, which can progress causing the eye to become swollen shut. Diagnosis is usually clinical. Patients are treated with broad spectrum oral antibiotics.
2. Orbital (post-septal) cellulitis presents with a diffuse orbital infection and inflammation without abscess formation and with associated proptosis and chemosis with ophthalmoplegia and decreased visual acuity. Orbital cellulitis represents an inflammation and cellulitis of the orbital contents with varying degrees of proptosis, chemosis, limitation of extraocular movement, and/or visual loss that depend on the severity of the process. Orbital involvement causes diffuse edema and bacterial infiltration of the adipose tissue, but no abscess. Diagnosis is initially clinical confirmed with imaging. Treatment is often with IV antibiotics and close observation with frequent visual acuity checks.
3. Subperiosteal abscess is often a progression of orbital cellulitis, and forms beneath the periosteum of the ethmoid, frontal, and maxillary bone, reveals a collection of pus on imaging between the medial periosteum and lamina papyracea with impaired extraocular movement. These are patients with a progressively worsening orbital cellulitis with worsening proptosis and gaze restriction. May lead to blindness by direct optic nerve compression, elevation of intraocular pressure or proptosis causing a stretch optic neuropathy. Treated with IV antibiotics, ophthalmology consult and +/- surgical intervention.
4. Orbital abscess reveals a discrete pus collection on imaging in the orbital tissues with associated proptosis and chemosis with ophthalmoplegia and decreased visual acuity. The abscess develops because of an extended infection into the orbital fat and is associated with inflammatory edema, purulence, and fat necrosis. Severe chemosis, ptosis and complete ophthalmoplegia (cranial nerves II, III, IV, V, and VI are involved) and moderate-to-severe visual loss are present. The visual impairment is attributed to an increase in orbital pressure that causes retinal artery occlusion or optic neuritis. If prompt surgical and medical therapy is not provided, permanent blindness can result. Generally, a displacement of the globe forward, or downward and outward, occurs.
5. Cavernous sinus thrombosis presents with bilateral orbital involvement with rapidly progressing chemosis and ophthalmoplegia. This is a life-threatening complication that is diagnosed by ptosis, orbital pain, severe loss of visual acuity, prostration, hypoesthesia, dysesthesia, and paresthesia along cranial nerves VI or VII, rapid progression chemosis and limitation of extraocular muscle motility, severe retinal venous engorgement, spread of orbital cellulitis and visual loss to the contralateral eye, and clinical deterioration with the development of meningitis, toxicity, and sepsis. Temperature is high with septic emboli, which cause fever spikes. The rate of blindness and death is up to 20%.