Orbital infection can be a commonly encountered entity.
It is important to differentiate between orbital and periorbital cellulitis, as this has therapeutic and prognostic implications:
periorbital cellulitis (preseptal cellulitis) is limited to the soft tissues anterior to the orbital septum 1
- often managed with oral antibiotics
orbital cellulitis (post-septal cellulitis) extends posterior to the orbital septum 1
- more serious condition requiring hospitalisation and parental antibiotics
- complications such as intraorbital abscess formation may require surgical intervention
Orbital infections represent more than half of primary orbital disease processes 2. These infections typically present in children and yound adults but can affect any age group.
- painful ophthalmoplegia
- reduced visual acuity
Periorbital cellulitis often results from contiguous spread of an infection of the face, teeth, or ocular adnexa. Orbital cellulitis typically results from extension of a paranasal sinusitis infection 1.
Urgent imaging is indicated to assess the anatomic extent of disease, including postseptal, cavernous sinus and intracranial involvement; evaluate for sources of contiguous spread, such as with sinusitis or trauma; and identify orbital abscesses that require exploration and drainage 3. CT is the imaging investigation of choice as it is:
- readily available at all hours and quick
- ideal for assessing for underlying sinus disease
- will identify a subperiosteal reaction or intracranial extension
Diffuse soft-tissue thickening and areas of enhancement anterior to the orbital septum are seen on periorbital cellulitis. It is very difficult to differentiate between preseptal oedema and periorbital cellulitis on CT 4.
- poor definition of orbital planes
- inflammatory stranding in the intraconal fat
- intraconal or extraconal soft tissue mass
- oedema of the extraocular muscles
- intra-orbital abscess
- subperiosteal abscess
Rarely performed, as not usually necessary or will not add anything to the assessment. It will identify like CT a subperiosteal abscess and appear:
- T1: low signal
- T2: high signal
- DWI/ADC: diffusion restricton
- T1 + C: rim enhancement
Treatment and prognosis
Periorbital cellulitis is treated with oral antibiotic therapy. Orbital cellulitis is treated with intravenous antibiotic therapy. However, if a subperiosteal abscess is present, surgical drainage may be necessary 1.
Complications of orbital cellulitis include 1:
- superior ophthalmic vein thrombosis
- cavernous sinus thrombosis
- loss of vision
- intracranial abscess
- 1. Lebedis CA, Sakai O. Nontraumatic orbital conditions: diagnosis with CT and MR imaging in the emergent setting. Radiographics. 2008;28 (6): 1741-53. doi:10.1148/rg.286085515 - Pubmed citation
- 2. Capps EF, Kinsella JJ, Gupta M et-al. Emergency imaging assessment of acute, nontraumatic conditions of the head and neck. Radiographics. 2010;30 (5): 1335-52. doi:10.1148/rg.305105040 - Pubmed citation
- 3. Sepahdari AR, Aakalu VK, Kapur R et-al. MRI of orbital cellulitis and orbital abscess: the role of diffusion-weighted imaging. AJR Am J Roentgenol. 2009;193 (3): W244-50. doi:10.2214/AJR.08.1838 - Pubmed citation
- 4. Emergency Radiology: Imaging of Acute Pathologies. Springer. ISBN:1441995919. Read it at Google Books - Find it at Amazon