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QuestionChoice
This patient likely has orbital cellulitis, as indicated by the presence of erythema and swelling surrounding the left eye, fever, diplopia (due to extraocular eye muscle involvement) and pain. The diplopia occurs due to complex ophthalmoplegia, which is when eye signs cannot be attributed to a single cranial nerve. The orbit is made up of seven bones, including the zygomatic, palatine and maxillary bones. Fractures of any of these bones are a risk factor for developing orbital cellulitis. This is a potentially sight-threatening emergency and can be further complicated by infective extension into the cavernous sinus. The best test is a CT orbit for this condition.
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CT orbit
QuestionChoice
This is a highly sensitive imaging modality for evaluating thromboses within the venous sinuses, not for identifying orbital cellulitis.
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c
CT venogram
QuestionChoice
An MRI is rarely done because a CT orbit is quicker to carry out and most often confirms the diagnosis. On T1, a low signal will be observed.
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T1 MRI brain with orbits
QuestionChoice
This is a reasonable option and a CT of the head is often performed alongside a dedicated scan of the orbit. However, a dedicated scan of the orbit is still required, so this is not the best investigation.
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b
CT head with contrast
QuestionChoice
An MRI is rarely done because a CT orbit is quicker to carry out and most often confirms the diagnosis. On T2, a high signal will be observed.
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e
T2 MRI brain with orbits
QuestionComment
What is a T1 vs T2 MRI?
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User
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Embolism Intubation
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ct a child?
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RNA Synthase
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seeing T1 and T2 scared me 
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Pulseless Electrical Activity
Concept
Chapter
# Summary

Orbital cellulitis is a serious infection of the structures behind the orbital septum, presenting a sight- and life-threatening emergency. Key signs and symptoms include periocular pain and swelling, fever, malaise, erythematous, swollen and tender eyelid, chemosis, proptosis and restricted eye movements. The gold standard investigation for orbital cellulitis is a CT orbit. Management involves hospital admission for IV antibiotics and close monitoring. Preseptal cellulitis is a less severe infection of the tissue anterior to the orbital septum, which can progress to orbital cellulitis if not properly managed. 

# Definition

**Orbital cellulitis** is a sight- and life-threatening emergency. It describes infection of the structures behind the orbital septum.

The orbital septum is a membranous sheet that forms the anterior border of the orbit, extending from the orbital rims (superior and inferior) and into the eyelids. 

**Preseptal cellulitis** refers to infection of tissue anterior to the orbital septum. It is much more common than orbital cellulitis and 80% of cases occur in children under the age of 10 years. It is less severe than orbital cellulitis, unless it spreads past the septum (which is not fully developed) and becomes orbital cellulitis.

# Epidemiology

Orbital cellulitis is less common than preseptal cellulitis, with the latter accounting for 80% of cases, mostly occurring in children under the age of 10.


# Risk factors 

* Trauma
* Surgical – ocular, adnexal or sinus
* Sinus disease – ethmoidal sinusitis is the most common site of infection that spreads to the orbit
* Other facial infections – preseptal, dental abscess or dacryocystitis

# Signs and Symptoms

Orbital cellulitis:

* Periocular pain and swelling
* Fever
* Malaise
* Erythematous, swollen and tender eyelid
* Chemosis
* Proptosis
* Restricted eye movements +/– diplopia

The typical patient with **preseptal cellulitis** is a *child with an erythematous swollen eyelid, mild fever and erythema surrounding the orbit.*

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Important findings that suggest preseptal cellulitis, rather than orbital cellulitis, are:

* No proptosis
* Normal eye movements
* No chemosis
* Normal optic nerve function


# Investigations

- Blood tests: FBC, CRP to screen for raised inflammatory markers
- Swabs sent for microscopy, culture and sensitivity
- **CT orbit** is the gold standard investigation to distinguish orbital cellulitis from preseptal cellulitis

# Management

- Patients with orbital cellulitis require admission for IV antibiotics and close monitoring with input from the ophthalmology, ear, nose and throat and medical teams.
- Preseptal cellulitis - Young or systemically unwell children should be admitted for IV antibiotics.
Otherwise, treatment is with oral antibiotics and daily outpatient review.


# References

Denniston AK, Murray PI. Oxford Handbook of Ophthalmology. Fourth Edition. Oxford University Press. 2018.
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A typical appearance of orbital cellulitis.
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Topic
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Ophthalmology
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Orbital and preseptal cellulitis
Topic
16
Ophthalmology
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A CT scan of the orbit is an essential imaging tool for evaluating orbital cellulitis, as it helps to identify the extent of infection, detect any associated complications such as orbital abscess or sinusitis, and distinguish it from other conditions that may affect the orbital structures.
A 14-year-old adolescent is brought to A&E after a week-long history of painful left eye movements and diplopia. One week ago, she was struck in the face with a hockey stick and sustained an undisplaced fracture of the zygomatic bone. She was sent home with analgesia and clinic follow-up with ophthalmology. On examination, you note swelling and erythema around the left eye. She has a complex ophthalmoplegia but the remainder of her cranial nerve examination is unremarkable. Her temperature is 38.7 °C.

Which of the following is the next best investigation?
a