Differentials
Peri-orbital or orbital cellulitis
SIGNS / SYMPTOMS
Visual symptoms are more prominent in orbital cellulitis because of the involvement of the optic nerve.
May manifest in only one eye, whereas CST progresses more commonly to both eyes.[63]
Less likely to have profound sepsis, meningeal signs, and early fixation of the globe compared with CST.[63][64]
INVESTIGATIONS
CT scan and MRI of the head can differentiate between early CST and peri-orbital or orbital cellulitis by the presence of enlargement and expansion of the cavernous sinus in CST.[64]
If an lumbar puncture is performed, 75% of people with septic CST will have inflammatory cells on cerebrospinal fluid analysis, unlike people with peri-orbital or orbital cellulitis.
Superior orbital fissure syndrome
SIGNS / SYMPTOMS
Presents as ocular pain, proptosis, external ophthalmoplegia (owing to the paralysis of cranial nerves III, IV, VI) and neuralgic pain/anaesthesia of the involved areas supplied by the first and second branch of the trigeminal nerve.[65]
All differentiating features are subtle and relative.
INVESTIGATIONS
CT scan or MRI of the head will show involvement of the cavernous sinuses in CST.
Orbital apex syndrome
SIGNS / SYMPTOMS
Presents with internal and external ophthalmoplegia, visual loss, and trigeminal nerve (cranial nerve V1) anaesthesia. Visual impairment present because of optic nerve involvement. This is less likely to be a feature in CST.
Trigeminal nerve anaesthesia is also a differentiating sign.
INVESTIGATIONS
CT scan or MRI of the head will show involvement of the cavernous sinuses in CST.
Sino-orbital aspergillosis
SIGNS / SYMPTOMS
Presentation similar to superior orbital fissure syndrome.
All differentiating features are subtle and relative.
INVESTIGATIONS
CT scan or MRI of the head will show involvement of the cavernous sinuses in CST.
Sub-peri-osteal mucoceles
SIGNS / SYMPTOMS
Presentation similar to superior orbital fissure syndrome.
All differentiating features are subtle and relative.
INVESTIGATIONS
CT scan or MRI of the head will show involvement of the cavernous sinuses in CST.
Tolosa-Hunt's syndrome
SIGNS / SYMPTOMS
Presentation the same as superior orbital fissure syndrome.
All differentiating features are subtle and relative.
Characteristically, responds well to corticosteroids.[66]
INVESTIGATIONS
Clinical diagnosis may be differentiating.
MRI of the head, with and without contrast, is useful in demonstrating inflammatory changes in the superior orbital fissure/orbital apex or the cavernous sinus.
Meningioma
SIGNS / SYMPTOMS
Location can be either spheno-orbital, superior orbital fissure, or cavernous sinus.
Presenting signs depend on the site of involvement but, generally, this diagnosis results in focal neurological symptoms.
There is generally an absence of sepsis, fever, and bilateral eye involvement.
INVESTIGATIONS
MRI of the head demonstrating the meningioma as hyper-intense on T1, mixed intensity on T2, and enhancement with gadolinium with a dural tail sign (extension of a mass toward the dura giving the appearance of a tail).
Carotid-cavernous fistula
SIGNS / SYMPTOMS
Usually a history of trauma, especially basilar skull fractures.[67][68]
Can also be caused by rupture of an intra-cavernous carotid aneurysm or an atherosclerotic internal carotid artery and there may be a history of these conditions.[69]
Can either be direct with shunts between the cavernous sinus and the internal carotid or as dural shunts between the cavernous sinus and the meningeal branches of the internal or external carotid artery.[69]
The direct shunt usually causes pulsatile exophthalmos, in addition to the other symptoms of ophthalmoplegia, a reduced visual acuity and venous congestion.[70]
INVESTIGATIONS
MRI/magnetic resonance angiography (MRA) or carotid angiography: these tests will demonstrate blockage of the cavernous sinus in CST compared with abnormal connections between the carotid and cavernous sinus in carotid-cavernous fistula.
Rhino-cerebral mucormycosis
SIGNS / SYMPTOMS
Usually occurs in immunocompromised patients, especially people with diabetes mellitus, renal failure, or neutropenia.[71]
Characterised by the presence of black necrotic eschar in the nasal cavity, invasion of bone and blood vessels, and earlier exophthalmos.[72]
INVESTIGATIONS
CT scan or MRI of the head will show significant invasion of bone and blood vessels.
There is characteristic hypo-density on T2-weighted MRI.[72]
CT scan or MRI of the head will show involvement of the cavernous sinuses in CST.
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