Clinical History
A 55-year-old man, with a history of acromegaly caused by pituitary macroadenoma infiltrating the skull base, was diagnosed with an aneurism of the left internal carotid artery (ICA) in the cavernous sinus. After some months the patient presented with lateral non-pulsating exophtalmos and ectropion of his left eye.
Imaging Findings
Despite transsphenoidal surgery, MRI (Fig. 1) showed persistence of macroadenoma tissue extending through right cavernous sinus. In close proximity to left carotid siphon, a round signal void on T2-W images characterised by flow signal on MR Angiography (MRA) (Fig. 2) suggested an ICA aneurysm.
CT Angiography (Fig. 3) confirmed a saccular broad base aneurysm of left carotid siphon.
Images showed maxillary and ethmoid sinusitis.
As patient presented with eye signs, MRI with MRA was performed on suspicion of carotid-cavernous fistula consequent to aneurysm rupture. Images showed (Fig. 4, Fig.5) left exophtalmos, dilatation and thrombosis of left superior ophtalmic vein extending to cavernous and sigmoid sinuses, thickening of left extraocular muscles with periorbital oedema caused by venous congestion and stasis. The ICA aneurysm was unchanged. Images confirmed ethmoid as well as frontal and sphenoid sinusitis.
Patient started heparin therapy but he died from a pulmonary embolism in a state of unexplained thrombophilia.
Discussion
Weakness of artery walls due to mechanical or biochemical reasons could explain presence of ICA aneurysms in patients with somatotroph macroadenomas [1].
Spontaneous or traumatic rupture of carotid aneurysm in cavernous sinus doesn’t cause subarachnoid haemorrhage but carotid-cavernous fistula whose typical presentation is bruit, pulsating exophtalmos, chemosis, periorbital oedema and retro-orbital pain [2]. Eye signs secondary to venous congestion and impaired extraocular muscles motility are also initial presentation of Cavernous Sinus Trombosis (CST) [3] which is extremely rare in association with ICA aneurysm. In general CST has infectious causes - sinusitis, orbital infections, otitis - or aseptic causes - surgery, trauma or thrombophilic states such as connective tissue diseases, malignancies, oral contraceptives and hereditary prothrombotic conditions [3, 4].
CST represents a rare but devastating disease. Extension of thrombus to other sinuses such as petrosal and sigmoid ones can occur. CST induces oedema and haemorrhagic infarction in the drainage area with consequent neurological manifestations [3, 5].
Before the availability of CT or MRI, CST was diagnosed by clinical presentation or at autopsy. The use of cerebral angiography or orbital venography has been reported; however, these techniques have the potential for serious complications, including dissemination of infection. CT and MR Angiography are better non-invasive diagnostic techniques [4] for definitive assessment of this condition. On a CT examination the main direct sign of acute thrombosis is high density in a venous sinus; indirect signs are low density lesions or haemorrhage in the drainage area. Enhanced CT shows the “empty delta sign” [5].
MRI is more sensitive than CT. Early signs of thrombosis include flow shadow disappearance and signal intensity changes in the venous sinus. Secondary signs include brain swelling, oedema and/or haemorrhage. Direct signs of CST include expansion of the cavernous sinus, convexity of the normally concave lateral wall and irregular filling defects. Indirect signs include dilation of superior ophthalmic vein, exophthalmos, thrombi in veins and sinuses tributaries to cavernous sinus, venous stasis and collateral circulation formation [3, 5].
Clinical assessment should guide the need for adjunctive studies in CST diagnosis. Prompt recognition and management of CST is critical. The underlying condition, particularly sepsis and malignancies, adversely affect outcome [3, 4]. Symptomatic treatment includes antimicrobials, hydration, control of seizures and intracranial pressure. The antithrombotic treatment includes heparin, oral anticoagulants, thrombolysis and endovascular approaches [3, 4]. Treatment guidelines are necessary but challenging to develop because of the rarity of the disease.
Differential Diagnosis List
Cavernous sinus thrombosis causing exophtalmos in patient with ICA aneurysm.
Carotid-cavernous fistula
Orbital trauma
Orbital tumours
Orbital infections
Final Diagnosis
Cavernous sinus thrombosis causing exophtalmos in patient with ICA aneurysm.
