CT Case 008
A 28 yo male presents with progressive right eye proptosis, scleral injection, decreased vision and diplopia.
Three months prior, he was assaulted and sustained extradural haemorrhages which required bilateral craniotomies and resulted in a traumatic cranial VI nerve palsy.
Describe and interpret the CT scan
What stands out most on this CT angiogram is the dramatic distension of the right superior ophthalmic vein. This is causing proptosis.
There is also bilateral distension of the cavernous sinuses.
This patient is suffering from a traumatic Carotid Cavernous Fistula (CCF).
A traumatic laceration of the right carotid artery at the level of the cavernous sinus which has caused a direct connection between the internal carotid artery and the cavernous sinus.
This causes high arterialised pressure in the cavernous sinus, which results in retrograde flow into with dilation of the superior ophthalmic vein (SOV) (and to a lesser extent retrograde flow into cortical veins).
This is a classical presentation of CCF. It most commonly occurs following head trauma (it can be an acute presentation, or can manifest after days / months). However, about 30% of cases of CCF are spontaneous (typically due to connective tissue disorders).
Patients with CCF present with ophthalmic manifestations due to impaired venous drainage;
- the classical examination finding is pulsatile proptosis
- other findings are reduced visual acuity and scleral injection
- if you decide to place your stethoscope on your patients eye you will hear a whooshing noise – an orbital bruit, caused by increased and turbulent blood flow
CCF can also cause steal syndrome, with reduced blood flow to the MCA and ACA on the side of the lesion. Our patient when on to be successfully treated with endovascular embolisation.
- Henderson AD, Miller NR. Carotid-cavernous fistula: current concepts in aetiology, investigation, and management. Eye (Lond). 2018 Feb;32(2):164-172. doi: 10.1038/eye.2017.240.
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Dr Leon Lam FRANZCR MBBS BSci(Med). Clinical Radiologist and Senior Staff Specialist at Liverpool Hospital, Sydney
Emergency Medicine Education Fellow at Liverpool Hospital NSW. MBBS (Hons) Monash University. Interests in indigenous health and medical education. When not in the emergency department, can most likely be found running up some mountain training for the next ultramarathon.
Sydney-based Emergency Physician (MBBS, FACEM) working at Liverpool Hospital. Passionate about education, trainees and travel. Special interests include radiology, orthopaedics and trauma. Creator of the Sydney Emergency XRay interpretation day (SEXI).