Acute Distal Internal Carotid Artery Occlusion in Which Angiography during Mechanical Thrombectomy Revealed a Shunt between the Internal Carotid Artery and the Cavernous Sinus: A Case Report.

Objective: We report a patient with occlusion of the distal internal carotid artery (ICA), in whom angiography during mechanical thrombectomy revealed a shunt between the ICA and the cavernous sinus.

Case presentation: A 79-year-old man with bile duct cancer, a liver abscess, septic shock, and atrial fibrillation presented to our hospital with sudden disturbance of consciousness, conjugate eye deviation, and right hemiplegia. A cranial CT revealed a hyperdense middle cerebral artery (MCA) and loss of gray-white matter differentiation, suggesting large vessel occlusion. Endovascular therapy was immediately initiated. Left internal carotid angiography indicated occlusion of the distal ICA at the origin of the ophthalmic artery. Injection of contrast medium at a site just proximal to the ICA occlusion depicted the cavernous sinus and inferior petrosal sinus. We withdrew the aspiration catheter to the petrous segment of the ICA and injected contrast medium again. This time, however, neither the cavernous sinus nor the inferior petrosal sinus was visualized. We deployed a stent retriever at the occlusion site and successfully removed the thrombus. The final angiography showed complete recanalization of the affected arterial segment with no sign of a carotid cavernous fistula. The patient was finally discharged on day 73 after endovascular therapy with a cerebral infarction in the territory of the left MCA.

Conclusion: In the present case, angiographic visualization of the cavernous sinus varied depending on the site of contrast medium injection. It appears that the high pressure of the contrast medium generated in the stump of the ICA opened up microvascular shunts between the normal capillaries of the ICA and the cavernous sinus, leading to visualization of the cavernous sinus. Therefore, it is important to be aware that injection of contrast medium into the blind alley of the ICA near the cavernous sinus could result in early visualization of the cavernous sinus.