Abstract No: eEdE-103 Submission Number: 2420

Disclosure There is no disclosure.

Brain Parenchymal Contrast Staining After Mechanical Thrombectomy for Acute Ischemic Stroke. P Appuhamy, S Kumar, H Koay, F Hui National Neuroscience Institute, Singapore.

Purpose: To increase awareness of brain parenchymal contrast staining following intra-arterial injection of iodinated contrast for mechanical thrombectomy in the treatment of acute stroke.

On the post-thrombectomy plain computed tomography (CT) scan of the brain the contrast extravasation appears hyperdense and mimics hemorrhagic conversion. This may alter antithrombotic treatment and should be recognized.

Method We retrospectively reviewed serial CT scan images of 30 consecutive patients who underwent mechanical thrombectomy using retrievable stents for treatment of acute stroke between 1 Jan 2015 and 10 Dec 2015.

Rationale We identified parenchymal hyperdensity on initial CT within 24 hours of mechanical thrombectomy. It was considered to be contrast staining if: 1.On the subsequent MRI, there was no susceptibility. 2.The hyperdensity cleared within 48 hours of thrombectomy.

Findings: 6 out of 30 patients who underwent mechanical thrombectomy for acute stroke, had new hyperdensities within 24 hours of the procedure, on the CT scan. One patient did not undergo a CT at 24 hours.

In 2 patients the hyperdensities resolved within 48 hours. In 2 patients the hyperdensities reduced initially and subsequently increased. In the remaining 2 patients the hyperdensities persisted beyond 48 hours.

Of the 30 patients with acute stroke, the sites of occlusion were: –Middle cerebral artery (MCA) n= 14 –Internal carotid artery (ICA) n= 13 –Basilar artery n= 3

Case 1- Contrast staining following right ICA infarction. DWI/ADC- Restricted diffusion in the right lentiform nucleus

Case 1- Contrast staining following right ICA infarction cont. Pre thrombectomy- Complete occlusion of the right ICA Post thrombectomy - Recanalization of the Right ICA

Case 1- Contrast staining following right ICA infarction cont. Non contrast CT within 24hrs of thrombectomy- hyperdensity in the affected region. Non contrast CT within 48hrs of thrombectomy - resolution of hyperdensity.

Case 2- Hemorrhagic conversion following right MCA infarction. DWI/ADC- Restricted diffusion in the right basal ganglia

Case 2- Hemorrhagic conversion following right MCA infarction cont. Pre thrombectomy- complete occlusion of the right MCA Post thrombectomy - Recanalization of the right MCA

Case 2- Hemorrhagic conversion following right MCA infarction cont. Non contrast CT within 24hrs of thrombectomy - hyperdensity in the affected region. Non contrast CT within 48 hrs of thrombectomy – persistence of hyperdensity (haemorrhagic conversion).

Pattern of hyperdensity In all cases, the pattern of hyperdensity on the initial CT was diffuse parenchymal hyperdense staining. In one patient there was additional gyriform hyperdensity which progressed for mild haemorrhagic conversion.

Case 3- Gyriform hyperdensity following right MCA infarction. DWI/ADC- Restricted diffusion in the right MCA territory.

Case 3- Gyriform hyperdensity following right MCA infarction cont. Post thrombectomy - Recanalization of the right MCA Pre thrombectomy- Complete occlusion of the right MCA

Case 3- Gyriform hyperdensity following right MCA infarction cont. Non contrast CT within 24hrs of thrombectomy- Gyriform hyperdensity in the affected region. Non contrast CT within 72 hrs of thrombectomy – mild haemorrhagic conversion.

Discussion New hyperdensities seen on a CT scan within 24 hours of mechanical thrombectomy may be secondary to hemorrhage and/or contrast extravasation.

The physiology behind contrast staining of parenchyma in stroke is not clearly understood. –Lack of sufficient revascularization at the capillary level in cerebral infarction, and thus a lack of blood flowing through the territory at the capillary levels to "wash out" contrast, could be a contributing factor to contrast staining of brain parenchyma. – Although some believe it to predict subsequent hemorrhagic transformation, other studies have shown that these do not carry an increased risk of symptomatic hemorrhage or negative prognosis.

In our experience contrast staining is not an uncommon occurrence. Contrast staining in our experience does not predict hemorrhagic transformation nor clinical deterioration.

Summary: It is important to recognize contrast staining in the early (within 24 hours) CT scan after intra-arterial thrombectomy. Contrast staining shows marked reduction in density on the follow-up CT scan, in contrast to hemorrhagic conversion.

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