Internal Carotid Artery Stenosis
The prevalence of asymptomatic carotid occlusion is not known, and the incidence of ipsilateral stroke in neversymptomatic carotid occlusion is negligible 1).
When an internal carotid artery (ICA) occludes, a patient may develop cerebral infarction (CI). Ishikawa et al investigated whether CI caused by ICA occlusion (ICAO) is associated with collateral flow through the anterior and posterior communicating arteries (ACoA and PCoA).
In 100 patients with ICAO, they investigated CI and white matter disease by performing an MRI and the anatomy of the ACoA and PCoA were investigated by performing magnetic resonance angiography. All patients were divided into the symptomatic CI group or the no-CI group. The collateral flow pathway was estimated by the anterior cerebral artery (ACA)-PCoA score and the collateral flow volume after ICAO was estimated by the middle cerebral artery (MCA) flow score, based on how well the MCA was visualized.
Of 100 patients with ICAO, the symptomatic CI group included 36 patients. ACA-PCoA score and white matter disease grades were significantly higher in the CI group (indicating poor collateral flow). More than 80% of patients with an ACA-PCoA score of 4 (poor collateral) experienced symptomatic CI. Thirty-one symptomatic CI patients (86%) had an MCA flow score of 1 or 2 (decreased MCA flow).
The ACA-PCoA score and white matter disease grade may suggest an increased risk of CI following ICAO 2).
Clinical Significance of the Circle of Willis in Patients with Symptomatic Internal Carotid Artery Occlusion 3).
Treatment
10–15% of patients presenting with internal carotid artery territory stroke or transient ischemic attacks (TIA) are found to have internal carotid artery occlusion. This amounts to an estimated 61,000 first ever strokes and 19,000 TIAs per year in the United States. Prevention of subsequent stroke in symptomatic patients with carotid artery occlusion remains a difficult challenge. The overall rate of subsequent stroke is 7% per year for all stroke and 5.9% per year for ischemic stroke ipsilateral to the occluded carotid artery 4).
These risks persist even despite treatment with antiaggregants and anticoagulants 5).
Mechanical Thrombectomy for Internal Carotid Artery Stenosis
Case reports
Deshpande and Giri presented a unique case of a middle-aged gentleman, who recovered from asymptomatic Covid-19 infection and presented again with delayed stroke. He had vision loss secondary to internal carotid artery occlusion in the absence of neurological symptoms. This is the first case that describes cerebrovascular stroke due to delayed large vessel occlusion secondary to Covid-19 infection presenting as monocular vision loss 6).