key: cord-0949057-crbknwtg authors: Uginet, M.; Breville, G.; Hofmeister, J.; Machi, P.; Lalive, P. H.; Rosi, A.; Fitsiori, A.; Vargas, M. I.; Assal, F.; Allali, G.; Lövblad, K. O. title: Answer to Letter to the Editor: High-resolution Black Blood Vessel Wall Imaging in COVID-19 Encephalopathy—is it Really Endotheliitis? date: 2021-11-10 journal: Clin Neuroradiol DOI: 10.1007/s00062-021-01113-2 sha: ec739afdfafcbcbafb36d2904cf0d3218edbb5f1 doc_id: 949057 cord_uid: crbknwtg nan Dear Madam, Dear Sir, We thank you for giving us the opportunity to clarify this crucial point [1] . First of all, we acknowledge that vessel wall enhancement can be due to vasa vasorum involvement [2] [3] [4] [5] ; however, the enhancement seen is in older patients and is less extensive than in the cases we have seen, i.e. it usually is at the entrance of the vertebral arteries at the dura mater also in regions where arteriosclerotic inflammation may be present. In our cases the enhancement is more extensive and also goes up to the junction of both vertebral arteries and even into the basilar artery, which is in our experience not the case in vessel wall enhancement due to vasa vasorum enhancement only. We are currently re-evaluating these patients in a prospective study with the same MR protocol [6, 7] and in the cases we have examined until now, the enhancement has disappeared (Allali, Assal, Lövblad, unpublished data). We provide a figure showing this phenomenon in one of our patients (Fig. 1) . Enhancement of cerebral vessels has been documented by other groups in patients with the disease but with other protocols [8] . This follow-up is in our opinion highly suggestive of a real vascular involvement. High-Resolution Black Blood Vessel Wall Imaging in COVID-19 Encephalopathy-Is it Really Endotheliitis? Vasa vasorum of the intracranial arteries Vasa vasorum of proximal cerebral arteries after dural crossing -potential imaging confounder in diagnosing intracranial vasculitis in elderly subjects on blackblood MRI Intracranial cerebrovascular vasa vasorum associated with atherosclerosis and large thick-walled aneurysms Intracranial vasa vasorum: insights and implications for imaging COVID-19 encephalopathy: Clinical and neurobiological features Cerebrovascular Complications and Vessel Wall Imaging in COVID-19 Encephalopathy-A Pilot Study Large and Small Cerebral Vessel Involvement in Severe COVID-19: Detailed Clinical Workup of a Case Series