Abstract
The purpose of this article is to address several challenging questions in the management of young patients (those age 60 and under) who present with ischemic stroke. Do genetic thrombophilic states, strongly associated with venous thrombosis, independently cause arterial events in adults? Should cases of patent foramen ovale be closed with mechanical devices in patients with cryptogenic stroke? What are the optimal treatments for cerebral vein thrombosis, carotid artery dissection, and antiphospholipid syndrome and are DOACs acceptable treatment for these indications? What is the mechanism underlying large vessel stroke in patients with COVID-19? This is a narrative review. We searched PubMed and Embase and American College of physicians Journal club database for English language articles since 2000 looking mainly at randomized clinical trials, Meta analyses, Cochran reviews as well as some research articles viewed to be cutting edge regarding anticoagulation and cerebrovascular disease. Searches were done entering cerebral vein thrombosis, carotid dissection, anticoagulation therapy and stroke, antiphospholipid antibody and stroke, stroke in young adults, cryptogenic stroke and anticoagulation, patent foramen ovale and cryptogenic stroke, COVID-19 and stroke.
Cerebral Vein Thrombosis
Cerebral vein thrombosis (CVT) is associated with an identifiable hypercoagulable state in 85% of cases. These are most frequently hormone related conditions such as pregnancy, birth control pills and estrogens. 1 Other causes include paroxysmal nocturnal hemoglobinuria, myeloproliferative disorders, antiphospholipid antibody, and hereditary thrombophilia such as factor V Leiden or prothrombin 20210A mutations. 1 The patient frequently presents with headaches, which can be mistaken for a migraine with aura. It generally is slow in onset, building over several days, however, it also can present as a severe, ice-pick headache mimicking an acute migraine. 2,3
Papilledema is a frequent finding in thrombosis involving the superior sagittal sinus and should be sought after. Because a thrombosis can involve the inferior, sagittal, sigmoid, or straight sinus, funduscopic examination can be negative. Head CT is abnormal in only 30% of cases. 4 The diagnosis is frequently made by MRI, but the best screening tests, depending on the institution, would be either a CT angiogram. CT Venogram, MRI, MRA and MR Venogram.
Predictive factors of poor prognosis includes CNS infection, thrombosis of the deep veins, intracranial hemorrhage, any malignancy, abnormal mental status, age greater than 37 and male gender. 1 There is a good outcome in 80% patients on heparin or low molecular weight heparin (LMWH). 1 CVT may present with intracranial bleeding due to back pressure from the thrombosis and presentation may be with a brain hemorrhage, counterintuitively requiring heparin. 5
Two studies comparing heparin or low molecular weight heparin versus placebo have shown a trend favoring heparin, but did not reach statistical significance. 6,7 Both studies lacked precision due to small sample size. A Cochrane review with meta-analysis of the same 2 trials involved only 79 patients and revealed a relative risk of .33 and relative risk of death or dependency of 0.46 in heparin treated patients versus untreated. 8 There was no increase in symptomatic cerebral hemorrhages with the anticoagulants. 8
Based upon these studies, international organizations such as the American College of Chest physicians and the American Heart Association/ American Stroke Association have recommended either unfractionated or low molecular weight heparin as initial treatment for cerebral vein thrombosis. 9,10 LMWH seems to be more effective and equally safe as heparin based on 2 comparative studies. 11,12
There is insufficient evidence that endovascular thrombolysis may be performed as a therapeutic option, however in patients with a poor prognosis and/or poor response to anticoagulation, it is not unreasonable to try. 3 With respect to duration of therapy, European guidelines recommend 3 months of oral anticoagulation for patients with CVT provoked by a transient risk factor and 6 to 12 months for patients with idiopathic CVT and those with “mild” thrombophilia. They recommend indefinite oral anticoagulation for patients with either recurrent CVT or 1 episode of CVT and “severe” thrombophilia. 5
With respect to direct oral anticoagulants (DOACs), the European stroke organization 2017 guidelines recommended against their use, because patients with this diagnosis weren’t included in the pivotal trials of deep venous thrombosis comparing DOACs and vitamin K antagonists. 13 However it would not be unreasonable to use them since they were non-inferior to vitamin K antagonist in treatment of venous thromboembolism in all of the pivotal trials and were associated with a 50% reduction in cerebral hemorrhage. 14,15
The randomized RESPECT trial was performed with 60 patients with cerebral vein thrombosis randomized to each group in a parallel group, open label, multicenter clinical trial with blinded endpoint adjudication. 16 One group received Dabigatran 150 mg twice a daily and the other adjusted dose warfarin with the INR maintained between 2 and 3. They were followed for 22-23 weeks. These were patients who had acute cerebral vein thrombosis and were stable after 5-15 days of treatment with parenteral heparin.
Patients with CVT associated with central nervous system infection or major trauma were excluded, however, those with intracranial hemorrhage were allowed. No recurrent venous thromboembolism was noted in either group. There was 1 major bleed in the Dabigatran group and 2 with warfarin. Whether other DOACs would perform equally was not addressed in this trial. This would be a concern in someone with CVT and renal disease, who would not be a candidate for Dabigatran.
A second prospective observational trial involved consecutive patients with clinical features of cerebral vein thrombosis confirmed with either CT or magnetic resonance imaging. 17 People with infection or trauma were excluded.
A total of 111 patients were included, 45 on DOACs and 66 on warfarin. The groups were comparable except the DOAC patients had a higher incidence of headaches, 93% versus 63% and were significantly more likely than those in the warfarin group to have intracerebral hemorrhage on initial imaging. Follow-up ranged from 6-13 months and all patients underwent neurological examination at 6 months. Clinical neurologic worsening was reported in only 1 patient, and that was in the warfarin group. 6 patients reported major bleeding, 2 in the DOAC arm and 4 in the warfarin arm. This trial seems to confirm the RESPECT finding that DOACs are safe in this situation, including Rivaroxaban, which was the main DOAC in this trial.
A Meta-analysis of 5 studies published in 2020 consisting of 1 randomized and 4 observational trials showed an excellent functional outcome in 81.8% of DOAC patients versus 76.1% with warfarin. 18 There was a 56% decrease in major bleeding with the DOACs at 1.32% versus 3.45%; however this was not statistically significant (CI 0.12 to 1.59).
Another trial of 20 patients receiving Rivaroxaban with no previous heparin reported an excellent outcome in 19 of 20 patients at 6 months. 19 Two other relatively small trials also showed favorable results with DOACs 20,21 (see Table 1).
DOACS in Cerebral Vein Thrombosis.
A new phase 3 trial called Secret will compare Rivaroxaban 20 mg daily versus standard of care which would be either unfractionated heparin, low molecular weight heparin with transition to vitamin K antagonists or continuation with low molecular weight heparin. 22 The primary outcome measure will be a composite rate of all-cause mortality, symptomatic intracranial bleeding, and major extracranial bleeding over 180 days. Secondary outcome measures will be all cause mortality, symptomatic intracranial bleeding, major extracranial bleeding, recurrent venous thromboembolism, and major bleeding or clinically relevant non major bleeding.
At this time it would seem that DOACs, particularly Dabigatran, and to a lesser degree Rivaroxaban would be reasonably safe alternatives to warfarin for preventing recurrent DVTs in patients with CVT after initial unfractionated heparin or preferably LMWH. While the American Heart Association and American Stroke Association recommended against DOACs, those statements were generated in 2013. 23 The American Society of Hematology in their 2019 DVT treatment guidelines was silent in this area.
Cervical Artery Dissection
Cervical artery dissection (CD) is a rare cause of stroke, but among people under 45, it comprises 25% of cases. 24 CD are more commonly seen in the upper cervical spine internal carotid or vertebral artery. 25 It may seem risky and counterintuitive to administer anticoagulation for a torn blood vessel, but cerebrovascular dissections are rarely actual ruptures of the vessel; more often, they are separations of the intima from the rest of the vascular wall and the prothrombotic intimal flap is a source of distal emboli. 26
Dissections can occur from trauma associated with mechanical forces of rapid acceleration, deceleration, and torsional forces (e.g. motor vehicle accident, chiropractic neck manipulation, roller coasters), but most occur spontaneously and are labeled as “idiopathic.” 27,28 The etiology of spontaneous dissections is unknown but structural anomalies (e.g. Eagle Syndrome) or underlying collagen vascular diseases have been associated with CD. 29,30 In a large series of patients with cervical artery dissections, those with internal carotid artery dissection (ICAD) were more common than vertebral artery dissections (VAD) and ICAD had less neck trauma to report than VAD patients. 31 Patients with dissection related stroke have not been excluded from thrombolysis trials despite the theoretic risk of hematoma. Carotid dissection with flow limiting stenosis is occasionally considered for stenting, but this is a controversial point, as treatment is basically medical management with antithrombotic, either antiplatelet therapy or anticoagulation.
In a systematic review of 762 patients with cervical dissections, Menon et al did not find a significant difference in the risk of stroke with antiplatelet therapy (1.9%) versus anticoagulant therapy (2.0%). 32 The risk of death was 1.8% with antiplatelet therapy and 1.8% with anticoagulants. A 2012 meta-analysis of nonrandomized studies with over 1600 patients with cervical artery dissection also reported no significant difference in recurrent stroke risk or mortality comparing anticoagulation with antiplatelet therapy. 33
A review of 38 studies, none of which were randomized, involving 1398 patients showed no differences in death, death and disability, ischemic stroke or symptomatic intracranial hemorrhage between recipients of antiplatelet and anticoagulant therapy. The authors felt that absent a randomized trial there was no good means of distinguishing between the options. 34
The CADISS trial was a randomized trial comparing antiplatelet versus anticoagulation therapy in patients with cervical artery dissection. It involved 250 patients; 118 with carotid dissection and 132 with vertebral dissection. 126 patients were assigned to antiplatelet treatment versus 124 to anticoagulation. In the entire trial 4/250 (2%) patients experienced a stroke recurrence. Stroke or death occurred in 3 of the 126 patients in the antiplatelet group (2%) versus 1 of 124 in the anticoagulant room (1%). The confidence interval was 0.006-4.233. There was no difference in the efficacy of antiplatelet and anticoagulant drugs in preventing stroke and death. 35
A second large trial, which was not randomized, looked at anticoagulation versus antiplatelet treatment in patients with carotid and vertebral artery dissection, but in contrast to CADISS, included patients with intracranial involvement. The mean follow-up in the study was 24 months. 55% of patients received antiplatelet therapy, with the choice of drug or combination at the discretion of the treating doctor. 29.4% of those in the trial received anticoagulation and 12.6% received combined treatment.
Ischemic or hemorrhagic events occurred in 9.6% of the patients on antiplatelet and 10.4% of those on anticoagulation, and 13.3% occurred on combined treatment. This study included both traumatic and spontaneous dissections. In intracranial versus cervical dissection, it was more likely the patient with intracranial dissection would be placed on antiplatelet therapy, however, the results were no different. 36 Another trial prospectively collected data from 298 patients with spontaneous dissection of the cervical carotid artery and showed very low incidence of ischemic events during follow-up. There was no difference in ischemic or hemorrhagic events between those treated with anticoagulants and those with aspirin 37 (see all trials in Table 2).
Anticoagulant Versus Antiplatelet Therapy in Cervical and Vertebral Artery Dissection.
While the American College of chest physician’s 2012 guidelines recommended 3-6 months of anticoagulant therapy, many studies since then indicate no evidence for superiority of anticoagulation over antiplatelet agents. 38 Given both antiplatelet and anticoagulation are acceptable treatment options for carotid dissection, stroke prevention, experts may weigh a patient’s comorbidity profile or history of compliance in choosing the patient’s antithrombotic treatment.
For those with recurrent ischemic events despite optimized medical management, endovascular treatment options like stenting may be considered. 39 Imaging studies indicating flow discrepancy in the culprit CD artery territory may be helpful in consideration for endovascular treatment options. Flow limitation due to CD may cause perfusion dependent dysfunction that may be salvageable, e.g. penumbral tissue. In such cases, stenting may restore vessel caliber and intracranial perfusion given antithrombotic treatment alone may not restore normal cerebrovascular flow. 40 Imaging studies such as Transcranial Doppler (TCD), CT perfusion (CTP), and MR perfusion (MRP) can demonstrate hypoperfusion associated with CD.
Antiphospholipid Antibody Syndrome
Antiphospholipid antibody syndrome (APS) involves an arterial or venous thrombotic event, or pregnancy losses in connection with positivity of an antiphospholipid antibody. There needs to be a confirmation of the tests 12 weeks later. 41 The 3 relevant antibodies are lupus anticoagulant, anticardiolipin antibody, and anti-beta-2 glycoprotein. Anti-phosphatidyl serine has been correlated with thromboembolism in patients with APS but has not yet been accepted as an official criterion. 42
It has been suggested that more than 20% of strokes in patients under 45 are associated with APS. 43 Although the mechanisms of cerebral involvement are not completely understood, multiple mechanisms are postulated. These include disruption of the Annexin shield, allowing antiphospholipid antibody to disrupt the endothelium, inhibition of the protein C pathway, activation of platelets as well as diffuse expression of adhesion molecules, and tissue factor in the endothelium. 44,45 More recently, and the activation of complement has been discovered and found to be particularly relevant in catastrophic antiphospholipid antibody syndrome. 46 A complement factor, platelet bound C4d, which sits at the intersection of the anticoagulation and complement pathways, also has value in predicting thrombosis risk among lupus patients. 47
Ischemic stroke is the most common and severe complication of arterial disease of antiphospholipid syndrome. 48 The stroke mechanism in APS may be thrombotic or embolic. 49 The clinical manifestations will depend on the location and size. It can involve not only small arteries but also larger arteries as well. 50,51 Embolic stroke occurs mainly because of valvular lesions due to deposition of immune complex Libman-Sacks vegetations in association with systemic lupus erythematosus (SLE). 32,52
There are numerous other neurological signs of cerebrovascular disease in APS as it has been associated with cognitive dysfunction, 53 migraine, 54 seizures, 55 multiple sclerosis type syndrome, 56 neuro-ophthalmology involvement, 57 psychiatric manifestations, 58 as well as transverse myelitis, 59 and movement disorders. 60 Patients who are positive for lupus anticoagulant are more susceptible to thrombosis than those with anticardiolipin or anti-beta-2 glycoprotein. 61 Also patients who are triple positive are more susceptible than double or single positive patients to an initial event as well as recurrent thrombosis. 62
Heparin use in antiphospholipid syndrome has been restricted to the treatment of catastrophic antiphospholipid syndrome as well as 2 studies involved with the rescue of people who were felt to be resistant to warfarin. 63 With respect to arterial disease, the recommended treatment is heparin transitioning to warfarin. More controversial is the dose of warfarin. 2 studies showed that maintaining the INR between 2 and 3 was superior to higher dosages with respect to both thrombosis and bleeding complications in both arterial and venous disease. 46,64 However, the European league against rheumatism (EULAR) recommendations are for a target INR between 3 and 4 in APS patients with ischemic stroke in antiphospholipid syndrome. 65 The American College of chest physician’s recommends the INR prolongation to be between 2 and 3.
There has only been one trial which has compared antiplatelet therapy with Warfarin. Based on the APASS trial involving 1770 individuals with stroke, it appears that both warfarin and aspirin appear to be reasonable antithrombotic treatment options for patient with a first-time arterial ischemic stroke with antiphospholipid syndrome. 66
With respect to the use of direct oral anticoagulants in APS, a trial from England involving 120 patients with thrombotic antiphospholipid syndrome compared 6 months of Rivaroxaban; 20 mg a day versus dose adjusted warfarin with an INR between 2 and 3. While the trial was not considered successful because the primary endpoint was endogenous thrombin potential (ETP) which was higher in Rivaroxaban patients than those on warfarin, the study nonetheless showed no cases of thrombosis or bleeding in either group at 6 months. However, there were very few patients with triple positive antibodies, and people with arterial disease were excluded. 67
The TRAPS study. focusing on triple positive patients. studied a population highly enriched for thrombotic risk. The dose of Rivaroxaban was 20 mg compared with Coumadin with an INR maintained between 2-3 after initial treatment with heparin. The trial was terminated prematurely after the enrollment of 120 patients because of an excessive number of events in the Rivaroxaban arm. There were 11 events (19%) in the Rivaroxaban arm and 2 (3%) in the warfarin group. Major bleeding occurred in 6 patients, 4 in the Rivaroxaban group (7%) and 2 (3% in the warfarin group. There were no deaths. 68
A randomized clinical trial from Spain also compared Rivaroxaban 20 mg per day versus vitamin K antagonist therapy, maintaining the INR between 2 and 3, or between 3 and 4, for people with a previous history of multiple thromboses. Approximately 60% of those had triple positivity. Recurrent thrombosis occurred in 11.6% in the Rivaroxaban arm and 6.3% on the vitamin K antagonist arm. Specifically ischemic stroke occurred in 4/ 50 in the Rivaroxaban group and 0/61 in the warfarin group. The results of overall thrombotic events were driven by arterial thrombosis and not statistically significant in venous thrombosis. 69
Lastly, a meta-analysis involving 447 APS patients treated with DOACs including Dabigatran, Apixiban, and mostly Rivaroxaban reported a recurrent thrombosis rate of 16.9% while on factor Xa inhibitors and 15% on Dabigatran. Triple positivity was associated with an increased risk up to 56%. 70 Summary of recent trials of DOACs versus vitamin K antagonist in APS are listed in Table 3.
DOACs in Antiphospholipid Antibody Syndrome.
No precedent exists for the standard dose of DOACs in patients who have APS with arterial thrombosis and evidence from randomized clinical trials suggests that such patients are at increased risk for recurrent thrombosis while on DOACs. 71 The phase 2/3 RISAPS trial will assess the efficacy of high-intensity Rivaroxaban at 15 mg twice daily versus high intensity warfarin INR 3.5 in patients with APS with a history of stroke or other ischemic brain manifestations. 72 Also, an international Registry of DOACs use in patients with APS is being set up with the intent to capture information on all DOAC use and outcomes in these patients. 73
Based upon these trials, the European Medicines Agency 74 and the European Society of cardiology 75 came out with recommendations against DOACs for antiphospholipid syndrome. In patients who have events on warfarin, other treatments such as rituximab, hydroxychloroquine, and statins have been discussed.
Since Coumadin requires several days of transition with low molecular heparin and has many other inconveniences, there are ongoing trials to try to isolate a population of antiphospholipid antibody patients who might be candidates for DOACs.
One of the new developments in APS is the increasingly recognizable phenomenon of complement activation in antiphospholipid antibody syndrome. Patients with catastrophic antiphospholipid antibody syndrome have a high incidence of this activity. 76 Patients, who have not responded to the usual measures for catastrophic APS such as corticosteroids, plasma exchange, intravenous immunoglobulin, and Rituxan, could be candidates for Eculuzimab, 77 an inhibitor of C5. This drug has been very successful in the treatment of 2 other diseases characterized by excess complement activity, including paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome.
It would seem at this time that triple positive patients and people with a history of arterial disease should unequivocally not receive DOACs. Whether a suitable population can be found where it would be acceptable to give DOACs will depend on future studies (summary of these trials in Table 3).
Closure of Patent Foramen Ovale to Prevent Paradoxical Embolus
Patent foramen ovale occurs in about 25% of adults. Some studies have shown young adults with strokes secondary to patent foramen ovale had a high incidence of accompanying prothrombotic states 78,79 3 randomized trials performed a decade ago compared trans catheter surgical closure of these defects to medical therapy with antiplatelet agents or anticoagulants. 80 –82 People in the surgical intervention arm also received antiplatelet therapy. None of these trials showed a statistically significant advantage in intention to treat toward closure. However, they all demonstrated trends in favor of the intervention and the trials using the Amplatzer occluder device showed greater safety versus those using the Starflex.
Of the 3, the RESPECT trial came the closest to showing superiority in intention to treat with a hazard ratio of 0.5 and a P value of 0.08 for superiority with respect to closure versus medication. It actually did achieve superiority in on treatment analysis. However, the study’s precision was undermined by a wide confidence interval due to the small number of patients.
People with a large shunt and with a septal aneurysm did have a statistically significant advantage in that trial. The other 2 trials, the PC trial and the Closure I trials also showed a decreased hazard ratio with respect to measures such as recurrent stroke, TIA non-fatal stroke, but neither demonstrated statistical significance in intention to treat.
An editorial which accompanied the Respect and PC publications, while stating the pros and cons, opined that one should be circumspect about interpreting the low hazard ratios and decreased complication with the Amplatzer device as license to freely employ closure strategy. 83
More recently the needle has shifted in favor of these devices, based upon new randomized trials. 84 –87 Meta-analyses which include all of these trials have shown that the intervention is associated with a decreased risk for recurrent ischemic stroke compared with those on antiplatelet treatment. However, all of these trials have had limitations, including the exclusion of people over 60. They also do not show an improvement in TIA recurrence rate or mortality benefit and some of them have shown temporary increases in atrial fibrillation. Features such as large shunt size and presence of an aneurysm in the atrial septum have been factors more likely to be associated with success. 71
Also unsettled is the role of anticoagulant therapy. If a person has an ischemic stroke and patent foramen ovale with an accompanying deep venous thrombosis, are they better off with closure versus long-term anticoagulation therapy, whether stand alone or combined with closure procedures? Long-term anticoagulation therapy for this condition would be associated with a risk of major bleeding of 3% per year and 0.3% per year of cerebral hemorrhage.
It would appear at this time that these procedures are safe and indicated in numerous patients age 60 or under, with a cryptogenic stroke and patent foramen ovale, especially people with a large shunt with or without septal aneurysm. Reasons brought up to explain the difference between the 3 most recent trials and the initial 3 could be longer follow-up, better occlusive devices, and/or better selection of patients (summary of these trials is shown in Table 4).
Closure of Patient Foramen Ovale Versus Medical Therapy in Cryptogenic Stroke.
Hereditary Thrombophilia
Are mutations for factor V Leiden, Prothrombin 20210A, or deficiencies in antithrombin, protein C, or protein S causative or incidental in the pathogenesis of cryptogenic stroke in patients without a patent foramen ovale?
The controversy is fueled by findings from small case reports and meta-analyses which have shown mild trends of these thrombophilic conditions causing stroke mainly in children. 88 –90 however it is questionable whether a single mutation would be sufficient to predispose a child to a stroke. It is also unclear why there would be a difference in this predisposition between children and adults.
Regarding adults, large prospective cohort studies like the Physician’s Health Study and the Cardiovascular Health Study have not shown such a relationship in patients with factor V Leiden or prothrombin 20200A mutations, and the standard of practice has been to treat patients having these abnormalities on a case by case basis, mainly using antiplatelet therapy. 91 –93 Case reports have suggested that protein S and C deficiencies may play a causative role in young patients and middle aged women with cryptogenic stroke. 94,95 However, these findings have not been substantiated in case controlled or prospective studies, therefore protein S and C levels have not been routinely sought in stroke patients. 96,97
A large German meta-analysis showed a statistically significant increase in factor V Leiden mutation associated with patients with ischemic stroke versus those without the mutation but not with prothrombin 20210A mutations. 98
Another trial from Italy looked at 97 patients whose main age was 40.9 years with first ever cerebrovascular events. They were compared to age-matched control patients. Factor V Leiden and prothrombin 20210A mutations were detected with a 4.7 fold greater incidence in stroke patients than in the controls. These were all patients with patent foramen ovale who had been referred for percutaneous trans catheter closure. 99 An additional retrospective review showed a 13% incidence of protein C, protein S, or antithrombin deficiency in adults less than 45 years with ischemic stroke. Only 3% had factor 5 Leiden and prothrombin 20210A mutations. 100
A retrospective review studied all patients with stroke and TIA ≤60 years presenting to University College London Hospital stroke unit and daily TIA clinic from 1 January 2015 to 1 August 2016 with the average age of the patients being 49.1 years. Thrombophilia testing was reported in 360 patients including 171 with stroke and 189 with TIA. 14% of patients had positive tests with antiphospholipid antibody being most common. Thrombophilia mutations and deficiencies of protein C and S, and AT, were very uncommon. Follow-up testing was done in less than 10% of patients. 101
Another retrospective, observational, single center study involving 143 patients with stroke or TIA, reported that the most common positive tests were elevated factor VIII activity in 18% and protein S in 11%. Testing altered clinical management in only 1% of the total patients tested. 33 patients (75%) had the potential for carrying a misdiagnosis due to positive tests that were only never verified. The collective annual cost of testing was approximately $62,000. The conclusion was that thrombophilia testing in the inpatient setting rarely impacted clinical management of patients admitted with stroke or TIA. 102
It appears that case reports are most likely to report this association between thrombophilia and cryptogenic stroke versus registry, and other larger observational trials which show that thrombophilia testing in the acute, inpatient setting of stroke or TIA, in patients without a PFO rarely changes management. This remains a controversial area (see Table 5).
Thrombophilia and Cryptogenic Stoke.
COVID-19 Strokes in Young Patients
It remains to be seen exactly what the mechanisms are behind large vessel strokes in young people with COVID-19. Mechanisms for the increased risk of acute stroke include an inflammatory cascade and hypercoagulable state with serum elevated C-reactive protein, D-dimer, and ferritin. 103 According to Varga et al there was evidence of direct viral infection of endothelial cells and inflammation with the virus utilizing the ACE2 receptor. 104 The ACE2 receptor is prominent in lung epithelium but is also expressed on endothelial cells across multiple organs. Specifically in the brain, the SARS-CoV2 virus binds to angiotensin converting enzyme 2(ACE2) receptors present on brain endothelial cells. ACE2 is a key part of the renin–angiotensin system and is a counterbalance to angiotensin converting enzyme I (ACEI) which gives rise to angiotensin II, which is a pro-inflammatory vasoconstrictor, which can promote organ damage. With the depletion of ACE2 by SARS-COV2, the balance may be tipped in favor of the harmful ACEI / angiotensin II axis, with the promotion of brain injury, including both hemorrhagic and ischemic stroke. 105
Post-mortem evaluation from patients who deteriorated from COVID-19 multiorgan dysfunction, showed evidence of endothelial disruption and large artery mononuclear and neutrophil infiltration. The cascade of endothelial dysfunction may be vascular, endothelial injury and excessive platelet activation with resultant related thrombosis in cerebrovascular vessels. 105
A recent retrospective cohort study of 1916 patients from New York City hospitals showed that approximately 1.6% of adults with COVID-19 who visited the emergency room or were hospitalized, experienced an ischemic stroke. 106 This was a higher rate compared with a cohort of patients with influenza.
Another review of 165 patients hospitalized for Covid 9 showed that the main risk factor for stroke was severity of disease. This was confirmed in a systemic systematic review and meta-analysis involving 576 patients which showed that aside from a tendency toward a higher proportion of past history of cerebrovascular disease and increased serum interleukin-6 levels in stroke patients, no difference in demographics, vascular comorbidities, or -19 laboratory values were present in Covid stroke patients compared to known stroke patients. 107 This finding however does not lead to a good explanation regarding the patient’s to be described below with isolated large vessel stroke.
COVID-19 stroke patients who require reperfusion or mechanical thrombectomy may pose complicated management problems because of concerns regarding neuroimaging and safety to healthcare workers performing this procedure. 108 In fact, the number of these recanalization procedures has dropped considerably since the beginning of the pandemic. 109
With respect to young patients and the possible role of antiphospholipid antibodies in COVID-19 related strokes, a recent anecdotal report looked at 3 COVID-19 patients in China with strokes and found them to have antiphospholipid antibodies (APLAs). These patients had anticardiolipin IgA antibodies as well as anti-β2-glycoprotein I IgA and IgG antibodies. None were positive for lupus anticoagulant testing. The small number of patients, and the fact that they were predominantly IgA, generated skepticism as to their relevance, particularly since transient positivity for APLAs is common in acute infection.
110
There are, however, data to suggest that IgA positivity but not IgM
A recent collection of 5 COVID cases showed that large vessel stroke was a presenting sign in New York during the initial surge of COVID-19 hospitalizations in March and early April 2020. 113 These were all individuals under age 50, who were previously healthy. None required mechanical ventilation. The report did not offer enough information to determine what the precise cause was for the possible Covid-19 related strokes. None of them had echocardiograms reported except the first of the 5 cases. Furthermore, none of them had tests reported for APLA; it is unknown whether patients could have had paradoxical emboli, an arrhythmia, valvular lesions or APLAs, the most common causes of stroke in people under 50. D-dimer levels were significantly elevated in 3 of the 5 cases but there was no evidence of DIC. Furthermore among Stroke centers across the country, this spike of large-vessel occlusions in young people did not occur in the vast majority of centers.
In those people who have evidence of cytokine and thrombotic storm, strokes are probably part and parcel of the entire ongoing thrombotic process. However, there is a certain population of patients who sustain isolated large vessel thrombosis who may have other underlying pathologies that may be exacerbated by the acute viral infection, COVID-19.
Conclusions
Cerebral vein thrombosis can be treated with direct oral anticoagulants after initial heparin therapy and may possibly be used as a standalone drug in the future; however, that point needs to be clarified with further trials. Antiplatelet therapy or anticoagulation can be used to prevent stroke in cervical and vertebral dissection. There is no significant efficacy or safety difference between the 2. Anticoagulation with warfarin is preferred over DOACs for antiphospholipid syndrome; however concerns regarding negative data with DOAC use were mainly reported in arterial and triple positive patients. Eculuzumab is a promising agent for catastrophic antiphospholipid antibody syndrome.
Most cryptogenic ischemic stroke patients, age 60 or younger, with a patent foramen ovale, will benefit from closure, particularly those with large shunt size with and without septal aneurysm.
It is still unclear whether hereditary thrombophilia in patients without a patent foramen ovale predisposes to arterial stroke, however if it does, it is rare in adults. The data on COVID-19 associated strokes is still evolving. There is accumulating information regarding increased megakaryocytes deposition in multiple organs 114 NETS formation 115 as well as abnormal platelet function and cytokines driving these atypical strokes in young people.
Footnotes
Authors' Note
Both Dr Song and Dr Berkman wrote the manuscript equally.
Declaration of Conflicting Interests
The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Dr Berkman is a speaker for Janssen pharmaceuticals and Alexion. Dr Song is a principal investigator for the NIH StrokeNet site at Cedars-Sinai, a GORE REDUCE co investigator and has reeived honoraria for IMPACT-LIVE CME lectures.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
