Case 1 (Fig. 1 panels a-e)

A six-year-old boy was diagnosed with recurrent posterior circulation stroke. He had developed three non-disabling strokes despite being treated with aspirin, over a span of 2 months, after which he worsened rapidly. His initial intracranial magnetic resonance (MR) time-of-flight angiogram was unrevealing. His new MR angiogram showed basilar artery (BA) occlusion (Table I). A digital subtraction angiography (DSA), showed a dissection involving the left vertebral artery (VA) with filling defect suggestive of thrombus and complete occlusion of the distal BA. The clot was retrieved by stent-retriever with complete recanalization of the BA.

Fig. 1 Case 1: MRI at admission showing pontine infarcts [arrow] (A) with basilar occlusion on MRA* (B) and DSA [arrow] (C). Post thrombectomy DSA [arrow] (D) showing complete recanalization and MRI [arrow] (E) showing no evolution of infarcts; Case 2: MRI at presentation showing right pontine infarcts [arrow] (F) with basilar occlusion on MRA* (G) and DSA [arrow] (H). Post thrombectomy DSA [arrow] (I) showing complete recanalisation and CT scan after 24 hours showing small right pontine infarct [arrow] (J); Case 3: CT at admission showing dense MCA sign on left [arrow] (K) with left MCA occlusion on CTA* (L) and DSA [arrow] (M). Post thrombectomy DSA [arrow] (N) showing complete recanalisation and CT scan after 24 hours showing small left frontal infract [arrow] (O).

Case 2 (Fig. 1 f-j)

A six-year-old boy came with history of giddiness and irritability for 24 hours with difficulty breathing and quadriparesis soon after waking up. MRI brain with MR angiogram showed multiple infarcts in right hemi-pons with occluded BA. DSA showed complete occlusion of the distal BA (Table I). The clot was retrieved with complete recanalization of the BA. Extensive workup for etiology including 2D Echo and hemoglobin electro-phoresis did not reveal any cause.

A 17-year-old boy presented with sudden onset of loss of speech and right hemiplegia for two hours. A contrast enhanced CT (CECT) scan of brain showed ill-defined hypodensities in left fronto-temporo-parietal lobes and ganglio-capsular region with occlusion of M1 segment of middle cerebral artery (MCA). DSA showed complete occlusion of left M1 (Table I). The clot was retrieved using stent retriever. Detailed evaluation for etiology revealed iron deficiency anemia, a normal 2D Echo & antiphospholipid antibody and ANA (anti neutrophillic antibody) panel.

A 13-year-old boy, known case of severe rheumatic mitral valve stenosis with severe pulmonary hypertension (PH), underwent mitral valve replacement at our center. On post-operative day three, he developed acute onset of left hemiplegia with gaze deviation to right side. A CECT scan of brain with angiogram showed subtle loss of grey white differentiation in right frontal lobe with complete occlusion right internal carotid artery (ICA) (table 1). DSA showed complete occlusion of right ICA. The clot was retrieved by stent retriever (Fig. 2). Twenty four hours later he was started on conventional heparin, and was later switched to oral acenocoumarol (Acitrom).

Fig. 2 Schematic representation of procedure of Mechanical Thrombectomy using Retrievable stent, (A) Internal carotid artery (c) and its branches Middle cerebral artery (a) and anterior cerebral artery (b). There is occlusion of the proximal MCA (arrow) with clot shown in brown color with absence of flow (shown as grey color) distal to the clot; B. A guide catheter is shown in the ICA (d) through which a microcatheter, shown in green color (f), over a microwire (e), has been negotiated across the clot into distal MCA; C. The microwire has been removed and the stent retriever (g), shown in blue color, has been negotiated through the microcatheter and deployed across the clot and flow re-established (shown as pink color); D. After keeping the stent open into the clot for 3-5 minutes, it is slowly withdrawn back into the guiding catheter; E. Normal flow (shown in red color) and complete recanalization achieved.

A 13-year-old boy, known case of Ebstein’s anomaly with tricuspid regurgitation with severe PH, underwent Blalock-Taussig shunt at our center. On post-operative day two, he developed acute onset of right hemiplegia with gaze deviation to left with profound drowsiness (Table I). A CECT scan of brain with angiogram showed subtle focus of hypodensity in left corona radiata and lentiform nucleus with left MCA occlusion. DSA showed occlusion of left M1 segment of MCA. The clot was retrieved using stent retriever.

Five boys aged between six to seventeen years (median 13 y) underwent MT. Common femoral artery was used for vascular access in all cases. None of the patient received intravenous (IVT) or intra-arterial thrombolysis (IAT). Case 1 and 2 were out of the window period while case 4 and 5 had undergone cardiac surgery and hence IVT was contraindicated in them. Only one patient (Case 3) was eligible for IVT however the guardians opted to skip IVT and go for MT directly. All patients received injection heparin 60 units per kilogram of bodyweight through the sheath at the beginning of the procedure. Case 1, 4 and 5 received oral anticoagulation following the procedure. Case 3 received conventional heparin initially (7 days) followed by dual antiplatelets while case 2 was discharged on single antiplatelet drug only. The mRS at approximately 90 days ranged from 0 to 1 with no death or dependency. Angiographically, mTICI 3 grade reperfusion was achieved in 4 patients while 2b was achieved in one. There were no periprocedural complications.

The 2012 Thrombolysis in Pediatric Stroke trial [8] to which the medical fraternity was looking forward to for answers was stopped in 2014 due to failure to recruit patients. It is thus less likely to have more trials for intravenous thrombolysis and even more so for intrarterial thrombolysis or MT in the near future. Hence careful extrapolation of adult treatment protocols seems the only plausible alternative at present. For adult AIS, IVT within 4.5 hours of symptom onset and MT till 6 hours [9] (in select few cases upto 24 hours if there is significant deficit-to-infarct mismatch [10]) are the two major treatment options available. However, owing to developmentally immature nature of the hemostatic and fibrinolytic system in children, there is low endogenous plasminogen level and higher plasminogen activator inhibitor-1 (PAI-1) level which makes the dose and response of tissue plasminogen activator (tPA) unpredictable [3,11].

Similarly MT may not be as straightforward as it may seem in adults as LVO in children may be because of cerebral arteriopathy wherein the vessels are inflamed and friable. Along with this the disparity in size of vessels makes MT challenging in pediatric population [12]. Hence careful selection of patients and devices is of utmost importance to avoid any therapeutic misadventure. In our series two patients had cardioembolic stroke and one had dissection, such patients may be the ideal candidates in whom adult recommendations can be applied safely. Most of the current data on EVT in pediatric stroke comprise of small case series or individual case reports. As per the 2017 review on EVT for AIS in children, till 2016, only 68 cases using EVT have been reported out of which 24 were using IAT while 44 used MT with or without IAT [13]. The patients who underwent IA mechanical thrombectomy had significantly better clinical (79.5% versus 20.5%; P=0.001) and radiographic outcomes (complete recanalisation, 79.1% versus 38.9%; P=0.002) with fewer complications (13.6% versus 37.5%; P=0.006) than those who underwent IA fibrinolysis only [13]. These findings are also reflected in our series where there were no complications with clinical and radiological outcomes (table no. 1) comparable to previously reported series. The major limitation of this study is its retrospective nature, based on review of case records. Small sample size and lack of any control group are the other major limitations.

Stroke in children, though infrequent, is disabling and hence there is need to sensitize caregivers and physicians to the necessity of timely intervention. Our series suggests that MT may be a safe and effective procedure for pediatric AIS with LVO. MT may be strongly considered for severe pediatric strokes with LVO on a case to case basis, as it is life saving and decreases long-term morbidity.

Contributors: All authors contributed to management of cases, manuscript writing, and approved the final version of manuscript. They agree to be accountable for authenticity and integrity of the work.

Funding: None; Competing interest: None stated.