Stem cell therapy for ischemic stroke holds great promise for the treatment of neurological impairment and has moved from the laboratory into early clinical trials. The mechanism of action of stem cell therapy includes the bystander effect and cell replacement. The bystander effect plays an important role in the acute to subacute phase, and cell replacement plays an important role in the subacute to chronic phase. Intraarterial (IA) transplantation is less invasive than intraparenchymal transplantation and can provide more cells in the affected brain region than intravenous transplantation. However, transplanted cell migration was reported to be insufficient, and few transplanted cells were retained in the brain for an extended period. Therefore, the bystander effect was considered the main mechanism of action of IA stem cell transplantation. In most clinical trials, IA transplantation was performed during the acute and subacute phases. Although clinical trials of IA transplantation demonstrated safety, they did not demonstrate satisfactory efficacy in improving patient outcomes. To increase efficacy, increased migration of transplanted cells and production of long surviving and effective stem cells would be crucial. Given the lack of knowledge on this subject, we review and summarize the mechanisms of action of transplanted stem cells and recent advancements in preclinical and clinical studies to provide information and guidance for further advancement of acute/subacute phase IA stem cell transplantation therapy for ischemic stroke.

Background and Objectives: Non-cystic manifestation of autosomal dominant polycystic kidney disease (ADPKD) is an important risk factor for cerebral aneurysms. In this report, we describe a rare spontaneous internal carotid artery (ICA) dissection in a patient with ADPKD. Observations: A 38-year-old woman with a history of ADPKD and acute myocardial infarction due to coronary artery dissection experienced severe spontaneous pain on the left side of her neck. Magnetic resonance imaging (MRI) revealed a severe left ICA stenosis localized at its origin. Carotid plaque MRI showed that the stenotic lesion was due to a subacute intramural hematoma. Close follow-up by an imaging study was performed under the diagnosis of spontaneous extracranial ICA dissection, and spontaneous regression of the intramural hematoma was observed uneventfully. Conclusions: When patients with a history of ADPKD present with severe neck pain, it is crucial to consider the possibility of a spontaneous ICA dissection. A carotid plaque MRI is beneficial in the differential diagnosis. Conservative management may benefit patients without ischemic symptoms.

T2*-weighted magnetic resonance angiography (SWAN) detects hemodynamic insufficiency as hypointense areas in medullary or cortical veins. We therefore investigated whether SWAN can help predict ischemic penumbra-like lesions in patients with acute ischemic stroke (AIS). Magnetic resonance imaging (MRI) records—including SWAN, diffusion-weighted imaging (DWI), and magnetic resonance angiography (MRA)—of consecutive patients with major vessel occlusion within 6 h from AIS onset were analyzed. Acute recanalization was defined as an arterial occlusive lesion score of 2–3. A modified Alberta Stroke Program Early CT Score (mASPECTS) was used to evaluate ischemic areas revealed by SWAN and DWI. SWAN- and DWI-based mASPECTSs were calculated, and correlations between DWI-SWAN mismatches with final infarct lesions or clinical outcomes were evaluated. Among the 35 patients included in this study, we confirmed cardioembolic stroke in 26, atherothrombotic stroke in 4, and unknown stroke etiology in 5. Overall, recanalization was achieved in 23 patients, who showed a higher follow-up DWI-based mASPECTS and lower modified Rankin Scale (mRS) score at 90 days than patients without recanalization. Initial SWAN- and follow-up DWI-based mASPECTSs were significantly higher for atherothrombotic stroke than for cardioembolic stroke. Of 12 patients without recanalization, DWI-SWAN mismatch was significantly correlated with infarct growth. Patients with recanalization showed no such correlation. In the assessment of clinical outcome, follow-up DWI-based mASPECTS and patient's age were significantly correlated with mRS at 90 days after stroke. A multivariate logistic regression analysis revealed that the follow-up DWI-based mASPECTS was independently associated with a favorable outcome 90 days after stroke. For patients with AIS, DWI-SWAN mismatch might show penumbra-like lesions that would predict infarct growth without acute recanalization. Assessment of ischemic lesions from the venous side appears to be useful for considering the etiology and revascularization therapy.

Mechanical thrombectomy with a stent retriever has been reported to achieve high rates of successful recanalization, and reduce disability and mortality in patients with acute ischemic stroke (AIS) due to proximal vessel occlusion. However, in a few cases, the treatment is difficult due to artery tortuosity or other factors. The authors present a case of a 94-year-old man presenting with acute right middle cerebral artery occlusion. We attempted to treat using a stent retriever via transfemoral approach, but failed to advance the guiding catheter into the right internal carotid artery due to femoral artery tortuosity and a type III arch. By changing approaches from transfemoral to transbrachial and by using TrevoProVue through a 4.2 Fr Simmons-type catheter without a guiding catheter, we were able to achieve rapid recanalization in only 26 minutes from brachial artery puncture to reperfusion. In conclusion, rapid reperfusion in an AIS patient was successfully achieved by combining a stent retriever with a 4.2 Fr catheter (without a guiding catheter) and a transbrachial approach (as opposed to a transfemoral approach). When the transfemoral approach is not feasible, we recommend consideration of this strategy as an alternative.