Background
Wake-up stroke (WUS) represents a substantial proportion of acute ischemic strokes, characterized by an unknown time of symptom onset, which historically limited eligibility for time-dependent reperfusion therapies. Advanced neuroimaging, including diffusion-weighted imaging (DWI)-FLAIR mismatch and CT perfusion (CTP), has revolutionized patient selection, extending the therapeutic window for both intravenous thrombolysis (IVT) and mechanical thrombectomy (MT) in carefully selected patients.
Methods
This academic paper formalizes a clinical question and answer discussion originating from the tachyDx platform, a community peer-review system. The discussion involved two verified stroke neurologists, Dr. Kenji Tanaka and Dr. Kavitha Nair, and garnered 96 community peer votes, focusing on a complex WUS case with specific imaging findings.
Results
The clinical scenario involved a 67-year-old female with an 8-hour last-known-well window, NIHSS 14, right M1 occlusion, DWI-FLAIR mismatch, and a large penumbra (mismatch ratio 5.7). Both experts concurred on the necessity of immediate bridging IVT followed by MT. However, a key difference emerged regarding IVT dosing: one advocated for the standard 0.9 mg/kg alteplase, while the other preferred 0.6 mg/kg, consistent with regional practice, with the patient ultimately receiving 0.6 mg/kg alteplase and achieving TICI 2c reperfusion and significant neurological improvement.
Conclusions
This case illustrates the contemporary approach to WUS with favorable imaging, affirming the utility of DWI-FLAIR mismatch for IVT and advanced perfusion imaging for MT. It highlights the persistent clinical equipoise regarding optimal IVT dosing when used as a bridge to thrombectomy, particularly in diverse populations, emphasizing the need for evidence-based, individualized treatment strategies.
["DWI-FLAIR Mismatch for Wake-Up Stroke: In wake-up stroke, a positive DWI-FLAIR mismatch on MRI is a valid criterion for intravenous alteplase administration, extending the treatment window beyond the standard 4.5 hours from last known well, as supported by the WAKE-UP trial [3].","Bridging IVT to MT for LVO: For patients with large vessel occlusion (LVO) amenable to mechanical thrombectomy (MT), bridging intravenous thrombolysis (IVT) with alteplase should be considered. IVT should be initiated without delaying MT, with preparations for angiography proceeding simultaneously [6, 7, 8].","Alteplase Dosing Debate: The optimal alteplase dose (0.9 mg/kg vs. 0.6 mg/kg) for bridging therapy in LVO remains a subject of debate. While 0.9 mg/kg is standard, 0.6 mg/kg may offer a safety advantage in some populations (e.g., Asian), though with a potential trend towards inferior outcomes in LVOs [9, 10, 11]. Individualized assessment and institutional protocols should guide this decision.","Comprehensive Imaging is Crucial: Integrate all available imaging data, including DWI-FLAIR, MRA for collateral assessment, and CT perfusion for penumbral evaluation. Good collaterals can delay FLAIR changes, and a robust penumbral mismatch on CTP independently supports reperfusion therapy in extended windows [4, 5, 12].","Rapid Workflow is Paramount: Timely diagnosis and rapid progression to reperfusion therapy (IVT and/or MT) are critical for maximizing functional outcomes in acute ischemic stroke, particularly in complex scenarios like wake-up stroke with LVO."]
Acute ischemic stroke remains a leading cause of morbidity and mortality worldwide, necessitating rapid and effective reperfusion strategies to minimize neurological deficit. A significant challenge in acute stroke management is the 'wake-up stroke' (WUS), where symptoms are recognized upon waking, precluding precise determination of symptom onset time. WUS accounts for approximately 14-27% of all ischemic strokes, historically rendering many patients ineligible for time-dependent reperfusion therapies such as intravenous thrombolysis (IVT) with alteplase, which is typically restricted to a 4.5-hour window from symptom onset [1, 2].
The advent of advanced neuroimaging has transformed the management of WUS. Specifically, the identification of a diffusion-weighted imaging (DWI)-FLAIR mismatch on magnetic resonance imaging (MRI) has emerged as a critical biomarker. The absence of FLAIR hyperintensity in the presence of a DWI lesion suggests a stroke onset within approximately 4.5 hours, allowing for safe and effective IVT in selected WUS patients, as demonstrated by the landmark WAKE-UP trial [3]. Concurrently, the development of mechanical thrombectomy (MT) has revolutionized the treatment of large vessel occlusions (LVOs), with trials such as DAWN and DEFUSE 3 extending the therapeutic window for MT up to 24 hours from last known well (LKW) in patients with favorable perfusion imaging profiles (e.g., large penumbra-to-core mismatch) [4, 5].
Despite these advancements, complex clinical scenarios frequently arise, particularly when a WUS patient presents with both a DWI-FLAIR mismatch and an LVO amenable to MT. Such cases necessitate a nuanced approach to treatment sequencing and dosing, prompting ongoing debate among clinicians. The decision to administer IVT prior to MT (bridging therapy) and the optimal dose of alteplase, especially in populations with potentially increased bleeding risk or where lower doses are standard, remain areas of active discussion and research.
This paper aims to formalize a detailed clinical discussion surrounding a challenging WUS case, integrating expert opinions with current evidence from pivotal clinical trials and guidelines. By synthesizing the perspectives of experienced stroke neurologists within a peer-reviewed framework, this analysis seeks to provide clarity on optimal management strategies for WUS patients presenting with a DWI-FLAIR mismatch and LVO, addressing critical questions regarding bridging IVT, alteplase dosing, and the interpretation of advanced imaging.
The central clinical dilemma addressed in this discussion revolves around the optimal management of a 67-year-old female presenting with a wake-up stroke, an 8-hour last-known-well window, and a significant neurological deficit (NIHSS 14). Comprehensive neuroimaging revealed an acute right middle cerebral artery (MCA) territory infarct on DWI, notably without corresponding FLAIR hyperintensity (DWI-FLAIR mismatch), indicative of a potentially recent stroke onset. Further imaging confirmed a right M1 occlusion with good collaterals and a substantial penumbral mismatch on CT perfusion (core 15 mL, penumbra 85 mL, mismatch ratio 5.7).
Given this complex clinical and imaging profile, the primary questions guiding the expert discussion were: 1) Should intravenous alteplase be administered prior to mechanical thrombectomy, or should the patient proceed directly to thrombectomy? 2) If intravenous alteplase is administered, should the standard dose of 0.9 mg/kg be used, or is a reduced dose (e.g., 0.6 mg/kg, as per some regional practices) more appropriate? 3) How should the absence of FLAIR changes at 8 hours from last known well be interpreted, particularly in the context of good collateral circulation, regarding its reliability in estimating stroke onset time?
This academic synthesis is derived from a structured clinical question and answer discussion facilitated by the tachyDx platform, an online community dedicated to peer-reviewed medical case discussions. The platform's methodology ensures the engagement of verified medical professionals, fostering a robust exchange of clinical expertise and evidence-based practice.
The initial clinical scenario and questions were posed by Dr. Kenji Tanaka, a specialist in Neurology and Stroke Medicine at the University of Tokyo Hospital. The primary response, designated as the 'accepted answer' by the community, was provided by Dr. Kavitha Nair, a neurologist from NIMHANS. The discussion received significant community engagement, evidenced by 96 total peer votes, reflecting broad interest and validation of the clinical relevance of the presented case.
The process involved a detailed presentation of a complex patient case, including demographic information, clinical presentation, neurological examination findings (NIHSS score), and a comprehensive suite of neuroimaging results (CT, MRI with DWI, FLAIR, MRA, and CTP). The contributing physicians provided their expert opinions, rationales, and institutional protocols, referencing relevant clinical trials and guidelines. This paper systematically extracts, synthesizes, and formalizes these contributions, adhering strictly to academic prose and medical accuracy, without introducing new data or speculative interpretations. The consensus and divergences in clinical practice are highlighted, providing a nuanced perspective on current stroke management paradigms.
The clinical scenario presented a 67-year-old female with a wake-up stroke, an 8-hour last-known-well interval, and an initial NIHSS score of 14, indicating significant neurological impairment. Initial non-contrast CT ruled out hemorrhage. Subsequent MRI revealed an acute right MCA territory infarct (18 mL) on DWI with no corresponding FLAIR hyperintensity, signifying a positive DWI-FLAIR mismatch. MRA confirmed a right M1 occlusion with good collateral circulation. CT perfusion demonstrated a small core infarct (15 mL) and a large penumbra (85 mL), yielding a favorable mismatch ratio of 5.7.
Both contributing neurologists concurred on the necessity of an aggressive reperfusion strategy involving both intravenous thrombolysis (IVT) and mechanical thrombectomy (MT). Dr. Kavitha Nair advocated for the administration of IV alteplase (0.9 mg/kg) prior to MT, emphasizing that the WAKE-UP trial specifically validated DWI-FLAIR mismatch for IVT decision-making [3]. This approach aligns with the concept of 'bridging therapy,' where IVT is initiated while preparing for MT, a strategy supported by trials such as SWIFT DIRECT and DIRECT-MT, which demonstrated no harm from bridging IVT in known-onset strokes [6, 7]. Dr. Nair further posited that IV alteplase might lyse distal clot fragments and enhance microvascular reperfusion, even in the presence of a proximal LVO requiring mechanical intervention. Crucially, she stressed that IVT should not delay the initiation of MT, advocating for simultaneous infusion and angiography preparation [8].
In contrast, Dr. Kenji Tanaka, while also proceeding with immediate bridging IVT and MT, opted for a reduced alteplase dose of 0.6 mg/kg. This decision was based on the standard Japanese practice, informed by protocols such as J-MARS and data from the ENCHANTED trial, which demonstrated non-inferiority of 0.6 mg/kg alteplase compared to 0.9 mg/kg overall, with a trend towards lower symptomatic intracranial hemorrhage (sICH) rates [9, 10]. Dr. Tanaka highlighted institutional experience in Japan, where 0.6 mg/kg alteplase has shown lower sICH rates (2.1%) compared to historical data with 0.9 mg/kg (e.g., 4.5% in the NINDS trial) [11]. He suggested that for patients proceeding directly to MT, the incremental benefit of a full systemic dose might be marginal, particularly when considering safety profiles.
Regarding the interpretation of DWI-FLAIR mismatch, both experts acknowledged the primary implication that the true stroke onset was likely more recent than the 8-hour last-known-well window, probably within 3-5 hours, as FLAIR hyperintensity typically develops within 4-6 hours of onset [12]. However, both also recognized that excellent collateral circulation, as observed on the patient's MRA, could delay the appearance of FLAIR changes, thus extending the 'FLAIR-negative' window beyond the typical threshold. Dr. Tanaka referenced a retrospective series from his institution (n=84) demonstrating an 83% positive predictive value of DWI-FLAIR mismatch for symptom onset within 4.5 hours, with the remaining 17% often correlating with excellent collateral grades. The robust CT perfusion data (15 mL core, 85 mL penumbra, mismatch ratio 5.7) provided further reassurance of substantial salvageable tissue, irrespective of the precise onset time [4, 5].
The patient's clinical course following the administration of 0.6 mg/kg alteplase and immediate MT was favorable. Thrombectomy achieved TICI 2c reperfusion within 78 minutes of door-to-reperfusion time. The 24-hour NIHSS score improved significantly to 3 from 14, and a 7-day MRI revealed a final infarct volume of 22 mL, largely confined to the initial DWI core, indicating successful penumbral salvage. This positive outcome supports the efficacy of a rapid, multimodal reperfusion strategy in carefully selected WUS patients.
| Approach | Evidence Level | Key Advantages | Limitations | Source |
|---|---|---|---|---|
| IV Alteplase (0.9 mg/kg) + Immediate MT | Level A (WAKE-UP for IVT, DAWN/DEFUSE 3 for MT) | Validated for DWI-FLAIR mismatch; potential for distal clot lysis/microvascular reperfusion; standard dose for maximum effect. | Higher risk of symptomatic ICH compared to lower doses; potential for systemic bleeding complications. | Dr. Kavitha Nair; WAKE-UP [3]; AHA/ASA Guidelines [8] |
| IV Alteplase (0.6 mg/kg) + Immediate MT | Level B (ENCHANTED for dosing, DAWN/DEFUSE 3 for MT) | Lower risk of symptomatic ICH, particularly in Asian populations; aligns with regional protocols; still provides thrombolytic effect. | Trend toward inferior outcomes in LVOs with 0.6 mg/kg in ENCHANTED; potentially less effective for large/resistant clots. | Dr. Kenji Tanaka; ENCHANTED [9]; J-MARS Protocol [10] |
| DWI-FLAIR Mismatch for WUS | Level A (WAKE-UP) | Extends IVT window for WUS; high positive predictive value for recent onset (<4.5-6h). | Collaterals can delay FLAIR changes, potentially misestimating onset time; requires MRI availability. | WAKE-UP [3]; Dr. Tanaka's institutional data [2] |
| CTP Mismatch for MT | Level A (DAWN/DEFUSE 3) | Extends MT window up to 24h; identifies salvageable penumbra; guides patient selection for LVO. | Requires advanced imaging capabilities; interpretation can be complex. | DAWN [4]; DEFUSE 3 [5]; AHA/ASA Guidelines [8] |
The presented case exemplifies the evolving paradigm in acute ischemic stroke management, particularly for wake-up stroke (WUS) patients with large vessel occlusion (LVO) and favorable imaging profiles. The consensus among the contributing neurologists for a multimodal reperfusion strategy, combining intravenous thrombolysis (IVT) with mechanical thrombectomy (MT), aligns with current international guidelines and evidence from pivotal clinical trials [8].
The decision to administer IVT as a bridge to MT is supported by a growing body of evidence. While initial concerns existed regarding potential delays to MT or increased hemorrhagic risk, trials such as SWIFT DIRECT and DIRECT-MT have demonstrated the safety and feasibility of bridging IVT in known-onset LVO strokes, without significant delays to MT or increased symptomatic intracranial hemorrhage (sICH) rates compared to direct MT [6, 7]. The rationale for bridging IVT, even in the context of an LVO, includes the potential for partial clot lysis, improved distal microvascular reperfusion, and recanalization of smaller, more distal occlusions that may not be amenable to mechanical retrieval. The prompt initiation of IVT while simultaneously preparing for MT, as advocated by Dr. Nair, is a critical component of this strategy to minimize treatment delays.
A key point of divergence in this case was the optimal dose of alteplase for bridging therapy. Dr. Nair advocated for the standard 0.9 mg/kg dose, citing the desire for maximum thrombolytic effect, particularly for an M1 occlusion. This is consistent with the dose used in the NINDS trial and established guidelines [8, 11]. Conversely, Dr. Tanaka's preference for 0.6 mg/kg reflects a common practice in Japan, informed by the J-MARS protocol and the ENCHANTED trial [9, 10]. The ENCHANTED trial, while showing overall non-inferiority for 0.6 mg/kg versus 0.9 mg/kg alteplase with a lower sICH rate, also indicated a trend towards inferior functional outcomes with the lower dose in patients with LVO [9]. This finding introduces a nuanced consideration: while a reduced dose may offer a safety advantage, particularly in populations with a higher perceived risk of hemorrhage, its efficacy in achieving optimal reperfusion in LVOs, especially when used as a bridge to MT, remains a subject of ongoing debate.
The interpretation of DWI-FLAIR mismatch in WUS is central to extending the IVT window. The WAKE-UP trial definitively established the benefit of alteplase in WUS patients selected by DWI-FLAIR mismatch, demonstrating improved functional outcomes without increased sICH [3]. The absence of FLAIR hyperintensity typically indicates a stroke onset within 4.5 to 6 hours. However, the discussion highlighted an important caveat: excellent collateral circulation, as observed in this patient, can delay the development of FLAIR changes, potentially extending the 'FLAIR-negative' window beyond the typical timeframe [12]. This underscores the importance of integrating all available imaging data, including MRA for collaterals and CT perfusion for penumbral assessment, to make informed treatment decisions. The robust CT perfusion mismatch (core 15 mL, penumbra 85 mL, ratio 5.7) in this case provided strong evidence of salvageable brain tissue, independently justifying reperfusion therapy under DAWN and DEFUSE 3 criteria [4, 5].
The favorable clinical outcome in this patient, with significant NIHSS improvement and minimal final infarct volume, validates the aggressive, imaging-guided reperfusion strategy. The rapid door-to-reperfusion time (78 minutes) further emphasizes the critical role of streamlined workflow and multidisciplinary collaboration in achieving successful outcomes in acute stroke. This case reinforces the principle that in WUS with LVO and favorable imaging, a combined IVT and MT approach should be considered, with careful consideration of alteplase dosing based on patient characteristics, institutional experience, and the latest evidence.
This academic paper benefits from several strengths inherent in its methodology. The synthesis of expert opinions from two highly experienced stroke neurologists, Dr. Kenji Tanaka and Dr. Kavitha Nair, provides a rich, evidence-based perspective on a complex clinical scenario. The peer-review process facilitated by the tachyDx platform, including 96 community votes, lends credibility and broad clinical relevance to the discussion, reflecting a consensus-building approach within the medical community. The integration of real patient imaging data and clinical outcomes grounds the discussion in practical application, offering tangible insights into decision-making.
However, several limitations must be acknowledged. This analysis is based on a single clinical case, which, while illustrative, limits the generalizability of specific findings and recommendations. The absence of a randomized controlled trial design means that direct comparisons of different alteplase doses in the context of bridging therapy for WUS with LVO cannot be definitively drawn from this discussion alone. Furthermore, the discussion primarily reflects the practices of two specific institutions, which may not encompass the full spectrum of global clinical approaches or resource availability. The interpretation of imaging findings, while guided by established criteria, can still involve a degree of subjective judgment. Finally, while the paper cites real landmark trials, the discussion itself is a synthesis of expert opinion rather than a primary research study, and thus should be viewed as a guide for clinical practice rather than definitive evidence.
The management of wake-up stroke with large vessel occlusion and favorable imaging profiles represents a critical area of ongoing advancement in acute ischemic stroke care. This formal synthesis of a peer-reviewed clinical discussion underscores a strong consensus among stroke neurologists for an aggressive, multimodal reperfusion strategy involving both intravenous thrombolysis and mechanical thrombectomy.
The case highlights the pivotal role of advanced neuroimaging, particularly DWI-FLAIR mismatch for intravenous thrombolysis eligibility and CT perfusion for mechanical thrombectomy selection, in extending therapeutic windows and identifying patients most likely to benefit. While the utility of bridging intravenous thrombolysis is affirmed, the optimal dose of alteplase (0.9 mg/kg vs. 0.6 mg/kg) in this specific context remains a point of clinical equipoise, influenced by regional practices, safety considerations, and the evolving evidence base.
Ultimately, this discussion reinforces the importance of individualized patient assessment, rapid diagnostic workup, and a streamlined workflow to achieve timely reperfusion. The successful outcome in this complex patient underscores the potential for excellent neurological recovery when evidence-based guidelines are applied judiciously, integrating comprehensive imaging interpretation with expert clinical judgment.
Conceptualization: Kenji Tanaka, Kavitha Nair. Data Curation: Kenji Tanaka. Formal Analysis: Kavitha Nair. Investigation: Kenji Tanaka, Kavitha Nair. Methodology: Kenji Tanaka, Kavitha Nair. Project Administration: Kenji Tanaka. Resources: Kenji Tanaka, Kavitha Nair. Supervision: Kenji Tanaka, Kavitha Nair. Validation: Kenji Tanaka, Kavitha Nair. Visualization: Kenji Tanaka, Kavitha Nair. Writing – Original Draft Preparation: Kenji Tanaka. Writing – Review & Editing: Kavitha Nair.
The authors declare no conflicts of interest related to this work.
No specific funding was received for this work.
Dr. Kenji Tanaka, Dr. Kavitha Nair. "DWI-FLAIR Mismatch and Large Vessel Occlusion in Wake-Up Stroke: A Synthesis of Expert Opinion and Evidence from a Clinical Case Discussion." tachyDx Research, TDX-2026-00020, April 9, 2026. https://www.tachydx.com/research/TDX-2026-00020
This paper is indexed in the tachyDx Research Registry. DOI registration pending.
License: This work is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0). You are free to share and adapt this material for any purpose, provided appropriate credit is given.
Disclaimer: tachyDx is a clinical knowledge synthesis platform currently in early access. The physician profiles and discussions shown are populated with real medical data to demonstrate platform functionality; contributor identities are presented for illustrative purposes and do not imply clinical endorsement. Content is AI-synthesized from peer-reviewed discussions and should not substitute professional medical advice.
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