Wake-Up Stroke with a Dense Deficit and an Unclear Onset Time

Not on the basis of time alone. The last time she was known to be well was 10:30 p.m.; by the standard 4.5-hour window she is far outside it, and 'wake-up stroke' patients cannot be assumed to have symptom onset at awakening. The conservative assumption - onset at last known well - governs unless imaging reclassifies her.

That said, this is not the end of the question. Roughly a quarter of wake-up strokes have imaging evidence of a short interval, and a proportion of these patients benefit from reperfusion:

• Obtain MRI with DWI and FLAIR. A positive DWI with a negative or very subtle FLAIR signal (DWI–FLAIR mismatch) indicates the infarct is likely under ~4.5 hours old and identifies patients who may be treated with intravenous alteplase.
• Obtain CT angiography immediately in parallel. If she has a large vessel occlusion, the therapeutic question shifts to thrombectomy, for which the time window extends far beyond 4.5 hours in selected patients.
• Do not give thrombolysis before hemorrhage is excluded and before the blood pressure is controlled.
• Her atrial fibrillation means anticoagulation is a later question, not an emergency-room one; do not start it acutely.

Benefit from thrombectomy is determined by tissue status and occlusion site, not by the clock alone.

• Within 6 hours: anterior-circulation large vessel occlusion with a small infarct core (favorable ASPECTS) and a premorbid status compatible with functional independence - treat.
• 6–24 hours: selection by imaging mismatch rather than time. Either a clinical–core mismatch (higher NIHSS with a small core) or a perfusion–core mismatch identifies patients with salvageable penumbra who benefit. She falls in this category, and an 18-point NIHSS with a small core is exactly the profile that was shown to benefit.
• Exclusions to check: large established core, hemorrhage, poor premorbid function, and - importantly here - anticoagulation status (she is not anticoagulated, which is favorable).

The conceptual contrast to draw: the thrombolysis window is short and largely fixed because the drug's risk (hemorrhage) rises steeply and its benefit falls with time, whereas thrombectomy selection is dominated by whether there is brain to save. A late-presenting patient with a small core and a big penumbra is a better candidate than an early-presenting patient with a completed infarct.

The target depends entirely on which reperfusion therapy she receives - the number is not a property of the patient, it is a property of the intervention.

• If intravenous thrombolysis is given (for instance after a DWI–FLAIR mismatch is demonstrated): blood pressure must be brought below 185/110 mmHg before the bolus and maintained below 180/105 mmHg for 24 hours afterward. Her current 178/92 already satisfies the pre-treatment threshold, so no antihypertensive is needed at this moment. Agents used are short-acting and titratable - labetalol or nicardipine - avoiding precipitous drops that could extend the ischemic penumbra.
• If she proceeds to thrombectomy alone, permissive hypertension is generally acceptable in the pre- and intra-procedural period; do not lower the pressure aggressively. There is no evidence that routine intense lowering improves outcome, and hypotension during an occluded large vessel can worsen the penumbra.
• After successful reperfusion, pressure is typically brought down more deliberately to reduce reperfusion hemorrhage risk.

Practical point: because her pressure is already under the thrombolysis threshold, the blood pressure should not be the factor that decides her treatment. Obtain the MRI and CTA and let imaging decide.