MRI after ischemic stroke

  • related: Neurology
  • tags: #literature #neuro

The treatment of acute ischemic stroke continues to change dramatically. The newest frontier in stroke treatment is treatment of patients who are outside of previously accepted time windows. In cases in which patients with stroke symptoms are recognized on waking when the time last known well is not clear (wake-up stroke) or when the patient cannot describe the time of onset, advanced imaging is used to assess the extent of core infarct, the viability of poorly perfused tissue remaining at risk, and the presence of a large vessel occlusion to determine whether thrombolysis is indicated. MRI is one such technique (choice B is correct). Using proprietary software, MRI helps evaluate the relationship between the infarcted or stunned tissue (diffusion-weighted image) and the part of the brain that has impaired perfusion (gadolinium perfusion scan). The software produces a ratio of core infarct to tissue at risk (less core and more tissue at risk is favorable for therapy). Core infarct and tissue at risk can also be evaluated with perfusion CT scanning.

Supportive medical care alone, without evaluating the patient for potential beneficial thrombolysis, harkens to days before therapies were available (choice A is incorrect). Likewise, administering tissue plasminogen activator (tPA) outside of the accepted time window or attempting thrombectomy without an understanding of the core infarct exposes the patient to the potential of risk without clear benefit (choices C and D are incorrect). The 2018 WAKE-UP trial showed evidence that tPA could be administered safely in patients with unknown time of onset, but only after screening with MRI.

It is important to understand that the NIHSS does not guide the potential for intervention, with certain caveats. The NIHSS is a modified neurological examination that is reproducible, easy to perform, and provides a number that can be used to communicate consistently. It covers the domains of cognition, speech, language, cranial nerves, motor responses, sensation, and neglect. Unlike common neurological examinations, it does not include gait or deep tendon reflexes. Although there is defined categorization, typically, mild strokes have NIHSS scores less than 4; moderate, between 5 and 8; large, higher than 8; severe, higher than 14 for right-sided symptoms and 16 for left-sided symptoms (the difference in sides is due to language dysfunction in left hemisphere stroke). Previously, mild strokes were excluded from intervention trials, but more recently there has been an acceptance that thrombolytic therapies are less risky in small strokes and may have some benefit.123

Footnotes

  1. SEEK Questionnaires ↩

  2. Nogueira RG, Jadhav AP, Haussen DC, et al; DAWN Trial Investigators. Thrombectomy 6 to 24 hours after stroke with a mismatch between deficit and infarct. N Engl J Med. 2018;378(1):11-21. PubMed ↩

  3. Thomalla G, Simonsen CZ, Boutitie F, et al; WAKE-UP Investigators. MRI-guided thrombolysis for stroke with unknown time of onset. N Engl J Med. 2018;379(7):611-622. PubMed ↩