In patients with stuttering stroke symptoms, when does the TPA clock start? At first onset of symptoms or at the last time patient was symptom free?

The current definition of the time of stroke onset is when patients were at their previous baseline.

Often a patient's current neurological symptoms are preceded by similar symptoms that subsequently resolved. For patients who had neurological deficits that COMPLETELY resolved, the therapeutic clock is reset and the time of symptom onset begins anew. Important to note, however, is that the longer the transient neurological deficits last, the greater is the chance of detecting neuroanatomically relevant focal abnormalities on diffusion-weighted imaging. Whether this represents an increased risk of hemorrhage with thrombolysis has not been determined.


Source

Adams, H. et al. "AHA/ASA Guideline: Guidelines for the Early Management of Adults with Ischemic Stroke" Stroke. 2007; 38: 1655 - 1711.