We present a 63-year-old female with critical stenosis of the extracranial portion of the internal carotid artery (ICA), diagnosed using color-coded Duplex ultrasonography (CCDU) and magnetic resonance imaging. Nine days later, the patient showed profound clinical improvement, at which time spontaneous recanalization of the previously highly stenosed ICA was seen in follow-up CCDU and magnetic resonance angiography (MRA) and confirmed by three-dimensional computed tomography angiography (CTA). The detection of recanalization is important in predicting the patient's prognosis and deciding a suboptimal secondary prophylaxis strategy of medical or surgical treatment. Therefore, we suggest performing imaging studies immediately in patients, especially potential surgical or stenting candidates showing great changes in neurological function, through examination with CCDU and confirmation with MRA or CTA, all safe and minimally invasive methods, to see whether recanalization has occurred.