During transcranial Doppler screening for sickle cell disease, which arteries are typically evaluated, and what is the normal upper limit for the middle cerebral artery velocity?

• A. Internal carotid artery and middle cerebral artery; less than 170 cm/s
• B. Middle cerebral artery and anterior cerebral artery; less than 200 cm/s
• C. Internal carotid artery and posterior cerebral artery; less than 140 cm/s
• D. Anterior cerebral artery and posterior cerebral artery; less than 150 cm/s

Answer: (A)

Transcranial Doppler screening in sickle cell disease focuses on vessels where intracranial vasculopathy commonly develops and stroke risk rises. The middle cerebral artery is the primary vessel evaluated because it supplies a large territory of the brain and is the site where flow acceleration from stenosis is most often detected. The terminal internal carotid artery is also included because it feeds the MCA, so velocities measured there reflect upstream intracranial flow changes and help identify vasculopathy earlier. The normal upper limit for the middle cerebral artery velocity is less than 170 cm/s; velocities at or above this threshold suggest elevated risk and warrant closer monitoring, with higher velocities (around 200 cm/s or more) indicating a higher stroke risk.