Dynamic changes in blood flow of a bypassed superficial temporal artery with unstable internal carotid artery stenosis

BACKGROUND: There are limited indications for superficial temporal artery to middle cerebral artery (STA–MCA) bypass in the treatment of cerebral atherosclerotic disease. However, recent reports emphasize that STA–MCA bypass may be beneficial for select patients. In this report, we describe a case in which a flow-dependent STA–MCA bypass was achieved in a patient with unstable internal carotid artery (ICA) stenosis. CASE DESCRIPTION: A 51-year-old woman presented with left ICA occlusion. A severely elongated mean transit time (MTT) indicated misery perfusion. STA–MCA bypass was performed immediately and blood flow through the graft appeared excellent on magnetic resonance angiography (MRA). Two weeks later, MRA revealed normal anterograde ICA blood flow and the bypass graft was not visible. Three years later, the left ICA stenosis again became severe and the patient developed contralateral hemiparesis. She underwent endovascular surgery and the ipsilateral MCA became occluded during the procedure. The STA–MCA bypass graft appeared immediately after the MCA occlusion and became a major provider of blood flow to the ipsilateral MCA area. She recovered with almost no deficit. CONCLUSION: This is a rare case which shows that dynamic flow changes through an STA–MCA bypass can occur with variable ICA blood flow. STA–MCA bypass can be beneficial for the treatment of unstable ICA stenosis.