A regressed superficial temporal artery–middle cerebral artery bypass cannot accommodate a decrease in cerebral blood flow caused by a re-exacerbation of middle cerebral artery stenosis: illustrative case

BACKGROUND Early superficial temporal artery–middle cerebral artery (STA-MCA) bypass is sometimes considered a salvage therapy for acute MCA territory strokes that fail medical and/or endovascular treatment. OBSERVATIONS A 77-year-old man presented with left hemiparesis for 2 days. Conservative treatment was initiated without acute recanalization. A few hours after hospitalization, his symptoms worsened. An STA-MCA bypass was performed after completing diffusion-weighted imaging (DWI) and perfusion-weighted imaging and observing a DWI-clinical mismatch. After 2 months of rehabilitation, the patient was discharged to home. Magnetic resonance angiography (MRA) at discharge showed that the stenosis in the right MCA had become mild and that the STA-MCA bypass had regressed with increased antegrade blood flow. Two weeks after discharge, the patient experienced worsening left hemiplegia at night and called for emergency medical assistance the following day. Magnetic resonance imaging showed scattered infarcts in the subcortical border zone, and MRA showed progression of the right M1 stenosis, requiring repeat revascularization due to hemodynamic changes caused by the improvement and subsequent re-exacerbation of the MCA stenosis. LESSONS Early STA-MCA bypass for symptomatic and progressive MCA stenosis can be effective; however, symptomatic MCA stenosis can be histologically dynamic. Symptoms can improve or worsen in a short period of time after STA-MCA bypass. https://thejns.org/doi/10.3171/CASE24673