Emergency superficial temporal artery-superior cerebellar artery bypass for the refractory vertebro basilar insufficiency with partial mastoidectomy: A technical case report.

•The refractory vertebrobasilar insufficiency are well known to bring poor outcomes.•The refractory VBI are considered the indication for emergency STA-SCA bypass under referencing DWI-symptomatic mismatch.•The anastomosis field for STA-SCA bypass under partial mastoidectomy is required the wide and shallow anastomotic field.