It is called moyamoya and it an extremely rare genetic condition.
Circle of Willis
Cerebral arterial circle or circle of Willis
Circle of Willis or the cerebral arterial circle
Willis McGahee's birth name is Willis Andrew McGahee.
Willis Harman's birth name is Willis Walter Harman.
Willis Hudlin's birth name is George Willis Hudlin.
Willis Granger's birth name is Rosamond Willis Granger.
Willis Holman's birth name is Willis Leonard Holman.
Willis Cook's birth name is Willis R. Cook.
Caylee Willis's birth name is Caylee Lynn Willis.
Dontrelle Willis's birth name is Dontrelle Wayne Willis.
Ellen Willis's birth name is Ellen Jane Willis.