Is arnold-chiari different from chiari?

Same. Arnold chiari or chiari malformation is same , a congenital structural defect in of brain ( cerebellam ) but bud chiari syndrome is different which is thrombosis of hepatic vein ( liver vein ) not a congenital malformation.
Same thing. But: There are 4 types of arnold-chiari, or simply chiari, malformations and they all describe malformations of the hindbrain. This should not be confused with budd-chiari syndrome, which happens when a large blood clot blocks the hepatic vein. All named after hans chiari, late 19th centry pathologist from austria.