GO:0021642

The process that gives rise to the trochlear nerve. This process pertains to the initial formation of a structure from unspecified parts. The trochlear nerve is a motor nerve and is the only cranial nerve to exit the brain dorsally. The trochlear nerve innervates the superior oblique muscle. [GO_REF:0000021, GOC:cls, GOC:dgh, GOC:dph, GOC:jid, GOC:mtg_15jun06, ISBN:0838580343]