Cranial nerve emerging from dorsal surface of brain-

Ans. is 'b' i.e., Trochlear o "The nucleus (deep origin) is situated in the ventral wall of aqueduct of midbrain at the level of inferior colliculus and the nerve emerges from the dorsal surface of the midbrain below the inferior colliculus (superficial origin) after decussating with nerve of opposite side - Essentials of neuroanatomyo Unique features of trochlear nerve arei) Most selender cranial nerve.ii) Only cranial nerve to emerge on the dorsal aspect of brain.iii) Only cranial nerve to undergo complete internal decussation before emerging i.e. right trochlear nerve arises from left trochlear nucleus and vice versa.iv) Has longest intracranial course (Vagus nerve has overall longest course).v) Thinnest cranial nerve (smallest nerve in terms of the number of axons it contains).