Cranial Nerves Anatomy

There are twelve cranial nerves in total. The olfactory nerve (CN I) and optic nerve (CN II) originate from the cerebrum. Cranial nerves III – XII arise from the brain stem (Figure 1). They can arise from a specific part of the brain stem (midbrain, pons or medulla), or from a junction between two parts: Midbrain – the trochlear nerve (IV) comes from the posterior side of the midbrain. It has the longest intracranial length of all the cranial nerves. Midbrain-pontine junction – oculomotor (III). Pons – trigeminal (V). Pontine-medulla junction – abducens, facial, vestibulocochlear (VI-VIII). Medulla Oblongata – posterior to the olive: glossopharyngeal, vagus, accessory (IX-XI). Anterior to the olive: hypoglossal (XII). The cranial nerves are numbered by their loca