| Brainstem Structures |
| Structure | Cranial Nerves | Comments |
| Midbrain (Mesencephalon) | Oculomotor nerve (CN III)Trochlear nerve (CN IV) | Reticular activating systeminvolved in arousal and alertnesslesion can lead to comaSuperior colliculusconjugate vertical gaze centerInferior colliculusauditory information processorParinaud’s syndrome due to compression of dorsal midbrain and pretectal area(e.g., pinealoma, hydrocephalus) lesions the superior colliculusconjugate vertical gaze palsy |
| Pons (Metencephalon) | Trigeminal nerve (CN V)Abducens nerve (CN VI)Facial nerve (CN VII)Vestibulocochlear nerve (CN VIII) | Medial longitudinal fasciculuslesion leads to intranuclear ophthalmoplegia (INO) |
| Medulla (Myelencephalon) | Glossopharyngeal nerve (CN IX)Vagus nerve (CN X)Hypoglossal nerve (CN XII) | Vasomotor centerRespiratory centerArea postremaincomplete blood-brain barrierchemoreception of toxinstriggers nausea and vomiting Medial lemniscusformed by decussating fibers of the nucleus gracillis and cuneatusPyramidscontain corticospinal tractsmost decussate in the caudal medullaOlivessend fibers through the inferior cerebellar peduncledistinguishing feature of medulla |
