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Brainstem Sayan Biswas 4 year Intercalating Medical Student University of ManchesterContents + Embryology + Brainstem + External Features of the brainstem + Quiz 1 + Internal Feature of the brainstem + Quiz 2Embryology of the brainstem + At 4 weeks gestation, the neural tube will give rise to three outpouchings- prosencephalon (forebrain), the mesencephalon (midbrain), and the rhombencephalon (hindbrain) + At 6 weeks of gestation, the rhombencephalon divides into metencephalon and myelencephalon + Mesencephalon will not divide any further and will give rise to the midbrain and cerebral aqueductBrainstem + Often referred to as the ‘bulb’ + Horizontal divisions: Midbrain + Pons + Medulla; from rostral to caudal + Important anatomical relations + Internally contains: white matter tracts, CN nuclei and reticular formationVertical divisions of the brainstemCN nuclei architecture + CN nuclei from medial to lateral: 1. Somatomotor nuclei 2. Visceromotor nuclei 3. Branchial motor nuclei 4. Viscerosensory and special sensory nucleiExternal Features of the Brainstem Anterior View Posterior view CN location + CN I and II – not part of brainstem + CN III – Midbrain, interpedencular fossa + CN IV – Midbrain, inferior to IC, dorsal exit + CN V – Pons, anteriolateral margins + CN VI – Pontomedullary sulcus, Medial + CN VII – Pontomedullary junction, Lateral, CP angle + CN VIII – Pontomedullary junction, Lateral, CP angle + CN IX – Posterolateral sulcus of the medulla + CN X – Posterolateral sulcus of the medulla + CN XI – Posterolateral sulcus of the medulla, combines with spinal roots + CN XII – Anterolateral sulcus of the medullaCorticobulbar tract + Motor tract: UMN + LMN + Cerebral cortex à CN nuclei à Effectors + UMNs arise from both hemispheres à 50% decussation of fibers + Decussation is at the level of the CN nuclei + Except: Facial nerve nuclei and Hypoglossal nerve nuclei + Bulbar and Pseudobulbar palsy affects these tractsQUIZ 1 + What are the four somatomotor nuclei of the brainstem? 1. III, V, VI, VII 2. V, VI, VII, XII 3. III, IV, VI, XII 4. III, IV, V, VIQUIZ 1 + Of the following nuclei, which is the source of the preganglionic parasympathetic axons traveling with this cranial nerve? 1. Inferior salivatory nucleus. 2. Facial nucleus. 3. Superior salivatory nucleus. 4. Nucleus ambiguus 5. Dorsal motor nucleus of vagusQUIZ 1 + Where does the hypoglossal nerve leave the brainstem? 1. Anterolateral sulcus 2. Posterolateral sulcus 3. Anterior median fissure 4. OliveQUIZ 1 + What are the inputs of the nucleus tractus solitarius? 1. VII, IX 2. VII, X 3. VII, IX, X 4. IX, XQUIZ 1 + Mixed motor problems where a patient presents with contralateral UMN deficient & ipsilateral tongue problem. You would expect to find the lesion where? 1. Pons 2. Medulla 3. Midbrain 4. Spinal cordInternal Structure of the MedullaInternal Structure of the MedullaInternal Structure of the MedullaInternal Structure of the PonsInternal Structure of the PonsInternal Structure of the PonsInternal Structure of the MidbrainInternal Structure of the MidbrainInternal Structure of the MidbrainQUIZ 2 + Consider this nucleus, where do its axons exit the medulla? 1. Between the pons and medulla 2. Between the two pyramids 3. At the sulcus limitans 4. Between the pyramid and the olive.QUIZ 2 + Where do the axons of this nucleus terminate? 1. Muscles of pharynx and larynx 2. Preganglionic parasympathetic ganglions 3. Smooth muscle of viscera 4. Postganglionic parasympathetic ganglionsQUIZ 2 + What CN V sensory nuclei receives light touch? 1. Spinal 2. Principal 3. MesencephalicQUIZ 2 + What sensory information does the inferior colliculus receive? 1. Auditory 2. Visual 3. Auditory + Visual 4. GazeQUIZ 2 + Where is the fourth ventricle located? 1. Midbrain 2. Pons + Medulla 3. Medulla 4. Pons + MidbrainThank you for listening!! Email: sayan.biswas@nhs.net https://share.medall.org/events/christmas- neuroanatomy-revision-series-lecture-6- cerebellum