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The anatomy of midbrain
 

The anatomy of midbrain

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  • Top of the basilar:can result also in bilateral paramedian midbrain ischemia.

The anatomy of midbrain The anatomy of midbrain Presentation Transcript

  • Anatomy of the midbrain (mesencephalon) Karen Orjuela, MD Department of NeurologyLoyola University Medical Center June 2012
  • Midbrain/Mesencephalon• From the Greek mesos - middle, and enkephalos - brain• “bridge portion”• Landmarks: Rostral (superior) : superior colliculi Caudal (inferior): inferior colliculi
  • Upper midbrainRostral (superior):superior colliculi
  • Lower midbrainCaudal (inferior):inferior colliculi
  • Midbrain• Divided into: Dorsal (posterior): tectum or quadrigeminal plate (colliculi) superior and inferior colliculi Central: tegmentum ascending and descending tracts, reticular nuclei, nuclear masses Ventral (anterior): cerebral peduncles corticopontine fibers (frontopontine projection) medial 5th corticospinal fibers (middle three 5ths) temporopontine fibers (lateral 5ths)
  • Midbrain
  • MidbrainDorsal: tectum or quadrigeminal plate (colliculi)Central: tegmentumVentral: cerebral peduncles
  • Tectum: Ancient Greek τέγος (tegos, “roof; any covered room of a house”) www.charlotte.ucumberlands.edu
  • Tegmentum [Latin expression, covering.]1. ascending and descending tracts2. reticular nuclei (formation)3. nuclear masses www.charlotte.ucumberlands.edu
  • Midbrain• Landmarks: Dorsal: tectum or quadrigeminal plate (colliculi) superior and inferior colliculi Central: tegmentum ascending and descending tracts, reticular nuclei, nuclear masses Ventral: cerebral peduncles corticopontine fibers (frontopontine projection) medial 5th corticospinal fibers (middle three 5ths) temporopontine fibers (lateral 5ths)
  • Ventral: Cerebral PedunclesVentral: cerebral peduncles – Cruscerebri (crus. Lat. structure resembling leg)1. corticopontine fibers (frontopontineprojection) medial 5th2. corticospinal fibers (middle three 5ths)3. temporopontine fibers (lateral 5ths)
  • Ventral: cerebral pedunculesVentral: cerebral peduncles 1. corticopontine fibers (frontopontine projection) medial 5th motor fibers from the precentral gyrus (motor strip) to the nuclei of cranial nerves V (trigeminal), VII (facial) and XII (hypoglossal). 3. temporopontine fibers . Lateral 5th they originate in the temporal lobe and end in the nuclei pontis.
  • Ventral: cerebral peduncles2. Corticospinal tract (3/5th): somatotopically distribution: arm : medial, leglateral, trunk in between
  • Ventral: cerebral peduncles• Substantia nigra: Pigmented layer, melanin granules Dorsal to peduncles and ventral to the red nucleus . Composed dorsal zona compacta and ventral zona reticulata
  • Ventral : cerebral peduncles Substantia Nigra Dorsal: zona compacta, ventral: zona reticulata
  • NUCLEIRostral (superior):superior colliculi*(N) Nucleus of oculomotor nerve. Cranial nerve III (P)*(M) Nucleus of Edinger- Westphal supplies preganglionic parasympathetic fibers to the eye, constricting the pupil, accommodating the lens , and convergence of the eyes
  • NUCLEICaudal (inferior):inferior colliculi(K) Nucleus CN IV(trochlear)
  • Fig. 9-15-1 Lateral view of cranial nerves III, IV, and VI from the brainstem nuclei to the orbit. The third nerve exits the midbrain anteriorly,crosses near the junction of the internal carotid and posterior communicating artery in the subarachnoid space, and enters the cavernous sinus,where it runs in the lateral wall. The fourth nerve exits the midbrain posteriorly and crosses to the opposite side, to move forward in thesubarachnoid space and into the cavernous sinus. The sixth nerve exits the pons anteriorly, ascends along the clivus bone, crosses the petrousapex, and descends below the petroclinoid ligament to enter the cavernous sinus, where it runs between the lateral wall and the carotid artery.
  • Fig. 9-14-2 Anatomy of midbrain at the level of the third cranial nerve nucleus. The fascicles of thethird nerve pass through the red nucleus, substantia nigra, and crus cerebri before they exit into theinterpeduncular fossa. The medial lemniscus is nearby. Note the intimate relationship of the oculomotornerve nuclei to the medial longitudinal fasciculus, periaqueductal gray, and the cerebral aqueduct.
  • Mesencephalic tracts1. Crus cerebri2. Dentatorubrothalamic tract (red nucleus) (imaging)3. Medial tegmental tract (ventral part of the medial longitudinal fascicle. From nucleus of Darkschewitsh (central grey posterior comissure)
  • Mesencephalic tracts4. Medial longitudinal fasciculus: Connects the cranial nerve nuclei III (Oculomotor nerve), IV (Trochlear nerve) and VI (Abducens nerve) together, and integrates movements directed by the gaze centers (frontal eye field) and information about head movement (from cranial nerve VIII, Vestibulocochlear nerve). It is an integral component of saccadic eye movements as well as vestibulo-ocular and optokinetic reflexes
  • MLF (medial longitudinal fasciculus) (M) MLF Horizontal Dysconjugate Gaze Palsies. Internuclear ophtalmoplejia
  • Mesencephalic tracts4. Posterior comissure
  • Mesencephalic tracts5. Spinothalamic tract(pain, temperature,touch,pressure)6. Medial lemniscus (sensory info from the gracile and cuneate nuclei to the thalamus)
  • Vascular Supply of the Midbrain • Paramedian vessels from PCA Thalamoperforating arteries (thalamus) Penduncular arteries (medial peduncles, midbrain tegmentum, III nucleus, red nucleus, s.nigra
  • Vascular Supply of the Midbrain Circumferential arteries (peripeduncular) Quadrigeminal (from PCA) inf. Colliculi Superior cerebelar : cerebral peduncles Posterior choroidal: cerebral peduncles, lateral sup colliculi, thamalus, choroid plexus 3rd ventricle Anterior choroidal: from MCA or IC, to cerebral peduncles, or supra midbrain Posterior Cerebral arteries : mesencephalic branches
  • Mesencephalic Syndromes• Weber’s syndrome Medial peduncle. Pyarmidal fibers Fascicle CN III Contralateral hemiplegia (including face) Ipsilateral oculomotor paresis (including parasympathetic ie.dilated pupil)
  • Mesencephalic Syndromes• Benedickt’s syndrome Mesencephalic tegmentum Affect: red nucleus, brachium conjuntiva, fascicle of CN III Ipsilateral oculomotor paresis usually dilated pupil Contralateral involuntary movements (hemichorea, hemiatherosis, intention tremor) red nucleus
  • Mesencephalic Syndromes• Parynaud’s Syndrome:2/2 compression (tumors)Dorso mesencephalicsyndromehttp://www.youtube.com/watch?v=u7D1-zj98l8Paralysis of conjugate gazePupils large with near-lightdissociationConverge-retractionnystagmusPathologic lid retraction
  • http://www.youtube.com/watch?v=u7D1-zj98l8
  • Thank you.
  • Midbrain
  • Fig. 19.4 Midbrain at the superior colliculus level, showing the medial andlateral territories involved with occlusive stroke syndromes in this area.(Reprinted with permission from DeArmond, S.J., Fusco, M.M., Dewey,M.M., 1976. Structure of the Human Brain, second ed. Oxford UniversityPress, New York.)
  • Fig. 19.4 Midbrain at the superior colliculus level, showing the medial and lateral territories involved with occlusive strokesyndromes in this area.(Reprinted with permission from DeArmond, S.J., Fusco, M.M., Dewey, M.M., 1976. Structure of the Human Brain, seconded. Oxford University Press, New York.)