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Brainstem
- 1. Lecture.3 By Dr.Faris Al-Haddad M.B.Ch.B, PhDAnatomy College of Medicine, Hawler Medical University Arbil, Iraq e-mail: [email protected] BrainstemBrainstem
- 2. BrainstemBrainstem A stalklikeshaped structure occupiestheposteriorcranial fossaof theskull and connects thenarrow spinal cord with the expanded forebrain. It consistsof: 1. Medullaoblongata, 2. Pons, 3. Midbrain
- 3. Functionsof Brainstem: (1)A coduitfor ascending tracts and descending tracts connecting thespinal cord to thedifferent partsof thehigher centersin theforebrain; (2) it containsimportant reflex centersassociated with thecontrol of respirationand the cardiovascularsystemand with thecontrol of consciousness; (3) it containstheimportant nuclei of cranial nervesIII through XII.
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- 5. GrossGross Appearance:Appearance: • ConnectstheponsConnectsthepons superiorly withthesuperiorly with the spinal cord inferiorly.spinal cord inferiorly. • Itsconical in shapeItsconical in shape inferiorly, & isbroadinferiorly, & isbroad superiorlysuperiorly..
- 6. • Thejunction ofmedullaThejunction of medulla and spinal cord isat :and spinal cord isat : 1.1. correspondsapproximatelycorrespondsapproximately to thelevel of :to thelevel of : Foramen MagnumForamen Magnum 2. theorigin of theanterior2. theorigin of theanterior and posterior rootsof theand posterior rootsof the 1st cervical spinal nerve1st cervical spinal nerve..
- 7. • Thecentral canalThecentralcanal of thespinal cord contin-of thespinal cord contin- uesupward into theloweruesupward into thelower half of themedulla;half of themedulla; • in theupper half of thein theupper half of the medulla, it expandsasmedulla, it expandsas thecavity of the4ththecavity of the4th ventricleventricle
- 8. Anteriorsurface of medulla 1. Anteriormedian fissure: continueswith that of spinal cord. 2. Pyramid : Contains corticospinal fibers 3. Decussation of pyramids: siteof cross-over of cortico- spinal fibersto theopposite side.
- 9. 4. Olive: underliesInferior olivary nuclei. •rootletsof the hypoglossal nerve emergesfrom groove between pyramid & olive. 5. Inferior cerebellar peduncle: which connect the medullato the cerebellum
- 10. • In thegroovebetween theoliveandthe inferior cerebellar peduncleemergethe rootsof : 1. Glossopharyngeal 2. Vagusnerves 3. Cranial rootsof Accessory nerve
- 11. Posteriorsurface of Medulla • thesuperiorhalf of the medulla oblongataforms thelower part of thefloor of the4th ventricle. • Theposterior surfaceof the inferior half of themedulla is continuouswith posterior aspect of thespinal cord. UP1/2Low1/2
- 12. Featuresposteriorly are: • Posteriormedian sulcus. on each sideof themedian sulcus, thereisan, the • Graciletubercle, elongated swelling produced by theunderlying gracile nucleus. • Cuneatetubercle, lateral to thegraciletubercle isasimilar swelling, produced by theunderlying cuneatenucleus.
- 13. Blood Supply ofMedullaBlood Supply of Medulla issupplied by the: 1. Vertebral artery, 2. Anterior spinal artery 3. Posterior spinal artery 4. Posterior inferior cerebellar artery, 5. Basilar arteries.
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- 15. Level Decussation ofPyramids Cavity Central canal Nuclei Nucleusgracilis& Nucleuscuneatus, Spinal nucleusof cranial nerveV, Accessory nucleus MotorTracts Decussation of Corticospinal tracts, Pyramids Sensory Tracts Spinal tract of cranial nerveV, Posterior spinocerebellar tract, Lateral spinothalamic tract, Anterior spinocerebellar tract A
- 16. A.Transversesectionsof themedullaoblongata: Level ofdecussation of thepyramids Central canal
- 17. Nuclei : 1. N.Gracilis 2. N. Cunatus 3. Spinal N. of trigeminal nerve 4. Accessory N.
- 18. Tracts: 1. Spinal tractof cranial nerveV, 2. Posterior spinocerebellar tract, 3. Lateral spinothalamic tract, 4. Anterior spinocerebellar tract Fasciculi Cunatus& gracilis
- 19. Level Decussation ofmedial lemnisci Cavity Central canal Nuclei Nucleusgracilis, Nucleuscuneatus, Spinal nucleusof cranial nerveV, Accessory nucleus, Hypoglossal nucleus MotorTracts Pyramids Sensory Tracts Decussation of medial lemnisci, Posterior spinocerebellar tract, Lateral spinothalamic tract, Anterior spinocerebellar tract, Spinal tract of cranial nerveV, B
- 20. Medial Lemnisci : Axonsofrelay neuronsin theposterior column nuclei ( Gracile& Cunate)courseanteromedially (internal arcuatefibers) and crossto theopposite side(sensory decussation) abovethepyramidsto form themedial lemniscus. Themedial lemniscus thuscarriesthesamemodalitiesof sensation carried by thedorsal column.
- 21. B. Transversesectionsof themedullaoblongata: Levelof decussation of medial lemnesci Pyramids
- 22. Nuclei : 1. N.Gracilis 2. N. Cunatus 3. Spinal N. of trigeminal nerve 4. Accessory N. 5. Hypoglosal N
- 23. Tracts: 1. Spinal tractof cranial nerveV, 2. Posterior spinocerebellar tract, 3. Lateral spinothalamic tract, 4. Anterior spinocerebellar tract Fasciculi Cunatus& gracilis
- 24. Level Olives, Inferiorcerebellar peduncle Cavity Fourth ventricle Nuclei Inferior olivary nucleus, Spinal nucleusof cranial nerveV, Vestibular nucleus, Glossopharyngeal nucleus, Vagal nucleus, Hypoglossal nucleus, nucleus ambiguus, nucleusof tractus solitarius MotorTracts Pyramids, Medial longitudinal fasciculus, Tectospinal tract, Sensory Tracts Medial lemniscus, Lateral spinothalamic tract, Anterior spinocerebellar tract, Spinal tract of cranial nerveV C
- 25. Inferior olivary nucleusInferiorolivary nucleus OliveOliveof themedullaistheappearanceof theinferior olivary nuclei, which are laminaeof gray matterlaminaeof gray matter posterolateral to thepyramids. consistsof three nuclear groups: 1. Principal olive(thelargest of thecomplex) 2. Dorsal accessory olive 3. Medial accessory olive • Itsarelay station between thecortex, subcortical structures, medulla, spinal cord, & cerebellum • Themajor output of theinferior olivary complex is to thecerebellum (olivocerebellar tract).
- 26. NucleusAmbiguusNucleusAmbiguus • Isalso knownasVentral motor nucleusof vagus. • It isacolumn of cellssituated about halfway between theinferior olive and thenucleusof the spinal tract of thetrigeminal nerve. • Axonsof neuronsin thisnucleuscoursedorso- medially and then turn ventrolaterally to emerge from thelateral surfaceof themedullabetween the inferior oliveand theinferior cerebellar peduncle.
- 27. • Theseaxonsconvey specialvisceral efferent impulsesto musclesof the pharynx and larynxpharynx and larynx : (pharyngeal constrictors, cricothyroid, intrinsic musclesof thelarynx, levator veli palatini, palatoglossus, palatopharyngeus, and uvula). • In addition to thevagusnerve, thenucleus ambiguuscontributesefferent fibersto the 1. glossopharyngeal (cranial nerveIX) 2. accessory (cranial nerveXI) nerves.
- 28. Nucleusof TractusSolitariusNucleusof TractusSolitarius Dividedinto two zones: 1. Infero-medial zoneisconcerned with general visceral sensation and primarily cardio-respiratory function. The zonereceivesinput via • Glossopharyngeal (cranial nerveIX) • Vagus(cranial nerveX). 2. Supero-lateral zoneisconcerned with special visceral (taste) function. Thiszonereceivestastesensationsvia threecranial nerves: • Facial nerve(cranial nerveVII) conveystastesensations from theanterior 2/3 of thetongue, • Glossopharyngeal nerve(cranial nerveIX) conveystaste sensationsfrom theposterior 1/3 of thetongue, • Vagusnerve(cranial nerveX) conveystastesensations from theepiglottis
- 29. Medial longitudinal fasciculus •Issituated beneath thefloor of thefourth ventricle on either sideof themidline. • Itsthemain pathway that connectsthevestibular and cochlear nuclei with thenuclei controlling the extraocular muscles(oculomotor, trochlear, and abducent nuclei).
- 30. C. Transversesectionsof themedullaoblongata: Levelof decussation of Olivary nuclie I.C.P I.C.P : Inferior cerebellar peduncle
- 31. Nuclei : Spinal nucleusofcranial nerveV, Dorsal accessory olivary nucleus Inferior olivary nucleus, Medial accessory olivary nucleus
- 32. Nuclei : Vagal nuclei: 1. dorsal nucleus 2. nucleusof tractussolitarius 3. nucleusambigious
- 33. Nuclei : Hypoglossal nucleus, Glossopharyngealnuclei : 1. inferior salivatory n. 2. main motor n.
- 34. Vestibular nuclei : 1.medial n. 2. inferior n. Cochear nuclei : 1. posterior n 2. anterior n.
- 35. Tracts: 1. Spinal tractof cranial nerveV, 2. Anterior spinocerebellar tract 3. Lateral spinothalamic tract,
- 36. Medial longitudinal fasciculus, Tectospinaltract, Medial lemniscus,
- 37. Clinical Notes 1. RaisedPressurein thePosterior Cranial Fossaand ItsEffect on theMedullaOblongata: • In patientswith tumorsof theposterior cranial fossa, theintracranial pressureisraised, thereisa downward herniation of themedulla& cerebellar tonsilsthrough theforamen magnum. • Thiswill producethesymptomsof : A. headache, neck stiffness, B. paralysisof theglossopharyngeal, vagus, accessory, and hypoglossal nervesowing to traction.
- 38. • In thesecircumstances,it isextremely dangerousto perform alumbar puncturedangerousto perform alumbar puncture becausethesudden withdrawal of cerebrospinal fluid may precipitatefurther herniation of thebrain through theforamen magnum and a sudden failureof vitalsudden failureof vital functionsfunctions, resulting from pressureand ischemiaof thecranial nervenuclei present in themedullaoblongata.
- 39. 2. Vascular DisordersoftheMedullaOblongata A Lateral Medullary Syndrome:
- 40. • Thelateral partof themedullaoblongatais supplied by theposterior inferior cerebellar artery, which isusually abranch of thevertebral artery. • Thrombosisof either of thesearteries produces thefollowing signsand symptoms: 1.dysphagiaand dysarthriadueto paralysisof the ipsilateral palatal and laryngeal muscles (innervated by thenucleusambiguus); 2.analgesiaand thermoanesthesiaon the ipsilateral sideof theface(nucleusand spinal tract of thetrigeminal nerve);
- 41. 4. Vertigo, nausea,vomiting, and nystagmus (vestibular nuclei); 5. Ipsilateral Horner syndrome(descending sympathetic fibers); 6. Ipsilateral cerebellar signs—gait and limb ataxia(cerebellum or inferior cerebellar peduncle); 7. Contralateral lossof sensationsof pain and temperature(spinothalamic tract).
- 42. B. Medial MedullarySyndrome
- 43. • Themedial partof themedullaoblongatais supplied by thevertebral artery. • Thrombosisof themedullary branch produces thefollowing signsand symptoms: 1.Contralateral hemiparesis(pyramidal tract), 2.Contralateral impaired sensationsof position and movement and tactilediscrimination (medial lemniscus), 3.Ipsilateral paralysisof tonguemuscleswith deviation to theparalyzed sidewhen thetongue isprotruded (hypoglossal nerve).
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- 45. Anteriorsurface : • Theponsisanteriorto the cerebellum • connectsthemedulla oblongatato themidbrain. • Theanterior surfaceis convex from sideto side PONS
- 46. • Transversefibers that convergeoneach sideto form the middle cerebellar peduncle. • Basilar groove ashallow groovein the midline, lodgesthebasilar artery.
- 47. • Trigeminal nerve emergesoneach sidefrom theanterolateral surfaceof thepons. Each nerve consistsof asmaller, medial part, known asthemotor root, and alarger, lateral part, known asthesensory root.
- 48. • In thegroove betweenthepons and themedulla, emerge, from medial to lateral: 1. Abducent nerve, 2. Facial nerve, 3. Vestibulocochlear nerves.
- 49. Posterior surface • Itstriangularishidden by cerebellum • It formsfloor of upper1/2 of 4th ventricle • Theposterior surfaceislimited laterally by the superior cerebellar peduncles • divided into symmetrical halves by amedian sulcus.
- 50. • Lateral tomedian sulcus isan elongated elevation : Medial eminence, • Medial eminenceis bounded laterally by : Sulcuslimitans. • Inferior end of themedial eminenceisexpanded as: Facial colliculus, (which isproduced by theroot of thefacial nervewinding around the abducent nucleus)
- 51. • Lateral tothesulcus limitansisthe: Areavestibuli (produced by theunderlying vestibular nuclei).
- 52. Blood Supply ofPons: By the 1. basilar artery 2. Anterior cerebellar 3. Inferior cerebellar, 4. superior cerebellar arteries.
- 53.
- 54. Level Facial colliculus CavityFourth ventricle Nuclei Spinal nucleusof cranial nerveV, Abducent nucleus, Facial nucleus, Medial vestibular nucleus, Pontinenuclei, Trapezoid nuclei MotorTracts Corticospinal and Corticonuclear tracts, Transversepontinefibers, Medial longitudinal fasciculus Sensory Tracts Spinal tract of cranial nerveV; Medial lemnisci A
- 55. PontinenucleiPontinenuclei Thevery largemassof graymatter filling theponsand serving asamajor way station in impulseconduction from thecerebral cortex of onehemisphereto theposterior lobe of theoppositecerebellar hemispherethrough transverseransverse pontinefiberspontinefibersby way of themiddlecerebellar peduncle. Trapezoid BodyTrapezoid Body It isformed by ascending auditory fibersthat crossto the oppositesideof thebrainstem.
- 56. The corticobulbar (or corticonuclear) tract • A whitemater pathwayconnecting the cerebral cortex to the brainstem. • originatesin motor cortex of the frontal lobe, rostral to the central sulcus internal capsule, theposterior limb of the internal capsule, midbrain ( mid1/3 cerebral peduncles). • Themusclesof theface, head and neck arecontrolled by the corticobulbar system, which terminateson lower motor neurons within brainstem. • Thisisin contrast to the corticospinal tract in which the cerebral cortex connectsto spinal motor neurons, and thereby controlsmovement of theupper and lower limbs.
- 57. Transversesection through thepons: atthelevel of thefacial colliculus. M.C.P I.C.P MCP & ICP : Middle & Inferior cerebllar peduncles respectively 4th ventricle
- 58. Medial vestibular nucleus, Abducentnucleus, Facial nucleus
- 59. Spinal tract &nucleusof cranial nerveV, Trapezoid nucleus Pontinenuclei,
- 60. Transversepontinefibers Corticospinal and Corticonucleartracts, , Medial longitudinal fasciculus Medial lemniscus
- 61. Level Trigeminal nuclei CavityFourth ventricle Nuclei Main sensory and motor nucleusof cranial nerveV, Pontinenuclei, Trapezoid nuclei MotorTracts Corticospinal and corticonuclear tracts, Transversepontinefibers, Medial longitudinal fasciculus Sensory Tracts Medial lemnisci B
- 62. Transversesection through thepons: attheat thelevel of thetrigeminal nuclei.. S.C.P SCP: Superior cerebellar peduncle 4th ventricle
- 63. Nuclei of cranialnerveV: 1. Main sensory n. 2. Motor n. Trapezoid nuclei Pontinenuclei,
- 64. Medial longitudinal fasciculus Mediallemnisci Transversepontinefibers Corticospinal and Corticonuclear tracts,
- 65. Clinical Notes PontineHemorrhage If thehemorrhageoccursfromoneof thearteries and isunilateral, therewill be: 1. facial paralysison thesideof thelesion (involvement of thefacial nervenucleusand, therefore, resultsin lower motor neuron palsy) 2. paralysisof thelimbs on theoppositeside (involvement of thecorticospinal fibersasthey passthrough thepons). 3. Thereisoften paralysisof conjugateocular deviation (involvement of theabducent nerve nucleusand themedial longitudinal fasciculus).
- 66. • When thepontinehemorrhageisextensiveand bilateral,thepupilsmay be“pinpoint” (involvement of theocular sympathetic fibers); thereiscommonly bilateral paralysisof the faceand thelimbs. Thepatient may become poikilothermic becauseseveredamageto the ponshascut off thebody from theheat- regulating centersin thehypothalamus.
- 67.