Anatomy of brainstem and its clinical significance

gross anatomy of brainstem in relevance with the major clinical problems associated.

1. ANATOMY OF BRAINSTEM AND ITS CLINICAL SIGNIFICANCE Chairperson: Prof N B Debnath Presenter: Dr Snehasis Ghosh

2. Ventral aspect of the Brainstem

3. Dorsal aspect of the Brainstem

4. MEDULLA OBLONGATA

5. Medulla is broad above ,joins with pons narrow below, continous with spinal cord Length is about 3cm, width is about 2cm at its upper end Surfaces shows series of fissures Anterior median fissure Posterior median fissure Spinal cord Medulla oblongata Most inferior region of the brain stem. Becomes the spinal cord at the level of the foramen magnum. External structure of medulla

6. Ventral surface of medulla oblongata contains Pyramid elevation between anterior median and anterolateral sulcus Formed due to decussation of corticospinal fibres . Pyramid Olive Olive Oval swelling between anterolateral posterolateral sulcus,half an inch long Produced by large mass of gray matter called inferior olivary nucleus External surface of medulla

7. The posterior part of medulla contains Fasciculus gracilis medially ending in rounded elevation ,called nucleus gracilis Fasciculus cuneatus laterally ending in rounded elevation,called nucleus cuneatus Posterior part of the medulla forms the floor of the fourth ventricle Tuberculum cinereum , longitudinal elevation in the lower part of medulla lateral to fasciculus cuneatus . Posteror part of Medulla

8. SCHEME TO SHOW MAJOR TRACTS PASSING THROUGH BRAINSTEM

9. COURSE OF CORTICOSPINAL TRACT AND POSITION AT VARIOUS LEVELS OF BRAINSTEM

10. POSTERIOR COLUMN MEDIAL LEMNISCUS PATHWAY

11. SPINOTHALAMIC AND SPINOCEREBELLAR PATHWAYS

12. CRANIAL NERVE NUCLEI:ARRANGEMENTS AND FUNCTIONAL CLASSIFICATION

13. PROJECTIONS OF CRANIAL NERVE NUCLEI ON BRAINSTEM

14. Cross section at three levels Level of pyramidal decussation Internal Structure of Medulla

15. Cross section at the level of pyramidal decussation

16. Cross section at level of lemniscal decussation Internal Structure of Medulla

17. Cross section at the level of L emniscal decussation

18. Cross section at Level of inferior olivary nuclei

19. Cross section at the level of the olive

20. PONS

21. Pons The pons shows a convex anterior surface with prominent transversely running fibres . These fibres collect to form bundles,the middle cerebellar peduncles. Trigeminal nerve emerges from the anterior surface,at the junction between pons and middle cerebellar peduncle. The anterior surface of pons is marked in the midline by a shallow groove,the sulcus basilaris which lodges the basilar artery. Pons s Sulcus basilaris

22. Subdivided into ventral and dorsal part Ventral part of the pons contains Pontine nuclei: Recieves corticopontine fibres from frontal, temporal,parietal and occipital lobes of cerebrum The efferent fibres form the transverse fibres of pons. Vertically running corticospinal and corticopontine fibres . Transversely running fibres arising in pontine nucle i Pontine nuclei

23. The dorsal part of the pons may be regarded as continuation of the part of the medulla behind the pyramids. Superiorly continous with the tegmentum of the midbrain. Occupied predominately by reticular formation Posterior surface help to form floor of fourth ventricle The dorsal part is bounded laterally by inferior cerebellar peduncle in the lower part of the pons and superior cerebellar peduncle in upper part. Dorsal part of pons DORSAL PART Midpons Upper pons

24. Transverse section t hrough the upper part of Pons

25. Transverse section through the lower part of Pons

26. Midbrain

27. Shortest brain stem,not more than 2cm in length,lies in the posterior cranial Fossa . For descriptive purpose,divided into Dorsal tectum and right and left cerebral Peduncles. Each cerebral peduncles divide further into ventral crus cerebri and a dorsal Tegmentum by a pigmented lamina “ Substantia nigra ” Cerebral peduncles contains: -Descending fibers that go to the cerebellum via the pons -Descending pyramidal tracts Running through the midbrain is the hollow cerebral aqueduct which connects the 3 rd and 4 th ventricles of the brain. Connects pons and cerebrum with forebra in Midbrain Crus cerebri

28. 2 superior colliculi that control reflex movements of the eyes, head and neck in response to visual stimuli 2 inferior colliculi that control reflex movements of the head, neck, and trunk in response to auditory stimuli Corpora quadregemina Superior colliculi larger and darker than inferior colliculi,the difference In colour due to superficial neurons in Superior colliculi Superior and inferior colliculi seperated by cruciform sulcus

29. Internal Structure of Midbrain Cross section at two levels Level of inferior colliculus Level of superior colliculus

30. Cross section through Superior colliculus

31. Transverse section through Inferior colliculus

32. Reticular formation SOMATOMOTOR CONTROL:postural adjustment,locomotion,speechetc SOMATOSENSORY CONTROL:visual and auditory pathway VISCERAL CONTROL:RFM influences respiratory and cvs function[ gigantocellular and parvocellular nucleus] NEUROENDOCRINE CONTROL: adenohypophysis and neurohypophys Circardian rhythm Arousal

33. Inferior and Superior colliculus

34. Red Nucleus

35. The VERTEBRAL artery has 4 segments V1,V2,V3&V4 The fourth segment courses upward to join the other vertebral artery to form the basilar artery Only V4 gives rise to branches that supply the brainstem&cerebellum The PICA,in its proximal segment supplies the lateral medulla and in its distal branches the inferior surface of cerebellum BLOOD SUPPLY OF MEDULLA:

36. MEDULLARY SYNDROMES:

37. ON SIDE OF LESION: Pain,numbness,impaired sensation over one-half of face:5 th nerve nucleus Ataxia:restiform body,cerebellar hemisphere,spinocerebellar tract Nystagmus,diplopia,vertigo,nausea,vomting:vestibular nucleus Horner’s syndrome:descending sympathetic tract Dysphagia,paralysis of palate,vocal cord,diminished gag reflex:fibres of 9 th &10 th nerves LATERAL MEDULLARY SYNDROME:

38. 6) Loss of taste:nucleus&tractus solitarius 7) Numbness of I/L arm,trunk&leg : cuneate&gracile nucleus 8) Weakness of lower face:Genuflated UMN fibres to I/L facial nucleus ON SIDE OPPOSITE LESION: Impaired pain&thermal sense over half the body:Spinothalamic tract

39. On the side of lesion: Paralysis with atrophy of half the tongue: I/L 12 th nerve On the side opposite lesion: Paralysis of arm&leg sparing face;impaired tactile&proprioceptive sense over one half of the body:C /L pyramidal tract&medial leminiscus MEDIAL MEDULLARY OR DEJERINE SYNDROME:

40. Branches of basilar artery supply the base of the pons&superior cerebellum and fall into 3 groups: Paramedian,7-10 in number supply a wedge of pons on either side of midline Short circumferential,5-7 that supply lateral two-thirds of pons&middle,superior cerebellar peduncle B/L long circumferential(SCA&AICA) course around pons to supply the cerebellar hemispheres BLOOD SUPPLY OF PONS:

41. INFERIOR PONTINE SYNDROMES:

42. MEDIAL INFERIOR PONTINE SYNDROME: ON THE SAME SIDE: Paralysis of conjugate gaze to the side of lesion Nystagmus:vestibular nucleus Ataxia:middle cerebellar peduncle Diplopia on lateral gaze:abducens nerve ON THE OPPOSITE SIDE: Paralysis of face,arm&leg:CB&CS tracts Impaired tactile&proproiceptive sense over one-half of body:medial leminiscus

43. LATERAL INFERIOR PONTINE (AICA) SYNDROME: ON THE SIDE OF LESION: Horizontal gaze nystagmus,vertigo,nausea,vomting:vestibular nerve or nucleus Facial paralysis:7 th nerve Ataxia:middle cerebellar peduncle&cerebellar hemisphere Impaired sensation over face:descending tract&5 th nucleus ON THE SIDE OPPOSITE LESION: Impaired pain and thermal sense over one-half of body

44. MIDPONTINE SYNDROMES:

45. ON THE SIDE OF LESION: Ataxia of limbs and gait- pontine nucleii ON THE SIDE OPPOSITE LESION: Paralysis of face,arm&leg:corticobulbar and corticospinal tracts Variable impaired touch and proprioception:medial leminiscus MEDIAL MIDPONTINE SYNDROME:

46. ON THE SIDE OF LESION: Ataxia:middle cerebellar peduncle Paralysis of muscles of mastication:motor fibres or nucleus of 5 th nerve ON THE SIDE OPPOSITE LESION: Impaired pain and thermal sense on limbs and trunk:spinothalamic tract LATERAL MIDPONTINE SYNDROME:

47. SUPERIOR PONTINE SYNDROME:

48. MEDIAL SUPERIOR PONTINE SYNDROME: ON THE SIDE OF LESION: Cerebellar ataxia:superior /middle cerebellar peduncle Internuclear ophthalmoplegia:MLF Myoclonic syndrome,palate,pharynx,vocal cords-dentate projection,inferior olivary nucleus ON THE SIDE OPPOSITE LESION: Paralysis of face,arm&leg:CB&CS tract Rarely touch,vibration&position:medial leminiscus

49. LATERAL SUPERIOR PONTINE SYNDROME OR SCA OR MILLS’ SYNDROME: ON SIDE OF LESION: Ataxia:middle&superior cerebellar peduncles,dentate nucleus Dizziness,nausea,horizontal nystagmus:Vestibular nucleus Horner’s syndrome:descending sympathetic tract Tremor:red nucleus,superior cerebellar peduncle

50. ON SIDE OPPOSITE LESION: Impaired pain&thermal sense on face,limbs&trunk:spinothalamic tract Impaired touch,vibration&position sense:medial leminiscus (legs>arms)

51. MILLARD-GUBLER SYNDROME: I/L LMN type facial nerve palsy&C /L hemiparesis due to involvement of 7 th nerve nucleus&CST FOVILLE’S SYNDROME: I/L LMN type facial nerve palsy&horizontal gaze palsy with C/L hemiparesis due to involvement of horizontal gaze centre,7 th nerve nucleus&CST RAYMOND’S SYNDROME: I/L abducens palsy C/L hemiparesis due to involvement of 6 th cranial nerve&CST CLASSICAL PONTINE SYNDROMES:

52. MIDBRAIN SYNDROMES:

53. MEDIAL MIDBRAIN SYNDROME: ON THE SIDE OF LESION: Eye”down&out ” secondary to unopposed action of 4 th &6 th cranial nerves,with dilated&unresponsive pupil(3 rd cranial nerve) ON SIDE OPPOSITE LESION: paralysis of face,arm,leg (CB&CS tracts in crus cerebri ) LATERAL MIDBRAIN SYNDROME: ON THE SIDE OF LESION: eye down&out ON THE OPP. SIDE: hemiataxia,hyperkinesias,tremor:Red nucleus,dentatorubrothalamic pathway

54. WEBER’S syndrome: third nerve palsy on the I/L side due to involvement of occulomotor nerve fascicles,Hemiplegia on C/L side due to superior cerebral peduncle involvement CLAUDE’S syndrome: I /L 3 rd nerve palsy,C /L ataxia&tremor due superior cerebellar peduncle and red nucleus involvement[BENEDICT+NOTHNAGEL] BENEDIKT’S syndrome: 3 rd nerve palsy on I/L side&C /L side tremor due involvement of red nucleus CLASSICAL MIDBRAIN SYNDROMES:

55. CENTRAL HORIZONTAL OCULOMOTOR SYNDROMES I N O:ipsilateral adduction palsy and horizontal diplopia(involvement of M L F between VII and III) HORIZONTAL GAZE PALSY:due to involvement of VI ONE AND A HALF SYNDROME:Involvement of PPRF and MLF-only abduction of contralateral eye is preserved

56. Internuclear ophthalmoplegia Demylination - usually bilateral Vascular disease Important causes Tumours of brainstem Defective left adduction and ataxic nystagmus of right eye Normal left gaze Convergence intact if lesion discrete Lesion involving left MLF

57. ‘One-and-a-half syndrome ’ Ipsilateral (left) gaze palsy Defective left adduction Normal right abduction with ataxic nystagmus Combined lesion of left MLF and PPRF

58. Lesion is dorsal midbrain Structures involved are quadrigeminal plate region,periaqeuductal gray matter Clinical findings: impaired upgaze ; convergence&retraction nystagmus NOTHNAGEL’S SYNDROME: it is more a variant of parinaud’s with U/L or B/L 3 rd nerve palsy.lesion is in midbrain tectum PARINAUD’S SYNDROME:

59. Parinaud dorsal midbrain syndrome In young adults: demylination, trauma and a-v malformations In children: aqueduct stenosis, meningitis and pinealoma Supranuclear upgaze palsy Large pupils with light-near dissociation Lid retracton (Collier sign) Important causes Normal downgaze Convergence weakness Convergence-retraction nystagmus In elderly: vascular accidents and posterior fossa aneurysms

60. Thank You