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
OBLONGAT
A

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

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

16. Cross section at the level of pyramidal
decussation

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

18. Cross section at the level of Lemniscal
decussation

19. Cross section at
Level of inferior olivary nuclei

20. Cross section at the level of the olive

21. PONS

22. 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

23. 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
nuclei
Pontine nuclei

24. 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

25. Transverse section through the upper
part of Pons

26. Transverse section through the lower
part of Pons

27. Midbrain

28. 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
3rd and 4th ventricles of the brain.
Connects pons and cerebrum with forebrain
Midbrain
Crus cerebri

29. 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

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

31. Cross section through Superior
colliculus

32. Transverse section through Inferior
colliculus

33. Reticular formation
• SOMATOMOTOR
CONTROL:postural
adjustment,locomotion,speech
etc
• 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

34. Inferior and Superior colliculus

35. Red Nucleus

36. • 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:

37. MEDULLARY SYNDROMES:

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

39. 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:
1) Impaired pain&thermal sense over half the
body:Spinothalamic tract

40. On the side of lesion:
1) Paralysis with atrophy of half the tongue: I/L
12th nerve
 On the side opposite lesion:
1) 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:

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

42. INFERIOR PONTINE SYNDROMES:

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

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

45. MIDPONTINE SYNDROMES:

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

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

48. SUPERIOR PONTINE SYNDROME:

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

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

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

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

53. MIDBRAIN SYNDROMES:

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

55. • 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 3rd nerve palsy,C/L
ataxia&tremor due superior cerebellar peduncle and
red nucleus involvement[BENEDICT+NOTHNAGEL]
• BENEDIKT’S syndrome:3rd nerve palsy on I/L side&C/L
side tremor due involvement of red nucleus
CLASSICAL MIDBRAIN SYNDROMES:

56. 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

57. 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

58. ‘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

59. • 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 3rd nerve
palsy.lesion is in midbrain tectum
PARINAUD’S SYNDROME:

60. 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

61. Thank You