Brainstem

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Brainstem

• Dr. Sama ul haque

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Objectives

• Identify the gross features of the brainstem.
• Briefly describe the internal structure of the
  brainstems (ascending and descending pathways,
  sensory and motor cranial nuclei, substantia
  nigra, red nucleus, olivary nucleus and reticular
  formation).
• Describe the main connections of the sensory
  cranial nuclei.

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Objectives

• Describe the main connections of the motor
  cranial nuclei.
• Describe lesions in the brainstem such as medial
  medullary syndrome and lateral medullary
  syndrome.
• Describe the main connections of the substantia
  nigra and the red nucleus.

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Brainstem

• Composed of Medulla Oblongata, Pons and the
  Midbrain.
• It lies in the Posterior cranial fossa of the
  skull.
• Stalk like in shape.
• Connects spinal cord with forebrain.
• Functions
• It is a channel for the ascending and descending
  tracts.
• It contains important centers associated with
  respiratory and cardiovascular systems.
• It contains the nuclei of the cranial nerves.

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Medulla Oblongata
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Medulla Oblongata (External features)

• It connects Pons superiorly with Spinal Cord
  inferiorly.
• Begins caudally at foramen magnum.
• It is conical in shape.
• Central canal continues to the middle of the
  medulla and then expand as cavity of 4th
  ventricle.

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Medulla Oblongata (External features)

• Anterior median fissure
• Pyramids (Pyramidal Tract) Bundles of
  corticospinal fibers
• Decussation of pyramids Inferior part of
  pyramids
• Anterior external arcuate fibers Fibers emerging
  from anterior median fissure above decussation
  and run laterally to enter the cerebellum.
• Olives (Inferior Olivary Nuclei) Posterolateral
  to Pyramids
• Roots of hypoglossal nerve Between Pyramid and
  Olive

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Medulla Oblongata (External features)Anterior
View
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Medulla Oblongata (External features)

• Inferior cerebellar peduncles Posterior to
  olives connecting medulla to the cerebellum.
• Roots of glossopharyngeal, vagus and cranial
  roots of accessory cranial nerves Between olive
  and inferior cerebellar peduncle.
• Posterior median sulcus
• Floor of 4th ventricle
• Hypoglossal triangle
• Vagal triangle
• Gracile tubercle
• Cuneate tubercle

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Medulla Oblongata (External features)Posterior
View
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Medulla Oblongata (Internal structure)Level of
decussation of Pyramids

• Decussation of corticospinal tracts
• Gracile fasciculus and nucleus
• Cuneate fasciculus and nucleus
• Substantia Gelatinosa of posterior gray column of
  cord continue as Nucleus of the spinal tract of
  the trigeminal nerve.
• Anterior and posterior spinocerebellar tracts
• Lateral spinothalamic tract
• Medial accessory olivary nucleus

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Medulla Oblongata (Internal structure)Level of
decussation of Pyramids
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Medulla Oblongata (Internal structure)Level of
decussation of Medial Lemnisci

• Medial Lemniscus or Sensory Decussation (Internal
  arcuate fibers from nuclei gracilis and
  cuneatus).
• Nucleus of the spinal tract of the trigeminal
  nerve.
• Spinal tract of the trigeminal nerve.
• Anterior and posterior spinocerebellar tracts
• Lateral and Anterior spinothalamic tracts

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Medulla Oblongata (Internal structure)Level of
decussation of Medial Lemnisci
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Medulla Oblongata (Internal structure)Level of
the Olives

• Inferior Olivary Nucleus Gray matter is shaped
  like a crumpled bag ,facing medially.
• This nucleus is responsible for the elevation
  called Olive.
• Small dorsal and medial Olivary Nuclei.
• Medial Lemniscus
• Inferior cerebellar peduncle

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Medulla Oblongata (Internal structure)Level of
the Olives

• Medial longitudinal fasciculus
• Tectospinal tract
• Hypoglossal nucleus
• Dorsal vagal nucleus
• Inferior vestibular nucleus
• Pyramids

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Medulla Oblongata (Internal structure)Level of
the Olives
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Medulla Oblongata (Internal structure)Level just
inferior to the Pons

• Lateral Vestibular Nucleus
• Cochlear Nuclei are anterior and posterior to
  inferior cerebellar peduncle

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Medulla Oblongata (Internal structure)Level just
inferior to the Pons
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Pons
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Pons (External features)

• Lies anterior to the cerebellum.
• Connects Medulla to Midbrain.
• Anterior Surface
• Basilar groove
• Transverse fibers converging on each side to the
  Middle Cerebellar peduncle.
• Trigeminal nerve (Motor and Sensory Roots).
• Between Pons and Medulla Abducent, Facial and
  Vestibulocochlear arises.
• Superficial transverse pontine fibers

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Pons (External features) Anterior Surface
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Pons (External features)

• Posterior Surface
• Forms the upper half of the floor of 4th
  ventricle
• Limited laterally by Superior cerebellar peduncle
• Divided by Median sulcus
• Lateral to Median sulcus lies Medial eminence
• Lateral to Medial eminence lies Sulcus limitans
• Lateral to Sulcus limitans lies Vestibular area
• The inferior end of Medial eminence is expanded
  to form Facial colliculus

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Pons (External features)
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Pons (Internal structure)

• Trapezoid body It is a bundle of fibers and
  cells in Pons. It is a part of the Auditory
  Pathway.
• Pons is divided by transverse fibers of trapezoid
  body into
• The tegmentum posteriorly
• The basal part anteriorly

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Pons (Internal structure)Transvers section
through caudal part (Passing through Facial
Colliculus)

• Medial Lemniscus
• Motor nucleus of facial nerve
• Motor nucleus of Abducent (Facial Colliculus)
• Cavity of 4th ventricle
• Medial longitudinal fasciculus

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Pons (Internal structure)Transvers section
through caudal part (Passing through Facial
Colliculus)

• Medial Vestibular Nucleus
• Superior cerebellar peduncle
• Middle cerebellar peduncle
• Transverse pontine fibers
• Corticospinal and corticonuclear fibers
• Spinal nucleus of Trigeminal nerve

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Pons (Internal structure)Transvers section
through caudal part (Passing through Facial
Colliculus)
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Pons (Internal structure)Transvers section
through cranial part (Passing through Trigeminal
Nuclei)

• Cavity of 4th ventricle
• Medial longitudinal fasciculus
• Motor Nucleus of the Trigeminal Nerve
• Principal Sensory Nucleus of Trigeminal Nerve

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Pons (Internal structure)Transvers section
through cranial part (Passing through Trigeminal
Nuclei)

• Superior cerebellar peduncle
• Middle cerebellar peduncle
• Medial Lemniscus
• Trapezoid body

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Pons (Internal structure)Transvers section
through caudal part (Passing through Trigeminal
Nuclei)
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Thank You