Neurosurgery notes/Anatomy/White matter tracts/Projection fibres/Corona Radiata/Internal capsule

Internal capsule

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Corona Radiata

General

  • Most important projection fibre

Composed

  • Corticopontospinal fibres
  • Thalamocortical fibre

5 topographical portions

Anterior limb

  • contains
    • frontopontine fibres
    • Anterior thalamic peduncle
  • Blood supply
    • Superior portion
      • lenticulostriate branches of the middle cerebral artery,
    • Inferior portion
      • the recurrent artery of Heubner, a branch of the anterior cerebral artery
  • Function
    • Associated with different aspects of emotion, motivation, cognition processing, and decision-making.

Genu

  • Corticonuclear fibres
  • Thalamoprecentral fibres

Posterior limb

  • Superior thalamic peduncle
  • Corticospinal
  • Corticopontione
  • Cortoctegmental fibres

Retrolentiform components

  • Parietopontine fibers:
    • The acoustic radiation from the medial geniculate body to the superior temporal and transverse temporal gyri, and fibers connecting the thalamus with the temporal lobe and insula.
  • Occipitopontine fibers
  • Occipitocollicular fibers
  • Occipitotectal fibers
  • Posterior thalamic radiation
    • Optic radiation
      • Most important neurosurgical connection
      • Roof of temporal horn as a lateral extension of the thalamus
      • Starts from lateral geniculate body → occipital lobe
      • Can be damaged if you enter the temporal horn from the roof in the transslyvian approach or in standard temporal lobectomy
        • The roof of the temporal horn should not be removed too medially because of the risk of damaging the thalamus
    • Interconnections between the occipital and parietal lobes and caudal parts of the thalamus

Sublentiform components

  • Temporopontine fibers
  • Meyer's loop
  • Parietopontine fibers:
    • The acoustic radiation from the medial geniculate body to the superior temporal and transverse temporal gyri, and fibers connecting the thalamus with the temporal lobe and insula.
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Relations

  • Medial:
    • Rostrally
      • Caudate nuclei
    • Retrolenticular portion
      • Thalamus
      • Occipital horn
  • Lateral:
    • Lentiformis nucleus
    • Inferior occipitofrontal fasciculus
    • External capsule
    • Superior longitudianl fasciculus
  • Anteriorly
    • Anterior commissure
    • Nucleus accumbens
  • Posteriorly
    • Arcuate fibres of occipital lobe
  • Superiorly
    • Cerebral cortex and the short association fibres
  • Inferiorly
    • Root of the internal capsule is at the cerebral peduncle
    • Brainstem nuclei and fascicles
  • Corpus callosum intersection area:
    • Where the internal capsule fibres intersect with the horizontally crossing corpus callosum fibres

Function

  • Sensitive pathways
  • Auditive pathway
  • Visual pathway
  • Motor system

Deficit

  • Hypo/anesthesia
  • Deafness
  • Visual field defects
  • Paresis/paralysis

Images

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IC: internal capsule
EX: External capsulee
CR: Corona Radiata
GP: Globus pallidus
P: Putamen
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Genu of internal capsule
  • Same coronal plane level as
    • posterior short gyrus of insula (PSG),
    • Foramen Magnum (FM)
  • Behind: Ant. Commissure (yellow),
 
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  1. Splenium of the corpus callosum
  1. Head of the caudate nucleus
  1. Thalamus
  1. Genu of the internal capsule
  1. Anterior limb of the internal capsule
  1. Posterior limb of the internal capsule
  1. Calcar avis
  1. Glomus (choroid plexus)
  1. Retrolentiform part of the internal capsule
  1. Lentiform nucleus
  1. Collateral trigone
  1. Sublentiform part of the internal capsule and roof of the temporal horn