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Brain Internal Capsule – Structure Orientation and Nerve Tracts
Dr Sanjoy Sanyal
Neuroscience Professor Surgeon and Informatician
Preface• The Sub-cortical White Matter of Brain is graphically
represented
• The bulk of this presentation deals with Projection Fibers, more specifically the Internal Capsule
• Formation, Orientation of Internal Capsule and Important Tracts within it are pictorially described
• A brief tabulation of Stroke Syndromes involving the Internal Capsule is also included
• A quick description of Commissural and Association Fibers concludes the presentation
• Every slide is richly graphically illustrated
• Audio commentary accompanying each slide will follow in a separate presentation
SC White Matter
• Axial Section through Cerebral Hemispheres
• Sub-cortical (SC) / Central / Peri-ventricular White Matter
• Commissural (C), Association (A) Projection (P) Fibers
DTI – WMT • Diffusion Tensor Imaging (DTI)
• White Matter Tractography(WMT)
• Coronal View: Commissure (C), Association (A), Projection (P) Fibers
Legend: LF = Longitudinal Fissure; FL = Frontal Lobe; LS = Lateral Sulcus; TL = Temporal Lobe; CC = Crus Cerebri; Py = Pyramid
• Fan-shaped fibers in Cerebral Hemispheres
• Spread like a ‘Radiating Crown’; Oriented in Vertical axisP
roje
ction
Fibe
rs
Projection Fibers • Corona Radiatacontains Descending and Ascending Fibers
• Caudally, fibers are densely packed in region of Basal Ganglia
• Here, Projection Fibers are called Internal Capsule
Projection Fibers • DTI /WMT: Cortico-spinal Tracts (CST) Projection Fibers in Brain and Pyramids (Py) of Medulla
• Some White fibers in either Temporal Lobes are also seen
Internal Capsule – Develop• 5th Week IUL: StriatalEminence (SE) appears on lateral wall of TelencephalicVesicle
• Developing Internal Capsule splits SE into medial and lateral parts
• Internal Capsule descends lateral to developing Thalamus
Internal Capsule – Striatum • Striatum =
Caudate + Putamen
• Gray Matter strands connect the two, giving it Striated appearance
• Internal Capsule fibers pass through Striatum
• Medial part of Striatum is Caudate Nucleus
• Lateral part of Striatum is Putamen
Inte
rnal C
apsu
le• Internal Capsule fibers pass through Striatum
• Fibers pass between Caudate Nucleus medially and LentiformNucleus (Putamen + Globus pallidus) laterally
Axial Sections Through Brain and
Internal Capsule• Next slide shows the Axial
Section findings
Internal Capsule – Axial View• Anterior Limb: Between Caudate and Lentiform Nuclei
• Posterior Limb: Between Thalamus and Lentiform Nucleus
• Genu (‘Knee’): Bent portion connecting 2 Limbs of Internal Capsule
Inte
rnal C
apsu
le –
Tracts
Corticospinal Tract in IC • Diffusion Tensor Imaging (DTI) and White Matter Tracto-graphy(WMT) showing Cortico-spinal Tract (CST) inside Internal Capsule (IC)
• Corpus Callosum(CC) is also visible
Internal Capsule Stroke
Syndromes
CommissureFibers
• Connects corresponding areas of both Cerebral Hemispheres
• Corpus Callosum is largest Commissure
• Connects Neocortex of Cerebral Hemispheres
• 3rd Commissure to develop (12-22 Wk IUL)
• Commissurotomyproduces Sperry’s ‘Split-Brain Syndrome’
Asso
ciation
Fibe
rs• Association Fibers connects 2 areas in same Hemisphere in A-P axis
• Superior Longitudinal Fasciculus (SLF) Lesion causes ‘Conduction Aphasia’
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