Internal Capsule Anatomy and Blood Supply (ICABS
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The internal capsule is a central white matter structure that contains important projection fibers connecting the cerebral cortex with deep gray matter structures. It is divided into the anterior limb, genu, posterior limb, retrolenticular and sublenticular parts. The internal capsule receives its blood supply from the middle cerebral artery, anterior cerebral artery, and anterior choroidal artery. Strokes or lesions involving the internal capsule can cause motor or sensory deficits depending on the fibers affected.
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Internal Capsule Anatomy and Blood Supply (ICABS
- 1. INTERNAL CAPSULE SMS 1084 Dr. Mohanad R. Alwan
- 2. • Define internal capsule and enumerate the parts • Illustrate the internal capsule and describe the components of each part • Describe the blood supply and its clinical importance OBJECTIVES
- 3. Gray & White Matter Organization In brain stem similar to spinal cord (nuclei around ventricles, tracts on outside) In cerebrum and cerebellum: white matter covered with layer of neural cortex (grey)
- 4. White Matter of Cerebral hemisphere Gray surface (cortex) with white tracts internally Commissures – connect corresponding gyri of the two hemispheres 1) corpus callosum 2) anterior commissure Projection tracts (fibers) – connect more or less vertically Association tracts (fibers) connect one gyrus to another in the same hemisphere Coronal section
- 5. Commissures – connect corresponding gyri of the two hemispheres 1) corpus callosum 2) anterior commissure Association tracts (fibers) connect one gyrus to another in the same hemisphere
- 6. Commisural Fibres • Corpus callosum • Fornix • Anterior commisure • Posterior commisure • Habenular commisure
- 9. Association Fibres • Short association fibres • Long association fibres – Superior longitudinal fibres – Inferior longitudinal fibres – Cingulum
- 11. Coronal Section
- 12. • Projection fibres (white matter) between caudate nucleus and thalamus medially and lentiform nucleus laterally Internal Capsule
- 14. • The fibres projection from the cerebral cortex to the various nuclei of the extrapyramidal system (a neural network located in the brain that is part of the motor system involved in the coordination of movement e.g., the putamen and caudate nucleus). Shape of the Internal Capsule • It is a continuous sheet of fibres that forms the medial boundary of the lenticular nucleus. • It continues around posteriorly and inferiorly to partially envelop this nucleus. • Inferiorly, many of the fibres of the internal capsule funnel into the cerebral peduncles.
- 15. Superiorly, the fibres fan out into the corona radiata. Here, they travel in the cerebral white matter to reach their cortical origins or destinations. The entire fibre system is shaped like a trumpet with a large notch cut out of its bell. The notch corresponds to the location of where this sheet of fibres is interrupted by the lateral sulcus. The lenticular nucleus sits where a mute would sit in a trumpet.
- 16. Internal Capsule The internal capsule is divided into 5 regions: • The anterior limb is the portion between the lenticular nucleus and the head of the caudate nucleus; • The posterior limb is the portion between the lenticular nucleus and the thalamus; • The genu is the portion at the junction of the above 2 parts and is adjacent to the interventricular foramen; • The retrolenticular part is the portion posterior to the lenticular nucleus; • The sublenticular part is the portion inferior to the lenticular nucleus.
- 17. Portion Description Origin Destination Anterior Limb Anterior thalamic radiation • Anterior nucleus • DM • Cingulate gyrus • Prefrontal cortex Genu Relays to motor areas • VA • VL • Premotor cortex • Primary motor cortex Posterior Limb 1. Motor pathways: o Corticospinal tract o Corticobulbar tract 2. Somatosensory relays 1. Motor cortex 2. VPL/VPM 1. Motor pathways: o Spinal cord o Brainstem 2. Somatosensory relays: o Primary somatosentory cortex Retrolenticular • Association relay • Optic radiation • Pulvinar • LGN • Association cortex • Visual cortex Sublenticular • Optic radiation • Auditory radiation • LGN • MGN • Visual cortex • Auditory cortex
- 18. CAUDATE NUCLEUS LENTIFORM NUCLEUS THALAMUS Globus palidus Putamen CLAUSTRUM Internal capsule External capsule Extreme capsule
- 19. Parts of internal capsule Caudate n Lentiform n Thalamus
- 20. Parts of internal capsule Caudate nucleus Lentiform nucleus Thalamus Anterior limb Posterior limb Genu Thalamocortical fibres Corticopontine fibres Corticonuclear & corticospinal fibres Sublentiform Retrolentiform
- 22. Types of fibres • Thalamic radiation – Superior thalamic radiation – Anterior thalamic radiation – Posterior thalamic radiation- – Inferior thalamic radiation- • Corticospinal • Corticonuclear • Cortipontine – Fronto pontine – Parieto pontine – Temporo pontine • Extrapyramidal Superior Inferior Anterior Posterior
- 23. Thalamic radiation • Thalamocortical fibres – Thalamic nuclei -project to ipsilateral cerebral cortex (except for reticular nucleus) • Reach neocortex • Located entirely within internal capsule • Superior-from ventral nucleus – Becomes corona radiata • Anterior-from anterior & medial nuclei • Posterior-from optic radiation • Inferior-from auditory radiation
- 24. COMPONENTS – ANTERIOR LIMB • Anterior thalamic radiation • Frontopontine – GENU • Part of superior thalamic radiation • Frontopontine • Corticonuclear Thalamocortical fibres Corticopontine fibres Corticonuclear & corticospinal fibres Inferior Thalamic radiation Posterior Thalamic radiation
- 25. COMPONENTS – POSTERIOR LIMB • Superior thalamic radiation • Frontopontine • Corticonuclear (corticobulbar) • Corticospinal • Extrapyrimidal – RETROLENTIFORM • Post thalamic radiation - Optic radiation • Parieto-pontine • Temporo-pontine – SUBLENTIFORM • Inf thalamic radiation - Auditory radiation Thalamocortical fibres Corticopontine fibres Corticonuclear & corticospinal fibres Inferior Thalamic radiation Posterior Thalamic radiation
- 26. Thalamocortical fibres Corticopontine fibres Corticonuclear & corticospinal fibres ANTERIOR LIMB Anterior thalamic radiation Frontopontine GENU Part of superior thalamic radiation Frontopontine Corticonuclear – RETROLENTIFORM • Post thalamic radiation - Optic radiation • Parieto-pontine • Temporo-pontine – SUBLENTIFORM • Inf thalamic radiation - Auditory radiation POSTERIOR LIMB Superior thalamic radiation Frontopontine Corticonuclear (corticobulbar) Corticospinal Extrapyrimidal
- 27. Middle cerebral artery Anterior cerebral artery Posterior cerebral artery BLOOD SUPPLY
- 28. BLOOD SUPPLY HORIZONTAL SECTION • Lateral striate fr middle cerebral artery – Ant limb – Genu – Post limb – Basal ganglia • Medial striate fr anterior cerebral artery – Ant limb – Genu – Basal ganglia • Ant choroidal fr internal carotid – Post limb – Retrolenticular part
- 29. Anterior choroidal A Middle cerebral A Anterior cerebral A Internal carotid A
- 30. Internal capsule Lenticulostriate arteries Middle cerebral artery Internal carotid artery Anterior cerebral artery Medialstriate arteries CORONAL SECTION
- 32. *Anterior choroidal A Middle cerebral A Anterior cerebral A Medial striate - ACA
- 33. ANTERIOR LIMB • Ant cerebral artery through medial striate br. • Middle cerebral artery through lateral striate and lenticulostriate br. - pass through the lentiform N to supply the striate
- 34. GENU • Ant cerebral artery through medial striate br. • Middle cerebral artery through lateral striate and lenticulostriate br. • Branches of internal carotid artery
- 35. Internal capsule Lenticulostriate arteries Middle cerebral artery Internal carotid artery Anterior cerebral artery Medialstriate arteries CORONAL SECTION
- 36. POSTERIOR LIMB • Middle cerebral artery through lateral striate and lenticulostriate br. – Charcot’s artery of cerebral haemorrhage • Anterior choroidal artery, direct branch of internal carotid artery – Long and slender, thus has tendency to get thrombosis
- 37. CAUDATE NUCLEUS LENTIFORM NUCLEUS THALAMUS Globus palidus Putamen CLAUSTRUM INTERNAL CAPSULE
- 38. CAUDATE NUCLEUS LENTIFORM NUCLEUS THALAMUS Globus palidus Putamen CLAUSTRUM EXTERNAL CAPSULE Projection fibres from cerebral cortex to basal ganglia and midbrain
- 39. *Anterior choroidal A Middle cerebral A Anterior cerebral A