INTERNAL CAPSULE • Projection fibres- Internal capsule

r ~OnQih..!1c:llli~J ~asd· I.JS OOi 1n1ssur DEFINITION

Rostrum ol co,pi.c:; • Projection fibres c.allosum (white matter)

between nucleus • caudate nucleus and /---~.__~---- :r~~l thalamus medially capS,Jle

Pos1enu 1 1111-0 of 1mema1 • lentiform nucleus capsule

Thalamus laterally Actf'CNeflocular part of internal capsule

10.24 Horizontal sec11u11 01 lilt cerebral hemisphere st10win9 the Ooc1pr1~•pcerebral cortex to the various nuclei of the extrapyramidal system (e.g., the putamen and caudate nucleus). • 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. • 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 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. Portion Description Origin Destination Anterior Limb Anterior thalamic • Anterior nucleus • Cingulate gyrus radiation • DM • Prefrontal cortex

Genu  Premotor cortex  VA Relays to motor areas  Primary motor  VL cortex Posterior Limb 1. Motor pathways: 1. Motor pathways: o Spinal cord

o Corticospinal o Brainstem tract 1. Motor cortex 2. Somatosensory o Corticobulbar 2. VPL/VPM relays: tract

o Primary 2. Somatosensory relays somatosentory cortex Retrolenticular  Association relay • Pulvinar  Association cortex

 Optic radiation • LGN  Visual cortex

Sublenticular  Optic radiation  LGN  Visual cortex

 Auditory radiation  MGN  Auditory cortex Portion Descending fibres Ascending fibres Radiations Anterior Limb •Frontopontine Thalamofrontal Anterior thalamic •Frontothalamic radiation

Genu •Frontopontine Fibres carrying •Corticonuclear somaesthetic sensations from thalamus (VP nu.) to postcentral gyrus Posterior Limb

Superior or Dorsal •Frontopontine thalamic radiation •Corticospinal •Thalamoparietal fibres •Corticorubral •Subthalamic •Corticoreticular fasciculus •Parietothalamic

Retrolenticular •Parietopontine •Optic radiation •Occipitopontine Posterior or Caudal •Thalamo-occipital •Corticorubral thalamic radiation •Thalamo-parietal •Occipitothalamic Sublenticular •Parietopontine •Acoustic radiation •Temporopontine Inferior thalamic radiation •Thalamotemporal •Temporothalamic CAUDATE NUCLEUS

Globus palidus Internal capsule LENTIFORM NUCLEUS

External capsule

Extreme capsule

Putamen

THALAMUS CLAUSTRUM White Neural cortex Lateral matter ventricles

Septum pellucidum

Cerebral D.ie.ncephalon Third .nuclei ventricle Parts of internal capsule

Caudate nucleus Anterior limb

Genu . ',·. _. / ·:"-_·-:f-1=~ Thalamus ·.-. - ! :::,, . . - ...... Lentiform nucleus ...... - . - ~ ·~ L:::::l Sublentiform

Thalamocortical fibres Posterior limb Corticopontine fibres Retrolentiform Corticonuclear & L--1__ _JI corticospinal fibres Types of fibres • Thalamic radiation iirtal – Superior thalamic radiation fissure Superior – Anterior thalamic radiation – Posterior thalamic radiation- – Inferior thalamic radiation- • Corticospinal Anterior • Corticonuclear Posterior • Corticopontine – Fronto pontine Inferior – Parieto pontine – Temporo pontine • Extrapyramidal Thalamic radiation

• Thalamocortical fibres • Superior-from ventral – Thalamic nuclei -project nucleus to ipsilateral cerebral – Becomes corona radiata cortex (except for reticular nucleus) • Anterior-from anterior & medial nuclei • Reach neocortex • Posterior-from optic • Located entirely within radiation internal capsule • Inferior-from auditory radiation ANTERIOR LIMB – RETROLENTIFORM •Anterior thalamic radiation • Post thalamic •Frontopontine radiation - Optic radiation GENU • Parieto-pontine •Part of superior thalamic • Temporo-pontine radiation •Frontopontine – SUBLENTIFORM •Corticonuclear • Inf thalamic radiation - Auditory POSTERIOR LIMB radiation •Superior thalamic radiation •Frontopontine •Corticonuclear (corticobulbar) •Corticospinal ...... •Extrapyrimidal ......

...... Thalamocortical fibres ...... Corticopontine fibres Corticonuclear & corticospinal fibres BLOOD SUPPLY • Lateral striate fr middle cerebral artery HORIZONTAL SECTION

– Ant limb Rostrum ol cOJpus cauosum – Genu – Post limb – Basal ganglia • Medial striate fr anterior nucleus cerebral artery ------,,---~~=-..,...---- ::~ – Ant limb capS>Jle – Genu Pos1t:ir:iu1 1111'° of 1mema1 – Basal ganglia capsule • Ant choroidal fr internal Thalamus Aetrolenocular part of internal carotid capsule – Post limb – Retrolenticular part

10.24 Horizontal sec11u11 0 1 Int:: ce1·eoral hemisphere sflowin9 the Ooc::1pr1~•poae " n l l h ti r... .. ~.. ~, ...~ n1-e-11l it ies orBrain CORONAL SECTION

Corpus ·stria!tum(caudate .and!Mtiform nucleij c~Uoso:mirgin~ ~ne,ies · (branches., of ante1icr Lenticulostriate arteries o@r@b·ii if,t@ri@,s) . - ericallos'3J.arteries (b ranci'.es o f: an~im oerebr.al~teries}

ln:;;ul1 1(is!.andof Reil) T,unk of c01pus corpus c~~m Internal capsule

PireceMralfpe ~Ro1andic=) and cen~r-al(Rolandic:) suloal and p.a:rietalart@ries

Anterior cerebral artery Tempi.u~lbrinchi;is o1 . · 1m"ddf(- cerebi·al ane.ry Medialstriate arteries

Middle cerebral artery Internal carotid artery

• most common!~ arf

Lateral striate -MCA

Medial striate Left Right ACA middle middle cerebral cerebral artery artery 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 GENU

• Ant cerebral artery through medial striate br. • Middle cerebral artery through lateral striate and lenticulostriate br. • Branches of internal carotid artery ies orBrain CORONAL SECTION

Corpus ·stria!tum(caudate .and!Mtiform nucleij c~Uoso:mirgin~ ~ne,ies · (branches., of ante1icr Lenticulostriate arteries o@r@b·ii if,t@ri@,s) . - ericallos'3J.arteries (b ranci'.es o f: an~im oerebr.al~teries}

ln:;;ul1 1(is!.andof Reil) T,unk of c01pus corpus c~~m Internal capsule

PireceMralfpe ~Ro1andic=) and cen~r-al(Rolandic:) suloal and p.a:rietalart@ries

Anterior cerebral artery Tempi.u~lbrinchi;is o1 . · 1m"ddf(- cerebi·al ane.ry Medialstriate arteries

Middle cerebral artery Internal carotid artery

• most common!~ arf

• 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 INTERNAL CAPSULE CAUDATE NUCLEUS

Globus palidus

LENTIFORM NUCLEUS

Putamen

THALAMUS CLAUSTRUM EXTERNAL CAPSULE CAUDATE NUCLEUS

Globus palidus

LENTIFORM NUCLEUS

Projection fibres from cerebral cortex to basal ganglia and midbrain Putamen

THALAMUS CLAUSTRUM APPLIED ANATOMY

– Microaneurysm to lenticulostriate arteries - • contralateral side of the body – – Hemiplegia – Impaired sensation – Paralysis of lower half of face – Thrombosis – recurrent br of ACA • contralateral side of the body – – Upper limb – Paralysis of lower half of face – Anterior choroidal artery • may be symptomless – collateral circulation