Internal Capsule😍

Internal Capsule

Parts of Internal Capsule

• Lentiform nucleus divides internal capsule into
1. Anterior Limb
2. Genu
3. Posterior limb
4. Retrolentiform part
5. Sublentiform part

Tracts in Internal Capsule

Ascending Tract	Part if IC
Anterior thalamic radiation	Anterior Limb
Superior thalamic radiation	Genu
Inferior thalamic radiation	• Sublentiform part • Auditory radiation
Posterior thalamic radiation	• Retrolentiform • Optic radiation

• Other tracts
• Corticorubral tracts
• Corticopontine fibers
• Extrapyramidal tract

Corticopontine Fibres

1. Frontopontine Fibres

2. Parietopontine Fibres

3. Occipitopontine Fibres

4. Temporopontine Fibres

Blood Supply of Internal Capsule

• RGB IS (rostrum, genu, body, Ischium, splenium) stored in brain

Part Supplied	Artery
Superior parts of: ↳ anterior limb ↳ genu ↳ posterior limb	MCA Striate branches / Artery of Charcot / Lateral striate arteries M/c site of intracerebral (lenticulostriate) hemorrhage
Inferior part of anterior limb	ACA Recurrent artery of Heubner / Medial striate artery
Inferior part of ↳ posterior limb ↳ retrolentiform part	ICA Anterior choroidal artery
Inferior part of genu	ICA & PCom branches

Geniculate Body

Basal Ganglia

 

 

• SNc/SNpc → Substantia Nigra

• STN → Subthalamic nucleus

• GPi → Inhibitory

• GPe → Excitatory

Consists of:

Encephalons

Clinical link:

• Infantile progressive bulbar palsy → Medulla oblongata → Myelencephalon

Functional Components

• Anatomical Components
• Corpus Striatum
• Claustrum
• Amygdaloid body

• Substantia Nigra

• Subthalamus

• Red Nucleus

Connections of Corpus Striatum

Afferents

• Corticostriate fibres

• Thalamostriate fibres

• Nigrostriate fibres

 

• Sequence in direct pathway:
• Cortex → Striatum → Globus Pallidus → Substantia Nigra → Thalamus.

Efferents

• FL: Fasciculus Lenticularis

• AL: Ansa Lenticularis

Anatomy functions of Basal Ganglia

 

• Frontal horn of lateral ventricle adjacent to caudate nucleus.

• Thalamus is adjacent to 3rd ventricle

• Then medially to laterally
• Internal capsule → Lentiform nucleus → Insula

• White area indicates acute hemorrhage
• M/c: Putamen
• Most common cause: HTN.
• Management: Conservative

Functions of Basal Ganglia

Step	Function	Structure
1	Idea for movement	Cortical association area
2	Planning and programming of voluntary motor movement	Basal ganglia & Lateral cerebellum (cerebrocerebellum)
3	Prepare for execution	Premotor cortex & Motor cortex
4	Feedback to premotor/motor cortex	Basal ganglia & Cerebellum
5	Initiate movement	Motor cortex → α motor neurons
6	Receives initiation info (parallel input) Continuous sensory info during movement	Spinocerebellum
7	Skill and procedural memory	Striatum
8	Cognitive functions	Prefrontal cortex ↳ Motivation ↳ Emotional regulation ↳ Decision making ↳ Memory

Disorders of Basal Ganglia

Disorder	Lesion Site / Pathophysiology	Type	Key Features
Parkinsonism	Dopamine deficiency in substantia nigra → affects striatum	Mainly hypokinetic	Bradykinesia, akinesia, tremor (hyperkinetic)
Hemiballismus	Subthalamic nucleus	Hyperkinetic	(thala de thazhe (subthalamus) bale (hemibalismus))
Huntington disease → Chorea	Striatum damage - GABA (Putamen + Caudate)	Hyperkinetic	Choru (chorea) Puttu (putamen) Curry (caudate)
Dystonia	Direct pathway damage → thalamocortical overactivity	Hyperkinetic	Sustained involuntary contractions
Athetosis	Globus pallidus	Hyperkinetic	Slow, writhing movements (writing (writhing movement) on globe (globus pallidus))

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• SNc → Substantia Nigra

• Norepinephrine locked in ICU → Locus ceruleus

• ↑↑ Dopamine activity → Madly (Schizophrenia) hunting ()

• ↓↓ GABA → ↓↓ inhibitions → during anxiety () and hunting ()

• Norad → patients becomes anxious ()

• ↓↓ AcH → Alzheimer's, Huntintons (↑↑ in Park)

Condition	NT	Location
Alzheimer's disease	↓↓ Acetyl choline	Nucleus basalis of Meynert
Parkinson's disease	Dopamine ↓↓ ↳ bradykinesia ↑↑ Acetyl choline	Nigrostriatal Mnemonic: Mayil (Meynert) Basil (Basalis) nu Achingum (Acetylcholine) Alzheimersum vannu
Addiction	Dopamine	Nucleus accumbens Mesolimbic Location ↳ Medial Frontal area ↳ Ventral tegmental area
ALS	Glutamate Amy → Glue	Hippocampus, Subthalamic nucleus → Memory A-delta fibres → Fast pain
Huntington's chorea	Dopamine ↑↑ GABA ↓↓ AcH ↓↓	Loss of GABA in striatum
Tetanospasmin ↳ spastic paralysis ↳ Presynaptic	GABA	Inhibits release of GABA
Strychnine ↳ spastic paralysis ↳ Postsynaptic	Glycine Stry → Gly	Inhibits release of glycine.
Mesocortical	ㅤ	Prefrontal cortex ↳ Motivation ↳ Emotional regulation ↳ Decision making ↳ Memory
Tuberoinfundibular	Dopamine	• Hypothalamus • Physiologic inhibition of prolactin

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IDENTIFY

1-caudate nucleus
2-globus pallidus
3-putamen
4-external capsule

 

Transverse section of midbrain

At the level of Superior colliculus	At the level of Inferior colliculus
• III cranial nerve orginates • 3 lemnisci • Red nucleus	• 4 lemniscus • 4th CN originates ↳ Has internal decussation ↳ Only CN with dorsal origin