1 basal ganglia

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BASAL GANGLIAA journey into the deep nuclei

Dr Anil Dwivedi

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Motor Cortex

Basal Ganglia Cerebellum

+Via

ThalamusVia

Thalamus

Motor neurons & Interneurons in Spinal Cord

Modulation of motor activity by Basal Ganglia & Cerebellum

UMN

Skeletal Muscle

LMN

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Def:• Large masses of grey

matter • situated within the white

core of each cerebral hemisphere

• Essential constituents of the extra pyramidal system

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FUNCTIONS Modulation of motor activities through neuronal

circuits:

– Production of movements• Maintain purposeful motor activity while

suppressing unwanted or useless movement

– Regulate muscle tone• Inhibit muscle tone throughout the body

– proper muscle tone is maintained through a balance of excitatory and inhibitory inputs

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– Monitor and coordinate slow, sustained contractions related to posture and support.

– Avoid abnormal involuntary movements– Control group of movements for

emotional expretion– Memory, emotion, and other cognitive

functions.

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Basal Ganglia - Components

AnatomicalCorpus striatumClaustrumAmygdaloid body

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Physiological/clinical• Corpus striatum• Subthalamic nu• Substantia nigra

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• Phylogenetically:– Neostriatum:

• Caudate nuc + Putamen– Palaeostriatum:

• Globus Pallidus

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BASAL GANGLIA

• New classification

• Dorsal

• Dorsal striatum : Caudate Nu + Putamen

• Dorsal Pallidum : G Pallidus (Inner & outer segts)

• Ventral :

• Ventral striatum : Nu Acumbens & Olf tubercle• Ventral pallidum : Loc below Ant commissure in Ant perf

substance

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CAUDATE NUCLEUS • Comma shaped band of grey matter • 3 Parts : Head, Body & Tail

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CAUDATE NUCLEUS :• Lies in conformity with curvature of Lat ventricle

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HEAD of C Nucleus

Bulges into the floor of Ant horn of Lat V

Laterally : Ant limb of Int capsule & Lentiform Nu

(Ant limb)

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Relations of BODY:

Inferomedially :

• Floor of central part of Lat Ventricle

• Accompanied med by Stria terminalis & thalamostriate vein

Superolaterally : Corpus callosum, Fronto-occipital fasciculus

Body of caudate NuThalamo-striate vein

Stria terminalis

Lat ventricle (Central part)

Fronto-occipital Fasciculus

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TAIL

Tail of C N

Passes Dwn & Fwd along roof of Inf horn of Lat V

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Substantia Nigra

Caudate Nucleus

Lentiform Nu

Tail of C Nu

Inf horn of lat ventricle

Str Terminalis

TAIL of C N :

• Medially :

- Str Terminalis - Sublentiform part of IC & Thalamus

• anterior: Amygdaloid body

• Above : Lentiform Nu

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Substantia Nigra

Caudate Nucleus

Lentiform Nu

Tail of C Nu


Str Terminalis

•Large & wedge shaped

•Narrow part of wedge facing

medially

RELATIONS

• Laterally :

• Ext capsule & Claustrum

LENTIFORM NUCLEUS

Ext CapsuleClaustrum

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Substantia Nigra

Caudate Nucleus

Lentiform Nu

Tail of C Nu


Str Terminalis

• Medially :

Int Capsule

Thalamus

Head of Caudate Nu

• Above : Corona radiata


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Caudate Nucleus

Lentiform Nu

Tail of C Nu


Str Terminalis

• Below

• Ant Perf substance

• Inf horn of Lat V

• Sublentiform part of IC,

• Tail of C Nu &

• Stria terminalis


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Blood Supply• Arterial

– Medial Striate Brs. - MCA

– Lat. Striate Brs. – MCA– Recurrent Br – ACA– Ant. Choroidal Br -

MCA

• Venous– Striate veins– Int. cerebral vein– Basal Vein

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CONNECTIONS

• Afferent- Caudate Nucleus & Putamen • Efferent- Globus Pallidus

AFFERENTS

EFFERENTS

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CONNECTIONS : STRIATUM

AFFERENTS-

• Cortico-striate : from entire Neocortex

• Thalamo - striate : Centro-median nu of Thalamus• Nigro- striate : From Pars compacta of S Nigra

Efferents

Strio-pallidal

Strio nigral (To Pars reticularis of S Nigra)

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• Connections-Striatum

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GLOBUS PALLIDUS :

AFFERENTS :

• Strio-pallidal : from CN & Putamen

• From Subthalamus

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GLOBUS PALLIDUS :

EFFERENTS : Pallido-fugal • To Thalamus :

– Thru Ansa lenticularis & Fasciculus Lenticularis – Join to form Fasciculus thalamicus– End in VA, VL & CM nuclei

• To Subthalamus : From Outer Segt of GP

• To Reticular formation of MB

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• Connections - Paleostriatum

30Schematic Diagram showing connections of Basal Ganglia

p.c.- pars compacta p.r.- pars reticularis

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LEISIONS OF B G

Manifestations-

Two types.• Hypokinetic, hypertonic :

– Increased tone & rigidity – Eg : Parkinsonism

• Hyperkinetic hypotonic : – Abnormal involuntary movements - dyskinesias

Eg : Athetosis, Chorea & Ballism

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• Organic basis of Parkinson’s disease: – Degeneration of dopaminergic neurons from the

substantia nigra (Nigrostriate fibres)

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• The net effect is reduced excitation of motor cortex. – loss of dopamine

producing neurons

– globus pallidus becomes overactive

– inhibition of the VL nucleus of the thalamus

– reduced excitation of the cortex

hypokinesia

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PARKINSON’S DISEASE (Paralysis Agitans)

• Characterized by Rigidity

& tremors

• Rigidity – Caused by

increased muscle tone

– Due to increased

activity of static gama

fusiform fibers

• Affects all muscles, Cog-

wheel rigidity, Short quick

steps

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• Mask face : No emotional response

• Difficulty in taking initial steps & stopping movements

• Resting tremor – Pill rolling move of hands

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• Cause : • Degenerative changes in

Globus Pallidus & S Nigra• Marked reduction in Dopamine

• Treatment : • Admn of L- Dopa• Surgical destruction of GP /

VL Nu of Thalamus • Striatal implants of dopamine

containing neurons of fetal origin.

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ATHETOSIS

• Slow worm like writhing movements affecting fingers & wrist

• Due to damage of

Putamen – in birth injury

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HEMIBALLISM

• Wild flail like movements of one arm

• Degeneration of Subthalamic nucleus of Opp side• Damage to subthalamus decreases excitation of the

globus pallidus internal segment resulting in less inhibition of thalamus causing hyperkinetic disorder.

• Common cause is lacunar infarct of subthalamic nucleus.

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CHOREA • ”Dance like” movements• Brisk, jerky, purposeless

movements in distal parts of extremities asso with twitching of face

• Two types : – Sydenham’s Chorea– Huntington’s chorea

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Sydenham’s Chorea :

• In childhood –

• A complication of Rheumatic (Streptococcal) fever • Scattered minute hemorrhage & capillary emboli in

striatum

• Recover completely

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Huntington’s chorea :

• In middle age –

• Autosomal Dominant type

• Degeneration of Striatum & Cerebral cx

• Striatal neurons in caudate/Putamen degenerate leading

to decreased activity in the GP internal segment resulting

in less inhibition of thalamus causing a hyperkinetic

disorder.

• Mental deterioration

• Decreased level of GABA in Strio-nigral neurons

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WILSON’S DISEASE (Hepato-lenticular degeneration) :

• Genetic error of Copper metabolism

• Muscular rigidity, Tremor

• Impairment of movements

• Uncontrolled Laughing / Crying

• Degn & cavitation of Putamen, Cirrhosis of Liver

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Thank You

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