Topographic Anatomy of Basal Nuclei

Topographic Anatomy

of Basal Nuclei

Dr. Muhammad RafiqueAnatomy, DIMC

Objectives Define the basal nuclei Know the components of basal nucleiDiscuss the detlaited structures of Caudate, Putamen,

Globus Pallidus, Amygdaloid Nucleus & Claustrum.Know role of Substantia Nigra & Subthalamic NucleusUnderstand the Afferent and Efferent connection of

Basal Nuclei Have knowledge about the clinical manifestation of

basal nuclei

Nomenclatures What is

Nucleus?What is

Ganglion?What are Basal

Nuclei?

Definition The term basal nuclei is applied to a collection of masses of gray matter situated within each cerebral hemisphere.

They are Corpus striatumAmygdaloid nucleusClaustrumThe subthalamic nuclei, the

substantia nigra, and the red nucleus are functionally closely related to the basal nuclei, but they should not be included with them.

Components of Basal Nuclei

Components of Basal Nuclei

Function of Basal Nuclei

The basal nuclei play an important role in the control of posture and voluntary movement. Unlike many other parts of the nervous system concerned with motor control, the basal nuclei have no direct input or output connections with the spinal cord.

Corpus StriatumThe corpus striatum is situated

lateral to the thalamus and is almost completely divided by a band of nerve fibers, the internal capsule, into

Caudate nucleus (medially) Lentiform nucleus (laterally)The term striatum is used here

because of the striated appearance produced by the strands of gray matter passing through the internal capsule and connecting the caudate nucleus to the putamen of the lentiform nucleus

Terminology Used to Describe the Basal Nuclei

Neurological Structure Basal Nucleus (Nuclei)

Caudate nucleus Caudate nucleusLentiform nucleus Globus pallidus plus putamenClaustrum ClaustrumCorpus striatum Caudate nucleus plus lentiform

nucleusNeostriatum (striatum) Caudate nucleus plus putamenAmygdaloid body Amygdaloid nucleus

Caudate NucleusThe caudate nucleus is a large

C-shaped mass of gray matter that is closely related to the lateral ventricle and lies lateral to the thalamus . The lateral surface of the nucleus is related to the internal capsule, which separates it from the lentiform nucleus.

For purposes of description, it can be divided

Head Body Tail.

Head of the Caudate NucleusThe head of the caudate

nucleus is large and rounded and forms the lateral wall of the anterior horn of the lateral ventricle. The head is continuous inferiorly with the putamen of the lentiform nucleus (the caudate nucleus and the putamen are sometimes referred to as the neostriatum or striatu.

Head of the Caudate NucleusJust superior to this

point of union, strands of gray matter pass through the internal capsule, giving the region a striated appearance, hence the term corpus striatum.

Body of the CaudateThe body of the

caudate nucleus is long and narrow and is continuous with the head in the region of the interventricular foramen. The body of the caudate nucleus forms part of the floor of the body of the lateral ventricle.

Tail of the CaudateThe tail of the caudate

nucleus is long and slender and is continuous with the body in the region of the posterior end of the thalamus. It follows the contour of the lateral ventricle and continues forward in the roof of the inferior horn of the lateral ventricle. It terminates anteriorly in the amygdaloid nucleus

Lentiform NucleusThe lentiform nucleus is a

wedge-shaped mass of gray matter whose broad convex base is directed laterally and whose blade is directed medially. It is buried deep in the white matter of the cerebral hemisphere and is related medially to the internal capsule, which separates it from the caudate nucleus and the thalamus.

Lentiform NucleusThe lentiform nucleus is

related laterally to a thin sheet of white matter, the external capsule, which separates it from a thin sheet of gray matter, called the claustrum. The claustrum, in turn, separates the external capsule from the subcortical white matter of the insula.

Division of Lentiform NucleusA vertical plate of

white matter divides the nucleus into a larger, darker lateral portion, the putamen, and an inner lighter portion, the globus pallidus.

Globus PallidusThe paleness of the

globus pallidus is due to the presence of a high concentration of myelinated nerve fibers. Inferiorly at its anterior end, the putamen is continuous with the head of the caudate nucleus.

Amygdaloid NucleusThe amygdaloid nucleus is

situated in the temporal lobe close to the uncus. The amygdaloid nucleus is considered to be part of the limbic system. Through its connections, it can influence the body's response to environmental changes. In the sense of fear, for example, it can change the heart rate, blood pressure, skin color, and rate of respiration.

Substantia NigraThe substantia nigra of

the midbrain is functionally closely related to the activities of the basal nuclei. The neurons of the substantia nigra are dopaminergic and inhibitory and have many connections to the corpus striatum.

Subthalamic NucleiSubthalamic nuclei

of the diencephalon closely related to basal nuclei.

Neurons of the subthalamic nuclei are glutaminergic and excitatory and have many connections to the globus pallidus and substantia nigra.

ClaustrumThe claustrum is a thin

sheet of gray matter that is separated from the lateral surface of the lentiform nucleus by the external capsule. Lateral to the claustrum is the subcortical white matter of the insula. The function of the claustrum is unknown.

AFFERENT FIBERSS

Connections of the Corpus Striatum

Connections of Corpus Striatum & Globus Pallidus

The caudate nucleus and the putamen form the main sites for receiving input to the basal nuclei. The globus pallidus forms the major site from which the output leaves the basal nuclei.

They receive no direct input from or output to the spinal cord.

Corticostriate Fibers

All parts of the cerebral cortex send axons to the caudate nucleus and the putamen. Each part of the cerebral cortex projects to a specific part of the caudate-putamen complex. Most of the projections are from the cortex of the same side. The largest input is from the sensory-motor cortex. Glutamate is the neurotransmitter of the corticostriate fibers.

Thalamostriate FibersThe

intralaminar nuclei of the thalamus send large numbers of axons to the caudate nucleus and the putamen.

Nigrostriate FibersNeurons in the

substantia nigra send axons to the caudate nucleus and the putamen and liberate dopamine at their terminals as the neurotransmitter. It is believed that these fibers are inhibitory in function.

Brainstem Striatal Fibers

Ascending fibers from the brainstem end in the caudate nucleus and putamen and liberate serotonin at their terminals as the neurotransmitter. It is thought that these fibers are inhibitory in function.

Efferent Fibers

Striatopallidal FibersStriatopallidal fibers

pass from the caudate nucleus and putamen to the globus pallidus. They have gamma-aminobutyric acid (GABA) as their neurotransmitter

Striatonigral FibersStriatonigral fibers

pass from the caudate nucleus and putamen to the substantia nigra. Some of the fibers use GABA or acetylcholine as the neurotransmitter, while others use substance P.

AFFERENT FIBERS

Connections of the Globus

Pallidus

Striatopallidal FibersStriatopallidal fibers

pass from the caudate nucleus and putamen to the globus pallidus. These fibers have GABA as their neurotransmitter.

Efferent Fibers

Pallidofugal FibersPallidofugal fibers

are complicated and can be divided into groups

(1) Ansa lenticularis, which pass to the thalamic nuclei

(2) Fasciculus lenticularis, which pass to the subthalamus

Pallidofugal Fibers(3) Pallidotegmental

fibers, which terminate in the caudal tegmentum of the midbrain

(4) Pallidosubthalamic fibers, which pass to the subthalamic nuclei.

Clinical Conditions Related to

Basal Nuclei

Muhammad Ali in Alanta OlympicMuhammad Ali in Alanta Olympic

Parkinson’s Parkinson’s DiseaseDisease

Disease of mesostriatal Disease of mesostriatal dopaminergic systemdopaminergic system

PDPD

normalnormal

Substantia Nigra, Substantia Nigra, Pars Compacta (SNc)Pars Compacta (SNc)

DOPAminergic DOPAminergic

NeuronNeuron

Slowness of Movement-Difficulty in Initiationand Cessation of Movement

Clinical Feature (1)Clinical Feature (1)

Parkinson’s DiseaseParkinson’s Disease

Clinical Feature (2)Clinical Feature (2)

Resting TremorParkinsonian PostureRigidity-Cogwheel Rigidity

Parkinson’s DiseaseParkinson’s Disease

•Hyperkinetic disorders result from underactivity in the indirect pathway.

example: Lesions of STN result in Ballism. Damage to the pathway from Putamen to GPe results in Chorea, both of them are involuntary limb movements.

excitation

inhibition

directindirect

D1

D2

D1 & D2 Dopamine receptors

somatosensory cortices

Thalamus

Putamen

GPe

GPi

STN

SNc

motor cortices

GPe/i: Globus pallidus internal/external

STN: Subthalamus Nucleus

SNc: Pars Compacta Pars Compacta (part of substantia nigra)(part of substantia nigra)

SYDENHAM’S CHOREASYDENHAM’S CHOREASYDENHAM’S CHOREASYDENHAM’S CHOREA

- - Fine, disorganized , and random movements of extremities, face and tongue- Accompanied by Muscular Hypotonia- Typical exaggeration of associated movements during voluntary activity- Usually recovers spontaneously in 1 to 4 months

Clinical FeatureClinical Feature

Principal Pathologic Lesion: Principal Pathologic Lesion: Corpus StriatumCorpus Striatum

Clinical FeatureClinical Feature

Principal Pathologic Lesion: Principal Pathologic Lesion:

Corpus Striatum Corpus Striatum (esp. caudate nucleus) and (esp. caudate nucleus) and Cerebral CortexCerebral Cortex

- Predominantly autosomal dominantly inherited chronic fatal disease (Gene: chromosome 4)- Insidious onset: Usually 40-50- Choreic movements in onset- Frequently associated with emotional disturbances- Ultimately, grotesque gait and sever dysarthria, progressive dementia ensues.

HUNTINGTON’S CHOREAHUNTINGTON’S CHOREA

HEMIBALLISMHEMIBALLISMHEMIBALLISMHEMIBALLISM

- - Usually results from CVA (Cerebrovascular Accident) involving subthalamic nucleus- sudden onset- Violent, writhing, involuntary movements of wide excursion confined to one half of the body- The movements are continuous and often exhausting but cease during sleep- Sometimes fatal due to exhaustion- Could be controlled by phenothiazines and stereotaxic surgery

Clinical FeatureClinical Feature

Lesion:Lesion: Subthalamic NucleusSubthalamic Nucleus