Basal Ganglia | Anatomy2Medicine
Basal Ganglia

Basal Ganglia

Basal Ganglia

    • consists of subcortical nuclei (gray matter) within the cerebral hemispheres.
    • Components

 

  • Caudate nucleus
  • Putamen
  • Globus pallidus
  • Amygdala (amygdaloid nuclear complex)
  • Claustrum

 

    • Groupings of the basal ganglia

 

  • Striatum (neostriatum)

 

        • consists of the caudate nucleus and the putamen
        • have a common embryologic origin.

 

  • Lentiform nucleus

 

        • consists of the putamen and the globus pallidus.

 

  • Corpus striatum

 

        • consists of the lentiform nucleus and the caudate nucleus.

 

  • Striatal Motor System

 

        • is also called the extrapyramidal motor system.
        • plays a role in the initiation and execution of somatic motor activity, especially willed movement.
        • is involved in automatic stereotyped motor activity of a postural and reflex nature.
        • exerts its influences on motor activities via the thalamus, motor cortex, and corticobulbar and corticospinal systems.
    • Components of the striatal system

 

  • Striatum (caudatoputamen or neostriatum)
  • Caudate nucleus (caudatum)
  • Putamen
  • Globus pallidus (pallidum or paleostriatum)
  • Medial (internal) segment

 

          • is adjacent to the internal capsule.

 

  • Lateral (external) segment

 

          • is adjacent to the putamen.

 

  • Subthalamic nucleus
  • Thalamus
  • Ventral anterior nucleus
  • Ventral lateral nucleus
  • Centromedian nucleus
  • Substantia nigra
  • Pars compacta

 

          • contains dopaminergic neurons, which contain the pigment melanin.

 

  • Pars reticularis

 

          • contains gamma-aminobutyric acid (GABA) –ergic neurons.

 

  • Pedunculopontine nucleus

 

        • lies in the lateral tegmentum of the caudal midbrain.
    • Major connections of the striatal system

 

  • Striatum (caudate nucleus and putamen)

 

        • receives input from
          • largest input from the neocortex, from virtually all neocortical areas.

 

  • thalamus (centromedian nucleus
  • substantia nigra.

 

        • projects fibers to two major nuclei
          • the globus pallidus

 

  • substantia nigra (pars reticularis).
  • Globus pallidus

 

        • receives input from two major nuclei

 

  • the striatum
  • subthalamic nucleus.

 

        • projects fibers to three major nuclei
          • the subthalamic nucleus
          • the thalamus (ventral anterior, ventral lateral, and centromedian nuclei),

 

  • pedunculopontine nucleus
  • Subthalamic nucleus

 

        • receives input from the globus pallidus and from the motor cortex.
        • projects fibers to the globus pallidus.

 

  • Thalamus
  • Input to the thalamus
  • Globus pallidus

 

          • projects to the ventral anterior, ventral lateral, and centromedian nuclei.

 

  • Substantia nigra
  • projects from the pars reticularis to the ventral anterior, ventral lateral, and the mediodorsal nuclei of the thalamus
  • Projections from the thalamus
  • Motor cortex (area 4)

 

            • from the ventral lateral and centromedian nuclei

 

  • Premotor cortex (area 6)

 

            • from the ventral anterior and ventral lateral nuclei

 

  • Supplementary motor cortex (area 6)

 

            • from the ventral lateral and ventral anterior nuclei

 

  • Striatum

 

            • from the centromedian nucleus

 

  • Substantia nigra

 

            • receives major input from the striatum.
            • projects fibers to the striatum and the thalamus (ventral anterior, ventral lateral, and mediodorsal nuclei).

 

  • Pedunculopontine nucleus

 

            • receives GABA-ergic input from the globus pallidus.
            • projects glutaminergic fibers to the globus pallidus and to the substantia nigra.
    • Major neurotransmitters of the neurons of the striatal system

 

  • Glutamate-containing neurons

 

        • project from the cerebral cortex to the striatum.
        • project from the subthalamic nucleus to the globus pallidus.
        • excite striatal GABA-ergic and cholinergic neurons.

 

  • GABA-containing neurons

 

        • are the predominant neurons of the striatal system.
        • are found in the striatum, globus pallidus, and substantia nigra (pars reticularis).

 

  • give rise to GABA-ergic projections:
  • striatopallidal projections
  • striatonigral projections
  • pallidothalamic projections
  • nigrothalamic projections.

 

        • degenerate in Huntington disease.

 

  • Dopamine-containing neurons

 

        • are found in the pars compacta of the substantia nigra
        • give rise to the dopaminergic nigrostriatal projection.
        • are thought to regulate the production of striatal peptides and peptide mRNA.
        • degenerate in Parkinson disease.

 

  • Neurons containing acetylcholine (ACh)

 

        • are local circuit neurons found in the striatum.

 

  • Neuropeptide-containing neurons

 

        • include enkephalin, dynorphin, substance P, somatostatin, neurotensin, neuropeptide Y, and cholecystokinin.
        • are also found in the basal ganglia.
        • coexist with the major neurotransmitters (e.g., GABA and/or enkephalin and GABAand/or substance P).
    • Ventral striatopallidal complex and its connections

 

  • play a role in initiating movements in response to motivational and emotional activity (e.g., limbic functions).

 

      • Ventral striatum
        • consists of the nucleus accumbens and the olfactory tubercle.
        • receives input from the olfactory, prefrontal, and hippocampal cortices
        • projects to the ventral pallidum.
      • Ventral pallidum

 

  • consists of the substantia innominata.

 

        • receives input from the ventral striatum.

 

  • projects to the medial dorsal nucleus of the thalamus.

 

        • Clinical correlations

 

  • Parkinson disease

 

        • associated with degeneration and depigmentation of neurons in the substantia nigra.
        • results in the depletion of dopamine in the caudate nucleus and putamen.

 

  • Progressive supranuclear palsy

 

        • is associated with Parkinson disease.
        • together with Parkinson disease is called the Parkinson-plus syndrome.
        • is characterized by
          • supranuclear ophthalmoplegia, primarily downgaze paresis
          • followed by paresis of other eye movements

 

  • result in the clinical picture of pseudobulbar palsy
  • is characterized by neuronal cell loss in the globus pallidus, red nucleus, substantia nigra, periaqueductal gray, and dentate nucleus.

 

        • spares the cerebral and the cerebellar cortices.
        • results in neurofibrillary tangles in the surviving neurons.

 

  • Huntington disease (chorea major)

 

        • is an inherited autosomal dominant movement disorder
        • associated with severe degeneration of the cholinergic and GABA-ergic neurons, which are located in the caudate nucleus and putamen.
        • is usually accompanied by gyral atrophy in the frontal and temporal lobes.
        • can be traced to a single gene defect on chromosome 4.

 

  • is characterized by impaired initiation and slowness of saccadic eye movements

 

        • patients cannot make a volitional saccade without moving the head.

 

  • results in clinical manifestations of choreiform movements and progressive dementia.

 

        • results in hydrocephalus ex vacuo due to the loss of neurons located in the head of the caudate nucleus

 

  • Sydenham chorea (St. Vitus dance)

 

        • is the most common cause of chorea overall.
        • occurs mainly in girls as a sequela to rheumatic fever.

 

  • Chorea gravidarum

 

        • occurs usually during the second trimester of pregnancy.

 

  • Ballism and hemiballism

 

        • are extrapyramidal motor disorders most often resulting from a vascular lesion (infarct) of the subthalamic nucleus.
        • are characterized by violent flinging (ballistic) movements of one or both extremities
        • symptoms appear on the contralateral side.
        • may be treated with dopamine-blocking drugs or with GABA-mimetic agents.
        • may be treated surgically by ventrolateral thalamotomy.

 

  • Hepatolenticular degeneration (Wilson disease)

 

        • is an autosomal recessive disorder
        • due to a defect in the metabolism of copper (ceruloplasmin).
        • has its gene locus on chromosome 13.

 

  • results in clinical manifestations of tremor, rigidity, and choreiform or athetotic movements

 

        • Tremor is the most common neurologic sign.

 

  • has psychiatric symptoms, including psychosis, personality disorders, and dementia.

 

        • results in a corneal Kayser-Fleischer ring, which is pathognomonic.

 

  • is marked by lesions in the liver (cirrhosis) and in the lentiform nuclei (necrosis and cavitation of the putamen).
  • is diagnosed by low serum ceruloplasmin, elevated urinary excretion of copper, and increased copper concentration in liver biopsy.
  • is treated with the copper-chelating agent D-penicillamine and pyridoxine for anemia.
  • Tardive dyskinesia

 

        • is a syndrome of repetitive choreic movements affecting the face, limbs, and trunk.

 

  • results from treatment with antipsychotic drugs (e.g., phenothiazines, butyrophenones, or metoclopramide).