7. Basal Ganglia (3).pdf

BASAL GANGLIA DR NADINE RAMPF | PHD [email protected] LECTURE OUTLINE Overview 04 Anatomical components 06 Corpus striatum 07 Lentiform nucleus 09 Claustrum 10 Functional components 13 Amygdala 14 Subst...

BASAL GANGLIA DR NADINE RAMPF | PHD [email protected] LECTURE OUTLINE Overview 04 Anatomical components 06 Corpus striatum 07 Lentiform nucleus 09 Claustrum 10 Functional components 13 Amygdala 14 Substantia nigra 15 Subthalamus 16 Clinical correlations 19 02 OBJECTIVES Describe the anatomical and functional components of basal nuclei and their functions Describe the connections and functions of the corpus striatum Give the anatomical basis of Parkinsonism, chorea, and ballismus List the characteristic features of Parkinsonism 03 LECTURE OUTLINE Overview Anatomical components Corpus striatum Lentiform nucleus Claustrum Functional components Amygdala Substantia nigra Subthalamus Clinical correlations 04  Globus OVERVIEW Pallidus Caudate nucleus (body) Large masses of grey matter situated in the basal part of Caudate the white matter core of each cerebral hemisphere lateral nucleus to the thalamus (head) Anatomically, the basal ganglia include: Corpus striatum (caudate nucleus + lentiform nucleus) Claustrum Amygdaloid body Subthalamic Functionally, the basal ganglia also include: nucleus The substantia nigra The subthalamus Putamen Substantia Some also include the red nucleus nigra Supplied by the anterior and posterior perforating, striate and anterior choroidal arteries Amygdaloid Caudate The basal nuclei are important for: Body nucleus Organizing and coordinating somatic motor activities (tail) especially willed movements Involved in automatic stereotyped postural and reflex motor activities such as when normal individuals swing their arms while walking 05 LECTURE OUTLINE Overview Anatomical components Corpus striatum Lentiform nucleus Claustrum Functional components Amygdala Substantia nigra Subthalamus Clinical correlations 06 CORPUS STRIATUM Situated lateral to the thalamus Topographically it is almost completely divided into the caudate nucleus and the lentiform nucleus by a band of nerve fibres, the internal capsule However, anteroinferior ends of these nuclei remain connected by a few bands of grey matter across the anterior limb of the internal capsule These bands give it a striated appearance, hence the name corpus striatum The lentiform nucleus consists of two parts: Putamen (darker, lateral) Globus pallidus (paler, medial) Phylogenetically corpus striatum forms two distinct functional units, the paleostriatum and the neostriatum The globus pallidus is relatively ancient and termed paleostriatum/ pallidum The caudate nucleus and putamen being recent in development, together form the neostriatum/striatum The striatum is largely afferent whereas pallidum is a largely efferent structure 07 CAUDATE NUCLEUS Large comma-shaped mass of grey matter, which surrounds the thalamus and is itself surrounded by the lateral ventricle Length of its convexity projects into the cavity of the lateral ventricle Rounded anterior part in front of the interventricular foramen is the head The head tapers caudally into the body and then into a tail which merges at its anterior extremity with an almond-shaped mass of grey matter called amygdaloid body The head is large and rounded and forms the floor and lateral wall of the anterior horn of the lateral ventricle Bands of grey matter connect the head with the putamen across the anterior limb of the internal capsule The body is long and narrow and forms the floor of the central part of the lateral ventricle It is separated from thalamus by stria terminalis and thalamostriate vein The tail is long and slender and forms the roof of the inferior horn of the lateral ventricle It terminates anteriorly (topographically) in the amygdaloid body 08 LENTIFORM NUCLEUS Large lens-shaped (biconvex) mass of grey matter beneath the insula forming the lateral boundary of the internal capsule In horizontal sections of the cerebrum, it appears wedge-shaped with a broad convex base directed laterally Surfaces Lateral: Convex and related to a thin sheet of white matter, the external capsule It is grooved by the lateral striate arteries (the central branches of the middle cerebral artery) Medial: More convex and related to the internal capsule (limbs and genu) In transverse sections, the medial surface is angulated at the genu Inferior: Related to the sublentiform part of the internal capsule and lies close to the anterior perforated substance Parts A vertical plate of white matter (external or lateral medullary lamina) divides the lentiform nucleus into two parts: Putamen (large, lateral, darker in colour) Globus pallidus (small, medial, lighter in colour) The globus pallidus is further subdivided by an internal or medial medullary lamina of white matter into outer and inner segments 09 CLAUSTRUM A thin saucer-shaped mass of grey matter situated between the putamen and insula Considered as a detached part of the insula Separated from putamen by thin lamina of white matter, the external capsule The extreme capsule is a white matter band lateral to the claustrum Its connections and functions are not known 10 CONNECTIONS The striatum (caudate nucleus and putamen) is the receptive part while the globus pallidus is the efferent part (outflow centre) of the corpus striatum Afferent Connections Chiefly from the cerebral cortex, thalamus and substantia nigra Corticostriate fibres arise from a wide area of the ipsilateral cerebral cortex and reach the striatum through both internal and external capsules Thalamostriate fibres arise from mediodorsal, intralaminar and midline nuclei of the thalamus The majority of these fibres end in the caudate nucleus, the remaining pass through the internal capsule to reach the putamen Nigrostriate fibres arise from substantia nigra (pars impacta) and ascend up to terminate in the corpus striatum, mainly in the putamen and caudate nucleus These fibres carry dopamine synthesized by nerve cells of substantia nigra to the striatum (melanin normally present in the substantia nigra is a byproduct of dopamine metabolism) It is believed that these fibres have an inhibitory effect on the corpus striatum 11 CONNECTIONS Efferent Connections Most of the output of the striatum is via the globus pallidus, however, some efferents also go to the substantia nigra (pars reticulata) The globus pallidus is the main efferent component of the corpus striatum Outflow from the globus pallidus goes mainly to the thalamus via two fasciculi: Ansa lenticularis looping around the posterior limb of the internal capsule Fasciculus lenticularis traversing the internal capsule These fasciculi enter the region between the red nucleus and thalamus, where they unite with the dentatorubrothalamic tract to form the thalamic fasciculus, which ends in the ventrolateral and ventroanterior nuclei of the thalamus which in turn project to the motor and premotor areas of the cerebral cortex The subthalamic fasciculus passes through the internal capsule and forms direct reciprocal connections between the subthalamic nucleus and globus pallidus Some fibres from globus pallidus also pass to the substantia nigra (pallidonigral fibres) 12 LECTURE OUTLINE Overview Anatomical components Corpus striatum Lentiform nucleus Claustrum Functional components Amygdala Substantia nigra Subthalamus Clinical correlations 13 AMYGDALOID BODY Almond-shaped mass of grey matter in the temporal lobe Located anterosuperior to the tip of inferior horn of lateral ventricle It is situated deep to uncus which serves as a surface landmark for its location Developmentally it is related to basal nuclei but functionally it is included in the limbic system and therefore shares its functions Refer to Hippocampus and Limbic System lecture for further discussion 14  SUBSTANTIA NIGRA Subdivided into two parts: Dorsal part (pars compact) - contains dopaminergic neurons that project into the striatum Ventral part (pars reticulata) - receives striatal input 15 SUBTHALAMUS a.k.a. Subthalamic nucleus Small nucleus in the ventral part of the diencephalon Appears as a biconvex lens in coronal section Located caudal to the lateral half of the thalamus inferomedial to the globus pallidus It is separated from thalamus by a smaller nucleus, called zona inserta The subthalamic nucleus and globus pallidus are interconnected by the subthalamic fasciculus which traverses the internal capsule 16 FUNCTIONS OF THE BASAL GANGLIA Concerned with planning and programming of voluntary movements Determine how rapidly a movement is to be performed and how large the movement must be Decrease muscle tone and inhibit unwanted muscular activity Regulate muscle tone and thus helps in smoothening the voluntary motor activities of the body Control automatic associated movements, like swinging of arms during walking Control group of movements for emotional expression Control reflex muscular activity 17 NEURAL CIRCUITRY The striatum receives information from three major sources: 1. The cerebral cortex 2. The thalamus, 3. The substantia nigra The striatum projects to the globus pallidus and substantia nigra The globus pallidus (the outflow nucleus of the striatum) projects to the thalamus and subthalamic nucleus The substantia nigra also projects to the thalamus The thalamus projects to the cerebral cortex This information is integrated within the corpus striatum and outflow passes back to the above areas The activity of the basal ganglia is initiated by information received from the cerebral cortex, the thalamus, and the brainstem (substantia nigra and red nucleus) The outflow from the basal ganglia is channelled through the globus pallidus, which then influences the activities of the motor areas of the cerebral cortex The motor cortex then controls the motor activities through corticospinal and corticonuclear fibres Thus, basal ganglia can control muscular movements by influencing the cerebral cortex rather than through direct descending pathways to the brainstem and spinal cord 18 LECTURE OUTLINE Overview Anatomical components Corpus striatum Lentiform nucleus Claustrum Functional components Amygdala Substantia nigra Subthalamus Clinical correlations 19 CLINICAL CORRELATIONS Lesions of the basal ganglia result in various forms of unwanted involuntary movements and disturbance in muscle tone These disorders include Parkinsonism, chorea, athetosis and ballismus Parkinsonism a.k.a. Parkinson’s disease/paralysis agitans It is a second most common neurodegenerative disorder second only to Alzheimer disease This disease usually occurs after 50 years of age due to deficiency of the neurotransmitter dopamine in the corpus striatum following a lesion in substantia nigra and/or its projections (i.e. nigrostriate fibres) Dopamine is synthesized in the melanin-containing pigmented cells of substantia nigra and transported to the corpus striatum through nigrostriate fibres Dopamine causes inhibition of cells within the corpus striatum The neurological changes in Parkinsonism appear to be a release phenomenon due to lack of inhibitory influences following dopamine deficiency 20 CLINICAL CORRELATIONS Characteristic features of Parkinsonism Resting tremors Pill-rolling movements of hands Lead-pipe or cogwheel type of muscular rigidity Mask-like face or loss of facial expression Stiff, shuffling gait Stooped-posture Bradykinesia The 4 cardinal symptoms are tremor, rigidity, Bradykinesia and postural instability Treatment The administration of L-dopa, a precursor of dopamine By placing small lesions (stereotactic surgery) in the globus pallidus and thalamus to diminish the cortical effects of abnormal discharges from the corpus striatum By striatal implants of dopamine-containing neurons of fetal origin 21  RECAP Parkinson's Disease https://www.youtube.com/watch? v=7upHDhAmkqU 22  MICHEAL J. FOX Parkinson's Disease https://www.youtube.com/watch? v=5OLzuUVfoJ8 23 CLINICAL CORRELATIONS Chorea This is characterized by quick, jerky, irregular purposeless involuntary movements, which involve primarily, the tongue, face and limbs Swift grimaces and sudden movements of the head or limbs are good examples The chorea is of two types: Sydenham’s chorea Huntington’s chorea Ballismus Usually results due to vascular lesion of the subthalamic nucleus where normal smooth movements of different parts of the body are integrated Characterized by a violent burst of irregular movements in the trunk, girdles and proximal extremities It usually involves the proximal musculature of opposite extremity, and limb suddenly flies about in all directions out of control, i.e. contralateral flinging (ballistic) movements of one or both extremities The disease may be restricted to one limb (mono-ballismus), but usually involves both upper and lower limbs on the contralateral side of the lesion (hemiballismus) This is because the subthalamic nucleus of one side projects mainly to the ipsilateral cortex through globus pallidus and thalamus 24  HUNTINGTON'S DISEASE https://www.youtube.com/watch? v=rcFlo2fDMMs 25  JAMES'S STORY Huntington's Disease https://www.youtube.com/watch? v=m6SxJUjJGlc 26  THANK YOU FOR YOUR ATTENTION Content for this lecture: Chapter 10 | Snell's Clinical Neuroanatomy, 8th Edition