NEUROANATOMY Lecture : 4 Anatomy of the Cerebellum & the Basal Ganglia

1. NEUROANATOMY Lecture : 4 Anatomy of the Cerebellum & the Basal Ganglia Prepared and presented by: Dr. Iyad Mousa Hussein, MD, Ph.D in Neurology Head of Neurology Department Nasser Hospital

2. LECTURE OBJECTIVES: 1. Embryological, origin and Relations of the Cerebellum. 2. External Features, Subdivisions and Connections of the Cerebellum. 3. Internal Structure of the Cerebellum 4. Blood Supply of the Cerebellum 5. Lesion of the Cerebellum. 6. Definition and Classification of the Basal Ganglia. 7. The Structures and Connections of the Corpus Striatum. 8.The Claustrum and the Amygdaloid Nucleus 9.The Substantia Nigra and the Subthalamic Nuclei. 10.The Basal Ganglia Functions and Lesions. 11. The External and Internal Capsule

3. The Cerebellum The cerebellum (“a little brain") Embryological Origin: it is the largest part of the hindbrain. Hindbrain → Rhombencephalon → Metencephalon → cerebellum & pons. Site: it is the part of the brain, located dorsal to the pons and the medulla occupies most of posterior cranial fossa. Shape: the cerebellum is globular shape.

4. Relations of the Cerebellum • Superiorly: the tentorium cerebelli, separating it • from the cerebral hemispheres. • 2. Anteriorly: the cavity of the fourth ventricle • separating it from pons and medulla. • 3. On each side: it is related to the sigmoid venous • sinus and mastoid antrum.

8. Functions of the Cerebellum • Maintain equilibrium of the trunk. • Muscle tone regulation. • Coordination and regulation of fine voluntary motor activity.

9. Cerebellar Connections (Peduncles) Thecerebellum is connected with the brain stem , the cerebrum and the spinal cord by the cerebellar peduncles (afferent and efferent tracts): 1. Superior cerebellar peduncle: connected it with the midbrain. 2. Middle cerebellar peduncle: connected it with the pons. 3. Inferior cerebellar peduncle: connected it with the medulla oblongata.

12. External Feature of the Cerebellum The cerebellum has: Right and left cerebellar hemispheres connected by a median vermis (superior & inferior). Anterior lobe. Posterior (Middle) lobe. Flocculo-nodular lobe Primary Fissure: the main fissure between the anterior and middle lobes. Tonsil: one on either side of the inferior vermis. Horizontal fissure. Posteriolateral fissure: between the posterior and flocculo- nodular lobes.

15. Subdivisions of the Cerebellum • 1. Morphological subdivision: • a. Right cerebellar hemisphere. • b. Left cerebellar hemisphere. • c. Median vermis: midline central structure. • 2. True anatomical subdivision: • a. Anterior lobe: infront of the primary fissure. • b. Posterior lobe (Middle lobe): it major part of the • cerebellum, from the primary fissure to the posterolateral • sulcus. • c. Flocculo-nodular lobe: formed of two flocculi and nodule • in the middle . • 3. Functional subdivision: • a. Vestibular part or archicerebellum. • b. Paleocerebellum. • c. Neocerebellum.

18. Functional Subdivision of the Cerebellum

19. Internal Structure of the Cerebellum • The cerebellum consists of: • Outer gray mater: on the surface forming the • cerebellar cortex which contains nerve cells arranged • into 3 layer as follows: • 1. Outer molecular layer. • 2. Intermediate layer of Purkinji cells. • 3. Inner granular layer. • B. Inner white mater:nerve fibers. • C. Subcortical collection of gray mater nuclei.

21. Nuclei of the Cerebellum These nuclei include: 1. Dental nucleus: receives fibers for coordination and regulation of fine voluntary motor activity. 2. Emboliform nucleus: receives fibers for muscle tone regulation. 3. Globose nucleus: receives fibers for muscle tone regulation. 4. Fastigial nucleus: receives direct vestibular fibers.

23. Blood Supply of the Cerebellum 1. Posterior inferior cerebellar arteries of vertebral arteries. 2. Anterior inferior cerebellar arteries of basilar artery. 3. Superior cerebellar arteries of basilar artery.

25. Lesion of the Cerebellum 1. Ataxia (discoordination). 2. Muscle hypotonia. 3. Tremor. 3. Dysmetria (error in termination of movement). 5. Adiadochokinesia (delay in initiation of successive movements). 6. Dysarthria (a type of slurred speech). 7. Nystagmus.

27. The Basal Ganglia Definition: are collections of gray matter situated within each cerebral hemisphere (deep).

28. Functions of the Basal Ganglia 1. Receive afferent information from the cerebral hemisphere, thalamus, subthalamus and brain stem. 2. Control muscular movement and regulation of voluntary movement. 3. The learning of the motor skills. 4. 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.

29. Components of the Basal Ganglia • The Caudate Nucleus. • The Lentiform Nucleus (Putamen and Globus pallidus). • The claustrum. • The amygdaloid nucleus. • The subthalamic nuclei, the substantia nigra, and the red nucleus are functionally related to basal ganglia but they should not be included with them.

33. 1. The Caudate Nucleus • It is a large C-shaped mass of a gray matter. • Related to lateral ventricle and lies lateral to the thalamus. • It is divided into a head, body, and tail.

36. 2. Lentiform Nucleus • It is a wedge-shaped mass of gray matter. • Lies between the internal capsule (medially) and the external capsule (laterally). • The lentiform nucleus divided into: a. Putamen: a larger, darker lateral part. b. Globus Pallidus:the smaller, lighter medial part.

39. The Corpus Striatum The corpus striatum is situated lateral to the thalamus and divided by the internal capsule, into: 1. The caudate nucleus. 2. The lentiform nucleus: a. Putamen. b. Globus pallidus.

41. Corpus Striatum ═ Caudate Nucleus + Lentiform Nucleus. Lentiform Nucleus ═ Putamen + Globus Pallidus. Neostriatum (striatum) ═ Caudate Nucleus + Putamen.

43. Connections of the Corpus Striatum A. Afferent fibers: 1. Corticostriate fibers. 2. Thalamostriate fibers. 3. Nigrostriate fibers. 4. Brain stem striatal fibers. B. Efferent fibers:fibers descend to the: 1. Tegmentum of midbrain. 2. Substantia nigra. 3. Red nucleus. 4. Thalamus. 5. Hypothalamus. 6. Reticular formation of the midbrain.

44. 3. The Claustrum • It is a thin layer of gray mater. • Lies between the external capsule (medially) and the white matter of the insula laterally. • The function of the claustrum is unknown.

46. 4. Amygdaloid Nucleus • The amygdaloid nucleus is so named because it resembles an almond. • The amygdaloid nucleus is situated in the temporal lobe. • It is considered to be part of the limbic system. • Function: • 1. 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. • 2. Smell function.

49. The Substantia Nigra and the Subthalamic Nuclei • The substantia nigra of the midbrain and the subthalamic nuclei of the diencephalon are functionally related to basal ganglia. • The neurons of the substantia nigra are dopaminergic.