Basal Ganglia

There is no association between the neurological manifestations of Wilson’s disease and basal ganglia calcification.

Ref: Wilson’s Disease By George J. Brewer; Pages 3 – 5; Differential Diagnosis in Neurology and Neurosurgery By S. Tsementzis.

D i.e., Dentate nucleus

C i.e. Thalmus

A. i.e. Planning and voluantry movements

Function of basal ganglia i.e. (caudate nucleus, putamen, globus pallidus, substantia nigra, subthalmic nucleus,
amygdaloid nucleus, striatum, & lenticular nucleus) is planning & programming of voluntary movements

C i.e. Caudate nucleus

D i.e. Putamen

B i.e. Subthalamic Nucleus

–                       Basal ganglia consists of – caudate nucleusQ, putamen, globus pallidus, subthalmic nucleus, and substantia nigraQ. Striatum (term derived from the striated appearance of these nuclei) refers to the caudate nucleus and putamen. Whereas the combination of putamen and globus pallidus is often referred to as lentiform nucleus

–                       Efferent fiber bundle of substantia nigra (pars compacta) transmit dopaminergic fibers to corpus striatum/ striatum (dopaminergic nigro striatal projection).

–                       Subthalamic nucleus (a diencephalic grey matter part of basal ganglia) is the only nucleus of basal ganglia that actually produce excitatory neurotransmitter glutamate. Subthalamic nucleus receives inhibitory (GABA – nergic) imput from globus pallidus external segment (GPe) and has excitatory (glutaminergic) projections to both GPe and GPi (globus pallidus internal segment). Subthalamic nucleus plays an important role in stimulation of indirect SNpc-GPi (substantia nigra – pars compacta – globus pallidus internal segment) pathway.

–   Although the majority of striatal neurons are GABA nergic medium spiny neurons, the highest density of glutamate receptors in basal ganglia is found in corpus striatum (putamen + caudate nucleus)Q, which receives 2 main inputs (both of which are excitatory glutaminergic) from cerebral cortex (cortico striatal pathway) and from intralaminar nuclei of thalamus (thalamostriatal pathway).

B i.e. Skilled movement

A i.e. Planning

Basal ganglia is concerned with planning and organizing voluntary movementsQ whereas, spinocerebellum (spinocerebellar tract) smoothen & coordinates movementsQ

Control of Posture & Movements

Control of Posture & Movement

Cortical Motor Areas

• Motor response are produced by stimulation 01

– Motor Cortex (M1)

– Supplementary motor area

– Premotor cortex

– Somatic sensory area I (in post central gyrus)

– Somatic sensory area II (in wall of sylvian fissure)

• These observations fit with the fact that 30% of fibers making contricospinal & corticobubar tracts come from the motor cortex but 30% come from premotor cortex and 40% from parietal lobe, especially the somatic sensory area.
• The various body parts are represented in precentral gyrus with the feet at the top & face at the bottom. The facial area is represented bilaterally but the rest of representation is generally unilateral. The size of representation is proportionate to the skill with which the part is used in fine, voluntary movements.
• The axial musculature & proximal portion of limbs are represented along the anterior edge of the precentral gyms and distal part of limbs along the posterior edge
• Motor cortex show same kind of plasticity as the sensory cortex (i.e. the motor maps are not immutable & they change with experience)

Corticospinal & Corticobulbar System

• The nerve fibers that pass from motor cortex to cranial nerve nuclei form corticobulbar tract
• The nerve fibers that cross the midline in medullary pyramids and form lateral corticospinal tract make up — 80% of fibers in corticospinal tract. The remaining 20% make up the anterior or ventral corticospinal tract which does not cross up the midline until it reaches the level of the muscles it control.
• In the brain stem & spinal cord medial or ventral pathways & neurons are concerned with the control of muscles of the trunk & proximal portion of limb, whereas lateral pathways are concerned with the control of muscles in the distal portions of the limb
• The axial muscles are concerned with postural adjustments & gross movements where as the distal limb muscles are those that mediate fine, skilled movements
• So ventral corticospinal tract & medial descending paths (tectospinal, reticulospinal & vestibulospinal tracts) are concerned with adjustments of proximal muscles and posture, whereas the lateral corticospinal tract & rubrospittal tract ^.,reconcerned with distal muscles & skilled voluntary movements

Postural Reflexes

• Optical rightning reflex, placing reactions % hopping reactions are integrated in cerebral cortex

– Labyrinthine / Neck / Body on head/Body on body – rightining reflexes are integrated in midbrain

– Tonic neck reflex, tonic labyrinthine reflexes & streth reflex are integrated in medulla.

– Negative supporting reaction, positive supporting (magnet) reaction and stretch reflexes are integrated in spinal cord

Antigravity reflexes in medulla and locomotor reflex in midbrain & thalamus

D i.e. Wilson’s disease

A i.e. Hyperparathyroidism; C i.e. Hypoparathyroidism

HypoparathyroidismQ, pseudo-hypoparathyroidismQ, hyperparathyroidismQ & hypothyroidismQ cause basal ganglia calcification. Calcification usually occurs in globus pallidus.

Causes of Basal Ganglia Calcification

1. Endocrinal                       – Hypo & Pseudo hypo-parathyroidismQ,(Albright’s syndrome),
2. Secondary hyperparathyroidismQ    –HypothyroidismQ
3. Toxic                               – Hypoxia (Birth anoxia)Q Co/Pb = Carbonmonoxide/Lead poisoning
4. Chemo/Radio                      Therapy
5. Infection                          – TORCHQ (toxoplasma, congenital rubella, cytomegalo virus, Herpes simplex) HIV – CysticercosisQ – TB
6. Metabolic                         – Fahr’s dsQ, Cockayne’s syndrome, mitochondrial disorder (Cytopathy)
7. Vascular malformationQ      – Mineralizing micro angiography
8. Tumor
9. Physiological with aging, idiopathic, familial

Answer is B (Basal ganglia):

The basal ganglia is the most common site of hypertensive haemorrhage

The most common site of hypertensive haemorrhage within basal ganglia is the Putamen.

The most common sites of hypertensive haemorrhage are :

1. The basal ganglia (putamen, thalamus and adjacent deep white matter)- commonest
2. Deep cerebellum
3. Pons

The most common site of hypertensive haemorrhage within basal ganglia is the Putamen.

External capsule refers to a thin layer of white matter that separates the lateral part of lentiform nucleus (putamen) from claustrum and is invariably damaged along with the putamen.

Ans. A i.e. Basal ganglia

Ans. is ‘b’ i.e., Planning & programming of movement

The basal ganglia are involved in planning and programming of movement or more broadly, in the process by which on abstract thought is converted into a voluntary action. Like, lateral cerebellum, neurons in the basal ganglia discharge before the movements begin. They influence the motor cortex via the thalamus, and corticospinal tract is the final common pathway to motor neuron. Putamen circuit is involved in complex pattern motor activity and skilled movement.

Basal ganglia is part of extrapyramidal system and therefore is involved in regulation of tone and posture.

The basal ganglia, particularly the caudate nuclei, also play a role in some cognitive proces So, caudate nucleus plays a major role in cognitive control of motor activity.

Ans. is ‘a’ i.e., Anterior nucleus

Motor nuclei (ventral anterior and ventral lateral) of thalamus relay and process messages from basal ganglia (especially globus pallidus) and cerebellum to motor and premotor cortex.

From functional point of view, thalamic nuclei are divided into :‑

A) Specific sensory nuclei (relay nuclei) :- These nuclei receive all sensory afferents from ascending pathways and project to the somatosensory cortex. These include ventroposterior nucleus and medial & lateral geniculate bodies.

B) Association nuclei :- These nuclei have reciprocal connections with the association areas of the cerebral cortex and therefore help in integration of different type of sensory information. These nuclei include the lateral group of nuclei (Pulvinar, lateral dorsal, lateral posterior nuclei) and part of medial dorsal nucleus.

C) Nonspecific nuclei :- These nuclei also receive sensory information but project to the cortex in a diffuse manner. Therefore they seem to be involved in the arousal induced by sensory stimuli. These nuclei are intralaminar and reticular nuclei.

D) Motor nuclei :- There nuclei relay and process messages from the basal ganglia and cerebellum to motor and premotor cortex. These nuclei are ventral anterior and ventral lateral nuclei.