Magnetic resonance imaging (MRI) is the modality of choice for assessment of pathology involving the deep grey matter nuclei, due to its superior contrast resolution compared to computed tomography (CT). The thalamostriate veins collect the venous drainage of both the basal ganglia and thalami, the blood then flows through the internal cerebral veins and basal veins of Rosenthal, which form the great vein of Galen, and pass into the straight sinus. The difference in embryological origin is also reflected in the arterial blood supply: the basal ganglia are supplied by perforating branches of the anterior cerebral artery, including Heubner’s artery, middle cerebral artery and the anterior choroidal artery, all originating from the internal carotid artery perforating branches of the posterior cerebral artery and posterior communicating artery supply the thalami. The thalami, situated along the borders of the third ventricle, originate from the embryonic diencephalon and consist of grey matter nuclei but also of white matter tracts. The lentiform nucleus is a descriptive collective term for both the putamen and globus pallidus, which are divided by a thin layer of white matter, the lateral medullary lamina. Embryologically and functionally, the caudate nucleus and putamen form a unit, the striatum. The substantia nigra and subthalamic nucleus originate from the mesencephalon and diencephalon, respectively, and are not considered a part of the basal ganglia in this review.
For the purpose of this review, the term “basal ganglia” is used in the strictest sense (the telencephalic basal ganglia) and refers to the corpus striatum (comprising the caudate nucleus, putamen and globus pallidus). The components of the basal ganglia and the method of naming depend on which aspect (biochemical, embryological or functional) of these complex structures is considered. The terminology can be confusing because of the variety of names and definitions, complex interconnections and interactions. Thalamic lesions can cause chronic pain, sensory loss, amnesia, dystonia and other disorders. The thalamus is a complex hub receiving subcortical sensory and motor input that projects to both the cortex and striatum. Basal ganglia pathologies typically cause movement disorders, but their role extends beyond the extrapyramidal system to memory, emotion and other cognitive functions. They are involved in the regulation of autonomic, motor, sensory, limbic and endocrine functions, and consequently, their metabolic demand exceeds that of the cerebral cortex in the resting state. The basal ganglia and thalami are paired grey matter structures, embedded deep in the brain hemispheres and are often referred to as the “central grey matter”.
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