putamen

The putamen is part of the basal ganglia, a group of subcortical nuclei involved in voluntary motor control, procedural learning, and habit formation. Anatomically, the putamen and caudate nucleus together form the striatum (neostriatum), which receives excitatory glutamatergic input from the cerebral cortex and thalamus. The putamen, along with the globus pallidus, forms the lentiform (lenticular) nucleus. Functionally, the putamen is part of the motor circuit—it projects to the globus pallidus internus (GPi) and substantia nigra pars reticulata via direct (D1 receptor-mediated, facilitates movement) and indirect (D2 receptor-mediated, inhibits movement) pathways, which are modulated by dopaminergic input from the substantia nigra pars compacta. Clinically, the putamen is significant in several disease processes: (1) Parkinson's disease—loss of dopaminergic input from substantia nigra to putamen leads to bradykinesia, rigidity, and tremor; (2) Huntington's disease—though primarily affects caudate, putamen atrophy also occurs; (3) Hypertensive intracerebral hemorrhage—the putamen is the most common site of hypertensive hemorrhage due to rupture of lenticulostriate arteries (branches of the middle cerebral artery), presenting with contralateral hemiparesis, hemisensory loss, and sometimes aphasia or neglect depending on hemisphere; (4) Wilson's disease—copper deposition can cause putaminal degeneration, contributing to the classic 'face of the giant panda' sign is midbrain, but putaminal necrosis also occurs. On imaging, the putamen has a characteristic location just lateral to the internal capsule, and hemorrhage here can be seen as an intraparenchymal hyperdensity on CT. Understanding putaminal anatomy and function is essential for localizing lesions causing movement disorders and stroke syndromes.