caudate nucleus

The caudate nucleus is one of the components of the basal ganglia, along with the putamen, globus pallidus, subthalamic nucleus, and substantia nigra. Anatomically, it has a head, body, and tail, curving around the thalamus and forming part of the lateral wall of the lateral ventricles—making it clinically relevant in identifying ventricular enlargement on imaging. Functionally, the caudate is part of the dorsal striatum (caudate + putamen) and receives excitatory glutamatergic input from the cortex and dopaminergic input from the substantia nigra pars compacta via the nigrostriatal pathway. It plays a key role in the direct and indirect pathways of the basal ganglia motor circuit, modulating voluntary movement, procedural/habit learning, and cognitive functions such as goal-directed behavior and reward processing.

Clinically, the caudate nucleus is most notably associated with Huntington disease, an autosomal dominant trinucleotide repeat disorder (CAG repeat expansion in the HTT gene) causing progressive neurodegeneration. This leads to atrophy of the caudate nucleus (and putamen), resulting in characteristic "boxcar" ventricles on imaging due to loss of caudate bulk. Clinically, Huntington disease presents with chorea, psychiatric disturbances (e.g., depression, psychosis), and dementia due to loss of GABAergic/enkephalinergic neurons in the indirect pathway, leading to disinhibition of movement. The caudate is also implicated in circuits relevant to obsessive-compulsive disorder (OCD) and other basal ganglia-related conditions such as Parkinson disease and Sydenham chorea (post-streptococcal, associated with anti-basal ganglia antibodies affecting the caudate).