What are the parts of the lentiform nucleus?

Lentiform Nucleus Anatomy

Structural Components

The lentiform nucleus consists of two distinct parts: the putamen (laterally) and the globus pallidus (medially). 1, 2

• The putamen forms the lateral component of the lentiform nucleus and is positioned adjacent to the external capsule 1, 2
• The globus pallidus comprises the medial component and is further subdivided into two segments:
  • Globus pallidus externus (external segment) 3
  • Globus pallidus internus (internal segment) 4, 3

Anatomical Relationships

The lentiform nucleus is bounded by several key structures that help define its position within the basal ganglia:

• Laterally: The putamen is separated from the insula by the external capsule 2
• Medially: The globus pallidus is bordered by the internal capsule, which separates it from the thalamus 1, 5
• Anteriorly: The lentiform nucleus is continuous with the caudate nucleus at the level of the anterior perforated substance 2

Clinical Significance of Each Component

Putamen

• Lesions restricted to the putamen cause predominantly motor hemisyndrome (hemiparesis affecting face, arm, and leg) 5
• Putaminal damage is found in 69% of patients with dyskinetic cerebral palsy 6
• Putamen sends projections to both segments of the globus pallidus and to the substantia nigra pars reticulata 3

Globus Pallidus

• The external segment (globus pallidus externus) projects primarily to the subthalamic nucleus via the middle division of the ansa lenticularis 3
• The internal segment (globus pallidus internus) is the primary output nucleus, sending thick fibers through the fasciculus lenticularis to the thalamus (specifically nuclei ventralis lateralis and ventralis anterior) 3
• Isolated globus pallidus damage is rare (only 20% of cases) and almost always occurs with concurrent putaminal involvement 6
• Bilateral globus pallidus lesions can cause parkinsonism (19% of cases) or dystonia-parkinsonism (6% of cases) 1

Functional Distinction

The putamen primarily serves motor control functions, while the globus pallidus acts as the main output station of the basal ganglia. 1, 3

• Dystonia is the most common movement disorder from lentiform lesions (49% overall, 63% when putamen is involved) 1
• Unlike caudate lesions which cause behavioral disturbances (abulia in 28%), lentiform lesions rarely produce abulia (10%) and do not cause disinhibition 1
• The lentiform nucleus connects functionally with prefrontal, temporal, and parietal cortices, explaining associated deficits like aphasia, hemineglect, and sensory dysfunction when damaged 5