accessory medullary lamina of globus pallidus

The accessory medullary lamina of globus pallidus (accessory medullar lamina of pallidum) is a thin bundle of myelinated axons (white matter) that divides the medial segment (internal segment) of the globus pallidus into distinct outer and inner portions. It is a fiber plate within this deep brain structure.

The accessory medullary lamina is located within the globus pallidus — a part of the basal ganglia deep within the cerebral hemisphere. Specifically, it lies within the medial (internal) pallidal segment (GPi), dividing it into two functional sub-regions.

The accessory medullary lamina serves as an organizational boundary within the medial globus pallidus, separating neuron populations with potentially distinct connectivity patterns and functions. The neurons on either side of this lamina may project to different targets — the thalamus or brainstem — as part of the basal ganglia output circuit.

The globus pallidus and its internal organization are relevant to movement disorders, particularly Parkinson's disease and dystonia. Deep brain stimulation (DBS) targeting the globus pallidus internus (GPi) must account for the internal anatomy including the accessory lamina for optimal electrode placement and therapeutic efficacy.

The medial medullary lamina of the globus pallidus is the main myelinated fiber plate separating the external (GPe) and internal (GPi) pallidal segments, while the accessory medullary lamina is an additional, smaller subdivision specifically within the GPi, creating two sub-portions of the internal segment.