Intracerebral displacement of basal ganglia following septal cannulation

The effects of septal cannulation on the displacement of basal ganglia form the basis of the present communication. In experimental rats, in which a cannula is chronically implanted for 30 days between the medial and lateral septal nuclei by stereotaxic procedures, considerable shift of the basal ganglion is always observed on the operated side. The displacement takes place along the long axis of the ganglion either rostrally or caudally. Besides gross asymmetry in their relative sizes, no histological differences are observed between the ganglia of the two sides. Control animals, in which the cannula is withdrawn immediately after the septal lesion, manifest similar, but less pronounced movements of the basal ganglia. The probable underlying mechanisms for such intracerebral shifts are discussed and the role of indirect mechanical forces is outlined. The extraordinary degree of plasticity of the subcortical nuclear masses in terms of mobility is also emphasized.