Cerebrocerebellar system and Arnold’s bundle - A tractographic study: preliminary results

The cerebellum, traditionally considered a structure involved in balance and movement control, was more recently recognized as important in cognitive, emotional and behavioral functions. These functions appear to be related to the more recent parts of the cerebellum that belong to the cerebrocerebellar system. One of the key segments of this system is the (pre)fronto-[penduncule]-pontine projection that represents the Arnold’s bundle. Diffusion tensor imaging and tractography (DTI-TR) has permitted in vivo virtual dissection of white matter tracts, including those of the cerebellar. OBJECTIVE: To study the fronto-[peduncule]-pontine projection (Arnold’s bundle), with DTI-TR. METHODS: Ten normal subjects were included (mean age 30 years). Standard acquisitions in three planes were obtained with a 1.5T GE Signa Horizon scanner, complemented with DTI acquisitions. Post-processing and analysis was performed using an ADW 4.3 workstation running Functool 4.5.3(GE Medical Systems). A single ROI was placed on the medial third of the cerebral peduncle base, considered the site of convergence of the fibers of Arnold’s bundle, bilaterally. RESULTS: Twenty tractograms were obtained. All were constituted by a significant number of fibers in correspondence to the frontal lobe, and part of them anterior to the coronal plane at the anterior commissure, which characterizes them as associated to the prefrontal region. CONCLUSIONS: For the first time, frontal lobe related projections were systematically revealed with DTI-TR seeded from cerebral peduncle base ROIs. They showed anatomic coherence with Arnold’s bundle, which includes the prefrontopontine segment of the cortico-ponto-cerebellar path, one of the components of the cerebrocerebellar system, acknowledged as fundamental for non-motor functions such as cognition, emotion and behavior.