Microsurgical and Tractographic Anatomy of the Anterior Thalamic Nucleus: Delineation of a Dorsal Anterior Thalamo-Temporal Projection and Its Relevance to Precision Neuromodulation

Abstract

Featured Application This study delineates the anterior thalamo-temporal projection (ATTP), a dorsal fiber bundle extending between the anterior nucleus of the thalamus and the amygdalo-uncal region. Its course provides an anatomical reference structure for patient-specific analyses of electrode position, volume of tissue activated, and fiber recruitment in anterior thalamic deep brain stimulation.Abstract The anterior nucleus of the thalamus (ANT) is a key node of the hippocampal-diencephalic memory system and an established target for deep brain stimulation in drug-refractory epilepsy, yet its temporal connectivity remains incompletely characterized. This study delineates a dorsal posterolateral fiber bundle between the ANT and the amygdalo-uncal region, for which we propose the term anterior thalamo-temporal projection (ATTP). Fourteen hemispheres from seven human brains were examined using Klingler fiber dissection. The ATTP was identified in all 14 dissected hemispheres, following a dorsal posterolateral course through the pulvinar-lateral geniculate corridor and forming one macroscopic endpoint at the ANT, with no demonstrable ventral continuation. The reproducibility of a corresponding tractographic pattern was evaluated in 20 hemispheres from 10 Human Connectome Project participants using a repeated-run diffusion tractography protocol. An anatomically concordant tractographic pattern was reconstructed in 17 of 20 hemispheres (85%). The position of the ANT relative to the anterior commissure-posterior commissure line was also measured. The ANT position varied predominantly along the anteroposterior axis. To our knowledge, this study provides the first systematic microsurgical and tractographic delineation of the ATTP, establishing an anatomical framework for future investigations of medial temporal connectivity and patient-specific ANT neuromodulation.