Microsurgical and White Matter Anatomy of the Hypothalamus: A Fiber Dissection Study Correlating With Magnetic Resonance Tractography

Abstract

BACKGROUND: The hypothalamus has been shown to be a hub for the control of autonomic and endocrine functions as well as the emotional and behavioral state due to having white matter connections to both brainstem and the cerebrum. However, the white matter connectivity of the hypothalamus is not completely unraveled and there is no consensus in the literature regarding anatomical parcellation and target selection for deep brain stimulation (DBS) surgery. OBJECTIVE: To define and showcase the microsurgical and the white matter anatomy of the hypothalamic region by utilizing fiber dissection technique and fiber tractography. METHODS: A total of 24 formalin-fixed human brain hemispheres were dissected according to Klingler's fiber dissection method with the aid of a surgical microscope. Following morphometric measurements, the hypothalamus was segmented into 6 parts as anteromedial, anterolateral, posteromedial, posterolateral, superior, and inferior according to landmarks of anterior commissure- posterior commissure line and mamillary body. RESULTS: The diagonal band of Broca, the ventral amygdalohypothalamic fiber, stria terminalis, and fornix were related with the anteromedial part; cingulate bundle, supraoptic commissure, and frontopontine tracts were related with the anterolateral part; medial longitudinal fasciculus, dorsal longitudinal fasciculus were related with the posteromedial part; and fasciculus mamillaris princeps, the corticospinal tract, the temporo-parietooccipito pontine tract, medial lemniscus, spinothalamic tract, mammillotegmental fasciculus, and dentatorubrothalamic tract were related with the posterolateral part of the hypothalamus. CONCLUSION: Understanding the detailed fiber tract anatomy of the hypothalamus would provide guidance to neurosurgeons in surgical planning, target selection for DBS and intraoperative orientation.