Topographic Classification of the Thalamus Surfaces Related to Microneurosurgery: A White Matter Fiber Microdissection Study

OBJECTIVE: To describe the topographic anatomy of surgically accessible surfaces of the human thalamus as a guide to surgical exploration of this sensitive area. METHODS: Using the operating microscope, we applied the fiber microdissection technique to study 10 brain specimens. Step-by-step dissections in superior-inferior, medial-lateral, and posterior-anterior directions were conducted to expose the surfaces and nuclei of the thalamus and to investigate the relevant anatomic relationships and visible connections. RESULTS: There were 4 distinct free surfaces of the thalamus identified: lateral ventricle surface, velar surface, cisternal surface, and third ventricle surface. Each is described with reference to recognizable anatomic landmarks and to the underlying thalamic nuclei. The neural structures most commonly encountered during the surgical approach to each individual surface are highlighted and described. CONCLUSIONS: Observations from this study supplement current knowledge, advancing the capabilities to define the exact topographic location of thalamic lesions. This improved understanding of anatomy is valuable when designing the most appropriate and least traumatic surgical approach to thalamic lesions. These proposed surface divisions, based on recognizable anatomic landmarks, can provide more reliable surgical orientation.