A Fiber Dissection Study of the Anterior Commissure: Correlations with Diffusion Spectrum Imaging Tractography and Clinical Relevance in Gliomas.

The anterior commissure, which connects bilateral temporal lobes and olfactive areas, remains elusive in many aspects of its structure and functional role. To comparatively describe anatomical details of the anterior commissure using cadaveric fiber dissection (FD) and diffusion spectrum imaging (DSI) thus refining our knowledge of the tract and exploring its clinical relevance in glioma migration. Twelve normal postmortem hemispheres were treated with Klingler's method and subjected to FD with medial, inferior, and lateral approaches. The FD findings were correlated with DSI tractography results. To illustrate the clinical relevance, two patients with recurrent temporal high-grade glioma are described. Our FD and DSI tractography of the anterior commissure disclosed a new anatomical paradigm. The FD confirmed that the anterior limb (absent sometimes and variable) and the lateral/temporal extension include the rostral portion and caudal portion, respectively, of the anterior commissure fibers. The shape of the lateral/temporal extension predominantly resembles an 'H'. The DSI tractography findings corresponded to these FD results. According to the FD, the Virchow-Robin space is continuous with the subarachnoid space and very close to the anterior commissure. The two clinical cases presented severe disturbances of consciousness and behavior despite good local tumor control. Subsequent magnetic resonance images showed new lesions infiltrating the contralateral temporal lobes. FD combined with DSI provided anatomical details facilitating a better understanding of the anterior commissure. Glioma migration routes to the contralateral temporal lobe included the anterior commissure, Virchow-Robin space, and subarachnoid space and were clinically relevant.