3D Endoscope-Assisted Transcallosal Approach to the Third Ventricle Using a Minimally Invasive Tubular Retractor System - A Feasibility Study

Background: Surgical approaches to deep-seated brain pathologies, specifically lesions of the third ventricle, have always been a challenge for neurosurgeons. Factors including type of pathology, age at presentation, and presence of hydrocephalus may be used to determine the optimal surgical approach. In certain cases, the transcallosal approach remains the best option for targeting lesions of the third ventricle. Retraction of the fornices and the wall of the third ventricle during this approach have been associated with neuropsychological and hypothalamic deficits. We investigate the feasibility of an interhemispheric 3D endoscope-assisted trancallosal approach through a minimally invasive tubular retractor system for the management of third ventricular lesions.

Methods: Interhemispheric transcallosal approaches were performed in 5 preserved cadaveric heads (10 sides) injected with colored latex. A ViewSite™ Brain Access System (Vycor Medical, Inc., Boca Raton, FL, USA) of tubular retractors was used. Each specimen underwent a small parasagittal craniotomy with the use of neuronavigation (Brainlab AG, Feldkirchen, Germany). The tubular retractor was introduced under direct 3D endoscopic visualization. Following observation of crucial vascular structures and the corpus callosum, fenestration of the corpus callosum was performed using bayonetted microinstruments. The retractor was passed through the opening and secured. Feasibility of different modifications of the transcallosal approach through the tubular retractor system (transforaminal, interfornicial, etc.) was assessed using a scoring system.

Results: This approach, with use of the tubular retractor system, provided better visualization of third ventricle and more stable and rigid retraction of corpus callosum and fornices. Byonetted instruments and bipolar cautery were passed through the tubular retractor with no difficulty, and the tubular retractors applied rigid, constant, and equally distributed pressure on corpus callosum. The technique allowed for the splitting of white matter tracts rather than their transection.

Conclusion: Though some authors have advocated the benefits of retractorless microsurgical techniques in approaching the third ventricle, the use of routine retractors and their potential complications, in some cases, cannot be avoided. An increase incidence of cortical damage has been reported in a rat model, wherein retractors were held in place for more than 15 minutes at a pressure of 20 mm Hg. We found the interhemispheric 3D endoscope-assisted trancallosal approach through tubular retractors to be feasible for the management of pathologies of the third ventricle. Further clinical studies are necessary to determine potential complication rates.