Postmortem Dissections of the Papez Circuit and Nonmotor Targets for Functional Neurosurgery.

BACKGROUND: The Papez circuit was first described as the anatomic basis of emotion. Subsequent studies consolidated recognition of its limbic activities but showed a more important role in memory. Anatomic dissections and advanced neuroimaging have deepened our understanding of the various interconnections and white matter tracts present in this circuit. The aim of our study is to describe the anatomy of the Papez circuit through cadaveric dissection with correlation to ultrahigh-field magnetic resonance imaging (MRI) and MRI tractography. METHODS: White fiber dissection was performed on 5 cadaveric human brain hemispheres. The Papez circuit was dissected mediolaterally to show its anatomy and relation to other nuclei and tracts. Open-source MRI tractography data from the Human Connectome Project is combined with ultrahigh resolution, 7T structural MRI, and 17.6T diffusion tractography to further show the anatomy. RESULTS: The network connecting the anterior and posterior cingulate, entorhinal cortex, hippocampus, fimbria, dentate gyrus, fornix, mammillary bodies, and anterior thalamus was described using white matter fiber dissection and compared with MRI tractography and ultrahigh-field structural and diffusion MRI. We showed for the first time (through portmortem dissection) fibers directly connecting the anterior thalamic nucleus and the subgenual cingulate via the septal area. CONCLUSIONS: The description of the anatomy of the Papez circuit through cadaveric dissection and comparisons with advanced neuroimaging studies allow a better understanding of its three-dimensional spatial layout, in addition to showing new areas of connectivity with adjacent structures and possibilities for surgical approaches or stimulation.

Evaluation of Accuracy and Reliability of a Smartphone Stereotactic Coordinates Checking Application.

BACKGROUND: Surgical assistance applications for smartphones have the potential to be used in daily practice; however, regular reviews of these tools are required. StereoCheck (Mevis, São Paulo, São Paulo, Brazil) is a mobile application (app) designed to compute stereotactic coordinates as a checking tool. The present study evaluated the accuracy and reliability of the StereoCheck app. METHODS: The present observational and prospective study included 26 patients who had undergone frame-based stereotactic brain biopsy. A standard stereotactic planning software (Framelink, version 5.0 [Medtronic, Minneapolis, Minnesota, USA]) was used to define the target coordinates. The surgical planning images were transferred to StereoCheck using 2 image input methods: photographs of the screen monitor and digitally exported images of the screen monitor. Five examiners performed the target coordinate definitions using StereoCheck on 2 occasions. The accuracy and reliability of the app were evaluated in tests that compared the planning methods (app vs. standard software), multiple examiners, and sequential tests. RESULTS: The StereoCheck accuracy using photographs of the screen was 2.71 ± 0.86 mm (95% confidence interval, 2.37-3.06). Using the digitally exported images, it was 0.82 ± 0.61 mm (95% confidence interval, 0.58-1.07). The accuracy between the 2 methods was greater using the exported images (P < 0.01) and was not affected by the clinical and radiological features. The accuracy of StereoCheck among multiple examiners and in sequential tests showed a mean distance between the targets and coordinates of <1.00 mm. Thus, an excellent level of reliability for the StereoCheck coordinates (intraclass correlation coefficient ≥0.8) was verified in all contexts. CONCLUSION: StereoCheck showed satisfactory accuracy and reliability. The use of photographs to compute the coordinates could lead to a significant decrease in the accuracy of the app.