The telovelar approach reshaped: a new perspective from inside the fourth ventricle

Purpose: In recent decades, trans-cerebellomedullary fissure (trans-CMF) approaches have gained prominence in fourth ventricle surgery and are largely based on cadaveric anatomical studies of normally sized ventricles. In clinical practice, however, the fourth ventricle is often dilated and distorted by tumor growth. Recent endoscopic in vivo anatomical studies depicting the internal surfaces of both normal and enlarged fourth ventricles have prompted a reassessment of traditional schematic representations of trans-CMF approaches. This refinement does not introduce new surgical strategies but aims to provide neurosurgeons with a realistic in vivo perspective of the ventricular roof prior to its incision across different ventricular sizes. Methods: Very selected panoramic endoscopic views of the inner roof of twelve cases of both hydrocephalic dilated and normal fourth ventricles were reviewed and analyzed. Results: The anatomical landmarks were identified, and the schematic cutlines of telovelar procedures were redesigned according to the classical diagrams by Matsushima. In this way, realistic models of roof dissections viewed from inside were obtained, indicating the safest and less safe tracks of the telovelar approach. Conclusion: This study has enabled the anatomical representation of the internal surface of the roof of very dilated fourth ventricles, creating a more realistic model that better aligns with the clinical realities of fourth ventricles dilated and deformed by tumors. By replicating the classic trans-CMF dissections on these internal roof images, the study provides a more comprehensive and reliable anatomical understanding of the approach.