LETTER TO THE EDITOR - NEUROSURGICAL TECHNIQUES Endoscopic approaches to the craniovertebral junction Emanuele La Corte & Philipp R. Aldana & Marco Schiariti & Alberto Maccari & Paolo Ferroli Received: 19 November 2013 /Accepted: 28 November 2013 /Published online: 15 December 2013 # Springer-Verlag Wien 2013 Dear Editor, We read with great interest the article by Visocchi et al. [7] published online in October 2013 in Acta Neurochirurgica regarding an “Anterior video-assisted approach to the craniovertebral junction: transnasal or transoral? A ca- daver study”. The authors performed a valuable anatom- ical and radiological study of two different endoscopic approaches to the craniovertebral junction (CVJ) that were compared by means of X-ray. The two approaches were compared in this study by inserting thin probes into the two natural corridors and surgical exposition distances and angles, in both sagittal and axial planes, were evaluated by the aid of X-ray. They finally found that the endoscopic transoral approach (ETA) “provides a better CVJ exposure in sagittal and axial planes, providing a larger working channel and an easier ma- neuverability” than endonasal approach. When evaluat- ing the merits of the endonasal approach, it is important to consider an extended endonasal approach, which augments the surgical exposure and provides wider working angles that are comparable to the ETA, as already outlined by Baird et al. [2], rather than working through the simple nasal natural corridor. Furthermore, we would like to point out that our group examined the actual lower limit of the endoscopic endonasal approach (EEA) through cadaveric dissection and found it to be no lower than the middle third of C2. Also, we found that the nasopalatine line routinely overestimated the lower limit of the EEA (average 84 mm below the actual lower limit). We devised a novel line the naso-axial line (NAxL), which more accurately predicts the inferior limit of the EEA to the CVJ (Fig. 1) [1]. It is defined as the line in the midsagittal plane that starts from the midpoint of the distance from rhinion to the anterior nasal spine of maxillary bone and ends on C2 vertebra, tangential to the posterior nasal spine of palatine bone. It can be used easily in preoperative images and help the surgeon in the planning and choice of the right surgical approach. In order to evaluate the rostro-caudal extent of the lesion at the CVJ, we would like to suggest the use of the hard palate as a reference to, rather than the base of C2 as described by El Sayed et al. [3, 4]. The palate serves as the floor or roof to the endonasal or transoral corridors to the CVJ, it can help in the E. La Corte Cerebrovascular and Skull Base Unit, Department of Neurosurgery, Neurological Institute “Carlo Besta”, San Paolo Medical School - University of Milan, Milan, Italy P. R. Aldana Division of Pediatric Neurosurgery, University of Florida College of Medicine Jacksonville/Wolfson Children’ s Hospital, Jacksonville, FL, USA M. Schiariti : P. Ferroli (*) Cerebrovascular and Skull Base Unit, Department of Neurosurgery, Neurological Institute “Carlo Besta”, Milan, Italy e-mail: pferroli@istituto-besta.it A. Maccari Department of Otorhinolaryngology, San Paolo Hospital, University of Milan, Milan, Italy Acta Neurochir (2014) 156:293–295 DOI 10.1007/s00701-013-1966-8