Background/Aims: The field of minimally invasive neurosurgery has grown dramatically especially in the last decades. This has been possible, in the most part, due to the advancements in technology especially in tools such as the endoscope. The contemporary classification scheme for endoscopic procedures needs to advance as well. Methods: The present classification scheme for neuroendoscopic procedures has become confusing because it mainly describes the use of the endoscope as an assisting device to the microscope. The authors propose an update to the current classification that reflects the independence of the endoscope as a tool in minimally invasive neurosurgery. Results: The proposed classification groups the procedures as ‘intraendoscopic’ neurosurgery or ‘extraendoscopic’ neurosurgery (XEN) in relation to the ‘axis’ of the endoscope. A review of the literature for the XEN group together with exemplary cases is presented. Conclusion: We presented our proposed classification for the endoscope-only surgical procedures. The XEN group is expanded in this article.

Di X, Sui A, Hakim R, Wang M, Warnke JP: Endoscopic minimally invasive neurosurgery: emerging techniques and expanding role through an extensive review of the literature and our own experience – part I: intraendoscopic neurosurgery. Pediatr Neurosurg DOI: 10.1159/000336017.
de Divitiis O, Cavallo LM, Dal Fabbro M, Elefante A, Cappabianca P: Freehand dynamic endoscopic resection of an epidermoid tumor of the cerebellopontine angle: technical case report. Neurosurgery 2007;61(suppl 2):E239–E240; discussion E240.
Kassam A, Snyderman CH, Mintz A, Gardner P, Carrau RL: Expanded endonasal approach: the rostrocaudal axis. I. Crista galli to the sella turcica. Neurosurg Focus 2005;19:e3.
Cappabianca P, de Divitiis E: Back to the Egyptians: neurosurgery via the nose. A five-thousand year history and the recent contribution of the endoscope. Neurosurg Rev 2007;30:1–7; discussion 7.
Guiot J, et al: Intracranial endoscopic explorations (in French). Presse Méd 1963;71:1225–1228.
Gamea A, Fathi M, el-Guindy A: The use of the rigid endoscope in transsphenoidal pituitary surgery. J Laryngol Otol 1994;108:19–22.
Helal MZ: Combined micro-endoscopic trans-sphenoid excisions of pituitary macroadenomas. Eur Arch Otorhinolaryngol 1995;252:186–189.
Jankowski R, et al: Endoscopic pituitary tumor surgery. Laryngoscope 1992;102:198–202.
Carrau RL, Jho HD, Ko Y: Transnasal-transsphenoidal endoscopic surgery of the pituitary gland. Laryngoscope 1996;106:914–918.
Jho HD: Endoscopic microscopic transpedicular thoracic discectomy. Technical note. J Neurosurg 1997;87:125–129.
Jho HD: Endoscopic transsphenoidal surgery. J Neurooncol 2001;54:187–195.
Jho HD, Alfieri A: Endoscopic endonasal pituitary surgery: evolution of surgical technique and equipment in 150 operations. Minim Invasive Neurosurg 2001; 44:1–12.
Jho HD, Carrau RL: Endoscopic endonasal transsphenoidal surgery: experience with 50 patients. J Neurosurg 1997;87:44–51.
Jho HD, et al: Endoscopic pituitary surgery: an early experience. Surg Neurol 1997;47:213–222; discussion 222–223.
Jho HD, et al: Endoscopic transsphenoidal resection of a large chordoma in the posterior fossa. Case report. Neurosurg Focus 1996;1:e3; discussion 1p following e3.
Cappabianca P, et al: Surgical complications associated with the endoscopic endonasal transsphenoidal approach for pituitary adenomas. J Neurosurg 2002;97:293–298.
Cappabianca P, et al: Endoscopic endonasal transsphenoidal approach: outcome analysis of 100 consecutive procedures. Minim Invasive Neurosurg 2002;45:193–200.
Duz B, et al: Transsphenoidal approaches to the pituitary: a progression in experience in a single centre. Acta Neurochir (Wien) 2008;150:1133–1138; discussion 1138–1139.
Kabil MS, Eby JB, Shahinian HK: Fully endoscopic endonasal vs transseptal transsphenoidal pituitary surgery. Minim Invasive Neurosurg 2005;48:348–354.
Dehdashti AR, et al: Pure endoscopic endonasal approach for pituitary adenomas: early surgical results in 200 patients and comparison with previous microsurgical series. Neurosurgery 2008;62:1006–1015; discussion 1015–1017.
O’Malley BW Jr, et al: Comparison of endoscopic and microscopic removal of pituitary adenomas: single-surgeon experience and the learning curve. Neurosurg Focus 2008;25:e10.
Jain AK, et al: Excision of pituitary adenomas: randomized comparison of surgical modalities. Br J Neurosurg 2007;21:328–331.
Jho HD, Ha HG: Endoscopic endonasal skull base surgery. 3. The clivus and posterior fossa. Minim Invasive Neurosurg 2004;47:16–23.
Jho HD, Ha HG: Endoscopic endonasal skull base surgery. 2. The cavernous sinus. Minim Invasive Neurosurg 2004;47:9–15.
Jho HD, Ha HG: Endoscopic endonasal skull base surgery. 1. The midline anterior fossa skull base. Minim Invasive Neurosurg 2004;47:1–8.
Aydin S, et al: The endoscopic endonasal trans-sphenoidal approach to the sellar and suprasellar area. Anatomic study. J Neurosurg Sci 2007;51:129–138.
Cavallo LM, et al: Extended endoscopic endonasal transsphenoidal approach to the suprasellar area: anatomic considerations. Part 1. Neurosurgery 2007;61(3 suppl):24–33; discussion 33–34.
Kassam A, et al: Evolution of reconstructive techniques following endoscopic expanded endonasal approaches. Neurosurg Focus 2005;19:e8.
Kassam A, et al: Expanded endonasal approach: the rostrocaudal axis. II. Posterior clinoids to the foramen magnum. Neurosurg Focus 2005;19:e4.
Kassam AB, et al: Expanded endonasal approach: fully endoscopic, completely transnasal approach to the middle third of the clivus, petrous bone, middle cranial fossa, and infratemporal fossa. Neurosurg Focus 2005;19:e6.
de Divitiis E, et al: Extended endoscopic endonasal transsphenoidal approach for the removal of suprasellar tumors. Part 2. Neurosurgery 2007;60:4658; discussion 58–59.
de Divitiis E, et al: Extended endoscopic transsphenoidal approach for tuberculum sellae meningiomas. Neurosurgery 2007;61(suppl 2):229–237; discussion 237–238.
Gardner PA, et al: Outcomes following endoscopic, expanded endonasal resection of suprasellar craniopharyngiomas: a case series. J Neurosurg 2008;109:6–16.
Kanaan HA, et al: Expanded endoscopic endonasal resection of an olfactory schwannoma. J Neurosurg Pediatrics 2008;2:261–265.
Chakrabarti I, et al: Long-term neurological, visual, and endocrine outcomes following transnasal resection of craniopharyngioma. J Neurosurg 2005;102:650–657.
McMurry FG, et al: Long-term results in the management of craniopharyngiomas. Neurosurgery 1977;1:238–241.
Van Effenterre R, Boch AL: Craniopharyngioma in adults and children: a study of 122 surgical cases. J Neurosurg 2002;97:3–11.
Hopf NJ, Perneczky A: Endoscopic neurosurgery and endoscope-assisted microneurosurgery for the treatment of intracranial cysts. Neurosurgery 1998;43:1330–1336; discussion 1336–1337.
Kassam AB, et al: Completely endoscopic resection of intraparenchymal brain tumors. J Neurosurg 2009;110:116–123.
Otsuki T, Jokura H, Yoshimoto T: Stereotactic guiding tube for open-system endoscopy: a new approach for the stereotactic endoscopic resection of intra-axial brain tumors. Neurosurgery 1990;27:326–330.
Di X: Multiple brain tumor nodule resections under direct visualization of a neuronavigated endoscope. Minim Invasive Neurosurg 2007;50:227–232.
Fratzoglou M, Leite dos Santos AR, Gawish I, Perneczky A: Endoscope-assisted microsurgery for tumors of the septum pellucidum: surgical considerations and benefits of the method in the treatment of four serial cases. Neurosurg Rev 2005;28:39–43.
Abdullah J, Caemaert J: Endoscopic management of craniopharyngiomas: a review of 3 cases. Minim Invasive Neurosurg 1995;38:79–84.
Harris AE, Hadjipanayis CG, Lunsford LD, Lunsford AK, Kassam AB: Microsurgical removal of intraventricular lesions using endoscopic visualization and stereotactic guidance. Neurosurgery 2005;56(1 suppl):125–132; discussion 125–132.
Cai R, Di X: Combined intra- and extra-endoscopic techniques for aggressive resection of subependymal giant cell astrocytomas. World Neurosurg 2010;73:713–718.
Cappabianca P, Cinalli G, Gangemi M, Brunori A, Cavallo LM, de Divitiis E, Decq P, Delitala A, Di Rocco F, Frazee J, Godano U, Grotenhuis A, Longatti P, Mascari C, Nishihara T, Oi S, Rekate H, Schroeder HW, Souweidane MM, Spennato P, Tamburrini G, Teo C, Warf B, Zymberg ST: Application of neuroendoscopy to intraventricular lesions. Neurosurgery 2008;62(suppl 2):575–597; discussion 597–598
Wang H, Zhang D, Wang B: Endoscopic surgery of the cerebellopontine angle (in Chinese). Zhonghua Er Bi Yan Hou Ke Za Zhi 1996;31:153–155.
Jarrahy R, et al: Fully endoscopic vascular decompression of the trigeminal nerve. Minim Invasive Neurosurg 2002;45:32–35.
Jarrahy R, et al: Fully endoscopic vascular decompression of the glossopharyngeal nerve. J Craniofac Surg 2002;13:90–95.
Shahinian HK, Eby JB, Ocon M: Fully endoscopic excision of vestibular schwannomas. Minim Invasive Neurosurg 2004;47:329–332.
Kabil MS, Eby JB, Shahinian HK: Endoscopic vascular decompression versus microvascular decompression of the trigeminal nerve. Minim Invasive Neurosurg 2005;48:207–212.
Barker FG 2nd, et al: The long-term outcome of microvascular decompression for trigeminal neuralgia. N Engl J Med 1996;334:1077–1083.
de Divitiis O, et al: Freehand dynamic endoscopic resection of an epidermoid tumor of the cerebellopontine angle: technical case report. Neurosurgery 2007;61(suppl 2):E239–E240; discussion E240.
Di X: Endoscopic Suboccipital decompression on pediatric Chiari type I. Minim Invas Neurosurg 2009;52:1–7.
Xiao D, Luciano M: A novel endoscopic technique to suboccipital decompression and atlas laminectomy for Chiari malformation type I: technical note. World Spine J 2007;2:27–31.
Kassam AB, et al: The expanded endonasal approach: a fully endoscopic transnasal approach and resection of the odontoid process: technical case report. Neurosurgery 2005;57(1 suppl):E213; discussion E213.
Laufer I, et al: Endonasal endoscopic resection of the odontoid process in a nonachondroplastic dwarf with juvenile rheumatoid arthritis: feasibility of the approach and utility of the intraoperative Iso-C three-dimensional navigation. Case report. J Neurosurg Spine 2008;8:376–380.
Leng LZ, et al: Endonasal endoscopic resection of an os odontoideum to decompress the cervicomedullary junction: a minimal access surgical technique. pine 2009;34:E139–E143.
Nayak JV, et al: Experience with the expanded endonasal approach for resection of the odontoid process in rheumatoid disease. Am J Rhinol 2007;21:601–606.
Frempong-Boadu AK, Faunce WA, Fessler RG: Endoscopically assisted transoral-transpharyngeal approach to the craniovertebral junction. Neurosurgery 2002;51(5 suppl):S60–S66.
McGirt MJ, et al: Endoscopic transcervical odontoidectomy for pediatric basilar invagination and cranial settling. Report of 4 cases. J Neurosurg Pediatrics 2008;1:337–342.
Wolinsky JP, et al: Endoscopic image-guided odontoidectomy for decompression of basilar invagination via a standard anterior cervical approach. Technical note. J Neurosurg Spine 2007;6:184–191.
Hadley MN, Spetzler RF, Sonntag VK: The transoral approach to the superior cervical spine. A review of 53 cases of extradural cervicomedullary compression. J Neurosurg 1989;71:16–23.
Alfieri A, Jho HD, Tschabitscher M: Endoscopic endonasal approach to the ventral cranio-cervical junction: anatomical study. Acta Neurochir (Wien) 2002;144:219–225; discussion 225.
Cavallo LM, et al: The extended endoscopic endonasal approach to the clivus and cranio-vertebral junction: anatomical study. Childs Nerv Syst 2007;23:665–671.
Messina A, et al: Pure endoscopic endonasal odontoidectomy: anatomical study. Neurosurg Rev 2007;30:189–194; discussion 194.
Obenchain TG: Laparoscopic lumbar discectomy: case report. J Laparoendosc Surg 1991;1:145–149.
Foley KT, Smith MM, Rampersaud YR: Microendoscopic approach to far-lateral lumbar disc herniation. Neurosurg Focus 1999;7:e5.
Baron EM, et al: Neuroendoscopy for spinal disorders: a brief review. Neurosurg Focus 2005;19:E5.
Henderson CM, et al: Posterior-lateral foraminotomy as an exclusive operative technique for cervical radiculopathy: a review of 846 consecutively operated cases. Neurosurgery 1983;13:504–512.
Zeidman SM, Ducker TB: Posterior cervical laminoforaminotomy for radiculopathy: review of 172 cases. Neurosurgery 1993;33:356–362.
Krupp W, Schattke H, Muke R: Clinical results of the foraminotomy as described by Frykholm for the treatment of lateral cervical disc herniation. Acta Neurochir (Wien) 1990;107:22–29.
Frykholm R: The mechanism of cervical radicular lesions resulting from friction or forceful traction. Acta Chir Scand 1951;102:93–98.
Aldrich F: Posterolateral microdisectomy for cervical monoradiculopathy caused by posterolateral soft cervical disc sequestration. J Neurosurg 1990;72:370–377.
Fessler RG, Khoo LT: Minimally invasive cervical microendoscopic foraminotomy: an initial clinical experience. Neurosurgery 2002;51(5 suppl):S37–S45.
Adamson TE: Microendoscopic posterior cervical laminoforaminotomy for unilateral radiculopathy: results of a new technique in 100 cases. J Neurosurg 2001;95(1 suppl):51–57.
O’Toole JE, et al: Endoscopic posterior cervical foraminotomy and discectomy. Neurosurg Clin N Am 2006;17:411–422.
Ruetten S, et al: A new full-endoscopic technique for cervical posterior foraminotomy in the treatment of lateral disc herniations using 6.9-mm endoscopes: prospective 2-year results of 87 patients. Minim Invasive Neurosurg 2007;50:219–226.
Saringer WF, et al: Endoscopic anterior cervical foraminotomy for unilateral radiculopathy: anatomical morphometric analysis and preliminary clinical experience. J Neurosurg 2003;98(2 suppl):171–180.
Ruetten S, et al: Full-endoscopic anterior decompression versus conventional anterior decompression and fusion in cervical disc herniations. Int Orthop 2009;33:1677–1682.
Newton PO, et al: Anterior release and fusion in pediatric spinal deformity. A comparison of early outcome and cost of thoracoscopic and open thoracotomy approaches. Spine 1997;22:1398–1406.
Newton PO, Shea KG, Granlund KF: Defining the pediatric spinal thoracoscopy learning curve: sixty-five consecutive cases. Spine 2000;25:1028–1035.
Newton PO, et al: Prospective evaluation of 50 consecutive scoliosis patients surgically treated with thoracoscopic anterior instrumentation. Spine 2005;30(17 suppl):S100–S109.
Newton PO: The use of video-assisted thoracoscopic surgery in the treatment of adolescent idiopathic scoliosis. Instr Course Lect 2005;54:551–558.
Amini A, Beisse R, Schmidt MH: Thoracoscopic spine surgery for decompression and stabilization of the anterolateral thoracolumbar spine. Neurosurg Focus 2005;19:E4.
Dickman CA, Apfelbaum RI: Thoracoscopic microsurgical excision of a thoracic schwannoma. Case report. J Neurosurg 1998;88:898–902.
Rosenthal D, et al: Anterior decompression and stabilization using a microsurgical endoscopic technique for metastatic tumors of the thoracic spine. J Neurosurg 1996;84:565–572.
Kan P, Schmidt MH: Minimally invasive thoracoscopic approach for anterior decompression and stabilization of metastatic spine disease. Neurosurg Focus 2008;25:E8.
Kan P, Schmidt MH: Minimally invasive thoracoscopic resection of paraspinal neurogenic tumors: technical case report. Neurosurgery 2008;63(suppl 1):ONSE54; discussion ONSE54.
Dickman CA, et al: Thoracic vertebrectomy and reconstruction using a microsurgical thoracoscopic approach. Neurosurgery 1996;38:279–293.
Han PP, Kenny K, Dickman CA: Thoracoscopic approaches to the thoracic spine: experience with 241 surgical procedures. Neurosurgery 2002;51(5 suppl):S88–S95.
Rosenthal D, Dickman CA: Thoracoscopic microsurgical excision of herniated thoracic discs. J Neurosurg 1998;89:224–235.
Dickman CA, Mican CA: Multilevel anterior thoracic discectomies and anterior interbody fusion using a microsurgical thoracoscopic approach. Case report. J Neurosurg 1996;84:104–109.
Gardner PA, Ochalski PG, Moossy JJ: Minimally invasive endoscopicassisted posterior thoracic sympathectomy. Neurosurg Focus 2008;25:E6.
Johnson JP, Patel NP: Uniportal and biportal endoscopic thoracic sympathectomy. Neurosurgery 2002;51(5 suppl):S79–S83.
Khoo LT, Beisse R, Potulski M: Thoracoscopic-assisted treatment of thoracic and lumbar fractures: a series of 371 consecutive cases. Neurosurgery 2002;51(5 suppl):S104–S117.
Perez-Cruet MJ, et al: Thoracic microendoscopic discectomy. J Neurosurg Spine 2004;1:58–63.
Huang TJ, et al: Complications in thoracoscopic spinal surgery: a study of 90 consecutive patients. Surg Endosc 1999;13:346–350.
Nakagawa H, et al: Microendoscopic discectomy (MED) for lumbar disc prolapse. J Clin Neurosci 2003;10:231–235.
Muramatsu K, Hachiya Y, Morita C: Postoperative magnetic resonance imaging of lumbar disc herniation: comparison of microendoscopic discectomy and Love’s method. Spine 2001;26:1599–1605.
Isaacs RE, Podichetty V, Fessler RG: Microendoscopic discectomy for recurrent disc herniations. Neurosurg Focus 2003;15:E11.
Husain M, et al: Conical working tube: a special device for endoscopic surgery of herniated lumbar discs. J Neurosurg Spine 2005;2:265–270.
Chiu JC: Evolving transforaminal endoscopic microdecompression for herniated lumbar discs and spinal stenosis. Surg Technol Int 2004;13:276–286.
Cervellini P, et al: Micro-endoscopic-discectomy (MED) for far lateral disc herniation in the lumbar spine. Technical note. Acta Neurochir Suppl 2005;92:99–101.
Hoogland T, et al: Endoscopic transforaminal discectomy for recurrent lumbar disc herniation: a prospective, cohort evaluation of 262 consecutive cases. Spine 2008;33:973–978.
Palmer S, Turner R, Palmer R: Bilateral decompression of lumbar spinal stenosis involving a unilateral approach with microscope and tubular retractor system. J Neurosurg 2002;97(2 suppl):213–217.
Khoo LT, Fessler RG: Microendoscopic decompressive laminotomy for the treatment of lumbar stenosis. Neurosurgery 2002;51(5 suppl):S146–S154.
Guiot BH, Khoo LT, Fessler RG: A minimally invasive technique for decompression of the lumbar spine. Spine 2002;27:432–438.
Zucherman JF, et al: Instrumented laparoscopic spinal fusion. Preliminary Results. Spine 1995;20:2029–2034; discussion 2034–2035.
Regan JJ, Yuan H, McAfee PC: Laparoscopic fusion of the lumbar spine: minimally invasive spine surgery. A prospective multicenter study evaluating open and laparoscopic lumbar fusion. Spine 1999;24:402–411.
McAfee PC, et al: Minimally invasive anterior retroperitoneal approach to the lumbar spine. Emphasis on the lateral BAK. Spine 1998;23:1476–1484.
Mathews HH, et al: Laparoscopic discectomy with anterior lumbar interbody fusion. A preliminary review. Spine 1995;20:1797–1802.
Liu JC, et al: Is laparoscopic anterior lumbar interbody fusion a useful minimally invasive procedure? Neurosurgery 2002;51(5 suppl):S155–S158.
Khoo LT, et al: Minimally invasive percutaneous posterior lumbar interbody fusion. Neurosurgery 2002;51(5 suppl):S166–S161.
Ruetten S, Komp M, Godolias G: A New full-endoscopic technique for the interlaminar operation of lumbar disc herniations using 6-mm endoscopes: prospective 2-year results of 331 patients. Minim Invasive Neurosurg 2006;49:80–87.
Ruetten S, et al: Full-endoscopic interlaminar and transforaminal lumbar discectomy versus conventional microsurgical technique: a prospective, randomized, controlled study. Spine 2008;33:931–939.
Ruetten S, et al: Use of newly developed instruments and endoscopes: fullendoscopic resection of lumbar disc herniations via the interlaminar and lateral transforaminal approach. J Neurosurg Spine 2007;6:521–530.
Yeung AT, Tsou PM: Posterolateral endoscopic excision for lumbar disc herniation: Surgical technique, outcome, and complications in 307 consecutive cases. Spine 2002;27:722–731.
Tsou PM, Yeung AT: Transforaminal endoscopic decompression for radiculopathy secondary to intracanal noncontained lumbar disc herniations: outcome and technique. Spine J 2002;2:41–48.
Mayer HM, Brock M: Percutaneous endoscopic discectomy: surgical technique and preliminary results compared to microsurgical discectomy. J Neurosurg 1993;78:216–225.
Mathews HH: Transforaminal endoscopic microdiscectomy. Neurosurg Clin N Am 1996;7:59–63.
Lew SM, Mehalic TF, Fagone KL: Transforaminal percutaneous endoscopic discectomy in the treatment of far-lateral and foraminal lumbar disc herniations. J Neurosurg 2001;94(2 suppl):216–220.
Kambin P, Zhou L: History and current status of percutaneous arthroscopic disc surgery. Spine 1996;21(24 suppl):57S–61S.
Kambin P, Sampson S: Posterolateral percutaneous suction-excision of herniated lumbar intervertebral discs. Report of interim results. Clin Orthop Relat Res 1986;207:37–43.
Kambin P, et al: Transforaminal arthroscopic decompression of lateral recess stenosis. J Neurosurg 1996;84:462–467.
Ruetten S, Komp M, Godolias G: An extreme lateral access for the surgery of lumbar disc herniations inside the spinal canal using the fullendoscopic uniportal transforaminal approach-technique and prospective results of 463 patients. Spine 2005;30:2570–2578.
Sanderson PL, Wood PL: Surgery for lumbar spinal stenosis in old people. J Bone Joint Surg Br 1993;75:393–397.
Postacchini F: Surgical management of lumbar spinal stenosis. Spine 1999;24:1043–1047.
Katz JN, et al: Predictors of surgical outcome in degenerative lumbar spinal stenosis. Spine 1999;24:2229–2233.
Herron LD, Mangelsdorf C: Lumbar spinal stenosis: results of surgical treatment. J Spinal Disord 1991;4:26–33.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.