Analysis of safe entry zones into the brainstem

  • Yang Yang
  • Bas van Niftrik
  • Xiangke Ma
  • Julia Velz
  • Sophie Wang
  • Luca Regli
  • Oliver BozinovEmail author
Original Article


Intra-axial brainstem surgeries are challenging. Many experience-based “safe entry zones (SEZs)” into brainstem lesions have been proposed in the existing literature. The evidence for each one seems limited. English-language publications were retrieved using PubMed/MEDLINE. Studies that focused only on cadaveric anatomy were also included, but the clinical case number was treated as zero. The clinical evidence level was defined as “case report” when the surgical case number was ≤ 5, “limited evidence” when there were more than 5 but less than 25 cases, and “credible evidence” when a publication presented more than 25 cases. Twenty-five out of 32 publications were included, and 21 different SEZs were found for the brainstem: six SEZs were located in the midbrain, 9 SEZs in the pons, and 6 SEZs in the medulla. Case report evidence was found for 10 SEZs, and limited evidence for 7 SEZs. Four SEZs were determined to be backed by credible evidence. The proposed SEZs came from initial cadaveric anatomy studies, followed by some published clinical experience. Only a few SEZs have elevated clinical evidence. The choice of the right approach into the brainstem remains a challenge in each case.


Brainstem lesions Surgical safe entry zone Evidence level 


Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

Not required.

Informed consent

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  1. 1.
    Abla AA, Benet A, Lawton MT (2014) The far lateral transpontomedullary sulcus approach to pontine cavernous malformations: technical report and surgical results. Neurosurgery 10(Suppl 3):472–480. CrossRefGoogle Scholar
  2. 2.
    Abla AA, Lekovic GP, Turner JD, de Oliveira JG, Porter R, Spetzler RF (2011) Advances in the treatment and outcome of brainstem cavernous malformation surgery: a single-center case series of 300 surgically treated patients. Neurosurgery 68:403–414; discussion 414-405. CrossRefGoogle Scholar
  3. 3.
    Akiyama O, Matsushima K, Nunez M, Matsuo S, Kondo A, Arai H, Rhoton AL Jr, Matsushima T (2017) Microsurgical anatomy and approaches around the lateral recess with special reference to entry into the pons. J Neurosurg 129:1–12. Google Scholar
  4. 4.
    Albright AL, Sclabassi RJ (1985) Cavitron ultrasonic surgical aspirator and visual evoked potential monitoring for chiasmal gliomas in children. Report of two cases. J Neurosurg 63:138–140. CrossRefGoogle Scholar
  5. 5.
    Baghai P, Vries JK, Bechtel PC (1982) Retromastoid approach for biopsy of brain stem tumors. Neurosurgery 10:574–579. CrossRefGoogle Scholar
  6. 6.
    Bailey P, Buchanan DN, PC B (1939) Intracranial tumors of infancy and childhood. University of Chicago PressGoogle Scholar
  7. 7.
    Bertalanffy H, Benes L, Miyazawa T, Alberti O, Siegel AM, Sure U (2002) Cerebral cavernomas in the adult. Review of the literature and analysis of 72 surgically treated patients. Neurosurg Rev 25:1–53. CrossRefGoogle Scholar
  8. 8.
    Bertalanffy H, Tissira N, Krayenbuhl N, Bozinov O, Sarnthein J (2011) Inter- and intrapatient variability of facial nerve response areas in the floor of the fourth ventricle. Neurosurgery 68:23–31; discussion 31. Google Scholar
  9. 9.
    Bodensteiner J, Bell WE, Hart MN (1977) 13-year survival of a child with an untreated brainstem glioma. J Pediatr 90:842–843. CrossRefGoogle Scholar
  10. 10.
    Bozkurt B, Kalani MYS, Yagmurlu K, Belykh E, Preul MC, Nakaji P, Spetzler RF (2017) Low retrosigmoid infratonsillar approach to lateral medullary lesions. World Neurosurg 111:311–316. CrossRefGoogle Scholar
  11. 11.
    Bricolo A (2000) Surgical management of intrinsic brain stem gliomas. Oper Tech Neurosurg 3:137–154. CrossRefGoogle Scholar
  12. 12.
    Bricolo A, Turazzi S (1995) Surgery for gliomas and other mass lesions of the brainstem. Adv Tech Stand Neurosurg 22:261–341. CrossRefGoogle Scholar
  13. 13.
    Bricolo A, Turazzi S, Cristofori L, Talacchi A (1991) Direct surgery for brainstem tumours. Acta Neurochir Suppl 53:148–158CrossRefGoogle Scholar
  14. 14.
    Brown AP, Thompson BG, RF S (1996) The two-point method: evaluating brain stem lesions. BNI 12:20–24Google Scholar
  15. 15.
    Cavalcanti DD, Preul MC, Kalani MY, Spetzler RF (2016) Microsurgical anatomy of safe entry zones to the brainstem. J Neurosurg 124:1359–1376. CrossRefGoogle Scholar
  16. 16.
    Cavalheiro S, Yagmurlu K, da Costa MD, Nicacio JM, Rodrigues TP, Chaddad-Neto F, Rhoton AL (2015) Surgical approaches for brainstem tumors in pediatric patients. Childs Nerv Syst 31:1815–1840. CrossRefGoogle Scholar
  17. 17.
    Deshmukh VR, Rangel-Castilla L, Spetzler RF (2014) Lateral inferior cerebellar peduncle approach to dorsolateral medullary cavernous malformation. J Neurosurg 121:723–729. CrossRefGoogle Scholar
  18. 18.
    Elhammady MS, Teo C (2013) Surgical management of adult intrinsic brainstem tumors. Neurosurgery 60(Suppl 1):131–138. CrossRefGoogle Scholar
  19. 19.
    Ferroli P, Sinisi M, Franzini A, Giombini S, Solero CL, Broggi G (2005) Brainstem cavernomas: long-term results of microsurgical resection in 52 patients. Neurosurgery 56:1203–1214. CrossRefGoogle Scholar
  20. 20.
    Giliberto G, Lanzino DJ, Diehn FE, Factor D, Flemming KD, Lanzino G (2010) Brainstem cavernous malformations: anatomical, clinical, and surgical considerations. Neurosurg Focus 29:E9. CrossRefGoogle Scholar
  21. 21.
    Hauck EF, Barnett SL, White JA, Samson D (2010) The presigmoid approach to anterolateral pontine cavernomas. Clinical article. J Neurosurg 113:701–708. CrossRefGoogle Scholar
  22. 22.
    Hebb MO, Spetzler RF (2010) Lateral transpeduncular approach to intrinsic lesions of the rostral pons. Neurosurgery 66:26–29; discussion 29. Google Scholar
  23. 23.
    Ishihara H, Bjeljac M, Straumann D, Kaku Y, Roth P, Yonekawa Y (2006) The role of intraoperative monitoring of oculomotor and trochlear nuclei—safe entry zone to tegmental lesions. Minim Invasive Neurosurg: MIN 49:168–172. CrossRefGoogle Scholar
  24. 24.
    Kalani MY, Yagmurlu K, Martirosyan NL, Cavalcanti DD, Spetzler RF (2016) Approach selection for intrinsic brainstem pathologies. J Neurosurg 125:1596–1607. CrossRefGoogle Scholar
  25. 25.
    Kalani MY, Yagmurlu K, Martirosyan NL, Spetzler RF (2016) The retrosigmoid petrosal fissure transpeduncular approach to central pontine lesions. World Neurosurg 87:235–241. CrossRefGoogle Scholar
  26. 26.
    Kalani MYS, Yagmurlu K, Spetzler RF (2018) The interpeduncular fossa approach for resection of ventromedial midbrain lesions. J Neurosurg 128:834–839. CrossRefGoogle Scholar
  27. 27.
    Kumar R, Vinita S (2004) Tuberculous brain stem abscesses in children. J Pediatr Neurol 2:101–106Google Scholar
  28. 28.
    Kyoshima K, Kobayashi S, Gibo H, Kuroyanagi T (1993) A study of safe entry zones via the floor of the fourth ventricle for brain-stem lesions. Report of three cases. J Neurosurg 78:987–993. CrossRefGoogle Scholar
  29. 29.
    Lassiter KR, Alexander E Jr, Davis CH Jr, Kelly DL Jr (1971) Surgical treatment of brain stem gliomas. J Neurosurg 34:719–725. CrossRefGoogle Scholar
  30. 30.
    Menon G, Gopalakrishnan CV, Rao BR, Nair S, Sudhir J, Sharma M (2011) A single institution series of cavernomas of the brainstem. J Clin Neuromuscul Dis 18:1210–1214. Google Scholar
  31. 31.
    Moher D (2009) Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. Ann Intern Med 151:264. CrossRefGoogle Scholar
  32. 32.
    Parraga RG, Possatti LL, Alves RV, Ribas GC, Ture U, de Oliveira E (2016) Microsurgical anatomy and internal architecture of the brainstem in 3D images: surgical considerations. J Neurosurg 124:1377–1395. CrossRefGoogle Scholar
  33. 33.
    Porter RW, Detwiler PW, Spetzler RF, Lawton MT, Baskin JJ, Derksen PT, Zabramski JM (1999) Cavernous malformations of the brainstem: experience with 100 patients. J Neurosurg 90:50–58. CrossRefGoogle Scholar
  34. 34.
    Recalde RJ, Figueiredo EG, de Oliveira E (2008) Microsurgical anatomy of the safe entry zones on the anterolateral brainstem related to surgical approaches to cavernous malformations. Neurosurgery 62:9–15; discussion 15-17. Google Scholar
  35. 35.
    Schain RJ, Wilson G (1971) Brainstem encephalitis with radiographic evidence of medullary enlargement. Neurology 21:537–537. CrossRefGoogle Scholar
  36. 36.
    Spetzler RF, Kalani MY, Nakaji P, Yagmurlu K (2017) Color atlas of brainstem. Surgery:85–102Google Scholar
  37. 37.
    Strauss C, Romstock J, Fahlbusch R (1999) Pericollicular approaches to the rhomboid fossa. Part II. Neurophysiological basis. J Neurosurg 91:768–775. CrossRefGoogle Scholar
  38. 38.
    Yagmurlu K, Kalani MYS, Preul MC, Spetzler RF (2017) The superior fovea triangle approach: a novel safe entry zone to the brainstem. J Neurosurg 127:1134–1138. CrossRefGoogle Scholar
  39. 39.
    Yagmurlu K, Rhoton AL Jr, Tanriover N, Bennett JA (2014) Three-dimensional microsurgical anatomy and the safe entry zones of the brainstem. Neurosurgery 10(Suppl 4):602–619; discussion 619-620. CrossRefGoogle Scholar
  40. 40.
    Zaidi HA, Mooney MA, Levitt MR, Dru AB (2017) Impact of timing of intervention among 397 consecutively treated brainstem cavernous malformations. Neurosurgery 81:620–626. Google Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Yang Yang
    • 1
  • Bas van Niftrik
    • 1
  • Xiangke Ma
    • 1
  • Julia Velz
    • 1
  • Sophie Wang
    • 1
  • Luca Regli
    • 1
  • Oliver Bozinov
    • 1
    Email author
  1. 1.Department of NeurosurgeryUniversity Hospital of ZurichZurichSwitzerland

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