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Although glioblastoma is the commonest primary brain tumour in adults, its location in the cerebellum is extremely rare. We present thirteen cases (3 female, 10 male; median age at presentation 56 [age range 21-77]) of surgically managed, histologically confirmed, primary cerebellar glioblastoma (cGB) over a 17 year period (2005-2022). Pre-operative radiological diagnosis was challenging given cGB rarity, although MRI demonstrated ring enhancement in all cases. Surgical management included posterior fossa craniectomy and debulking in 11 cases and burr hole biopsy in two. CSF diversion was necessary in four cases. No evidence of IDH or ATRX gene mutations was found when tested. Survival ranged from 1 to 22 months after diagnosis (mean 10.9 months). We also seek to understand why glioblastoma is rare in this location and discuss potential reasons for this. We hypothesise that increasing anatomical distance from germinal regions and decreased local endogenous neural stem cell activity (which has been associated with glioblastoma) may explain why glioblastoma is rare in the cerebellum. We hereby seek to add to the limited literature on cGB as this is the largest UK cGB series to date.

Objective  An operative workflow systematically compartmentalizes operations into hierarchal components of phases, steps, instrument, technique errors, and event errors. Operative workflow provides a foundation for education, training, and understanding of surgical variation. In this Part 2, we present a codified operative workflow for the translabyrinthine approach to vestibular schwannoma resection. Methods  A mixed-method consensus process of literature review, small-group Delphi's consensus, followed by a national Delphi's consensus was performed in collaboration with British Skull Base Society (BSBS). Each Delphi's round was repeated until data saturation and over 90% consensus was reached. Results  Seventeen consultant skull base surgeons (nine neurosurgeons and eight ENT [ear, nose, and throat]) with median of 13.9 years of experience (interquartile range: 18.1 years) of independent practice participated. There was a 100% response rate across both the Delphi rounds. The translabyrinthine approach had the following five phases and 57 unique steps: Phase 1, approach and exposure; Phase 2, mastoidectomy; Phase 3, internal auditory canal and dural opening; Phase 4, tumor debulking and excision; and Phase 5, closure. Conclusion  We present Part 2 of a national, multicenter, consensus-derived, codified operative workflow for the translabyrinthine approach to vestibular schwannomas. The five phases contain the operative, steps, instruments, technique errors, and event errors. The codified translabyrinthine approach presented in this manuscript can serve as foundational research for future work, such as the application of artificial intelligence to vestibular schwannoma resection and comparative surgical research., Competing Interests: Conflict of Interest J.C. receives research grants and consultancy fees from Medtronic (Dublin, Ireland). J.C. is the associate medical director of CMR surgical (Cambridge, United Kingdom). D.S. is a shareholder in Odin Vision Ltd (London, United Kingdom) and is an employee of Digital Surgery (London, United Kingdom). H.L.H., H.J.M., C.H.K., and W.M. are supported by the Wellcome/EPSRC Centre for Interventional and Surgical Sciences, University College London. D.Z.K. is supported by an National Institute for Health and Care Research (NIHR) Academic Clinical Fellowship. H.J.M. is also funded by the NIHR Biomedical Research Centre at University College London. All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or nonfinancial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. ( https://creativecommons.org/licenses/by/4.0/ ).)

Objective  An operative workflow systematically compartmentalizes operations into hierarchal components of phases, steps, instrument, technique errors, and event errors. Operative workflow provides a foundation for education, training, and understanding of surgical variation. In this Part 1, we present a codified operative workflow for the retrosigmoid approach to vestibular schwannoma resection. Methods  A mixed-method consensus process of literature review, small-group Delphi's consensus, followed by a national Delphi's consensus, was performed in collaboration with British Skull Base Society (BSBS). Each Delphi's round was repeated until data saturation and over 90% consensus was reached. Results  Eighteen consultant skull base surgeons (10 neurosurgeons and 8 ENT [ear, nose, and throat]) with median 17.9 years of experience (interquartile range: 17.5 years) of independent practice participated. There was a 100% response rate across both Delphi's rounds. The operative workflow for the retrosigmoid approach contained three phases and 40 unique steps as follows: phase 1, approach and exposure; phase 2, tumor debulking and excision; phase 3, closure. For the retrosigmoid approach, technique, and event error for each operative step was also described. Conclusion  We present Part 1 of a national, multicenter, consensus-derived, codified operative workflow for the retrosigmoid approach to vestibular schwannomas that encompasses phases, steps, instruments, technique errors, and event errors. The codified retrosigmoid approach presented in this manuscript can serve as foundational research for future work, such as operative workflow analysis or neurosurgical simulation and education., Competing Interests: Conflict of Interest J.C. receives research grants and consultancy fees from Medtronic (Dublin, Ireland). J.C. is the associate medical director of CMR surgical (Cambridge, United Kingdom). D.S. is a shareholder in Odin Vision Ltd. (London, United Kingdom) and is an employee of Digital Surgery (London, United Kingdom). H.L.H., H.J.M., C.H.K., and W.M. are supported by the Wellcome/EPSRC Centre for Interventional and Surgical Sciences, University College London. D.Z.K. is supported by an National Institute for Health and Care Research (NIHR) Academic Clinical Fellowship. H.J.M. is also funded by the NIHR Biomedical Research Centre at University College London. All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or nonfinancial interest (such as personal or professional relationships, affiliations, knowledge, or beliefs) in the subject matter or materials discussed in this manuscript., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. ( https://creativecommons.org/licenses/by/4.0/ ).)

We present the case of a 65 year old gentleman who underwent craniotomy and debulking of a left temporal glioblastoma multiforme (GBM). Post-operatively he received chemotherapy and radiotherapy with good response demonstrated on interval MRI scans. At 17 months post-diagnosis and in the absence of clinical or radiological recurrence, he presented with respiratory distress. He was found to have an exudative right-sided pleural effusion, nodular pleural thickening, a hilar mass and associated lymphadenopathy. Percutaneous pleural biopsy revealed metastatic GBM. Systemic GBM metastasis despite good response to oncological treatments and in the absence of intracranial recurrence is exceedingly rare. We review the literature concerning extra-neuraxial GBM metastasis and speculate why this phenomenon is extremely rare.

We present the case of a 66 year old gentleman with trigeminal schwannoma whose only presenting feature was a single gelastic seizure. This is the first case report of pathological laughter in trigeminal schwannoma in the absence of other trigeminal, brainstem, cerebellar or other cranial nerve dysfunction.