Letter to the Editor: Endoscopic endonasal posterior clinoidectomy

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TO THE EDITOR: We read with interest the article by Fernandez-Miranda et al.1 regarding a new technique for performing endoscopic endonasal posterior clinoidectomy (Fernandez-Miranda JC, Gardner PA, Rastelli MM Jr, et al: Endoscopic endonasal transcavernous posterior clinoidectomy with interdural pituitary transposition. Technical note. J Neurosurg 121:91–99, July 2014).

The authors described an innovative surgical technique performed through the cavernous sinus, with an interdural dissection taking advantage of the natural corridor provided by the separation of the inner and outer dural layers at the lateral margin of the sellae. This corridor provides access to the posterior clinoid process, making the endoscopic endonasal posterior clinoidectomy a safe and effective procedure. The approach was performed in 12 patients (6 with chordomas, 5 with petroclival meningiomas, and 1 with an epidermoid tumor), with great clinical results and no permanent hypopituitarism, diabetes insipidus, or neurovascular injuries. The impeccable quality of the anatomical dissections together with the detailed description of the surgical approach helps the reader to understand the complex anatomy of this region seen from the endoscopic endonasal view. The authors are to be congratulated on the excellent quality of the study and the clinical results.

In contrast to the Pittsburgh group's experience, we have described a purely extradural posterior clinoidectomy.2 We have performed this approach safely in dozens of patients and have formed the opinion that in the majority of cases a purely extradural approach is sufficient to achieve an adequate posterior clinoidectomy. In those cases in which the extradural approach is not sufficient we have used the interdural approach, as described expertly in this article. Hence, we use the interdural approach more selectively, as needed, and it is possible to convert easily from the extradural to the interdural approach. Overall, it is our opinion that an extradural approach is safer because the dura mater can serve as a natural protector against neurovascular injury. There is also the option of working both above and below the pituitary gland to reach the interpeduncular fossa and retroinfundibular area, thereby avoiding damage to the pituitary gland and its blood supply.3 Making an analogy to the transcranial anterior clinoidectomy, which can be performed intra- or extradurally, there are probably indications for both inter- and extradural posterior clinoidectomy. Ultimately, the idea is to avoid a complete pituitary transposition, which often causes hypopituitarism.

Modern skull base neurosurgery is based on tailoring the approach for each patient. Thus, the new technique described by the authors is an important addition to skull base surgery, but in our opinion should be reserved for those posterior clinoids that cannot be removed extradurally, rather than being the default operation in all cases.

DISCLOSURE

Dr. Schwartz is a consultant for Karl Storz, and he owns stock in Vision Sense. He also receives support from the NIH for research not related to this study.

References

  • 1

    Fernandez-Miranda JCGardner PARastelli MM JrPeris-Celda MKoutourousiou MPeace D: Endoscopic endonasal transcavernous posterior clinoidectomy with interdural pituitary transposition. Technical note. J Neurosurg 121:91992014

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  • 2

    Silva DAttia MKandasamy JAlimi MAnand VKSchwartz TH: Endoscopic endonasal posterior clinoidectomy. Surg Neurol Int 3:642012

  • 3

    Silva DAttia MKandasamy JAlimi MAnand VKSchwartz TH: Endoscopic endonasal transsphenoidal “above and below” approach to the retroinfundibular area and interpeduncular cistern—cadaveric study and case illustrations. World Neurosurg 81:3743842014

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Response

Thank you for the opportunity to reply to the Letter to the Editor you received with regard to our article. We would also like to thank Drs. Silva, Attia, and Schwartz from Cornell University for their kind comments. However, we disagree with certain aspects of their letter.

First, and perhaps most important, it is key not to lose historical perspective when describing “new” or “modified” techniques. The surgical technique and application for an endoscopic endonasal, purely extradural posterior clinoidectomy was originally described in a seminal publication by the Pittsburgh group led by Amin Kassam in 2005.1 This publication literally states: “Subsellar extradural removal of the posterior clinoid and dorsum sellae … the posterior clinoid and dorsum sellae can also be removed via a completely extrasellar approach.… The pituitary, with dura mater intact, is elevated superiorly.… The dura over the sella is not opened.… With the pituitary gland elevated, the dorsum sellae and posterior clinoid can be drilled using a 1-mm diamond bit or a rongeur….” In 2012, the Cornell group provided a more complete description of the surgical anatomy for the extradural posterior clinoidectomy technique by performing dissections in 5 anatomical specimens.3

Continued clinical experience by the Pittsburgh group resulted in further refinement of the technique to provide a balance of optimal exposure with preservation of pituitary function, as documented in subsequent publications: the intradural pituitary transposition and posterior clinoidectomy by Kassam et al. in 2008,2 and then the interdural transcavernous posterior clinoidectomy described in the article under discussion. We have found that the purely extradural posterior clinoidectomy, although still very useful in selected cases, does not provide direct visualization and access to the top and posterolateral tip of the posterior clinoid and its ligamentous attachments. It is a blind maneuver that in case of prominent clinoids or calcified dural attachments is neither safe nor effective. In our experience in cases in which we had performed an extradural posterior clinoidectomy and thought we had removed the clinoid completely, there was often still a portion of the clinoid remaining.

In regard to the statement “an extradural approach is safer because the dura mater can serve as a natural protector against neurovascular injury,” we would like to point out that the posterior clinoid is an interdural (intracavernous) structure and as such, the outer dural layer of the cavernous sinus is always going to be opened, as evidenced by the typical venous bleeding that occurs after posterior clinoidectomy. The difference between the extradural and the interdural approach resides precisely on whether the outer dural layer is disrupted in a noncontrolled fashion while removing the posterior clinoid extradurally, or whether the outer dural layer is widely open in a controlled fashion, providing direct visualization of the internal carotid artery (ICA) and the inferior hypophyseal artery (IHA) when performing an interdural transcavernous approach. The outer layer of dura, rather than providing protection to the ICA and IHA, prevents their visualization when removing the clinoid. It is in fact the removal of the posterior clinoid from within the cavernous sinus that risks vascular injury, and we believe this is better prevented with direct visualization. We would also like to emphasize the importance of avoiding avulsion of the IHA from the ICA wall when removing the posterior clinoid, which we believe is better prevented with the interdural rather than the extradural approach.

Certainly there is always variability of the surgical anatomy depending on the patient and the pathology. Whereas it is clear that in some cases, such as clival chordomas without significant involvement of dorsum sella and posterior clinoids, a partial posterior clinoidectomy is sufficient, in many others, such as extensive chordomas or petroclival meningiomas, a complete posterior clinoidectomy is mandatory. The ease with which this can be performed and the technique used should be tailored to the individual patient and pathology. Like many newer techniques, this facet of endonasal surgery is likely to be better elucidated through further peer-reviewed clinical series. Our colleagues at Cornell have always been an important group in this process and we look forward to their future contributions.

References

  • 1

    Kassam ASnyderman CHMintz AGardner PCarrau RL: Expanded endonasal approach: the rostrocaudal axis. Part II. Posterior clinoids to the foramen magnum. Neurosurg Focus 19:1E42005

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  • 2

    Kassam ABPrevedello DMThomas AGardner PMintz ASnyderman C: Endoscopic endonasal pituitary transposition for a transdorsum sellae approach to the interpeduncular cistern. Neurosurgery (3 Suppl 1) 62:S57S742008

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  • 3

    Silva DAttia MKandasamy JAlimi MAnand VKSchwartz TH: Endoscopic endonasal posterior clinoidectomy. Surg Neurol Int 3:642012

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Article Information

INCLUDE WHEN CITING Published online December 19, 2014; DOI: 10.3171/2014.8.JNS141783.

© AANS, except where prohibited by US copyright law.

Headings

References

  • 1

    Fernandez-Miranda JCGardner PARastelli MM JrPeris-Celda MKoutourousiou MPeace D: Endoscopic endonasal transcavernous posterior clinoidectomy with interdural pituitary transposition. Technical note. J Neurosurg 121:91992014

    • Search Google Scholar
    • Export Citation
  • 2

    Silva DAttia MKandasamy JAlimi MAnand VKSchwartz TH: Endoscopic endonasal posterior clinoidectomy. Surg Neurol Int 3:642012

  • 3

    Silva DAttia MKandasamy JAlimi MAnand VKSchwartz TH: Endoscopic endonasal transsphenoidal “above and below” approach to the retroinfundibular area and interpeduncular cistern—cadaveric study and case illustrations. World Neurosurg 81:3743842014

    • Search Google Scholar
    • Export Citation
  • 1

    Kassam ASnyderman CHMintz AGardner PCarrau RL: Expanded endonasal approach: the rostrocaudal axis. Part II. Posterior clinoids to the foramen magnum. Neurosurg Focus 19:1E42005

    • Search Google Scholar
    • Export Citation
  • 2

    Kassam ABPrevedello DMThomas AGardner PMintz ASnyderman C: Endoscopic endonasal pituitary transposition for a transdorsum sellae approach to the interpeduncular cistern. Neurosurgery (3 Suppl 1) 62:S57S742008

    • Search Google Scholar
    • Export Citation
  • 3

    Silva DAttia MKandasamy JAlimi MAnand VKSchwartz TH: Endoscopic endonasal posterior clinoidectomy. Surg Neurol Int 3:642012

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