Analysis of various tracts of mastoid air cells related to CSF leak after the anterior transpetrosal approach

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OBJECTIVE

The anterior transpetrosal approach (ATPA) was established in 1984 and has been particularly effective for petroclival tumors. Although some complications associated with this approach, such as venous hemorrhage in the temporal lobe and nervous disturbances, have been resolved over the years, the incidence rate of CSF leaks has not greatly improved. In this study, some varieties of air cell tracts that are strongly related to CSF leaks are demonstrated. In addition, other pre- and postoperative risk factors for CSF leakage after ATPA are discussed.

METHODS

Preoperative and postoperative target imaging of the temporal bone was performed in a total of 117 patients who underwent ATPA, and various surgery-related parameters were analyzed.

RESULTS

The existence of air cells at the petrous apex, as well as fluid collection in the mastoid antrum detected by a postoperative CT scan, were possible risk factors for CSF leakage. Tracts that directly connected to the antrum from the squamous part of the temporal bone and petrous apex, rather than through numerous air cells, were significantly related to CSF leak and were defined as “direct tract.” All patients with a refractory CSF leak possessed “unusual tracts” that connected to the attic, tympanic cavity, or eustachian tube, rather than through the mastoid antrum.

CONCLUSIONS

Preoperative assessment of petrous pneumatization types is necessary to prevent CSF leaks. Direct and unusual tracts are particularly strong risk factors for CSF leaks.

ABBREVIATIONS ATPA = anterior transpetrosal approach.

Article Information

Correspondence Ryota Tamura: Keio University School of Medicine, Tokyo, Japan. moltobello-r-610@hotmail.co.jp.

INCLUDE WHEN CITING Published online March 16, 2018; DOI: 10.3171/2017.9.JNS171622.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

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Figures

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    Preoperative and postoperative radiographic characteristics of CSF leaks after the ATPA. A: Preoperative axial CT scan showing the development of air cells in the petrous apex. B: Preoperative axial CT scan showing the development of air cells in the squamous part of the temporal bone. C: Preoperative coronal CT scan showing an extremely thin tegmen tympani. D: Postoperative axial CT scan showing fluid collection in the mastoid antrum that is strongly related to CSF leaks after the ATPA. Figure is available in color online only.

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    Tracts of pneumatization in the temporal bone. A: Typical type of tracts from the squamous part of the temporal bone and petrous apex connecting to the mastoid antrum through numerous air cells. B: The squamous and petrous direct tracts connecting to the mastoid antrum, rather than through numerous air cells. C: Unusual tracts from the squamous part of the temporal bone and petrous apex to the attic, tympanic cavity, or eustachian tube. 1) The posterosuperior cell tract connecting to the attic directly from the petrous apex, rather than through the mastoid antrum. 2) The hypotympanic tract connecting to the tympanic cavity through the carotid canal and cochlea from the apical area of the petrous apex. 3) The peritubal tract connecting around the eustachian tube from the apical area of the petrous apex. 4) The squamous tympanic tract connecting to the tympanic cavity from the squamous part of the temporal bone, rather than through the mastoid antrum.

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    Blind area through microscopic angle demonstrated by a 3D printer. A: A petrous bone model made by a 3D printer of a patient with a CSF leak shows the resected area of the petrous bone after operation. The red area contains opened air cells. The figure on the left shows anatomical orientation, and the one on the right shows the microscopic angle. B: Autologous tissue (fat tissue) is placed into opened air cells of the petrous apex. The opened air cells seem to be closed by microscopic angle. However, incomplete coverage becomes apparent when viewed from above.

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    Operative strategies for CSF leak after the ATPA in different tracts. A: Typical and direct tracts. 1) Opened air cells in the squamous part of the temporal bone or petrous apex should be packed with autologous tissue (fat tissue). 2) If this method is not sufficient to prevent a CSF leak, packing the antrum with fat tissue may be required. B: Unusual tracts. 1) Opened air cells in the squamous part of the temporal bone or petrous apex should be carefully packed with autologous tissue. 2) If this method is not sufficient to prevent a CSF leak, packing the eustachian tube with autologous tissue (fat tissue) may be required.

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