10.14639/0392-100X-N1443
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1827-675X
1443
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Livio Presutti
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ACTA Otorhinolaryngologica Italica
Transmeatal microsurgery for intralabyrinthine and intrameatal schwannomas: literature review
Text.Serial.Journal
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41
Letters to the Editor-in-Chief
2021-07-07
2021-02-01
2021-07-08
2021-07-08
282-284
1
Livio Presutti
2021/07/07
10.14639/0392-100X-N1443
282
Otolaryngology-Head and Neck Surgery Department, Alma Mater Studiorum - University of Bologna, Bologna, Italy
1827-675X
284
Transmeatal microsurgery for intralabyrinthine and intrameatal schwannomas: literature review
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ACTA OTORHINOLARYNGOLOGICA ITALICA 2021;41:282-284; doi: 10.14639/0392-100X-N1443




Letter to the Editor


Transmeatal microsurgery for intralabyrinthine
and intrameatal schwannomas: literature review
Approccio transmeatale microchirurgico nei neurinomi intralabirintici e intrameatali:
revisione della letteratura
Daniele Marchioni1, Flavia Di Maro1, Livio Presutti2
1
 Otolaryngology-Head and Neck Surgery Department, University Hospital of Verona, Verona, Italy; 2 Otolaryngology-Head and Neck
Surgery Department, Alma Mater Studiorum - University of Bologna, Bologna, Italy
KEY WORDS: intracanalicular acoustic neuroma, transcanal approaches, internal auditory canal, transpromontorial corridor
PAROLE CHIAVE: neurinoma dell’acustico intracanalare, approcci transcanalari, condotto uditivo interno, via transpromontoriale


Dear Editor,
We have carefully read a recent issue published by Acta Otorhinolaryngolog-
ica Italica written by Mazzoni et al. 1 who intends to reconsider the transcanal
transvestibular approach to the labyrinth and Internal Auditory Canal (IAC)
for the treatment of acoustic neuroma. We have some considerations to make
in this regard.
In 1970, Alvarez de Cozar et al. described a transcanal transvestibular ap-
proach for the management of disabling unilateral Ménière’s disease. As stated             Received: February 1, 2021
                                                                                           Accepted: February 3, 2021
later by the authors, the aims of this approach were: to perform a labyrinthec-
tomy exploring both the Internal Auditory Canal (IAC) and the cochlea in                   Correspondence
order to exclude the presence of an undiagnosed intralabyrinthine neuroma, to              Flavia Di Maro
provide a diagnostic tool for neuromas requiring labyrinthectomy for removal               Otolaryngology-Head and Neck Surgery De-
                                                                                           partment, University Hospital of Verona
and for treatment of small < 3 mm, mobile and unexpected intracanalicular                  piazzale Aristide Stefani 1, 37126 Verona, Italy
neuromas 2. In 1975, the same authors reported their experience with this ap-              Tel. +39 045 8122330. Fax +39 045 8122313
proach on 178 patients with intractable vertigo; in three of them an intracana-            E-mail: flaviadimaro@yahoo.com
licular neuroma was found. In two of the patients the tumour was removed
                                                                                           Funding
with a transvestibular approach, and in one case it was necessary to perform a             None.
combined transvestibular and translabyrinthine approach 2. In the conclusions,
the authors specified that “In the case of a small < 3 mm, unexpectedly found,             Conflict of interest
acoustic neurinoma which is freely mobile within the canal, removal can be                 The Authors declare no conflict of interest.
attempted through this approach. We consider removal of larger tumours by
this approach hazardous for the preservation of the facial nerve function and                How to cite this article: Marchioni D, Di
do not recommend it under these circumstances” 2.                                            Maro F, Presutti L. Transmeatal microsur-
                                                                                             gery for intralabyrinthine and intrameatal
In 2015, we presented the Endoscopic Transcanal Transpromontorial ap-                        schwannomas: literature review. Acta Otorhi-
proach 3, the first transcanal transpromontorial endoscopic approach to the                  nolaryngol Ital 2021;41:282-284. https://doi.
IAC. With this approach it is possible to dominate the IAC through the prom-                 org/10.14639/0392-100X-N1443
ontory, preserving the medial wall of the vestibule. Actually, in the surgical
                                                                                           © Società Italiana di Otorinolaringoiatria
approach, after transcanal exposure of the vestibule, spherical recess and ba-             e Chirurgia Cervico-Facciale
sal, middle and apical turn of the cochlea, drilling is performed around the
inferior aspect of the vestibule until the fundus of the IAC is opened, exposing                          OPEN ACCESS

the most lateral portion of the pathology. The IAC is increasingly exposed by              This is an open access article distributed in accordance with
                                                                                           the CC-BY-NC-ND (Creative Commons Attribution-Non-
further drilling around the inferior aspect of the vestibule. The limits of the            Commercial-NoDerivatives 4.0 International) license. The
dissection are the tympanic segment of the facial nerve superiorly, the internal           article can be used by giving appropriate credit and mentio-
                                                                                           ning the license, but only for non-commercial purposes and
carotid artery anteriorly, the jugular bulb inferiorly and the mastoid portion             only in the original version. For further information: https://
of the facial nerve posteriorly. The anterior, inferior and posterior borders of           creativecommons.org/licenses/by-nc-nd/4.0/deed.en




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                                                   Transmeatal microsurgery for intralabyrinthine and intrameatal schwannomas: literature review




the IAC are exposed by drilling in a circumferential man-           that the technique was described 50 years ago, apparently
ner under the vestibule and around the IAC in a horseshoe           ignoring the aim and possible applications of the approach
shape, deepening from lateral to medial until reaching the          described by Alvarez de Cozar et al. 2.
reflection of the dura from the IAC meatus to the medial            In the case series, most of the articles describe transcanal
surface of the petrous bone. Subsequently, the IAC dura             approaches for neuromas limited to the vestibule or with
is opened to expose the tumour. The acoustic neuroma is             minimal extension to the cochlea, without access the IAC.
then removed from the meatus to the fundus of the IAC,              DeLozier 8 in a case of intractable vertigo, accesses the
preserving the facial nerve. When extension to the cerebel-         IAC for exploration purposes, finding no pathology; Jiang
lopontine angle (CPA) is found, additional bone is drilled          et al. 9 described 2 cases of intracochlear neuroma without
to enlarge the opening of the IAC meatus to allow manage-           extension to the vestibule or IAC treated with a retroauri-
ment of the residual tumour lying in the CPA. This drill-           colar transotic transcanal approach, recommending the tra-
ing is performed by following the acoustic-facial bundle            ditional transmastoid transotic approach for tumours with
toward the entry zone 4.                                            extension to the IAC; finally, Zhu et al. 10 presented a case
In our experience, the indications of this approach consist         report of an intracochlear neuroma with extension to the
of disease involving the cochlea, vestibule and the IAC in-         modiolus.
cluding minimal extension in the CPA (acoustic neuroma              None of the articles in the case series describe an approach
Koos I-II). At the end of surgery, depending on the extent of       allowing removal of tumours occupying the entire IAC (as
the disease and the extent of tissue extirpation, either repo-      opposed to the case reported in the main paper) with or
sitioning of the tympanomeatal flap or a cul-de-sac closure         without extension into the CPA.
of the skin of the ear canal can be performed 3. In the last        Furthermore, it is surprising how the author does not con-
few years this approach has been used in other departments          sider in the literature review our large series of 49 patients
worldwide 5.                                                        who underwent Endoscopic Transcanal Transpromontorial
Later 6 we developed a microscopic approach through the             approach (21 cases) or Expanded Transcanal Transpromon-
same route, the Expanded Transcanal Transpromontorial               torial approach (28 cases) for acoustic neuroma Koos I-III.
approach. It enlarges the surgical window to the CPA al-            To the best of our knowledge, this is the largest case series
lowing resection of acoustic neuroma previously resectable          of transcanal transpromontorial approach for intrameatal
only through more invasive approaches. The Expanded                 acoustic neuroma and in clinical practice there are today
Transcanal Transpromontorial approach allows complete               more than 100 procedures. We consider a serious short-
domination of the IAC and the corresponding portion of              coming that an Italian team does not consider in its review
CPA and is specifically indicated for the management of             an approach developed by another Italian team.
acoustic neuroma up to selected Koos III 7. As for the endo-        In conclusion, the Expanded Transcanal Transpromontorial
scopic approach, in this microscopic approach access to the         approach is an innovative approach for the management of
IAC occurs through a transpromontorial route, preserving            intracanalicular acoustic neuroma up to some Koos III tu-
the medial wall of the vestibule. Both techniques therefore         mour, first described in 2017 6. Although indications are
represent an absolute innovation in the panorama of ap-             limited to growing tumours with impaired hearing, surgical
proaches to the IAC and currently represent acknowledged            experience in these minimally invasive approaches is in-
options in the surgical treatment of neuromas previously            creasing, allowing the removal of acoustic neuromas previ-
removable only through retrosigmoid, middle cranial fossa           ously approachable only through more invasive techniques.
or translabyrinthine approaches. The choice between these
two transcanal approaches is made based on tumour ex-
tent: if the tumour is completely located in the IAC with or        References
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