Microsurgical endoscopy-assisted presigmoid retrolabyrinthine approach as a minimally invasive surgical option for the treatment of medium to large vestibular schwannoma

Abstract

The paper from Iacoangeli and his colleagues from Ancona and Rome in this issue of Acta Neurochirurgica is timely given the continuing controversy on best treatment options for vestibular schwannomas.Their report is on the preliminary experience with an old approach integrated with the endoscope. The case material includes ten cases of small and medium sized sporadic acoustic neuromas (five cases of 8 and 10 mm, five cases of 11-25 mm), selected on the basis of a favourable anatomy of the temporal bone.It is noteworthy, and rather exceptional in comparison to other's experiences, that only three cases out of ten had a preoperative normal facial nerve function, while four cases of 11-25 mm had a House-Brackmann (HB) grade 3 and three cases of 10 and 20 mm had a HB grade 2, which makes 70 % of preoperative facial dysfunction in small and medium-size tumors.The surgical outcome was outstanding, with unchanged postoperative facial function (with the exception of the case with preoperative radiotherapy), only one case experiencing a hearing loss from AAORLHNS class B to C, and no instances of deafness. The removal of tumors from the internal auditory canal without a drill meatotomy in this series might have been favoured by a limited extension into the canal. The results on the hearing and facial nerve are superior to the results reported in the literature.We dare to say that we never had a group of ten consecutive cases with only one postop limited hearing loss in over 300 cases of hearing preservation surgery on smaller tumors [8].This revived approach, which was already dismissed by experienced surgeons, although now implemented by endoscopic assistance needs further validation in order to assess its performance versus the standard retrosigmoid approach.Notwithstanding, Iacoangeli and his colleagues have further contributed to the debate upon the treatment of acoustic neuroma. This has indeed been an active dispute over the last decades, and is nowadays even keener thanks to the further inputs brought by neurosurgeons, otosurgeons, endoscopists, and, last but not least, radiotherapists.It should be considered that early diagnosis results in a patient's population mainly (in 70 % of cases, according to accredited studies) made up of small tumors: the current debate and renewal of treatment options is therefore nowadays addressed to such lesions.

Radiographic assessment of the presigmoid retrolabyrinthine approach

“…In 1980, the retrolabyrinthine approach was described as the “direct”[23] route to the CP angle, being well-liked by otologists and neurosurgeons alike, in the treatment of Meniere's disease,[22] petroclival meningiomas,[12] vestibular schwannomas,[47] and in the placement of auditory brainstem implants. [5] In the early 2000s, the retrolabyrinthine approach was described as “the unsung hero of skull base surgery.”[18] When compared to a retrosigmoid approach, the presigmoid exposure provides the benefits of a shorter working distance and less cerebellar retraction.…”

Audiological Characteristics of Vestibular Schwannoma Patients With Normal Pure‐Tone Audiometry

“…Vestibular schwannomas (VSs) are common benign tumors that represent approximately 80% of tumors of the cerebellopontine angle and 6% of all intracranial tumors 1,2 . Many studies support managing VSs conservatively or via observation because they have found that tumor progression occurs at very slow rates, between 1 and 2 mm/year 3,4 . Hearing loss (HL) is the most common presenting symptom for patients with VSs; more than 90% of patients with VSs have some level of auditory dysfunction when assessed 5,6 .…”

“…1,2 Many studies support managing VSs conservatively or via observation because they have found that tumor progression occurs at very slow rates, between 1 and 2 mm/year. 3,4 Hearing loss (HL) is the most common presenting symptom for patients with VSs; more than 90% of patients with VSs have some level of auditory dysfunction when assessed. 5,6 Some authors consider observation to result in a high risk of hearing dysfunction as the wait time increases, so early surgery to preserve useful hearing should be the first choice.…”

Surgical treatment of acoustic neuroma: Outcomes and indications

“…The surgical approaches used in microsurgery for acoustic neuroma can be summarized as: translabyrinthine, 2,3 enlarged translabyrinthine 4,5 with the possibility of its transapical extension, 5 retrosigmoid, 6 retrosigmoid with retrolabyrinthine meatotomy, 7 presigmoid retrolabyrinthine (an old approach that was recently adapted for use with the endoscopy-assisted technique), 8,9 and the middle cranial fossa approach. [10][11][12] All these approaches involve microsurgical methods, craniotomy or craniectomy, access being first extradural then intradural (translabyrinthine, middle cranial fossa), or intradural with cerebellar retraction (retrosigmoid).…”