Mobilization of the Anterior Inferior Cerebellar Artery When Firmly Adherent to the Petrous Dura Mater—A Technical Nuance in Retromastoid Transmeatal Vestibular Schwannoma Surgery: 3-Dimensional Operative Video

Abstract

The anterior inferior cerebellar artery (AICA) usually runs loosely within the cerebellopontine cistern; in rare cases, however, it is firmly adherent to the petrous dura mater.1,2 Recognizing this variation is particularly important in vestibular schwannoma surgery via the retrosigmoid transmeatal approach to prevent the high morbidity associated with vascular injury. This video demonstrates a surgical technique to effectively mobilize the AICA when firmly adherent to the petrous dura mater. A 39-year-old man presented with a history of progressive right-sided hearing loss without facial weakness or other associated symptoms3. Magnetic resonance imaging (MRI) demonstrated an intracanalicular lesion, suggestive of vestibular schwannoma. During follow-up, audiometry confirmed a further slight deterioration of hearing and repeated MRI demonstrated tumor growth (T2 according to Hannover classification). Since the patient opted against radiosurgery, a retrosigmoid transmeatal approach under continuous intraoperative monitoring was performed in supine position. Following drainage of cerebrospinal fluid and exposure of the cerebellopontine cistern, the AICA was found to be firmly adherent to the petrous dura mater. Both structures were elevated conjointly and displaced medially for safe drilling of the inner auditory canal, sufficient exposure, and complete excision of the vestibular schwannoma. The patient had an excellent recovery, hearing and facial function were preserved, and no secondary neurological deficits noted.The patient consented to publication of this anonymized video.

Anatomic Variants in the Anterior Inferior Cerebellar Artery Encountered During Resection of Vestibular Schwannomas

“…Many reports of AICA variants are case reports or small cohort series, although several provide valuable technical notes. 8,9,[14][15][16][17] Careful surgical consideration should be given for how to manage these variants when encountered during surgery, not only for risk to the primary artery but also additional important branches including the labyrinthine artery and brainstem microvascular perforators, which may limit manipulation of AICA during VS resection. Pending the discrete arterial location, an AICA stroke may cause lateral pontine syndrome.…”

A Classification for the Anterior Inferior Cerebellar Artery—Subarcuate Artery Complex Based on the Embryological Development

“…1,4,5,9,21,40,41 Contrarily, the SL and the SAA have been referred to in a succinct and isolated way in relation to the SF. 10,11,[18][19][20][21][22][23][24][25][26]28,29 However, a gradual spectrum of interaction between the AICA-SAA complex and the petrosal bone can be inferred.…”

“…1D, 2D, and 3C), has been described with a frequency ranging between 1 23,25 and 6%, 21 compared with 10.6% of the cases identified in our MRI results. In this case, although the AICA can be mobilized with the dura mater flap that covers the posterior edge of the acoustic meatus, 2,23,24 the risk of AICA tearing persists. Even achieving a meticulous dissection of the dura mater, the AICA can continue adhering to the petrosal bone by means of a SAA firmly included in the PMC.…”

“…[15][16][17] The patency and length of the SAA present significant variability. 8,10,[18][19][20][21][22] Indeed, also AICA variants have been reported, as covered by dura mater [23][24][25] and even by petrous bone. [25][26][27][28][29] These situations involve complex maneuvers for the identification and eventual mobilization of the AICA-SAA complex.…”