The Intraosseous Subarcuate Loop of Anterior Inferior Cerebellar Artery: Anatomic Management Guide, Single-Center MRI Study, and Scoping Review

Alessandro De Bonis; Pedro Plou; Megan M J Bauman; Filippos Athanasoulis; Sofia Kollia; Fabio Torregrossa; Simona Serioli; Luciano César P C Leonel; Matthew Carlson; Michael Link; Maria Peris-Celda

doi:10.1227/ons.0000000000001474

The Intraosseous Subarcuate Loop of Anterior Inferior Cerebellar Artery: Anatomic Management Guide, Single-Center MRI Study, and Scoping Review

Oper Neurosurg (Hagerstown). 2024 Dec 23. doi: 10.1227/ons.0000000000001474. Online ahead of print.

Authors

Alessandro De Bonis^{1

2

3}, Pedro Plou^{1

2

4}, Megan M J Bauman^{1

2}, Filippos Athanasoulis^{2

5}, Sofia Kollia^{2

5}, Fabio Torregrossa^{1

2

6}, Simona Serioli^{1

2

7}, Luciano César P C Leonel^{1

2}, Matthew Carlson⁸, Michael Link^{1

2

8}, Maria Peris-Celda^{1

2

8}

Affiliations

¹ Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota, USA.
² Rhoton Neurosurgery and Otolaryngology Surgical Anatomy Program, Mayo Clinic, Rochester, Minnesota, USA.
³ Department of Neurosurgery and Gamma Knife Radiosurgery, San Raffaele Scientific Institute, Vita-Salute University, Milan, Italy.
⁴ Department of Neurosurgery, Hospital Italiano de Buenos Aires, Buenos Aires, Argentina.
⁵ School of Medicine, National and Kapodistrian University of Athens, Athens, Greece.
⁶ Neurosurgical Unit, Department of Biomedicine, Neurosciences and Advanced Diagnostics (BiND), University of Palermo, Palermo, Italy.
⁷ Division of Neurosurgery, Department of Medical and Surgical Specialties, Radiological Sciences and Public Health, University of Brescia, Brescia, Italy.
⁸ Department of Otolaryngology-Head and Neck Surgery, Mayo Clinic, Rochester, Minnesota, USA.

PMID: 39716468
DOI: 10.1227/ons.0000000000001474

Abstract

Background and objectives: The intraosseous subarcuate loop (SL) is a unique variant of the anterior inferior cerebellar artery (AICA), where a loop of the artery is trapped in the petrous bone's subarcuate fossa (SF). Recognizing this variant is crucial for planning cerebellopontine angle (CPA) surgeries; however, data regarding its frequency and management vary in the published literature. A cohort from a single center was studied using MRI to assess its prevalence, and the findings were compared with the existing literature. In addition, an intraoperative guide for mobilizing the intraosseous AICA's SL was provided through a detailed step-by-step cadaveric dissection.

Methods: Two hundred fifty-eight patients who had undergone MRI scans of the CPA (516 sides) were retrospectively reviewed. MRIs displaying vascular loops visible in the axial view were analyzed using multiplanar reconstruction, and the intraosseous loop frequency was evaluated. A scoping review was undertaken to provide an overview of previously published data on its prevalence. One embalmed and latex-injected specimen with intraosseous AICA's SL was dissected through a retrosigmoid approach, and 1 surgical case was detailed, describing the procedure to release it.

Results: Intraosseous AICA's SL mobilization involves the identification of its entry and exit points within the petrous bone, dural incision to expose the SF, SF drilling, subarcuate artery division, and detaching the vascular loop. Preservation of a dural cuff is crucial to prevent vascular injury. We analyzed 258 brain MRIs (mean age 55 years, 42% male). The intraosseous AICA's SL was present in 4 of 516 evaluated CPAs (0.8%). The prevalence of the vascular anomaly in the reviewed literature using different radiological modalities ranged from 0.2% to 1.6%.

Conclusion: The intraosseous AICA's SL is an uncommon anatomic variation detectable by MRI, posing an added risk in CPA surgery. Identifying and properly mobilizing it is crucial for safe vascular preservation.