Nervus intermedius: Microsurgical and anatomic relationships to the cerebellopontine angle neurovascular complex

Authors

Ali Tayebi Meybodi, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona.
Allison S. Liang, Department of Neurosurgery, Rutgers New Jersey Medical School, Newark, New Jersey, United States.
Pooneh Mokhtari, Department of Neurosurgery, Rutgers New Jersey Medical School, Newark, New Jersey, United States.
Leandro Borba Moreira, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona.
Xiaochun Zhao, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona.
Michael T. Lawton, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona.Follow
Mark C. Preul, Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona.

Document Type

Article

Abstract

BACKGROUND: The nervus intermedius (NI) comprises fibers originating from the trigeminal, superior salivary, and solitary tract nuclei, which join the facial nerve (cranial nerve [CN] VII). Neighboring structures include the vestibulocochlear nerve (CN VIII), the anterior inferior cerebellar artery (AICA), and its branches. Microsurgical procedures at the cerebellopontine angle (CPA) benefit from understanding NI anatomy and relationships, especially for the microsurgical treatment of geniculate neuralgia, where the NI is transected. This study sought to characterize common relationships between the NI rootlets, CN VII, CN VIII, and the meatal loop of AICA at the internal auditory canal (IAC). METHODS: Seventeen cadaveric heads underwent retrosigmoid craniectomy. Following complete unroofing of the IAC, the NI rootlets were individually exposed to identify their origins and insertion points. The AICA and its meatal loop were traced to assess their relationship with the NI rootlets. RESULTS: Thirty-three NIs were identified. The median number of NI rootlets was 4 per NI (interquartile range, 3-5). The rootlets mainly originated from the proximal premeatal segment of CN VIII (81 of 141, 57%) and inserted onto CN VII at the IAC fundus (89 of 141, 63%). When crossing the acoustic-facial bundle, the AICA most frequently passed between the NI and CN VIII (14 of 33, 42%). Five composite patterns of neurovascular relationships were identified regarding NI. CONCLUSION: Although certain anatomical trends can be identified, the NI has a variable relationship with the adjacent neurovascular complex at the IAC. Therefore, anatomical relationships should not be used as the sole method of NI identification during CPA surgery.

Publication Date

1-1-2023

Publication Title

Surgical neurology international

ISSN

2229-5097

Volume

14

First Page

37

PubMed ID

36895247

Digital Object Identifier (DOI)

10.25259/SNI_1097_2022

Recommended Citation

Meybodi, Ali Tayebi; Liang, Allison S.; Mokhtari, Pooneh; Moreira, Leandro Borba; Zhao, Xiaochun; Lawton, Michael T.; and Preul, Mark C., "Nervus intermedius: Microsurgical and anatomic relationships to the cerebellopontine angle neurovascular complex" (2023). Neurosurgery. 1819.
https://scholar.barrowneuro.org/neurosurgery/1819