Letter: Internal Auditory Canal Variability: Anatomic Variation Affects Cisternal Facial Nerve Visualization

Abstract BACKGROUND The internal auditory canal (IAC) is an important landmark during surgery for lesions of the cerebellopontine angle. There is significant variability in the position and orientation of the IAC radiographically, and the authors have noted differences in surgical exposure depending on the individual anatomy of the IAC. OBJECTIVE To test the hypothesis that IAC position and orientation affects the surgical exposure of the IAC and facial nerve, especially when performing the translabyrinthine approach. METHODS The authors retrospectively reviewed magnetic resonance imaging studies of 50 randomly selected patients with pathologically confirmed vestibular schwannomas. Measurements, including the anterior (APD) and posterior (PPD) petrous distances, the anterior (APA) and posterior (PPA) petro-auditory angles, and the internal auditory angle (IAA), were obtained to quantify the position and orientation of the IAC within the petrous temporal bone. RESULTS The results quantitatively demonstrate tremendous variability of the position and orientation of the IAC in the petrous temporal bone. The measurement ranges were APD 10.2 to 26.1 mm, PPD 15.1 to 37.2 mm, APA 104 to 157°, PPA 30 to 96°, and IAA –5 to 40°. CONCLUSION IAC variability can have a substantial effect on the surgical exposure of the IAC and facial and vestibulocochlear nerves. Specifically, a horizontally oriented IAC with a small IAA may have significant impact on visualization of the facial nerve within its cisternal segment with the translabyrinthine approach. The retrosigmoid approach is less affected with IAC variability in position and angle.

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In Reply: Internal Auditory Canal Variability: Anatomic Variation Affects Cisternal Facial Nerve Visualization

Operative Neurosurgery ◽

10.1093/ons/opaa434 ◽

2020 ◽

Author(s):

William T Couldwell ◽

Michael A Cohen

Keyword(s):

Facial Nerve ◽

Anatomic Variation ◽

Internal Auditory Canal

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Otopathologic Abnormalities in CHARGE Syndrome

Otolaryngology ◽

10.1177/01945998211008911 ◽

2021 ◽

pp. 019459982110089

Author(s):

Rafael da Costa Monsanto ◽

Renata Malimpensa Knoll ◽

Norma de Oliveira Penido ◽

Grace Song ◽

Felipe Santos ◽

...

Keyword(s):

Facial Nerve ◽

Middle Ear ◽

Spiral Ganglion ◽

Internal Auditory Canal ◽

Semicircular Canals ◽

Charge Syndrome ◽

University Of Minnesota ◽

Bony Canal ◽

Ganglion Neurons ◽

Temporal Bones

Objective To perform an otopathologic analysis of temporal bones (TBs) with CHARGE syndrome. Study Design Otopathologic study of human TB specimens. Setting Otopathology laboratories. Methods From the otopathology laboratories at the University of Minnesota and Massachusetts Eye and Ear Infirmary, we selected TBs from donors with CHARGE syndrome. These TBs were serially sectioned at a thickness of 20 µm, and every 10th section was stained with hematoxylin and eosin. We performed otopathologic analyses of the external ear, middle ear (middle ear cleft, mucosal lining, ossicles, mastoid, and facial nerve), and inner ear (cochlea, vestibule, internal auditory canal, and cochlear and vestibular nerves). The gathered data were statistically analyzed. Results Our study included 12 TBs from 6 donors. We found a high prevalence of abnormalities affecting the ears. The most frequent findings were stapes malformation (100%), aberrant course of the facial nerve (100%) with narrow facial recess (50%), sclerotic and hypodeveloped mastoids (50%), cochlear (100%) and vestibular (83.3%) hypoplasia with aplasia of the semicircular canals, hypoplasia and aplasia of the cochlear (66.6%) and vestibular (91.6%) nerves, and narrowing of the bony canal of the cochlear nerve (66.6%). The number of spiral ganglion and Scarpa’s ganglion neurons were decreased in all specimens (versus normative data). Conclusions In our study, CHARGE syndrome was associated with multiple TB abnormalities that may severely affect audiovestibular function and rehabilitation.

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Facial Nerve Dissection by use of Acoustic (Loudspeaker) Facial EMG Monitoring

Otolaryngology ◽

10.1177/019459988609500407 ◽

1986 ◽

Vol 95 (4) ◽

pp. 458-463 ◽

Cited By ~ 7

Author(s):

Sam E. Kinney ◽

Richard Prass

Keyword(s):

Facial Nerve ◽

Acoustic Neuroma ◽

Internal Auditory Canal ◽

Subsequent Development ◽

Lateral Approach ◽

Nerve Function ◽

Facial Nerve Function ◽

Facial Emg ◽

Acoustic Neuroma Surgery ◽

Total Tumor Removal

The development of the surgical microscope in 1953, and the subsequent development of microsurgical instrumentation, signaled the beginning of modern-day acoustic neuroma surgery. Preservation of facial nerve function and total tumor removal is the goal of all acoustic neuroma surgery. The refinement of the translabyrinthine removal of acoustic neuromas by Dr. William House’ significantly improved preservation of facial nerve function. This is made possible by the anatomic identification of the facial nerve at the lateral end of the internal auditory canal. When the surgery is accomplished from a suboccipital or retrosigmoid approach, the facial nerve may be identified at the brain stem or within the internal auditory canal. Identifying the facial nerve from the posterior approach is not as anatomically precise as from the lateral approach through the labyrinth. The use of a facial nerve stimulator can greatly facilitate Identification of the facial nerve in these procedures.

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Resection of a Dumbbell-Shaped Facial Nerve Schwannoma With Preservation of Facial Nerve Function Through the Extended Middle Fossa Approach: 2-Dimensional Operative Video

Operative Neurosurgery ◽

10.1093/ons/opab335 ◽

2021 ◽

Author(s):

Kaith K Almefty ◽

Wenya Linda Bi ◽

Walid Ibn Essayed ◽

Ossama Al-Mefty

Keyword(s):

Facial Nerve ◽

Cerebellopontine Angle ◽

Internal Auditory Canal ◽

Growth Patterns ◽

Geniculate Ganglion ◽

Nerve Function ◽

Middle Fossa ◽

Facial Nerve Function ◽

Large Tumor ◽

Middle Fossa Approach

Abstract Facial nerve schwannomas are rare and can arise from any segment along the course of the facial nerve.1 Their location and growth patterns present as distinct groups that warrant specific surgical management and approaches.2 The management challenge arises when the facial nerve maintains good function (House-Brackmann grade I-II).3 Hence, a prime goal of management is to maintain good facial animation. In large tumors, however, resection with facial nerve function preservation should be sought and is achievable.4,5 While tumors originating from the geniculate ganglion grow extradural on the floor of the middle fossa, they may extend via an isthmus through the internal auditory canal to the cerebellopontine angle forming a dumbbell-shaped tumor. Despite the large size, they may present with good facial nerve function. These tumors may be resected through an extended middle fossa approach with preservation of facial and vestibulocochlear nerve function. The patient is a 62-yr-old man who presented with mixed sensorineural and conductive hearing loss and normal facial nerve function. Magnetic resonance imaging (MRI) revealed a large tumor involving the middle fossa, internal auditory meatus, and cerebellopontine angle. The tumor was resected through an extended middle fossa approach with a zygomatic osteotomy and anterior petrosectomy.6 A small residual was left at the geniculate ganglion to preserve facial function. The patient did well with hearing preservation and intact facial nerve function. He consented to the procedure and publication of images. Image at 1:30 © Ossama Al-Mefty, used with permission. Images at 2:03 reprinted from Kadri and Al-Mefty,6 with permission from JNSPG.

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Surgical Treatment of Hemifacial Spasm Caused by the Compression of Internal Auditory Canal of Facial Nerve

Journal of Craniofacial Surgery ◽

10.1097/scs.0000000000003872 ◽

2017 ◽

Vol 28 (6) ◽

pp. e564-e566 ◽

Cited By ~ 1

Author(s):

Jin Zhu ◽

Xin Zhang ◽

Hua Zhao ◽

Yin-Da Tang ◽

Ting-Ting Ying ◽

...

Keyword(s):

Surgical Treatment ◽

Facial Nerve ◽

Hemifacial Spasm ◽

Internal Auditory Canal

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Facial Nerve Meningioma: A Case Mimicking Facial Nerve Schwannoma

Ear Nose & Throat Journal ◽

10.1177/0145561320962582 ◽

2020 ◽

pp. 014556132096258

Author(s):

Wei Gao ◽

Dingjing Zi ◽

Lianjun Lu

Keyword(s):

Facial Nerve ◽

Internal Auditory Canal ◽

Growth Patterns ◽

Nerve Function ◽

Facial Nerve Function ◽

Nerve Reconstruction ◽

Radiological Features ◽

Facial Nerve Reconstruction ◽

Facial Nerve Schwannoma ◽

Grade Iii

Facial nerve meningioma is exceedingly rare and tends to affect the geniculate ganglion. We present a case of facial nerve meningioma located in the internal auditory canal with a “labyrinthine tail,” mimicking facial nerve schwannoma. The clinical and radiological features, growth patterns, and surgical management were reviewed. Progressive facial paralysis was the main syndrome, similar to other facial nerve tumors. When facial nerve function is worse than House-Brackmann grade III, surgical resection should be performed with facial nerve reconstruction.

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Suboccipital Surgical Approach to the Cerebellopontine Angle and Internal Auditory Canal

Journal of the Royal Society of Medicine ◽

10.1177/014107687807100410 ◽

1978 ◽

Vol 71 (4) ◽

pp. 273-274 ◽

Cited By ~ 1

Author(s):

Mansfield F W Smith

Keyword(s):

Facial Nerve ◽

Brain Stem ◽

Prone Position ◽

Surgical Approach ◽

Cerebellopontine Angle ◽

Internal Auditory Canal ◽

Total Removal ◽

Size And Shape ◽

Suboccipital Craniectomy ◽

The Brain

The suboccipital craniectomy done with the patient in the prone position using modern microsurgical methods gives good anatomical exposure essential for efficient, accurate, total removal of cerebellopontine angle neoplasms and allows adjacent. uninvolved neurological structures to be spared. Modifying the anatomical exposure by varying the size and shape of the osseous craniectomy and placing the dural incision closer to the porus acousticus permits extradural retraction of the cerebellum. Thus large cerebellopontine angle neoplasms can be excised with less chance of damage to the cerebellum and smaller risk of hydrocephalus. The suboccipital craniectomy may be extended anteriorly to the facial nerve, thereby combining the suboccipital with the translabyrinthine approach. and providing a more direct angle to a large neoplasm involving the brain stem and cerebellum.

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