Microanatomy and Histological Features of Central Myelin in the Root Exit Zone of Facial Nerve

This 68-year-old woman presented with repeated episodes of bilateral hemifacial spasm with headache for 5 years and with recent progression of left sided symptoms. Preoperative imaging showed a left sided tentorial meningioma with brain stem and cerebellar compression. Left facial nerve was compressed by the vertebral artery (VA) and the right facial nerve by the anterior inferior cerebellar artery (AICA). This patient underwent left side retrosigmoid craniotomy and mastoidectomy. The cisterna magna was drained to relax the brain. The tumor was very firm, attached to the tentorium and had medial and lateral lobules. The superior cerebellar artery was adherent to the lateral lobule of the tumor and dissected away. The tumor was detached from its tentorial base; we first removed the lateral lobule. Following this, the medial lobule was also completely dissected and removed. The root exit zone of cranial nerve (CN) VII was dissected and exposed. The compression was caused both by a prominent VA and AICA. Initially, the several pieces of Teflon felt were placed for the decompression. Then vertebropexy was performed by using 8–0 nylon suture placed through the VA media to the clival dura. A further piece of Teflon felt was placed between cerebellopontine angle region and AICA. Her hemifacial spasm resolved postoperatively, and she discharged home 1 week later. Postoperative imaging showed complete tumor removal and decompression of left CN VII. This video shows the complex surgery of microsurgical resection of a large tentorial meningioma and microvascular decompression with a vertebropexy procedure.The link to the video can be found at: https://youtu.be/N5aHN9CRJeM.

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Wide distribution of central myelin segment along the facial nerve might explain hemifacial spasm with distal nerve compression

Clinical Anatomy ◽

10.1002/ca.23664 ◽

2020 ◽

Author(s):

Kei Nomura ◽

Hiroshi Ryu ◽

Koji Ohno ◽

Kohji Sato

Keyword(s):

Facial Nerve ◽

Hemifacial Spasm ◽

Wide Distribution ◽

Nerve Compression ◽

Central Myelin ◽

Distal Nerve

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Hemifacial Spam: Endoscopic Assistance in Facial Nerve Decompression With Lateral Spread Response Corroboration: 2-Dimensional Operative Video

Operative Neurosurgery ◽

10.1093/ons/opaa301 ◽

2020 ◽

Author(s):

Cameron J Brimley ◽

Raghuram Sampath

Keyword(s):

Facial Nerve ◽

Symptomatic Improvement ◽

Lateral Spread ◽

Complex Case ◽

Anterior Inferior Cerebellar Artery ◽

Dramatic Improvement ◽

Auditory Evoked Responses ◽

Root Exit Zone ◽

Endoscopic Assistance ◽

Lateral Spread Response

Abstract This video depicts the case of a 48-yr-old female with 3 yr of progressive left hemifacial spasm (HFS) refractory to medication. Magnetic resonance imaging showed a large anterior inferior cerebellar artery (AICA) and also a labyrinthine artery loop around the facial nerve (FN) root exit zone. A large bony eminence was also noted in the superior and lateral aspects of the porous acousticus (PA). She preferred surgery if “cure” was possible in lieu of Botox injections. A left retro sigmoid craniotomy was performed with brainstem auditory evoked responses (BAERs) and FN monitoring along with lateral spread response (LSR) assessment. The large bony prominence was drilled in its lateral aspect. Despite this, visualization was still limited and therefore we utilized a 30-degree-angled endoscope to observe the vessels caudal and cranial to the FN. This view prompted us to then drill further at the PA to decompress the FN as well as mobilize the labyrinthine artery away from the nerve. The LSR showed a dramatic improvement when FN decompression was accomplished, and then a further improvement with arterial mobilization and Teflon pledget placement. The BAERS remained at baseline throughout. FN function and hearing were intact on postoperative clinical assessment. Her symptomatic improvement was recorded at 12 mo after surgery. This video illustrates a more complex case of microvascular decompression with skull base concepts and techniques. The patient provided consent for the procedure and use of her images and operative video for publication.

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Improved preservation of function during acoustic neuroma surgery

Journal of Neurosurgery ◽

10.3171/2014.8.jns132525 ◽

2015 ◽

Vol 122 (1) ◽

pp. 24-33 ◽

Cited By ~ 17

Author(s):

Hirofumi Nakatomi ◽

Hidemi Miyazaki ◽

Minoru Tanaka ◽

Taichi Kin ◽

Masanori Yoshino ◽

...

Keyword(s):

Action Potential ◽

Facial Nerve ◽

Acoustic Neuroma ◽

Compound Muscle Action Potential ◽

Dorsal Cochlear Nucleus ◽

Factors Affecting ◽

Root Exit Zone ◽

Muscle Action Potential ◽

Monitoring Response ◽

Potential Monitoring

OBJECT Restoration of cranial nerve functions during acoustic neuroma (AN) surgery is crucial for good outcome. The effects of minimizing the injury period and maximizing the recuperation period were investigated in 89 patients who consecutively underwent retrosigmoid unilateral AN surgery. METHODS Cochlear nerve and facial nerve functions were evaluated during AN surgery by use of continuous auditory evoked dorsal cochlear nucleus action potential monitoring and facial nerve root exit zone–elicited compound muscle action potential monitoring, respectively. Factors affecting preservation of function at the same (preoperative) grade were analyzed. RESULTS A total of 23 patients underwent standard treatment and investigation of the monitoring threshold for preservation of function; another 66 patients underwent extended recuperation treatment and assessment of its effect on recovery of nerve function. Both types of final action potential monitoring response and extended recuperation treatment were associated with preservation of function at the same grade. CONCLUSIONS Preservation of function was significantly better for patients who received extended recuperation treatment.

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Hemifacial spasm

Journal of Neurosurgery ◽

10.3171/jns.1982.57.6.0753 ◽

1982 ◽

Vol 57 (6) ◽

pp. 753-756 ◽

Cited By ~ 77

Author(s):

Tsutomu Iwakuma ◽

Akihisa Matsumoto ◽

Nishio Nakamura

Keyword(s):

Facial Nerve ◽

Hemifacial Spasm ◽

Microvascular Decompression ◽

Nerve Root ◽

Posterior Inferior Cerebellar Artery ◽

Content Type ◽

Stylomastoid Foramen ◽

Root Exit Zone ◽

Selective Neurectomy ◽

Fine Print

✓ Patients with hemifacial spasm were treated by three different surgical procedures: 1) partial sectioning of the facial nerve just distal to the stylomastoid foramen; 2) selective neurectomy of facial nerve branches; and 3) microvascular decompression. A retromastoid craniectomy with microvascular decompression was most effective in relieving hemifacial spasm and synkinesis. In a postmorten examination on one patient, microscopic examination of the facial nerve, which was compressed by an arterial loop of the posterior inferior cerebellar artery at the cerebellopontine angle, revealed fascicular demyelination in the nerve root. On the basis of surgical treatment, electromyography, and neuropathological findings, the authors conclude that compression of the facial nerve root exit zone by vascular structures is the main cause of hemifacial spasm and synkinesis.

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Transcranial Magnetic Stimulation Excites the Root Exit Zone of the Facial Nerve

Neurosurgery ◽

10.1097/00006123-199303000-00012 ◽

1993 ◽

Vol 32 (3) ◽

pp. 414???416 ◽

Cited By ~ 1

Author(s):

Hiroshi Tokimura ◽

Masayuki Yamagami ◽

Yoshika Tokimura ◽

Tetsuhiko Asakura ◽

Masayuki Atsuchi

Keyword(s):

Transcranial Magnetic Stimulation ◽

Facial Nerve ◽

Magnetic Stimulation ◽

Root Exit Zone

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Neurovascular compression findings in hemifacial spasm

Journal of Neurosurgery ◽

10.3171/jns/2008/109/9/0416 ◽

2008 ◽

Vol 109 (3) ◽

pp. 416-420 ◽

Cited By ~ 119

Author(s):

Mauricio Campos-Benitez ◽

Anthony M. Kaufmann

Keyword(s):

Facial Nerve ◽

Hemifacial Spasm ◽

Nerve Root ◽

Posterior Inferior Cerebellar Artery ◽

Anterior Inferior Cerebellar Artery ◽

Vascular Compression ◽

Neurovascular Compression ◽

Exit Point ◽

Root Exit Zone ◽

Cerebellar Artery

Object It is generally accepted that hemifacial spasm (HFS) is caused by pulsatile vascular compression upon the facial nerve root exit zone. This 2–3 mm area, considered synonymous with the Obersteiner–Redlich zone, is a transition zone (TZ) between central and peripheral axonal myelination that is situated at the nerve's detachment from the pons. Further proximally, however, the facial nerve is exposed on the pontine surface and emerges from the pontomedullary sulcus. The incidence and significance of neurovascular compression upon these different segments of the facial nerve in patients with HFS has not been previously reported. Methods The nature of neurovascular compression was determined in 115 consecutive patients undergoing their first microvascular decompression (MVD) for HFS. The location of neurovascular compression was categorized to 1 of 4 anatomical portions of the facial nerve: RExP = root exit point; AS = attached segment; RDP = root detachment point that corresponds to the TZ; and CP = distal cisternal portion. The severity of compression was defined as follows: mild = contact without indentation of nerve; moderate = indentation; and severe = deviation of the nerve course. Success in alleviating HFS was documented by telephone interview conducted at least 24 months following MVD surgery. Results Neurovascular compression was found in all patients, and the main culprit was the anterior inferior cerebellar artery (in 43%), posterior inferior cerebellar artery (in 31%), vertebral artery (in 23%), or a large vein (in 3%). Multiple compressing vessels were found in 38% of cases. The primary culprit location was at RExP in 10%, AS in 64%, RDP in 22%, and CP in 3%. The severity of compression was mild in 27%, moderate in 61%, and severe in 12%. Failure to alleviate HFS occurred in 9 cases, and was not related to compression location, severity, or vessel type. Conclusions The authors observed that culprit neurovascular compression was present in all cases of HFS, but situated at the RDP or Obersteiner–Redlich zone in only one-quarter of cases and rarely on the more distal facial nerve root. Since the majority of culprit compression was found more proximally on the pontine surface or even pontomedullary sulcus origin of the facial nerve, these areas must be effectively visualized to achieve consistent success in performing MVD for HFS.

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Etiology and definitive microsurgical treatment of hemifacial spasm

Journal of Neurosurgery ◽

10.3171/jns.1977.47.3.0321 ◽

1977 ◽

Vol 47 (3) ◽

pp. 321-328 ◽

Cited By ~ 402

Author(s):

Peter J. Jannetta ◽

Munir Abbasy ◽

Joseph C. Maroon ◽

Francisco M. Ramos ◽

Maurice S. Albin

Keyword(s):

Facial Nerve ◽

Hemifacial Spasm ◽

Mechanical Compression ◽

Postoperative Results ◽

Content Type ◽

Microsurgical Treatment ◽

Root Exit Zone ◽

Operative Findings ◽

Fine Print

✓ The clinical and operative findings are reviewed in 47 patients with intractable hemifacial spasm. The syndrome was classical in its features in 45 patients and atypical in two. Mechanical compression distortion of the root exit zone of the facial nerve was noted in all 47 patients. In 46 the abnormality was vascular cross-compression, usually by an arterial loop. In one patient, a small cholesteatoma was discovered and removed. Morbidity and postoperative results are discussed.

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Intraoperative Measuring of the Offending Vessel’s Pressure on the Facial Nerve at Root Exit Zone in Patients with Hemifacial Spasm During Microvascular Decompression: A Prospective Study

World Neurosurgery ◽

10.1016/j.wneu.2018.09.080 ◽

2019 ◽

Vol 122 ◽

pp. e89-e95

Author(s):

Pei Zhang ◽

M. Helmy Selim ◽

Haiyan Wang ◽

Wei Kuang ◽

Miaojing Wu ◽

...

Keyword(s):

Facial Nerve ◽

Prospective Study ◽

Hemifacial Spasm ◽

Microvascular Decompression ◽

Root Exit Zone ◽

A Prospective Study

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A “Sling Swing Transposition” Technique With Pedicled Dural Flap for Microvascular Decompression in Hemifacial Spasm

Operative Neurosurgery ◽

10.1227/neu.0b013e318246aa74 ◽

2012 ◽

Vol 71 (suppl_1) ◽

pp. ons25-ons31 ◽

Cited By ~ 2

Author(s):

Hui Ming Khoo ◽

Toshiki Yoshimine ◽

Takuyu Taki

Keyword(s):

Facial Nerve ◽

Hemifacial Spasm ◽

Microvascular Decompression ◽

Cerebellopontine Angle ◽

Symptom Relief ◽

Neurovascular Compression ◽

Posterior Surface ◽

Anatomic Structure ◽

Compression Syndrome ◽

Root Exit Zone

Abstract BACKGROUND: The key to successful microvascular decompression of the neurovascular compression syndrome is maintaining the separation between the nerve and the offending vessel. OBJECTIVE: We describe a transposition technique in which a local pedicled dural flap, fashioned from the petrous posterior surface, is used to retract the offending vessel away from the root exit zone of the facial nerve in hemifacial spasm cases. METHODS: We conducted a retrospective review of microvascular decompression operations in which the offending vessel was transposed and then retained by a local pedicled dural flap made from the dura of the petrous posterior surface. RESULTS: This technique was used in 7 consecutive cases of the most recently operated series. Postoperatively, complete symptom relief was achieved in 100% of the patients without any significant surgical complications. CONCLUSION: To our knowledge, this is the first report in which an autologous anatomic structure in the cerebellopontine angle, such as petrous dura mater, is used in the microvascular decompression of the facial nerve. This is a simple yet robust method and can be considered an option for the treatment of hemifacial spasm caused by arterial compression.

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