Microvascular decompression for geniculate neuralgia

Paramedian suboccipital craniectomy and approach to the cerebellopontine angle (superior retraction gains access to the lower cranial nerves, e.g. for geniculate neuralgia)

Microvascular decompression may be effective as a treatment. Along its cisternal course, the nerve may be difficult to distinguish from the facial nerve. Based on case reports and small series, long-term pain control can be seen after nerve sectioning or microvascular decompression, but no prospective studies exist. Such studies are now necessary to shed light on the efficacy of surgical treatment of nervus intermedius neuralgia 1).

A retrosigmoid approach is performed in the lateral decubitus position. The dura is opened and cerebrospinal fluid (CSF) is released from the cisterna magna and cerebellopontine cistern. Dynamic retraction without rigid retractors is performed. Subarachnoid dissection of the cerebellopontine angle exposes the 7th to 8th nerve complex. A neuromonitoring probe is used with careful inspection of the microsurgical anatomy to identify the facial nerve and the nervus intermedius as they enter the internal auditory meatus. The nervus intermedius is severed. A large vein coursing superiorly across the cranial 9th nerve was coagulated and cut. A Teflon pledget is inserted between a small vessel and the 5th nerve. Photographs of the region are borrowed from Dr. Rhoton's laboratory to illustrate the microsurgical anatomy. Participants The senior author performed the surgery. The video was edited by Drs. V.N. and J.B. Outcome Measures Outcome was assessed by postoperative neurological function. Results The nervus intermedius was successfully cut and the 5th and 9th nerves were decompressed. The patient's pain resolved after surgery and at later follow-up.

Understanding the microsurgical anatomy of the cerebellopontine angle is necessary to identify the cranial nerves involved in facial pain syndromes. Subarachnoid dissection and meticulous microsurgical techniques are key elements for a successful microvascular decompression. The link to the video can be found at: https://youtu.be/pV5Wip7WusE 2).

A 62-year-old female with a history of deep right-sided otalgia consistent with geniculate neuralgia. She failed appropriate medical treatment. Her magnetic resonance imaging (MRI) showed an ectatic vertebrobasilar system as well as an anterior inferior cerebellar artery (AICA) loop causing compression of the VII/VIII nerve complex in the cerebellopontine angle. Main Outcome Measures Resolution of right-sided otalgia. Results The patient underwent retrosigmoid craniotomy with microvascular decompression of the VII/VIII nerve complex and nervus intermedius sectioning. Intraoperatively, the patient was noted to have an ectatic vertebral artery and AICA that were compressing the root entry zone of the VII/VIII nerve complex. Microvascular decompression was performed of both the vertebral artery and AICA with Teflon. The nervus intermedius was sharply sectioned. The patient's postoperative course was uneventful with no complications. She continues to have resolution of her right sided otalgia at 6 months postoperatively. The link to the video can be found at: https://youtu.be/uRb_QfrINSk 3).

A 70-year-old woman who had deep-ear pain for more than 4 years and was diagnosed with trigeminal neuralgia and treated with carbamazepine without relief. Magnetic resonance tomographic angiography revealed no neurovascular conflict with the trigeminal nerve, whereas the anterior inferior cerebellar artery (AICA) was close to the VII/VIII complex. Song et al. performed left-sided suboccipital retrosigmoid craniotomy. Surgical exploration under endoscopy clearly showed that the nervus intermedius was compressed by the AICA from behind. The ear pain was completely relieved immediately after nervus intermedius sectioning. The intraoperative findings and postoperative results confirmed that the compression of the nervus intermedius by the AICA caused the otalgia. A patient's specific pain, combined with preoperative imaging examination, is useful in the diagnosis of NIN. Neuroendoscopy has the advantages of enabling a clear field of view and close observation, thus aiding in the identification and accurate cutting of the nervus intermedius during the operation 4).

George and Ridder presented the case of an adolescent boy with bilateral geniculate neuralgia treated at two different time points with sectioning of the NI and MVD 5).

A 37-year-old one-pack-per-day smoker with diabetes mellitus presented for evaluation of episodic lancinating pain localizing to the right periauricular region. The patient's symptoms were attempted to be managed medically, however, remained refractory to medical management for a period greater than one year. The patient’s exam demonstrated a trigger point slightly anterior and inferior to the right tragus, and the pain was reproducible when touched or tapped. The patient was otherwise neurologically intact. Magnetic resonance imaging (MRI) was performed and demonstrated a loop of the AICA in contact with the root entry zone of the facial nerve. This patient was offered an elective microvascular decompression (MVD) for treatment of geniculate neuralgia 6).

Case report of a patient with intermedius neuralgia. The main complaint was severe otalgia in the area innervated by the nervus intermedius, possibly caused by neurovascular compression of the nervus intermedius by the anterior inferior cerebellar artery. Microvascular decompression was undertaken, with good results.

Results: Post-operatively, the patient felt immediate and total relief of her otalgia, with normal facial nerve function and no otological morbidity. One year post-operatively, she was still free from otalgia 7).

Tubbs RS, Steck DT, Mortazavi MM, Cohen-Gadol AA. The nervus intermedius: a review of its anatomy, function, pathology, and role in neurosurgery. World Neurosurg. 2013 May-Jun;79(5-6):763-7. doi: 10.1016/j.wneu.2012.03.023. Epub 2012 Apr 3. Review. PubMed PMID: 22484073.
Nguyen VN, Basma J, Sorenson J, Michael LM 2nd. Microvascular Decompression for Geniculate Neuralgia through a Retrosigmoid Approach. J Neurol Surg B Skull Base. 2019 Jun;80(Suppl 3):S322. doi: 10.1055/s-0038-1676837. Epub 2018 Dec 24. PMID: 31143613; PMCID: PMC6534696.
Kenning TJ, Kim CS, Bien AG. Microvascular Decompression and Nervus Intermedius Sectioning for the Treatment of Geniculate Neuralgia. J Neurol Surg B Skull Base. 2019 Jun;80(Suppl 3):S316-S317. doi: 10.1055/s-0038-1675151. Epub 2018 Nov 30. PMID: 31143610; PMCID: PMC6534682.
Song Z, Chen J, Shen J, Jia Z, Wang Q, Jiang S, Xu X, Shi W. Endoscopy during neurotomy of the nervus intermedius for nervus intermedius neuralgia: a case report. Ann Transl Med. 2021 Jan;9(2):179. doi: 10.21037/atm-20-5951. PMID: 33569481; PMCID: PMC7867896.
George DD, Ridder TS. Geniculate neuralgia in an adolescent treated via sectioning of the nervus intermedius and microvascular decompression. J Neurosurg Pediatr. 2020 May 8:1-4. doi: 10.3171/2020.3.PEDS19584. Epub ahead of print. PMID: 32384271.
Saers SJ, Han KS, de Ru JA. Microvascular decompression may be an effective treatment for nervus intermedius neuralgia. J Laryngol Otol. 2011 May;125(5):520-2. doi: 10.1017/S0022215110002677. Epub 2011 Jan 12. PMID: 21223630.
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