Category: Cranial nerves

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Fully Endoscopic Microvascular Decompression for Hemifacial Spasm Using 2-Dimensional/3-Dimensional Endoscopy

Operative Neurosurgery 30:870–879, 2026

This clinical case series reports outcomes of 204 patients who underwent fully endoscopic microvascular decompression (MVD) for hemifacial spasm (HFS), comparing 2D and preliminary 3D endoscopic techniques and analyzing learning-curve effects. Detailed methods, operative technique, intraoperative monitoring (LSR), and complication rates are presented alongside imaging and intraoperative findings.

Results show a 97.1% overall effectiveness with low long-term complication rates and improving outcomes over time; the 3D endoscope afforded improved stereoscopic perception though with higher cost and minor drawbacks, and the authors recommend further study of 3D endoscopy in MVD.

Study scope Retrospective analysis of 204 hemifacial spasm patients treated with fully endoscopic microvascular decompression using 2D (191) or 3D (13) endoscopy (July 2017–Oct 2024); mean follow-up 20.4 months.

Surgical approach Procedures used a retrosigmoid infrafloccular route with LSR monitoring; polytetrafluoroethylene (Teflon) pledgets placed between facial nerve REZ and offending vessels, with further exploration if LSR persisted.

Effectiveness At last follow-up, 198/204 (97.1%) had cessation or significant reduction of spasms (excellent 86.8%, good 10.3%).

Complications Immediate postoperative complications included facial weakness (7), hearing loss (11), tinnitus (1), infection (1), dysphagia (1), and CSF leak (1); 10 patients had persistent complications at last follow-up (6 hearing loss, 3 facial weakness, 1 tinnitus).

Learning curve Outcomes improved over time: effectiveness 95.6% → 97.1% → 98.5% (early/middle/late), while complication rates decreased 5.9% → 5.9% → 2.9%.

Offending vessels Most common offending vessel was AICA (43.1%), with multiple vessels in 33.3% of cases (including combinations with VA and PICA).

3D endoscopy pros/cons 3D endoscope provided subjectively better stereoscopic vision/depth perception aiding surgery, but had drawbacks including slight vertigo and high cost.

Overall conclusion Fully endoscopic MVD offers wide visualization of the neurovascular conflict region and helps minimize brain injury from retraction; favorable outcomes and low complications once technical proficiency is achieved, with more research needed on 3D’s role.

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Defining the target for hemifacial spasm –regarding microvascular decompression

Acta Neurochirurgica (2026) 168:103

This paper argues that the physiologic target for microvascular decompression (MVD) in hemifacial spasm (HFS) is the full extent of the centrally myelinated facial root exit zone (fREZ), from the pontomedullary sulcus (root exit point) to the transitional zone, rather than the shorter REZ segment often emphasized. The authors critique recent anatomical definitions and highlight histological and intraoperative evidence supporting a longer susceptible CMP.

The manuscript details four fREZ segments (RExP, attached segment, root detachment point, TZ), presents frequency data of culprit compressions concentrated on the attached segment, and stresses diagnostic-imaging and surgical implications. Adopting the expanded fREZ map and subfloccular approach is presented as essential to reduce failed MVDs for HFS.

Target definition problem: Equating the cranial nerve REZ with just the short segment between the brainstem surface and the TZ does not accurately represent the physiologically vulnerable central myelin portion (CMP) of the facial nerve in hemifacial spasm surgery.

Facial CMP length: The facial nerve’s exposed centrally myelinated fibers extend proximally along the pontine surface and are considerably longer (about ~1 cm) than the commonly measured brainstem-to-TZ segment.

Expanded fREZ anatomy: A practical surgical definition divides the facial root exit zone (fREZ) into four parts—RExP (root exit point at the pontomedullary sulcus), AS (attached segment adherent to the pons), RDP (root detachment point), and distal TZ (2–3 mm beyond RDP).

Physiologic susceptibility zone: The vulnerable target for MVD in HFS is the entire exposed centrally myelinated facial segment from the pontomedullary sulcus (RExP) to the TZ, not only the short “REZ” segment near the brainstem edge.

Compression distribution: Culprit neurovascular compression in HFS occurs most often along the AS (~80%), less at RExP (~10%) and RDP–TZ (~10%), and only rarely on the distal cisternal portion (typically with severe distortion).

Imaging implication: Diagnostic imaging interpretation for HFS should assess the most proximal fREZ (RExP and AS) rather than focusing only distal to the RDP.

Surgical failure mechanism: Failed MVD can result when decompression is directed at more distal facial nerve portions, missing persistent compression at the true proximal anatomical target.

Approach to access target: A subfloccular approach helps reach the proximal fREZ by tracking glossopharyngeal fibers to the brainstem, supporting effective decompression of the susceptible proximal segment.

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Simple Microvascular Decompression for Hemifacial Spasm Caused by Dolichoectatic Vertebral Artery

Operative Neurosurgery 30:606–609, 2026

This operative case report describes a straightforward microvascular decompression (MVD) technique for hemifacial spasm (HFS) caused by a dolichoectatic vertebral artery (VA), emphasizing translocation and padding of the root entry zone (REZ) with Teflon pledgets. The 67-year-old patient underwent retrosigmoid craniotomy with safe mobilization of the VA, achieving immediate and sustained symptom resolution despite residual distal contact.

The authors compare REZ-focused decompression to more complex options such as sling transposition and binder-ring bypass, arguing that limited REZ decompression offers a simpler, lower-risk solution when complete arterial mobilization is unfeasible. Operative nuances, monitoring, outcomes, and literature context are provided to support this effective, pragmatic approach.

Condition Hemifacial spasm can be caused by neurovascular compression of the facial nerve at the root entry zone (REZ), and a tortuous/dolichoectatic vertebral artery (VA) is a rare culprit that makes complete decompression challenging.

Standard MVD outcomes Typical microvascular decompression for HFS (usually targeting AICA/PICA) provides >90% symptomatic relief at 1-year follow-up with notable complications including hearing loss (2.3%) and facial palsy (0.9%).

Limitations of sling transposition Macrovascular decompression with a Teflon/Gore-Tex sling can be effective but may be infeasible when anchoring is poor or when artery manipulation risks kinking/disrupted blood flow or distal nerve stretching.

Higher-complexity alternative The “binder ring” approach (VA transection, relocation, and reanastomosis) is described but is lengthy, requires temporary occlusion, and carries elevated risk (e.g., brainstem/cerebellar infarct).

Case presentation A 67-year-old woman with debilitating left HFS had a large tortuous VA abutting the facial nerve REZ; after retrosigmoid craniotomy, mobilization relieved REZ compression but residual distal cisternal contact persisted.

Key technique Simple REZ-focused decompression was achieved by mobilizing the VA as safely feasible and placing Teflon pledgets to pad the vessel away from the REZ; complete distal nerve decompression was not feasible and further manipulation was avoided due to risk to perforators/7th–8th nerve complex.

Outcome Despite residual cisternal segment contact, symptoms resolved immediately post-op and remained absent at 12-month follow-up after REZ decompression alone.

Core conclusion Targeting decompression of the REZ alone can be a simple, effective strategy for HFS due to dolichoectatic VA, potentially avoiding more complex and riskier techniques when full nerve-complex decompression is not achievable.

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How I do it: microvascular decompression for vago-glossopharyngeal neuralgia

Acta Neurochirurgica (2026) 168:62

This surgical how-to describes microvascular decompression (MVD) for vago‑glossopharyngeal neuralgia, detailing patient selection, imaging requirements, anesthesia, positioning, and a retrosigmoid infrafloccular approach to expose the IX–X root entry zones. It emphasizes preoperative high-resolution MRI identification of neurovascular conflict—most often PICA or vertebrobasilar compression—and perioperative neurophysiological monitoring.

The technique section outlines stepwise microsurgical maneuvers: arachnoid dissection, vessel mobilization or transposition, cautious Teflon interposition when needed, hemostasis, watertight closure, and targeted postoperative surveillance for dysphagia, hoarseness, CSF leak, and other complications. Practical tips for avoiding complications and key informed‑consent elements are provided.

Vago-Glossopharyngeal Neuralgia (VGN): Rare craniofacial pain syndrome (<1% of facial pain cases), often caused by neurovascular conflict involving the posterior inferior cerebellar artery (PICA) and sometimes the vertebrobasilar artery.

Clinical Features: Characterized by paroxysmal, lancinating pain in the oropharynx, tonsillar fossa, base of tongue, or deep ear canal, typically triggered by swallowing, talking, or coughing.

Diagnosis: High-resolution MRI (T2-weighted CISS/FIESTA/DRIVE, 3D TOF angiography) is mandatory to demonstrate neurovascular conflict and guide surgical planning.

First-line Surgical Treatment: Microvascular decompression (MVD) is the most effective and durable option for drug-refractory VGN, aiming to relieve neurovascular conflict without damaging nerve rootlets.

Surgical Approach: Keyhole retrosigmoid craniectomy with infrafloccular approach exposes the root entry zone of cranial nerves IX and X; careful arachnoid dissection and vessel mobilization or Teflon interposition are performed.

Intraoperative Considerations: Intraoperative neuromonitoring of lower cranial nerves is recommended to minimize risk of postoperative deficits such as dysphagia or hoarseness.

Complications: Main risks include transient dysphagia, hoarseness, or lower cranial nerve palsies, which are usually temporary and resolve within three months.

Outcomes: MVD offers superior and lasting pain relief with functional preservation compared to ablative procedures, making it the preferred surgical option.

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Long-term outcomes after microvascular decompression for glossopharyngeal neuralgia

Neurosurg Focus 59(3):E19, 2025

Microvascular decompression (MVD) without neurectomy is effective and safe for glossopharyngeal neuralgia (GPN), with 86% long-term pain freedom and minimal complications. Pain location or radiation did not affect outcomes. Redo MVD is effective for persistent neurovascular compression. High-resolution MRI is useful for preoperative assessment.

• Microvascular decompression (MVD) without neurectomy is effective for glossopharyngeal neuralgia (GPN), including redo procedures.

• In a cohort of 29 patients, 86% were pain free at long-term follow-up (mean 65.3 months); 83% were immediately pain free post-op.

• Complication rates were low: 10% immediate and 11% long-term, with mostly mild symptoms.

• Redo MVD was successful in 3 out of 4 patients with persistent neurovascular compression after prior procedures.

• Pain location or direction of radiation did not affect pain outcomes after MVD.

• Most patients had neurovascular compression (NVC) visible on preoperative MRI, commonly involving the posterior inferior cerebellar artery (PICA).

• MVD is effective even in elderly patients and those with failed prior treatments, provided NVC is present.

• Findings support MVD as a primary treatment for classical GPN, guiding patient selection and management.

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Trigeminal neuralgia or hemifacial spasm due to vertebrobasilar dolichoectasia

Neurosurg Focus 59(3):E6, 2025

Microvascular decompression (MVD) is the most effective treatment for trigeminal neuralgia and hemifacial spasm caused by vertebrobasilar dolichoectasia, offering higher symptom resolution and lower recurrence than radiosurgery or medication. Endoscope-assisted MVD reduces complications. Interposition and transposition surgical techniques show similar efficacy and recurrence rates.

• Vertebrobasilar dolichoectasia (VBD) is a rare vascular disorder that can compress cranial nerves, most commonly causing trigeminal neuralgia (TN) and hemifacial spasm (HFS).

• Microvascular decompression (MVD) is the most effective treatment, achieving symptom resolution in 87.3% of cases and having the lowest recurrence rate (6.5%) compared to radiosurgery and medication.

• Radiosurgery offers symptom relief in 63.7% of patients but has a high recurrence rate (47.2%) and is mainly used when surgery is contraindicated.

• Endoscope-assisted MVD significantly reduces complication rates (5.3% vs 23.8% with microscope) but does not improve symptom resolution compared to microscope-assisted surgery.

• Interposition and transposition techniques for nerve decompression show similar efficacy and recurrence rates, with no significant differences in complications.

• Nonsurgical treatments (medication, botulinum toxin, etc.) rarely result in full symptom resolution and are generally insufficient as standalone therapies.

• Multiple vessels (AICA, PICA, SCA) can be involved in nerve compression in VBD, affecting surgical planning and outcomes.

• Most patients experience long delays (mean 4–4.5 years) before diagnosis, and VBD-related cranial neuropathies remain challenging to manage due to anatomical complexity and limited high-quality evidence.

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Evaluation of 2 Surgical Techniques—Transposition Versus Interposition Microvascular Decompression for Hemifacial Spasm: A Systematic Review of 19 437 Patients

Neurosurgery 97:16–27, 2025

This systematic review of 19,437 patients compares transposition and interposition microvascular decompression techniques for hemifacial spasm. Both methods show similar efficacy and safety, with no conclusive evidence favoring one. Slightly higher facial nerve weakness was noted with transposition. Prospective trials are needed for definitive comparison.

Hemifacial spasm (HFS) is a rare disorder caused by compression of the facial nerve, leading to involuntary facial muscle contractions.

• Microvascular decompression (MVD) is an effective surgical treatment for HFS, with two main techniques: interposition (placing a prosthesis between nerve and vessel) and transposition (moving the vessel away without direct prosthesis contact).

• A systematic review of 62 studies (19,437 patients) compared outcomes of interposition (18,627 cases) and transposition (810 cases) in MVD for HFS.

• Spasm freedom rates were similar: 90.4% for transposition and 89.6% for interposition.

• Complication rates were similar, though temporary facial nerve weakness/palsy was higher with transposition (9.52% vs 6.03%).

• No conclusive evidence was found that one technique is superior in safety or efficacy; interposition may be preferred in certain clinical situations.

• A prospective trial is needed to determine true differences and optimal indications for each technique.

• The review highlights the need for future studies to stratify outcomes by technique and report prognostic factors.

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Microvascular Decompression Using the Gelatin Sponge Insertion Technique for Trigeminal Neuralgia

Operative Neurosurgery 28:52–58, 2025

Microvascular decompression (MVD) is the primary surgical intervention for trigeminal neuralgia (TN), with Teflon being the most conventional decompressing material. However, Teflon has been associated with adhesion and granulomas after MVD, which closely correlated with the recurrence of TN. Therefore, we developed a new technique to prevent direct contact between Teflon and nerve. The purpose of this study is to compare the efficacy of MVD using the gelatin sponge (GS) insertion technique with that of Teflon inserted alone in treating primary TN.

METHODS: We retrospectively analyzed the medical records and the follow-up data of 734 patients with unilateral primary TN who underwent MVD at our center from January 2014 to December 2019. After exclusions, we identified 313 cases of GS-inserted MVD and 347 cases of traditional MVD. The follow-up exceeded 3 years.

RESULTS: The operating time of the GS-inserted group was longer than that of the Teflon group (109.38 ± 14.77 vs 103.53 ± 16.02 minutes, P < .001). There was no difference between 2 groups in immediate surgical outcomes and postoperative complications. The yearly recurrence rate for GS-inserted MVD was lower at first (1.0%), second (1.2%), and third (1.2%) years after surgery, compared with its counterpart of Teflon group (3.7%, 2.9%, and 1.7% respectively). The first-year recurrence rate (P = .031) and total recurrence rate in 3 years (P = .013) was significantly lower in the GS-inserted group than Teflon group. Kaplan–Meier survival analysis demonstrated better outcomes in GS-inserted Microdescompresión vascular groups (P = .020).

CONCLUSION: The application of the GS insertion technique in MVD reduced first-year postoperative recurrence of TN, with similar complications rates compared with traditional MVD.

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Visualization of the nervus intermedius during microvascular decompression in hemifacial spasm: anatomical study

J Neurosurg 141:1049–1055, 2024

The surgical anatomy of the nervus intermedius (NI) is highly variable. The aim of this study was to describe the anatomy of the NI during endoscope-assisted microvascular decompression (MVD) in hemifacial spasm (HFS), and the involvement of the nerve in the vascular conflict.

METHODS The authors reviewed a prospectively maintained database for MVDs performed between 2002 and 2022 and extracted clinical data including patient demographics, symptoms, and offending vessel(s). Operative videos and photographs were analyzed retrospectively in an attempt to identify the NI.

RESULTS Endoscopic identification of the NI was possible in 139 of 435 MVDs. The anatomy is very variable. In 79 (56.8%) patients, a single-bundle pattern was detected, whereas a multiple-bundle pattern was identified in 60 (43.2%) patients. Overall the most common pattern was a single-bundle type A (49.7%). In 20.1%, a multiple-bundles type A was identified. In 4.3%, a single-bundle type B was detected. In 2.9% a single-bundle type C was found, and in just 0.7% a multiple-bundles type C was detected. A multiple-origin pattern (type D) was found in 31 patients (22.3%). The NI was frequently involved in the neurovascular conflict (approximately 85%). The type of NI or vascular compression pattern did not affect the results regarding the outcome or recurrence of HFS.

CONCLUSIONS The anatomy of the NI is for the first time evaluated endoscopically in MVD for HFS. The nerve had various anatomical patterns that were clearly identified. Further studies to evaluate the compression patterns in relation to NI neuralgia are warranted.

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Etiology and Management of Recurrent and Persistent Hemifacial Spasm

Neurosurgery 95:418–427, 2024

Despite a 90% success rate, microvascular decompression occasionally fails to resolve hemifacial spasm (HFS), necessitating revision surgery. We investigated recurrent cases to identify underlying causes. METHODS: We evaluated patients at our institution who underwent revision microvascular decompression because of recurrent or persistent HFS, assessing recurrence causes, decompression techniques, complications, and outcomes. Data considered included demographics, preoperative symptoms, disease duration, offending vessel, and magnetic resonance findings. Surgical notes and intraoperative videos were reviewed, and telephone interviews were conducted for recent outcomes.

RESULTS: Out of our ongoing series of 493 patients, 43 patients (8.7%) required revision surgery with a patient cohort of 33 females and 10 males. The average symptom duration was 10 years. The median time between primary and revision surgery was 14 months. Thirteen patients (30.2%) underwent initial surgery elsewhere. Adhesions of Teflon pledgets to the facial nerve were the primary cause of nonresolution in 23 patients (53.5%), while in 13 (30.2%), a missed vascular compression was identified. Sixteen patients (37.2%) had sufficient decompression by removing the conflicting pledgets. During 10 revisions (23.3%), additional Teflon pledgets were necessary. After a median follow-up of 67 months after revision surgery, 27 patients (62.8%) reported complete spasm resolution. Six patients (14.0%) had a good outcome with over 90% reduction of their spasms, 3 patients (7.0%) stated a fair outcome (50% improvement), while 7 patients (16.3%) had no improvement.

CONCLUSION: According to our results, adhesions of Teflon to the facial nerve may cause HFS recurrence. Therefore, whenever possible, Teflon should be placed without nerve contact between the brainstem and the offending vessel. Using a sling or bridge technique seems to be beneficial because it leaves the facial nerve completely free. Persistent symptoms often result from missed offending vessels in the pontomedullary sulcus indicating the benefit of endoscopic inspection of this area with an endoscope.

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Long-term tumor control in Koos grade IV vestibular schwannomas without the need for gross-total resection

J Neurosurg 140:1591–1604, 2024

The modern management of patients with Koos grade IV vestibular schwannomas (VSs) aims at functional preservation and long-term tumor control. Gross-total resection (GTR) leads to optimal tumor control but frequently also results in permanent facial nerve (FN) palsy. Subtotal resection (STR) or near-total resection (NTR) followed by a waitand-scan protocol and second-line radiation therapy (RT) in case of progressive residuals yields excellent tumor control rates with less permanent morbidity.

METHODS The authors present the results of their prospective cohort of Koos grade IV VS patients who underwent less-than-total resection followed by a wait-and-scan protocol between January 2009 and December 2019 and discuss the latest evidence on this controversial subject. The cohort was followed up with annual clinical and volumetric outcome analyses after standardized MRI.

RESULTS Forty-eight patients were included in the analysis. The mean extent of resection was 87% (median 91%, range 45%–100%), best fitting into the definition of STR rather than NTR. In 2 cases, the proximal portion of the FN at the brainstem could not be reliably identified and monitored during the initial operation, and a second-stage resection was necessary. At 4.4 years after surgery, 81% (39/48) of the tumor residuals regressed or were stable in size. The percentage of regressive tumor residuals increased over time. Nineteen percent (9/48) of the tumor residuals displayed volumetric progression within a mean time of 35 months (median 36 months, range 14–72 months), resulting in a Kaplan-Meier estimate for progression-free survival of 79% after 4 years; higher postoperative volume showed a linear correlation with higher volumetric progression (factor 1.96, 95% CI 1.67–2.30; p < 0.001). Thirty-four of the 48 (71%) patients continue to undergo a wait-and-scan protocol. Second-line RT was performed in 14 patients (29%) within a mean time of 25 months (median 23 months, range 5–54 months), 12 (86%) of whom responded with post-RT pseudoprogression, resulting in an overall tumor control rate of 96%. At the 4.4-year follow-up from the initial resection, 92% of the patients had a good facial outcome (House-Brackmann [HB] grade I or II), 6% had a fair facial outcome (HB grade III), and 2% had a poor facial outcome (HB grades IV–VI). So far, there has been no need for salvage surgery after RT.

CONCLUSIONS STR followed by observation and second-line RT in cases of progression leads to good facial outcome and an excellent tumor control rate in the longer term.

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Subclassification of Koos grade 4 vestibular schwannoma: insights into tumor morphology for predicting postoperative facial nerve function

J Neurosurg 140:127–137, 2024

OBJECTIVE Koos grade 4 vestibular schwannoma (KG4VS) is a large tumor that causes brainstem displacement and is generally considered a candidate for surgery. Few studies have examined the relationship between morphological differences in KG4VS other than tumor size and postoperative facial nerve function. The authors have developed a landmark-based subclassification of KG4VS that provides insights into the morphology of this tumor and can predict the risk of facial nerve injury during microsurgery. The aims of this study were to morphologically verify the validity of this subclassification and to clarify the relationship of the position of the center of the vestibular schwannoma within the cerebellopontine angle (CPA) cistern on preoperative MR images to postoperative facial nerve function in patients who underwent microsurgical resection of a vestibular schwannoma.

METHODS In this paper, the authors classified KG4VSs into two subtypes according to the position of the center of the KG4VS within the CPA cistern relative to the perpendicular bisector of the porus acusticus internus, which was the landmark for the subclassification. KG4VSs with ventral centers to the landmark were classified as type 4V, and those with dorsal centers as type 4D. The clinical impact of this subclassification on short- and long-term postoperative facial nerve function was analyzed.

RESULTS In this study, the authors retrospectively reviewed patients with vestibular schwannoma who were treated surgically via a retrosigmoid approach between January 2010 and March 2020. Of the 107 patients with KG4VS who met the inclusion criteria, 45 (42.1%) were classified as having type 4V (KG4VSs with centers ventral to the perpendicular bisector of the porous acusticus internus) and 62 (57.9%) as having type 4D (those with centers dorsal to the perpendicular bisector). Ventral extension to the perpendicular bisector of the porus acusticus internus was significantly greater in the type 4V group than in the type 4D group (p < 0.001), although there was no significant difference in the maximal ventrodorsal diameter. The rate of preservation of favorable facial nerve function (House-Brackmann grades I and II) was significantly lower in the type 4V group than in the type 4D group in terms of both short-term (46.7% vs 85.5%, p < 0.001) and long-term (82.9% vs 96.7%, p = 0.001) outcomes. Type 4V had a significantly negative impact on short-term (OR 7.67, 95% CI 2.90–20.3; p < 0.001) and long-term (OR 6.05, 95% CI 1.04–35.0; p = 0.045) facial nerve function after surgery when age, tumor size, and presence of a fundal fluid cap were taken into account.

CONCLUSIONS The authors have delineated two different morphological subtypes of KG4VS. This subclassification could predict short- and long-term facial nerve function after microsurgical resection of KG4VS via the retrosigmoid approach. The risk of postoperative facial palsy when attempting total resection is greater for type 4V than for type 4D. This classification into types 4V and 4D could help to predict the risk of facial nerve injury and generate more individualized surgical strategies for KG4VSs with better facial nerve outcomes.

 

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Preemptive strategies and lessons learned from complications encountered with microvascular decompression for hemifacial spasm

J Neurosurg 140:248–259, 2024

OBJECTIVE Microvascular decompression (MVD) is the only curative treatment modality for hemifacial spasm (HFS). Although generally considered to be safe, this surgical procedure is surrounded by many risks and possible complications. The authors present the spectrum of complications that they met in their case series, the possible causes, and the strategies recommended to minimize them.

METHODS The authors reviewed a prospectively maintained database for MVDs performed from 2005 until 2021 and extracted relevant data including patient demographics, offending vessel(s), operative technique, outcome, and different complications. Descriptive statistics with uni- and multivariable analyses for the factors that may influence the seventh, eighth, and lower cranial nerves were performed.

RESULTS Data from 420 patients were obtained. Three hundred seventeen of 344 patients (92.2%) with a minimum follow-up of 12 months had a favorable outcome. The mean follow-up (standard deviation) was 51.3 ± 38.7 months. Immediate complications reached 18.8% (79/420). Complications persisted in only 7.14% of patients (30/420) including persistent hearing deficits (5.95%) and residual facial palsy (0.95%). Temporary complications included CSF leakage (3.10%), lower cranial nerve deficits (3.57%), meningitis (0.71%), and brainstem ischemia (0.24%). One patient died because of herpes encephalitis. Statistical analyses showed that the immediate postoperative disappearance of spasms and male gender are correlated with postoperative facial palsy, whereas combined vessel compressions involving the vertebral artery (VA) and anterior inferior cerebellar artery can predict postoperative hearing deterioration. VA compressions could predict postoperative lower cranial nerve deficits.

CONCLUSIONS MVD is safe and effective for treating HFS with a low rate of permanent morbidity. Proper patient positioning, sharp arachnoid dissection, and endoscopic visualization under facial and auditory neurophysiological monitoring are the key points to minimize the rate of complications in MVD for HFS.

 

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Bilateral Low-Frequency Hearing Impairment After Microvascular Decompression Surgery

Neurosurgery 93:662–669, 2023

Hearing impairment is an important complication of microvascular decompression (MVD). In patients after MVD, we have occasionally noted slight to moderate hearing deterioration at low frequencies that is difficult to detect using pure tone average.

OBJECTIVE: To assess the incidence and features of low-frequency hearing impairment (LF-HI) after MVD and evaluate its associated factors.

METHODS: This single-center, retrospective observational study assessed the audiometric outcome of 270 patients who underwent MVD between January 2015 and December 2020. Preoperative and postoperative hearing levels were compared for each frequency. LF-HI was defined as a hearing deterioration of ≥15 dB at 125, 250, or 500 Hz. The incidence, symptoms, and associated factors of LF-HI were analyzed.

RESULTS: Statistical analysis of the patients overall demonstrated slight but significant decreases in the hearing level after MVD at lower frequencies on both the operative and contralateral sides. Eighty-one patients (30.0%) had LF-HI: 49 on the operative side, 24 on the contralateral side, and 8 on both sides, while pure tone average was worsened in 5 patients (1.8%). Subjective symptoms, including hearing deterioration, ear fullness, tinnitus, and dizziness, developed in 10.4% of the patients with LF-HI but improved subsequently within several weeks. “Older age” and “operative side” were associated with LF-HI.

CONCLUSION: Decreases in lower-frequency hearing levels in both the ipsilateral and contralateral (nonoperative) ears were observed after trigeminal neuralgia and hemifacial spasm surgery. LF-HI does not cause permanent symptoms but may be a noteworthy phenomenon, possibly involved in the contralateral hearing loss encountered occasionally after other types of posterior cranial fossa surgery.

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Ocular Optical Coherence Tomography in the Evaluation of Sellar and Parasellar Masses

Neurosurgery 92:42–67, 2023

Compression of the anterior visual pathways by sellar and parasellar masses can produce irreversible and devastating visual loss.

Optical coherence tomography (OCT) is a noninvasive high-resolution ocular imaging modality routinely used in ophthalmology clinics for qualitative and quantitative analysis of optic nerve and retinal structures, including the retinal ganglion cells.

By demonstrating structural loss of the retinal ganglion cells whose axons form the optic nerve before decussating in the optic chiasm, OCT imaging of the optic nerve and retina provides an excellent tool for detection and monitoring of compressive optic neuropathies and chiasmopathies due to sellar and parasellar masses.

Recent studies have highlighted the role of OCT imaging in the diagnosis, follow-up, and prognostication of the visual outcomes in patients with chiasmal compression. OCT parameters of optic nerve and macular scans such as peripapillary retinal nerve fiber layer thickness and macular ganglion cell thickness are correlated with the degree of visual loss; additionally, OCT can detect clinically significant optic nerve and chiasmal compression before visual field loss is revealed on automated perimetry. Preoperative values of OCT optic nerve and macular parameters represent a prognostic tool for postoperative visual outcome.

This review provides a qualitative analysis of the current applications of OCT imaging of the retina and optic nerve in patients with anterior visual pathway compression from sellar and parasellar masses. We also review the role of new technologies such as OCT-angiography, which could improve the prognostic ability of OCT to predict postoperative visual function.

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Indication for a skull base approach in microvascular decompression for hemifacial spasm

Acta Neurochirurgica (2022) 164:3235–3246

A thorough observation of the root exit zone (REZ) and secure transposition of the offending arteries is crucial for a successful microvascular decompression (MVD) for hemifacial spasm (HFS). Decompression procedures are not always feasible in a narrow operative field through a retrosigmoid approach. In such instances, extending the craniectomy laterally is useful in accomplishing the procedure safely. This study aims to introduce the benefits of a skull base approach in MVD for HFS.

Methods The skull base approach was performed in twenty-eight patients among 335 consecutive MVDs for HFS. The site of the neurovascular compression (NVC), the size of the flocculus, and the location of the sigmoid sinus are measured factors in the imaging studies. The indication for a skull base approach is evaluated and verified retrospectively in comparison with the conventional retrosigmoid approach. Operative outcomes and long-term results were analyzed retrospectively.

Results The extended retrosigmoid approach was used for 27 patients and the retrolabyrinthine presigmoid approach was used in one patient. The measurement value including the site of NVC, the size of the flocculus, and the location of the sigmoid sinus represents well the indication of the skull base approach, which is significantly different from the conventional retrosigmoid approach. The skull base approach is useful for patients with medially located NVC, a large flocculus, or repeat MVD cases. The long-term result demonstrated favorable outcomes in patients with the skull base approach applied. Conclusions Preoperative evaluation for lateral expansion of the craniectomy contributes to a safe and secure MVD.

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Prognostic factors for long-term outcomes of microvascular decompression in the treatment of glossopharyngeal neuralgia: a retrospective analysis of 97 patients

J Neurosurg 137:820–827, 2022

The authors aimed to investigate predictors of postoperative outcomes of microvascular decompression (MVD) for the treatment of glossopharyngeal neuralgia (GPN).

METHODS A cohort of 97 patients with medically refractory GPN who underwent MVD at the authors’ institution between January 2010 and July 2019 was retrospectively reviewed. Univariate and multivariate regression models were used to identify predictors of long-term outcome in patients after MVD.

RESULTS Eighty-nine patients (91.8%) reported immediate and complete relief of pain after the procedure. Of the remaining 8 patients (8.2%), 6 achieved partial pain relief and pain gradually diminished within 2 weeks after surgery, and 2 did not experience postoperative pain relief. In univariate Cox regression analysis, venous compression of the glossopharyngeal nerve root entry zone (HR 3.591, 95% CI 1.660–7.767, p = 0.001) and lower degree of neurovascular conflict (HR 2.449, 95% CI 1.177–5.096, p = 0.017) were significantly associated with worse pain-free survival. In multivariate Cox regression analysis, venous compression (HR 8.192, 95% CI 2.960–22.669, p < 0.001) and lower degree of neurovascular conflict (HR 5.450, 95% CI 2.069–14.356, p = 0.001) remained independently associated with worse pain-free survival.

CONCLUSIONS Venous compression of the glossopharyngeal nerve root entry zone and lower degree of neurovascular conflict were significantly correlated with shorter pain-free survival in patients who underwent MVD for GPN. Microvascular decompression is a safe, feasible, and durable approach with a low complication rate for the treatment of GPN.

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Surgical management of cerebellopontine angle epidermoid cysts: an institutional experience of 10 years

BRITISH JOURNAL OF NEUROSURGERY 2022, VOL. 36, NO. 2, 203–212

Cerebellopontine angle (CPA) epidermoids, although of benign nature, are of considerable neurosurgical interest because of their close proximity and adherence to the cranial nerves and brain stem. In this paper, we describe our experience and attempt to correlate the final outcomes with the extent of surgical removal. The main objectives were to study various modes of surgical management of CPA epidermoids with regard to removal and preservation of the cranial nerves and also to evaluate the role of endoscopic assisted microsurgical excision thereby minimizing recurrences. This case series is one of the largest series reported so far worldwide.

Materials and methods: From 2006 to 2016, 139 patients with CPA epidermoids were operated at Grant Medical College and J. J. Hospital, Mumbai. All patients underwent detailed magnetic resonance imaging (MRI) of brain. Lesions were classified according Rogelio Revuelta-Gutierrez et al. with respect to their anatomic extent: grade I- within the boundaries of the CPA, grade II- extension to the suprasellar and perimesencephalic cisterns, and grade III-parasellar and temporomesial region involvement. Retrosigmoidal and subtemporal approaches were taken to excise the lesions. Endoscopic assisted microsurgical excision was done in cases with extensions beyond the CPA. Patient follow-up was based on outpatient repeated brain MRI studies.

Results: The mean duration of symptoms before surgery was 42 months (range, 2 months to 6 years). The mean follow-up period was 27 months (range, 2–60 months). The main presenting symptom was headache in 69% (96/139) of the cases and trigeminal neuralgia in 30% cases was the second most common cause of consultation. Seventy-five percent of patients had some degree of cranial nerve (CN) involvement. Retrosigmoid approach was taken in 92% patients and 7 patients with supratentorial extension were operated by combined retrosigmoidal and subtemporal approach. Endoscopic assisted microsurgical excision was done in 40% cases. Use of angled views by an endoscope helped to excise residual tumor in 47 (83%) patients. Complete excision was achieved in 67% of cases. In 33% patients, small capsular remnants could not be removed completely because of their adherence to vessels, brainstem and cranial nerves. Compared with their preoperative clinical status, 74% improved and 20% had persistent cranial nerve deficits in the first year of follow up.

Conclusions: Epidermoid cysts are challenging entities in current neurosurgery practice due to tumor adhesions to neurovascular structures. Meticulous surgical technique with the aid of neurophysiological monitoring is crucial to achieve safe and effective total or subtotal removal of these lesions. A conservative approach is indicated for patients in whom the fragments of capsule is adhered closely to blood vessels, nerves, or the brainstem, in order to avoid risk of serious neurological deficits related to an inadvertent damage of these structures. Use of angled views by endoscope at the conclusion of the surgery may assure the surgeon of total removal of the tumor.

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Resection of supplementary motor area gliomas: revisiting supplementary motor syndrome and the role of the frontal aslant tract

J Neurosurg 136:1278–1284, 2022

The supplementary motor area (SMA) is an eloquent region that is frequently a site for glioma, or the region is included in the resection trajectory to deeper lesions. Although the clinical relevance of SMA syndrome has been well described, it is still difficult to predict who will become symptomatic. The object of this study was to define which patients with SMA gliomas would go on to develop a postoperative SMA syndrome.

METHODS The University of California, San Francisco, tumor registry was searched for patients who, between 2010 and 2019, had undergone resection for newly diagnosed supratentorial diffuse glioma (WHO grades II–IV) performed by the senior author and who had at least 3 months of follow-up. Pre- and postoperative MRI studies were reviewed to confirm the tumor was located in the SMA region, and the extent of SMA resection was determined by volumetric assessment. Patient, tumor, and outcome data were collected retrospectively from documents available in the electronic medical record. Tumors were registered to a standard brain atlas to create a frequency heatmap of tumor volumes and resection cavities.

RESULTS During the study period, 56 patients (64.3% male, 35.7% female) underwent resection of a newly diagnosed glioma in the SMA region. Postoperatively, 60.7% developed an SMA syndrome. Although the volume of tumor within the SMA region did not correlate with the development of SMA syndrome, patients with the syndrome had larger resection cavities in the SMA region (25.4% vs 14.2% SMA resection, p = 0.039). The size of the resection cavity in the SMA region did not correlate with the severity of the SMA syndrome. Patients who developed the syndrome had cavities that were located more posteriorly in the SMA region and in the cingulate gyrus. When the frontal aslant tract (FAT) was preserved, 50% of patients developed the SMA syndrome postoperatively, whereas 100% of the patients with disruption of the FAT during surgery developed the SMA syndrome (p = 0.06). Patients with SMA syndrome had longer lengths of stay (5.6 vs 4.1 days, p = 0.027) and were more likely to be discharged to a rehabilitation facility (41.9% vs 0%, p < 0.001). There was no difference in overall survival for newly diagnosed glioblastoma patients with SMA syndrome compared to those without SMA syndrome (1.6 vs 3.0 years, p = 0.33).

CONCLUSIONS For patients with SMA glioma, more extensive resections and resections involving the posterior SMA region and posterior cingulate gyrus increased the likelihood of a postoperative SMA syndrome. Although SMA syndrome occurred in all cases in which the FAT was resected, FAT preservation does not reliably avoid SMA syndrome postoperatively.

 

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Neurosurgical Causes of Pulsatile Tinnitus

Neurosurgery 90:161–169, 2022

Traditionally in the domain of the otolaryngologist, pulsatile tinnitus (PT) has become increasingly relevant to neurosurgeons.

PT may prove to be a harbinger of life-threatening pathology; however, often, it is a marker of a more benign process.

Irrespectively, the neurosurgeon should be familiar with the many potential etiologies of this unique and challenging patient population.

In this review, we discuss the myriad causes of PT, categorized by pulse-phase rhythmicity.

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