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Background  The superior petrosal vein (SPV) often obscures the surgical field or bleeds during microvascular decompression (MVD) for the treatment of trigeminal neuralgia. Although SPV sacrifice has been proposed, it is associated with multiple complications. We have performed more than 4,500 MVDs, including approximately 400 cases involving trigeminal neuralgia. We aimed to describe our operative technique and nuances to avoid SPV injury. Methods  We have provided a detailed description of our institutional protocol, including the anesthesia technique, neurophysiologic monitoring, patient positioning, surgical approach, and SPV management. The surgical outcomes and treatment-related complications were retrospectively analyzed. Results  No SPVs were sacrificed intentionally or accidentally during our MVD protocol for trigeminal neuralgia. In the 344 operations performed during 2006 to 2020, 269 (78.2%) patients did not require medication postoperatively, 58 (16.9%) tolerated the procedure with adequate medication, and 17 (4.9%) did not respond to MVD. Postoperatively, 35 (10.2%), 1 (0.3%), and 0 patients showed permanent trigeminal, facial, or vestibulocochlear nerve dysfunction, respectively. Wound infection occurred in five (1.5%) patients, while cerebrospinal fluid leaks occurred in three (0.9%) patients. Hemorrhagic complications appeared in four (1.2%) patients but these were unrelated to SPV injury. No surgery-related mortalities were reported. Conclusion  MVD for the treatment of trigeminal neuralgia can be achieved safely without sacrificing the SPV. A key step is positioning the patient's vertex at a 10-degree elevation from the floor, which can ease venous return and loosen the SPV, making it less fragile to manipulation and providing a wider surgical corridor. [ABSTRACT FROM AUTHOR]

Introduction: Patients with hemifacial spasm (HFS) experience improvement in symptoms after microvascular decompression (MVD); however, patient satisfaction is sometimes low. This study aimed to analyze the relationship between residual spasms and patient satisfaction, identify factors affecting satisfaction, and investigate the degree of improvement in spasms which result in patient satisfaction after surgery. Methods: 297 patients who completed a questionnaire after MVD for HFS between March 2020 and June 2020 were included. Information on surgical outcomes and patient satisfaction was collected using the questionnaire, and their relationships were analyzed. Results: Among the 297 patients, the mean residual spasm percentage and patient satisfaction score were negatively correlated with 14.0% and 8.8 points, respectively. In addition to residual spasms, discomfort caused by persistent spasms, psychological problem-solving, better social life, and interpersonal relationship improvement were associated with satisfaction. There was no significant association between the presence of complications and satisfaction. There was no significant difference in the satisfaction score at up to 30% residual spasm, and the patients with 0–30% residual spasm had a satisfaction score of 7 points or higher. Conclusion: Residual spasms and discomfort from residual spasms decreased patient satisfaction after MVD for HFS. It is then necessary to perform accurate surgical resolution to improve surgical outcomes and provide adequate management to reduce postoperative discomfort and anxiety, and ultimately to enhance satisfaction. Residual spasms of up to 30% compared with the preoperative severity can be considered a good outcome when evaluating surgical outcomes. [ABSTRACT FROM AUTHOR]

Microvascular decompression (MVD) is the most effective treatment for hemifacial spasm (HFS). However, surgical difficulties due to complex anatomy or revision surgery can endanger the functional integrity of the brainstem. We describe surgically challenging cases and provide operative guidance that may be helpful for neurosurgeons who perform MVDs. Of 3028 patients with HFS who underwent MVDs consecutively by a single neurosurgeon, complex or unusual cases associated with surgical difficulty were selected. Medical charts and images were reviewed, with the primary focus being intraoperative findings, operative techniques, and clinical outcomes. All MVDs were performed using the interposition method. Surgically difficult cases were categorized into six types: tandem, perforator, atypical location, encircling, revision, and penetrating types. During the follow-up period (11.5–42.7 months; median 24.9 months), the spasm-free rate was 88.4%. Intraoperative changes in brainstem auditory evoked potentials were observed in 31.5% of patients. Immediate postoperative facial palsy and deafness were observed in 6.0% and 1.5% of patients, respectively. Revision surgery showed the highest surgical morbidity among the unusual HFS types. Detailed illustrations and descriptions of MVD in patients with surgically challenging HFS are provided. Complex or unusual HFS types carry higher surgical risks in MVD. Neurosurgeons performing MVDs need to be prepared to manage complex HFS cases in order to achieve favorable clinical outcomes. [ABSTRACT FROM AUTHOR]

Introduction: Data regarding the association between thyroid dysfunction and hemifacial spasm (HFS) are limited. We conducted a single-center, retrospective study to investigate the predictive value of thyroid dysfunction in patients with HFS after microvascular decompression (MVD). Methods: Between July 2004 and January 2015, 156 patients who were tested for thyroid hormones after MVD for HFS were enrolled in the present study. We assessed their detailed history, clinical manifestations, serum thyroid hormone levels, and surgical outcomes. The patients were classified into low and high groups based on thyroid hormone concentrations, and clinical outcomes were evaluated in each group. Results: In a total of 156 patients with a median follow-up period of 40.9 months, the improvement rate was 87.8%. The patients were classified into low (76, 48.7%) or high (80, 51.3%) groups based on serum thyroxine (T4) levels. There was a difference between the 2 groups in terms of postoperative outcomes following MVD (p = 0.020). There were no differences in the outcomes according to serum tri-iodothyronine (T3) levels as well as other factors associated with the outcomes. Conclusions: We found that decreased serum T4 levels are associated with poor postoperative outcomes among patients with HFS. Further studies are needed to examine the clinical benefit of thyroid hormone replacement therapy for patients with suboptimal T4 concentrations as well as active thyroid hormone screening for patients with HFS. [ABSTRACT FROM AUTHOR]

Vascular complications in posterior fossa surgery, even in microvascular decompression (MVD) involving a small cranial opening, can have catastrophic consequences. We analyzed these complications to determine the incidence, risk factors, prognosis, and preventive measures involved. Between April 1997 and March 2018, 4000 consecutive patients with neurovascular compression syndrome were admitted and underwent MVD. We reviewed the medical records of patients who developed vascular complications after MVD, focusing on their past medical history, perioperative laboratory findings and images, surgical findings, and postoperative progress. Vascular complications developed in 28 patients (0.7%), including 24 with hemifacial spasm and 4 with trigeminal neuralgia. Twenty-two hemorrhagic (78.6%) and 6 ischemic (21.4%) complications occurred, with epidural hematoma the most frequent type identified. Ten patients (35.7%) patients were asymptomatic and 18 (64.3%) were symptomatic. Six patients (21.4%) underwent revision surgery, such as hematoma removal, craniectomy, or extraventricular drainage insertion. At the last follow-up, dizziness was the most commonly reported sequela from vascular complications. No deaths had occurred. Vascular complications are rare, but can be the most devastating adverse outcome of MVD surgery. Unusual signs and symptoms after MVD should prompt special attention to early management and patient safety. [ABSTRACT FROM AUTHOR]

To identify causes of recurrent hemifacial spasm (HFS) after initial microvascular decompression (MVD) and to assess the feasibility of redo MVD. The study included 21 patients who underwent redo MVD over the last 2 decades. Their medical charts were retrospectively reviewed for preoperative medical history, previous and redo MVD intraoperative findings, and previous and redo MVD postoperative outcomes. Redo MVDs were the second operation in 20 patients and the third operation in 1 patient. The median interval between previous and redo MVD was 46.3 months (range, 14.4–188.2 months). Compression of offending vessels such as a vein or perforating artery located medial to or at the cisternal segment of the facial nerve was found to be a possible cause of previous MVD failure. MVD failure resulted from neglect of offending vessels in 10 patients, insufficient decompression in 7 patients, and untouched neurovascular compression sites in 4 patients. Spasm-free rates after redo MVD were 80.5% at 1 year and 90.5% in the last year of follow-up (median, 15.8 months; range, 3.6–152.0 months). Permanent hearing loss and facial palsy were each observed in 2 patients (9.5%). In addition, 1 patient each experienced cerebellar infarction and vocal cord palsy. Redo MVD remains a feasible treatment option for patients with HFS who failed to benefit from previous MVD, but it is associated with an increased risk of cranial nerve and vascular injuries. [ABSTRACT FROM AUTHOR]

Objective To examine a new abnormal muscle response (AMR) monitoring method during microvascular decompression (MVD) for hemifacial spasm. Methods 486 patients with hemifacial spasm were monitored for an AMR during MVD with a new method involving preoperative mapping and intraoperative centrifugal stimulation of the facial nerve. For the last 62 patients, we performed the AMR monitoring using both, the new and conventional methods simultaneously. Results Preoperative facial nerve mapping showed that the maximal AMR was detected most frequently (66.9%) at the “F” location (the direction towards the frontalis muscle). An intraoperative AMR was observed in 86.2% of the patients, which disappeared after MVD in 96.4% of the patients. A comparison of the new and conventional methods respectively showed that AMR disappearance after MVD was observed in 98.2% and 61.8% of the patients, no AMR in 0% and 9.1%, and persistent AMR after MVD in 1.8% and 29.1%. Conclusions The new AMR monitoring method demonstrated greater AMR monitoring efficacy and supports the finding that disappearance of an AMR is a good indicator of effective decompression during MVD surgery. Significance Preoperative mapping and intraoperative centrifugal stimulation of the facial nerve during MVD surgery in HFS patients showed greater efficacy of AMR monitoring. [ABSTRACT FROM AUTHOR]

The purpose of this study was to analyze the pathogenesis of delayed epidural hematoma (EDH) after posterior fossa surgery. Non-traumatic, non-arterial origin delayed EDH after posterior fossa surgery is extremely rare. Moreover, the pathogenesis of its supratentorial extension is obscure. Between April 1997 and June 2016, over 3300 patients underwent microvascular decompression (MVD) for neurovascular compression syndrome. The medical chart of four patients with delayed EDH were retrospectively reviewed. The median time from MVD to re-CT scan was 58 h (range, 33–100). All patients underwent hematoma evacuations. Intraoperative findings during hematoma evacuation revealed only an oozing hemorrhage from the transverse sinus with no definitive bleeding focus. The patients spent a median of 21.5 days (range, 11–39) at the hospital. At the last follow-up, all patients had fully recovered without significant neurological deficits and exhibited complete relief or minimal symptoms from hemifacial spasm (HFS). Postoperative uncontrolled bleeding from the dural venous sinus can sometimes cause an insidious-onset or delayed posterior fossa EDH. [ABSTRACT FROM AUTHOR]

Although non-traumatic postoperative delayed epidural hematoma (EDH) after posterior fossa surgery is rare, measures to prevent it need to be pursued due to its catastrophic results. In this report, we describe a surgical strategy to prevent delayed EDH after posterior fossa surgery. Key dural tacking sutures were performed at the medial and cephalic margin of the dura. We have performed key dural tacking sutures on 454 patients with neurovascular compression syndrome during microvascular decompression surgeries since April 2016, and no hemorrhagic complication, including delayed EDH, occurred. We discovered that key dural tacking sutures can be helpful in preventing postoperative posterior fossa delayed EDH. [ABSTRACT FROM AUTHOR]

The postoperative course of hemifacial spasm (HFS) varies. We analyzed the clinical outcomes from 1 to ≥5 years after microvascular decompression (MVD) in patients with HFS. Between July 2004 and January 2015, 528 patients who were followed up for ≥5 years after MVD for HFS were included. We evaluated chronological patterns of clinical outcomes from 1 to ≥5 years. The outcomes at 2, 3, 4, and ≥5 years postoperatively were individually compared with those at 1 year postoperatively, and the relationships between clinical features, surgical findings, and outcomes over time were analyzed. Eight groups were created according to the similarity in the pattern of clinical outcomes from 1 to ≥5 years postoperatively. Individual postoperative outcomes at 2–4 years were consistent with those at 1 year postoperatively, whereas postoperative outcomes at ≥5 years were not (P = 0.020). There was substantial to moderate agreement between the outcomes at 1 year and at 2–4 years postoperatively, but the agreement decreased over time. Patients without diabetes (P = 0.015), an intraoperative offending vessel without a vein (P = 0.005), and intraoperative discoloration of the facial nerve (P = 0.036) showed better outcomes at ≥5 years postoperatively. Long-term outcomes from 1 to ≥5 years after MVD in patients with HFS were diverse. Nondiabetes, intraoperative offending vessel without a vein, and intraoperative discoloration of the facial nerve were better prognostic factors for outcomes at ≥5 years postoperatively. It is advisable to consider these results when evaluating the long-term outcomes of this surgery. [ABSTRACT FROM AUTHOR]

• Lateral spread response (LSR) findings may differ between different facial muscles. • LSR in the mentalis and orbicularis oris have different clinical implications in current monitoring protocol. • We detail technical points to be considered for interpreting LSR in the orbicularis oris muscle. Interpreting lateral spread response (LSR) during microvascular decompression (MVD) for hemifacial spasm (HFS) is difficult when LSRs observed in different muscles do not match. We aimed to analyze LSR patterns recorded in both the orbicularis oris (oris) and mentalis muscles and their relationships with clinical outcomes. The data of 1288 HFS patients who underwent MVD between 2015 and 2018 were retrospectively reviewed. LSR was recorded in the oris and mentalis muscles through centrifugal stimulation of the temporal branch of the facial nerve after preoperative mapping. The disappearance of LSR following surgery, clinical outcomes, and the characteristics of LSR in oris were analyzed. After surgery, LSR remained in 100 (7.7%) and 279 (21.6%) of the mentalis and oris muscles, respectively. The postoperative outcome correlated with LSR disappearance in the mentalis, not with that in the oris. LSR patterns differed in each muscle and may not be correlated with clinical outcomes. LSR in the mentalis and oris muscles should be interpreted differently. We describe a monitoring protocol characterized by preoperative facial nerve mapping, antidromic stimulation, and recording from multiple muscles. We analyze differences in LSRs in the mentalis and oris muscles and suggest technical points for interpretation. [ABSTRACT FROM AUTHOR]

The progression rate for clinical manifestations in hemifacial spasm (HFS) varies; however, little is known about the factors contributing to this. The purpose of this study was to identify independent factors affecting the rate of symptom progression and to evaluate clinical outcomes according to progression rates. The study enrolled 1335 patients who underwent microvascular decompression for HFS between July 2004 and January 2015. We assessed detailed history, clinical manifestations, and outcomes. Based on the duration and severity of symptoms, patients were classified into rapidly progressive and slowly progressive groups. We identified predisposing factors affecting the differences between the 2 groups and evaluated the clinical outcome in each group. Of 1335 patients with HFS, 825 (61.8%) were classified as rapidly progressive, and 510 (38.2%) were classified as slowly progressive. In univariable and multivariable analyses, younger age at surgery, older age at symptom onset, and absence of intraoperative facial nerve indentation were significant predisposing factors for rapid progression. The rapidly progressive group had worse outcomes than the slowly progressive group following microvascular decompression. In this study, patients with rapidly progressive HFS had worse clinical outcomes. Therefore, patients with rapidly progressive symptoms should be warned in advance that the prognosis may be worse after microvascular decompression. This study is also useful to understand the differences in symptom progression rates in HFS in order to inform patients about symptom progression. [ABSTRACT FROM AUTHOR]

Objective The aim of this study was to define the critical warning sign of real-time brainstem auditory evoked potential (BAEP) for predicting hearing loss (HL) after microvascular decompression (MVD) for hemifacial spasm (HFS). Methods Nine hundred and thirty-two patients with HFS who underwent MVD with intraoperative monitoring (IOM) of BAEP were analyzed. We used a 43.9 Hz/s stimulation rate and 400 averaging trials to obtain BAEP. To evaluate HL, pure-tone audiometry and speech discrimination scoring were performed before and one week after surgery. We analyzed the incidence for postoperative HL according to BAEP changes and calculated the diagnostic accuracy of significant warning criteria. Results Only 11 (1.2%) patients experienced postoperative HL. The group showing permanent loss of wave V showed the largest percentage of postoperative HL ( p  < 0.001). No patient who experienced only latency prolongation (≥1 ms) had postoperative HL. Loss of wave V and latency prolongation (≥1 ms) with amplitude decrement (≥50%) were highly associated with postoperative HL. Conclusions Loss of wave V and latency prolongation of 1 ms with amplitude decrement ≥50% were the critical warning signs of BAEP for predicting postoperative HL. Significance These findings elucidate the critical warning sign of real-time BAEP. [ABSTRACT FROM AUTHOR]

• Cerebellar retraction (CR) is the main cause of postoperative hearing loss (HL) during microvascular decompression. • Two different patterns were observed before significant changes in the brainstem auditory evoked potentials. • Wave III latency prolongation is a significant prewarning sign for postoperative HL. We aimed to define the prewarning sign of brainstem auditory evoked potentials (BAEPs) associated with cerebellar retraction (CR) during microvascular decompression surgery for hemifacial spasm. A total of 241 patients with a latency prolongation of 1 ms or an amplitude decrement of 50% of wave V were analyzed. According to BAEPs before significant changes during CR, patients were classified into Groups A (latency prolongation of wave I [≥0.5 ms] without prolongation of the I–III interpeak interval [<0.5 ms]) and B (no latency prolongation of wave I [<0.5 ms] with prolongation of the I–III interpeak interval [≥0.5 ms]). BAEPs and postoperative hearing loss (HL) were compared between the two groups. Group B comprised 160 (66.4%) patients. With maximal changes in wave V, latency prolongation (≥1 ms) with amplitude decrement (≥50%) was more common in Group B (p < 0.018). At the end of the operation, wave V loss was observed in 11 patients, including 10 patients from Group B. Five patients developed postoperative HL; all were from Group B. Latency prolongation of wave III during CR was associated with serious BAEPs changes and postoperative HL. Latency prolongation of wave III is a significant prewarning sign. [ABSTRACT FROM AUTHOR]

• Wave V loss of brainstem auditory evoked potentials is the critical sign for postoperative hearing loss during microvascular decompression for hemifacial spasm. • Wave V loss with wave I loss is associated with serious postoperative neurologic complications. • Total wave loss could occur more frequently after the decompressive procedure of MVD. We sought to define the significance of wave I loss of brainstem auditory evoked potentials (BAEPs) during microvascular decompression (MVD) surgery for hemifacial spasm. Out of 670 patients, 36 showed wave V loss during MVD surgery. These patients were classified into the following two groups based on wave I loss: Total wave loss, including wave I loss, and wave V loss with persistent wave I. We analyzed the differences in postoperative complications between the groups. We also investigated when wave I loss occurred during MVD surgery. Of the 36 patients, 24 (66.7%) exhibited wave I persistence and 12 (33.3%) exhibited total wave loss. The patients who showed total wave loss were significantly more likely to exhibit postoperative hearing loss (p = 0.009). In addition, these patients exhibited a significantly higher frequency of postoperative complications such as dizziness and tinnitus (p = 0.002 and p = 0.031, respectively). Total wave loss occurred more frequently after the decompressive procedure of MVD surgery. Total wave loss, including wave I loss, was more closely associated with severe postoperative complications. Total wave loss occurred more frequently after the decompressive procedure of MVD surgery. These findings suggest the significance of wave I loss of BAEPs. [ABSTRACT FROM AUTHOR]

Although microvascular decompression (MVD) is the primary treatment for hemifacial spasm (HFS), the postoperative course is variable. This study aimed to develop a prediction model of the outcome of MVD in patients with HFS by investigating influential factors. Electronic medical records of 1624 patients with HFS who underwent MVD from July 2004 to January 2015 were reviewed. The relationships between patient-related, disease-related, and surgery-related factors and postoperative outcome were analyzed using multinomial logistic regression. A predictive model for MVD outcome was developed using decision tree analysis. The mean follow-up duration after surgery was 30.2 months (median, 23.5 months; range, 6.0–133.3 months). For the 1624 patients, the overall improvement rate was 90.5%. Overall, 984 patients (60.6%) showed improvement of spasm immediately after surgery, 486 (29.9%) experienced delayed improvement, and 154 (9.5%) showed persistence of spasm. Outcome of patients with HFS after MVD was predicted by 4 items: postoperative delayed facial palsy, degree of preoperative spasm, intraoperative indentation on the facial nerve, and sex. The patients were classified into 6 categories and improvement of spasm immediately after surgery showed 35%–91%, delayed improvement 6%–46%, and persistence of spasm 0%–59%. The accuracy of the developed prediction model was 0.608. Male sex, mild degree of preoperative spasm, intraoperative indentation on the facial nerve, and postoperative delayed facial palsy were better favorable prognostic factors of MVD in patients with HFS. This novel algorithm may be useful to predict the outcome of MVD in these patients. [ABSTRACT FROM AUTHOR]