Anatomical considerations and surgical manipulation of the rhomboid lip in microvascular decompression for hemifacial spasm.

BACKGROUND: In microvascular decompression (MVD) procedures for hemifacial spasm (HFS), surgeons often encounter a rhomboid lip which may obscure the root exit zone (REZ) of the facial nerve. This study aims to explore the anatomical variations of rhomboid lips and their surgical implications to improve safety and effectiveness in MVD surgeries. METHODS: A retrospective analysis was conducted on 111 patients treated for HFS between April 2021 and March 2023. The presence of a rhomboid lip was assessed through operative video records, and its characteristics, dissection methods, and impact on nerve decompression outcomes were further examined. Preoperative magnetic resonance imaging (MRI) scans were reviewed for detectability of the rhomboid lip. RESULTS: Rhomboid lips were identified in 33% of the patients undergoing MVD, with a higher prevalence in females and predominantly on the left side. Two distinct types of rhomboid lips were observed: membranous and cystic variations. The membranous type was noted for its smaller size and position ventral to the choroid plexus. In contrast, the cystic variation was distinguished by its larger size and a thin membrane that envelops the choroid plexus. Preoperative MRI successfully identified rhomboid lips in only 21% of the patients who were later confirmed to have them in the surgical procedures. Surgical approaches primarily involved incisions on the dorsal wall and along the glossopharyngeal nerve root, with only limited need for extensive dissection from lower cranial nerves. Immediate spasm relief was observed in 97% of the patients. One case exhibited a lower cranial nerve deficit accompanied by brainstem infarction, which was caused by the dissection from the lower cranial nerves. CONCLUSIONS: Recognizing the two variations of the rhomboid lip and understanding their anatomical structures are essential for reducing lower cranial nerve injuries and ensuring effective nerve decompression.

Potential reasons for failure and recurrence in microvascular decompression for hemifacial spasm.

BACKGROUND: To examine the factors contributing to persistent and recurrent hemifacial spasms (HFS) following a microvascular decompression (MVD) procedure and to suggest technical improvements to prevent such failures. METHODS: A retrospective review was conducted on fifty-two cases of repeat surgery. The extent of the previous craniotomy and the location of neurovascular compression (NVC) were investigated. The operative findings were categorized into two groups: "Missing Compression" and "Teflon Contact". The analysis included long-term outcomes and operative complications after repeat MVD procedures. RESULTS: Missing compression was identified in 29 patients (56%), while Teflon contact was observed in 23 patients (44%). Patients with missing compression were more likely to experience improper craniotomy (66%) compared to those with Teflon contact (48%). Medially located NVC was a frequent finding in both groups, mainly due to compression by the anterior inferior cerebellar artery. In the missing compression group, during the repeat MVD, Teflon sling retraction was utilized in 79% of cases, while in the Teflon contact group, the most common procedure involved removing the Teflon in contact (65%). After the repeat MVD procedure, immediate spasm relief was achieved in 42 patients (81%), with six (12%) experiencing delayed relief. After a median follow-up of 54 months, 96% of patients were free from spasms. Delayed facial palsy, facial weakness, and hearing impairment were more frequently observed in the Teflon contact group. CONCLUSIONS: A proper craniotomy that provides adequate exposure around the REZ is crucial to prevent missing the culprit vessel during the initial MVD procedure. Teflon contact on the REZ should be avoided, as it poses a potential risk of procedure failure and recurrence.

Single-surgeon approach in microvascular decompression for trigeminal neuralgia: Lessons from an Indonesian Tertiary-Level Neurological Center.

BACKGROUND: Microvascular decompression (MVD) is effective for refractory trigeminal neuralgia (TN), but its accessibility is often limited in lower-to-middle-income countries (LMICs). This study aims to assess the impact of implementing a single-surgeon policy on MVD for TN in LMICs. METHODS: A prospective cohort study was conducted from 2014 to 2020, comparing outcomes between multi-surgeon and single-surgeon policies. Residents were included in MVD procedures starting in 2019. The Barrow Neurological Institute (BNI) pain scale (P), numbness scale (N), and result conclusion scale (P + N) were used to evaluate outcomes (1 week, 1 month, 1 year, and yearly thereafter). Propensity score matching was performed before comparing the groups. Pain-free survival was assessed using Kaplan-Meier and Cox-regression analysis. RESULTS: We comprehensively analyzed data from 72 patients with a minimum one-year follow-up. The implementation of the single-surgeon policy had several notable impacts. Firstly, it led to an increased referral rate (p < 0.05) and a reduced duration to surgery (p < 0.05). During MVD, there was a significant increase in the identification of complex compression (p < 0.05) and a reduced frequency of internal neurolysis (p < 0.05). After surgery, the single-surgeon group exhibited a superior pain-control profile (RR 1.9, p < 0.001; ARR 26-36%), higher pain-free survival rate (p < 0.001), lower likelihood of pain recurrence (HR 0.2, p < 0.0001), and fewer additional surgical interventions compared to the multi-surgeon group. Moreover, the involvement of residents did not significantly impact surgical outcomes. CONCLUSIONS: Implementing a single-surgeon policy for MVD in LMICs has the potential to improve surgical outcomes, provide social benefits, and offer educational opportunities.

Analyzing the cost-effectiveness of microvascular decompression and percutaneous radiofrequency rhizotomy for trigeminal neuralgia: the role of clinical classification.

Trigeminal neuralgia (TN) is a neuropathic pain that can be treated with microvascular decompression (MVD) or percutaneous radiofrequency rhizotomy (PRR) when medications fail. However, the cost-effectiveness of these interventions is uncertain, and it is unclear whether TN should be considered as a single entity for cost-effectiveness analysis. To address these issues, a prospective cohort study was conducted between 2017 and 2020, documenting Burchiel et al.'s clinical classification, pain-free survival, complications, and costs. Two models of quality-adjusted life years (QALYs) were calculated: pain-specific (PQALY) and pain-complication-specific (PCQALY), based on pain-free survival and complications data, followed by cost-effectiveness analysis. The study included 112 patients, of whom 70 underwent MVD and 42 underwent PRR. Our findings revealed that MVD was less cost-effective in the PCQALY model than PRR, but more cost-effective in the PQALY model and had an incremental cost-effectiveness ratio (ICER) that met the World Health Organization cost-effectiveness threshold in both models. Further clinical classification analysis showed that MVD was only cost-effective in type 1 TN patients, with an ICER of 0.9 and 1.3 times the GDP/capita, based on PQALY and PCQALY, respectively, meeting the cost-effectiveness criteria. Conversely, MVD was economically dominated by PRR for type 2 TN patients based on PQALY. These findings indicate that PRR may be more cost-effective for type 2 TN patients, while MVD remains the cost-effective option for type 1 TN patients. Our study highlights the importance of clinical classification and complication in determining the cost-effectiveness of MVD and PRR for refractory TN.

Case report: Teflon granuloma following microvascular decompression manifesting as light-triggered trigeminal neuralgia.

Trigeminal Neuralgia is commonly triggered by stimuli in the area of the trigeminal nerve innervation. We report an exceptionally rare case of a 61-year-old woman who complained of recurrent trigeminal neuralgia, which sole trigger was seeing a bright light. Teflon felt that was placed on the nerve root in the initial surgery was suspected of causing this rare type of trigeminal neuralgia. A reflex circuit linking luminance to trigeminal nerve activity may be implicated in activating a trigeminal nociceptive pathway by a bright light trigger.

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

BACKGROUND: 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.

Bridge technique for hemifacial spasm with vertebral artery involvement.

BACKGROUND: To assess efficacy and safety of a newly developed decompression technique in microvascular decompression for hemifacial spasm (HFS) with vertebral artery (VA) involvement. METHODS: A rigid Teflon (Bard® PTFE Felt Pledget, USA) with the ends placed between the lower pons and the flocculus creates a free space over the root exit zone (REZ) of the facial nerve (bridge technique). The bridge technique and the conventional sling technique for VA-related neurovascular compression were compared retrospectively in 60 patients. Elapsed time for decompression, number of Teflon pieces used during the procedure, and incidences of intraoperative manipulation to the lower cranial nerves were investigated. Postoperative outcomes and complications were retrospectively compared in both techniques. RESULTS: The time from recognition of the REZ to completion of the decompression maneuvers was significantly shorter, and fewer Teflon pieces were required in the bridge technique than in the sling technique. Lower cranial nerve manipulations were performed less in the bridge technique. Although statistical analyses revealed no significant differences in surgical outcomes except spasm-free at postoperative 1 month, the bridge technique is confirmed to provide spasm-free outcomes in the long-term without notable complications. CONCLUSIONS: The bridge technique is a safe and effective decompression method for VA-involved HFS.

Redo surgery for trigeminal neuralgia: reasons for re-exploration and long-term outcomes.

BACKGROUND: To investigate the causes of failure and recurrence after microvascular decompression (MVD) for trigeminal neuralgia (TGN) and to analyze the results of redo surgery. METHODS: Sixty-three cases of redo surgery were retrospectively reviewed. Reasons for re-exploration were categorized into 4 groups based on the operative findings. Patient characteristics, outcomes of re-exploration, and operative complications were analyzed by Kaplan-Meier and logistic regression analyses. RESULTS: Reasons for redo surgery were divided into arterial compression in 13 patients (21%), venous compression in 11 patients (17%), prosthesis-related in 25 patients (40%), and adhesion or negative exploration in 14 patients (22%). Immediate pain relief was obtained in 59 patients (94%) postoperatively with newly developed facial numbness in 17 patients (27%). Of these, 48 patients (76%) maintained pain-free 1 year postoperatively. Overall recurrence was noted in 17 patients (27%) during the median 49-month follow-up period. Most recurrences occurred within 1 year after redo surgery, but the prosthesis-related patients showed a continuous recurrence up to 4 years. Patients having vascular compression showed significantly better pain control than those without vascular contact in Kaplan-Meier analyses (p = 0.0421). No prognostic factor for pain-free 1 year after redo surgery was found. CONCLUSIONS: Redo surgery is effective for patients with remaining vascular compression rather than those without vascular contact. Teflon contact onto the nerve root should be avoided because it is a potential risk for recurrence and causes poor prognosis after redo surgery.

Location of the abducens nerve stretched by a tortuous vertebrobasilar artery in trigeminal neuralgia.

BACKGROUND: Trigeminal neuralgia (TGN) caused by the vertebrobasilar artery (VBA) is uncommon. The abducens nerve root is frequently dislocated by a tortuous VBA near the trigeminal nerve root. This unusual location of the root is not well known. This study aimed to investigate the location of the stretched abducens nerve root. METHODS: The objective is 26 patients with VBA-related TGN who underwent microvascular decompression (MVD). We retrospectively investigated the course of the abducens nerve root with magnetic resonance imaging (MRI) with three-dimensional (3D) imaging and surgical findings. The displacement of the abducens nerve root on the affected side was compared to the contralateral side. RESULTS: The abducens nerve root was distorted by a tortuous VBA (46.2%) or the anterior inferior cerebellar artery (53.8%). The average length of the cisternal segment was stretched to 23.4 mm versus 12.4 mm on the contralateral side. The peak point of the elevated abducens nerve root was mostly located rostro-medial (65.4%) or caudo-medial (34.6%) to the neurovascular compression site of the trigeminal nerve with a mean distance of 9.1 mm. Contact with the trigeminal nerve root was observed in 7 patients (26.9%). Three-dimensional imaging was consistent with the surgical findings and useful in predicting the location of the abducens nerve root. No abducens nerve palsy was noted in our series. CONCLUSIONS: The abducens nerve root is located near the trigeminal nerve root in VBA-related TGN. Preoperative understanding of the unusual course of the abducens nerve root contributes to avoiding accidental nerve injury during MVD.

Petrosal Vein Involvement in Neurovascular Conflict in Trigeminal Neuralgia: Surgical Technique and Clinical Outcomes.

BACKGROUND: Contact of the main stem of the petrosal vein (PV) to the nerve root is a rare cause of trigeminal neuralgia (TGN). The implication of the PV in relation with neurovascular contact (NVC) is not fully understood. OBJECTIVE: To assess the operative procedures in microvascular decompression (MVD) in patients with PV involvement in the long-term. METHODS: We retrospectively reviewed 34 cases (7.0%) in 485 consecutive MVDs for TGN, whose PV main stem had contact with the trigeminal nerve root (PV-NVC). PV-NVCs were divided into 2 groups: concomitant arterial contact or no concomitant arterial contact. Surgical techniques, outcomes, complications, and recurrence were assessed. RESULTS: The anatomical relationship of the PV with the trigeminal nerve root was consistent with preoperative 3-dimensional imaging in all patients. Pain relief was obtained in most patients immediately after surgery (97.1%) by separating the PV from the nerve root. Postoperative facial numbness was noted in 9 patients (26.5%). Symptomatic venous infarctions occurred in 2 patients (5.9%). Recurrence of facial pain occurred in 3 patients (8.8%) with a median 48 mo follow-up period. Re-exploration surgery revealed adhesion being the cause of recurrence. The statistical analyses showed no difference in the surgical outcomes of the 2 groups. CONCLUSION: Separating the PV from the nerve root contributes to pain relief in patients with PV conflict regardless of concomitant arteries. Preserving venous flow is crucial to avoid postoperative venous insufficiency.

Microvascular decompression for trigeminal neuralgia attributable to the vertebrobasilar artery: decompression technique and significance of separation from the nerve root.

BACKGROUND: Separation of the vertebrobasilar artery (VBA) from the trigeminal nerve root in microvascular decompression (MVD) is technically challenging. This study aimed to review the clinical features of VBA involvement in trigeminal neuralgia and evaluate surgical decompression techniques in the long term. METHODS: We retrospectively reviewed the surgical outcomes of 26 patients (4.4%) with VBA involvement in 585 consecutive MVDs for TGN using a Teflon roll for repositioning the VBA. The final operative status of the nerve decompression was categorized into two groups: the separation group and the contact group. Separation of the VBA from the nerve root was completed in 13 patients in the separation group, and slight vascular contact remained in the remaining 13 patients of the contact group. The clinical features of VBA-related TGN were investigated and the operative results were analyzed. RESULTS: Multiple arteries are involved in neurovascular compression (NVC) in most cases. The anterior inferior cerebellar artery was the most common concomitant artery (69%). The site of the NVC varies from the root entry zone to the distal portion of the root. All patients were pain-free immediately after surgery and maintained medication-free status during the follow-up period, except for one patient (3.8%) who had recurrent facial pain 8 years after surgery. Postoperative facial numbness was observed in six patients (23%). Of these, one patient showed improvement within 3 months and the other five patients had persistent facial numbness (19.2%). Other neurological deficits include one dry eye, one diplopia due to trochlear nerve palsy, two decreased hearing (< 50 db), two facial weaknesses, and two cerebellar ataxia. Although most of them were transient, one dry eye, two hearing impairments, and one cerebellar ataxia became persistent deficits. Statistical analyses revealed no difference in surgical efficacy or complications in the long term between the two groups. CONCLUSIONS: Slightly remaining vascular contact does not affect pain relief in the long term. Our study indicated that once the tense trigeminal nerve is loosened, further attempts to mobilize the VBA are not necessary.

Characteristics of Patients With Trigeminal Neuralgia Referred to the Indonesian National Brain Center Neurosurgery Clinic.

Trigeminal neuralgia (TN) is a debilitating neuropathic pain involving the fifth cranial nerve. There has been no study investigating the clinical and socioeconomical characteristics of patients with TN in Indonesia. A total of 100 patients were included in this study. Symptoms indicating a later stage of the illness, namely, involvement of all the trigeminal nerve branches, numbness, and concomitant persistent pain, were the common presentations found in our cohort. Only one TN diagnosis was made by a general practitioner (GP). None were immediately referred to a neurosurgeon following their diagnosis. Access to our clinic took as long as 4.7 ± 5.1 years (mean ± SD) from the onset. Older age was a significant predictor of an increased likelihood of not knowing their illness upon the referral (21.9%, p = 0.008). Upon their first presentation, 25.5% of patients had experienced drug-related side effects due to prolonged medication. Only 50% of patients were compensated by the universal health coverage (UHC) system. Seven patients spent ≥ 50 million rupiahs and eight patients had already lost their jobs. In conclusion, early contact with a neurosurgeon contributes to better management of TN, both for the patients and healthcare system in Indonesia. A refined understanding of TN nature is still needed in this country.

Resection of the suprameatal tubercle in microvascular decompression for trigeminal neuralgia.

BACKGROUND: The suprameatal tubercle (SMT) may obscure the neurovascular compression (NVC) in microvascular decompression (MVD) for trigeminal neuralgia (TGN). The aim of this study is to address the necessity of resecting SMT in MVD for TGN. METHODS: We retrospectively analyzed radiological findings of 461 MVDs in patients with TGN, focusing on the relation between SMT and the NVC site. Three-dimensional (3D) images were used for preoperative evaluation. The NVC sites were obscured by SMT in 48 patients (10.4%) via the retrosigmoid approach. This study was conducted to review the management of SMT among these patients. Resection of SMT was performed in 8 patients (resected group) for direct visualization of the NVC site. On the other hand, nerve decompression was achieved without resecting SMT for the rest of the 40 patients (non-resected group). Biographical data, radiological findings, intraoperative findings, and surgical outcomes were retrospectively evaluated. RESULTS: The mean height of SMT obscuring NVC was 5.0 mm (2.8-13.9 mm) above the petrous surface. The NVC was located at a mean of 1.9 mm (0-5.9 mm) from the porous trigeminus. The most common offending vessel was the superior cerebellar artery (SCA, 56.3%), followed by the transverse pontine vein (TPV, 29.2%). In the resected group, the transposing culprit vessels were feasibly performed after direct visualization of the NVC site, whereas in the non-resected group, the SCA was successfully transposed using curved instruments after thorough dissection around the nerve. TPV having contact with the nerve was coagulated and divided. Immediate pain relief was obtained in all patients except one who experienced delayed pain relief 1 month after surgery. Facial numbness at discharge was noted in 9 patients (18.8%); thereafter, numbness diminished over time. Numbness at the final visit was observed in 5 patients (10.4%) at mean of 49 months after MVD. Recurrent pain occurred in 4 patients (8.3%) in total. Statistical analysis showed no significant differences in surgical outcomes between both groups. CONCLUSIONS: Direct visualization of the NVC site by resecting the SMT does not affect surgical outcomes in the immediate and long term. Resecting the SMT is not always necessary to accomplish nerve decompression in most cases by use of suitable instruments and techniques.