Retrogasserian trigeminal radiofrequency-thermorhizotmoy for trigeminal neuralgia.

Based on a personal experience of 4200 surgeries, radiofrequency thermocoagulation is useful lesional treatment for those trigeminal neuralgias (TNs) not amenable to microvascular decompression (idiopathic or secondary TNs). Introduced through the foramen ovale, behind the trigemnial ganglion in the triangular plexus, the needle is navigated by radiology and neurophysiological testing to target the retrogasserian fibers corresponding to the trigger zone. Heating to 55-75 °C can achieve hypoesthesia without anaesthesia dolorosa if properly controlled. Depth of anaesthesia varies dynamically sedation for cannulation and lesioning, and awareness during neurophysiologic navigation. Proper technique ensures long-lasting results in more than 75% of patients.

A novel indicator to predict the outcome of percutaneous stereotactic radiofrequency rhizotomy for trigeminal neuralgia patients: diffusivity metrics of MR-DTI.

Magnetic resonance-diffusion tensor imaging (MR-DTI) has been used in the microvascular decompression and gamma knife radiosurgery in trigeminal neuralgia (TN) patients; however, use of percutaneous stereotactic radiofrequency rhizotomy (PSR) to target an abnormal trigeminal ganglion (ab-TG) is unreported. Fractional anisotropy (FA), mean and radial diffusivity (MD and RD, respectively), and axial diffusivity (AD) of the trigeminal nerve (CNV) were measured in 20 TN patients and 40 healthy control participants immediately post PSR, at 6-months, and at 1 year. Longitudinal alteration of the diffusivity metrics and any correlation with treatment effects, or prognoses, were analyzed. In the TN group, either low FA (value < 0.30) or a decreased range compared to the adjacent FA (dFA) > 17% defined an ab-TG. Two-to-three days post PSR, all 15 patients reported decreased pain scores with increased FA at the ab-TG (P < 0.001), but decreased MD and RD (P < 0.01 each). Treatment remained effective in 10 of 14 patients (71.4%) and 8 of 12 patients (66.7%) at the 6-month and 1-year follow-ups, respectively. In patients with ab-TGs, there was a significant difference in treatment outcomes between patients with low FA values (9 of 10; 90%) and patients with dFA (2 of 5; 40%) (P < 0.05). MR-DTI with diffusivity metrics correlated microstructural CNV abnormalities with PSR outcomes. Of all the diffusivity metrics, FA could be considered a novel objective quantitative indicator of treatment effects and a potential indicator of PSR effectiveness in TN patients.

Radiosurgical Decompression of Trigeminal Nerve and Its Correlation with Functional Outcome in Tumor-Related Trigeminal Neuralgia.

BACKGROUND: Target selection during Gamma Knife radiosurgery (GKRS) in cases of tumor-related trigeminal neuralgia is always debatable. We analyzed the correlation of regression of tumor size and degree of release of the nerve with long-term pain control. METHODS: Between March 2012 and March 2023, 50 cases of tumor-related trigeminal neuralgia were treated with GKRS (tumor was targeted). Radiological findings after GKRS were categorized into 3 types: 1) tumor volume remained same or decreased, additional segment of nerve not seen; 2) tumor volume decreased, additional segment of trigeminal nerve seen, but tumor still adherent to the nerve; 3) tumor volume decreased, adjacent nerve seen completely separated from tumor. Pain score before and after GKRS (Barrow Neurological Institute I-III: good; Barrow Neurological Institute IV and V: poor) was correlated with these subgroups. RESULTS: At median follow-up of 46.5 months, 18 cases showed type 1 radiological response, 23 showed type 2 response, and 9 showed type 3 response. Good pain control was achieved in 10 (55.5%) patients with type 1, 15 (65.21%) with type 2, and 7 (77.8%) with type 3 responses. The outcome differences among these 3 groups were not statistically significant (P = 0.519). Five patients with type 3 radiological response were off medication, which was statistically better than type 1 and type 2 radiological responses, with 3 patients (P = 0.012) and 2 patients (P = 0.002), respectively, still receiving medication. CONCLUSIONS: Tumor volume reduction after GKRS may be associated with good pain control in tumor-related trigeminal neuralgia. Further, this allows visualization of additional segment of nerve that can be targeted in a second session for treating recurrent or failed cases.

The Sagittal Angle of the Trigeminal Nerve at the Porus Trigeminus is a Radiologic Predictor of Surgical Outcome in Microvascular Decompression for Classical Trigeminal Neuralgia.

BACKGROUND AND OBJECTIVES: Classical trigeminal neuralgia (cTN) is a painful disease. Microvascular decompression (MVD) provides immediate and durable relief in many patients. A variety of positive and negative prognostic biomarkers for MVD have been identified. The sagittal angle of the trigeminal nerve at the porus trigeminus (SATNaPT) is an MRI biomarker that can identify a subset of patients with cTN whose trigeminal nerve anatomy is different from normal controls. The purpose of this case-control study was to determine whether an abnormally hyperacute SATNaPT is a negative prognostic biomarker in patients with cTN undergoing MVD. METHODS: Preoperative MRIs from 300 patients with cTN who underwent MVD were analyzed to identify patients with a hyperacute SATNaPT (defined as less than 3 SDs below the mean). The rate of surgical success (pain-free after at least 12 months) was compared between patients with a hyperacute SATNaPT and all other patients. RESULTS: Patients without a hyperacute SATNaPT had an 82% likelihood of surgical success, whereas patients with a hyperacute SATNaPT had a 58% likelihood of surgical success ( P < .05). Patients with a hyperacute SATNaPT who also had no evidence of vascular compression on preoperative MRI had an even lower likelihood of success (29%, P < .05). CONCLUSION: In patients with cTN being considered for MVD, a hyperacute SATNaPT is a negative prognostic biomarker that predicts a higher likelihood of surgical failure. Patients with a hyperacute SATNaPT, particularly those without MRI evidence of vascular compression, may benefit from other surgical treatments or a modification of MVD to adequately address the underlying cause of cTN.

Internal Neurolysis for Trigeminal Neuralgia: Technical Nuances and a Single-Institution Experience.

BACKGROUND: Trigeminal neuralgia is a facial pain syndrome most commonly caused by a neurovascular compression (NVC) of the trigeminal nerve. Microvascular decompression (MVD) is the most durable surgical treatment; however, patients without an NVC are not candidates for this procedure. Alternative treatments such as percutaneous rhizotomy and radiosurgery are effective but with higher recurrence rates. Internal neurolysis (IN) is a less frequently used procedure that aims to provide long-term relief to patients without NVC. OBJECTIVE: We present the surgical techniques for IN developed at our institution. We also discuss the technical nuances related to nerve consistency and present a new classification based on these findings. We provide pain and numbness outcomes for our cohort of patients stratified by the extent of neurolysis and nerve consistency. METHODS: Patients with medically intractable trigeminal neuralgia eligible for posterior fossa exploration are eligible for MVD and possible IN. If no NVC or a mild NVC is encountered, IN is performed. We have divided the procedure into 4 main steps: opening the outer connective sheath, fascicular dissection, inside-out dissection and the fascicular irrigation technique. Trigeminal nerve consistency has been classified into 3 main types: type 1 is soft and friable; type 2 is intermediate consistency and ideal for neurolysis; and type 3 is firm and presents a more challenging dissection. CONCLUSIONS: In the absence of microvascular compression, we advocate for a thorough neurolysis using the techniques described in our article.

Trigeminal Neuralgia as a Primary Demyelinating Disease: Potential Multimodal Evidence and Remaining Controversies.

Trigeminal neuralgia is a heterogeneous disorder with likely multifactorial and complex etiology; however, trigeminal nerve demyelination and injury are observed in almost all patients with trigeminal neuralgia. The current management strategies for trigeminal neuralgia primarily involve anticonvulsants and surgical interventions, neither of which directly address demyelination, the pathological hallmark of trigeminal neuralgia, and treatments targeting demyelination are not available. Demyelination of the trigeminal nerve has been historically considered a secondary effect of vascular compression, and as a result, trigeminal neuralgia is not recognized nor treated as a primary demyelinating disorder. In this article, we review the evolution of our understanding of trigeminal neuralgia and provide evidence to propose its potential categorization, at least in some cases, as a primary demyelinating disease by discussing its course and similarities to multiple sclerosis, the most prevalent central nervous system demyelinating disorder. This proposed categorization may provide a basis in investigating novel treatment modalities beyond the current medical and surgical interventions, emphasizing the need for further research into demyelination of the trigeminal sensory pathway in trigeminal neuralgia. PERSPECTIVE: This article proposes trigeminal neuralgia as a demyelinating disease, supported by histological, clinical, and radiological evidence. Such categorization offers a plausible explanation for controversies surrounding trigeminal neuralgia. This perspective holds potential for future research and developing therapeutics targeting demyelination in the condition.

Application of Sequential Thresholding-Based Automated Reconstruction of the Trigeminal Nerve in Trigeminal Neuralgia.

OBJECTIVE: High-resolution magnetic resonance imaging (MRI) of the trigeminal nerve is indispensable for workup of trigeminal neuralgia (TN) before microvascular decompression; however, the evaluation is often subjective and prone to variability. We aim to develop and assess sequential thresholding-based automated reconstruction of the trigeminal nerve (STAR-TN) as an algorithm for segmenting the trigeminal nerve and contacting structures that will allow for a structured method for assessing neurovascular conflict. METHODS: A total of 42 patients with TN who underwent high-resolution MRI before microvascular decompression in 2022 were included in our study. Segmentation of the trigeminal nerve and contacting structures was performed on preoperative MRI scans using STAR-TN. The segmentations were then evaluated for neurovascular conflict and compared to the preoperative radiology and operative notes. Geometric features, including the area of contact and distance to conflict, were extracted. RESULTS: Of the 42 patients, 32 (76.2%) were found to show neurovascular conflict based solely on their STAR-TN segmentations and 10 (23.8%) were found to not show neurovascular conflict. Compared with the intraoperative findings, this resulted in a sensitivity of 78.0% and specificity of 100%. In contrast, assessments of neurovascular conflict by radiologists using only 2-dimensional MRI views had a sensitivity of 68.3% and specificity of 100%. Of the 32 patients with neurovascular conflict, 29 (90.9%) had conflict within the root entry zone. Overall, the patients had a median area of contact of 10.66 mm2. CONCLUSIONS: STAR-TN allows for 3-dimensional visualization and identification of neurovascular conflict with improved sensitivity compared with neuroradiologist assessments from MRI slices.

Does Head Positioning After Percutaneous Glycerol Rhizotomy for Trigeminal Neuralgia Matter?

BACKGROUND: Percutaneous glycerol rhizotomy (PGR) is a minimally invasive procedure for patients with trigeminal neuralgia who are not candidates for microvascular decompression. PGR has widely varying success rates. It has been postulated that differences in post-injection head positioning might account for the various success rates. METHODS: By comparing glycerol dispersion after injection at various head positions, we provide the first evidence supporting post-injection head flexion positioning. Furthermore, we study the clival-Meckel cave (CMC) angle as a predictor of beneficial glycerol flow, measured on computed tomography images. Twenty-two dissected cadaveric specimens were injected with dyed glycerol through the Hartel approach. The glycerol dispersion was measured at prespecified intervals for 1 hour. The Mann-Whitney U and χ2 tests were used to determine the most ideal angle of head flexion to avoid posterior glycerol dispersion and ensure V1-V3 branch glycerol submersion. RESULTS: We found that 30° of anterior head flexion provided optimal trigeminal nerve glycerol submersion (81.82%) in comparison to neutral (27.27%) and 15° (68.18%), P < 0.001. There was minimal unfavorable dispersion beyond 30 minutes at all angles. More obtuse CMC angles were associated with higher rates of unfavorable BC dispersion (U = 6.0; P = 0.001). For specimens with CMC angles >75°, unfavorable BC dispersion was prevented by head flexion (U = 4.5; P = 0.021). We show that 30° of lateral head tilt achieves V1 submersion in all specimens by 30 minutes [X2(1,N = 44) = 22.759; P < 0.001]. CONCLUSIONS: We found that 30° anterior head flexion for >30 minutes provides ideal conditions for PGR to avoid BC dispersion and ensure V1-V3 branches achieve glycerol submersion. For patients with V1 symptoms, contralateral head flexion might help optimize treatment effects.

[Neurovascular decompression in trigeminal neuralgia: Functional outcome]. / Descompresión neurovascular en neuralgia trigeminal: resultado funcional.

INTRODUCTION: The most frequent pathology of the fifth cranial nerve is trigeminal neuralgia (TN), characterized by unilateral orofacial pain, of a paroxysmal nature, with distribution in one or more divisions of the trigeminal nerve. The main objective of this work is to demonstrate the efficacy and safety of neurovascular decompressive surgery (NVD). METHODS: Retrospective analytical study, patients operated on for NVD by TN (n: 155), from January 2006 - 2022, using a retrosigmoid approach and clinicalradiological follow-up, whose intraoperative recording was in 3D system (n: 42). RESULTS: 83.3% (n=35) presented classic NT and 16.7% (n = 7) idiopathic. The right side prevailed with 59.5% (n = 25) and paroxysmal pain with 81% (n=34) of representation in the entire series. Compression of arterial origin represented 76.2% (n: 32) of the cases, the superior cerebellar artery represented the first cause of neurovascular compression (NVC) in 52.4% (n: 22) in the exit zone of the trigeminal nerve. The validity of the magnetic resonance imaging (MRI) protocol selected for this series was analyzed; evidencing a high sensitivity of MRI with 97%, and a specificity of 86%. CONCLUSION: The sensitivity and specificity of highdefinition MRI studies and with special protocols for the evaluation of TN, as gold standard paraclinical, were presented. The DNV offered safe results, a high percentage of the patients were described as successful. The 3D recording allowed retrospective analysis with a vision identical to that of the surgeon during the intraoperative period, the type of NVC.

Introducción: La afección más frecuente del V nervio craneal es la neuralgia del trigémino (NT), se caracteriza por dolor orofacial unilateral, paroxístico, distribuyéndose en una o más divisiones del nervio trigémino. El objetivo de presente trabajo es demostrar la eficacia y seguridad de la cirugía descompresiva neurovascular (DNV). Métodos: Estudio analítico retrospectivo, pacientes intervenidos para DNV por NT (n: 155), desde enero de 2006 - 2022, mediante un abordaje retrosigmoideo y seguimiento clínico-radiológico, cuyo registro intraoperatorio fue en sistema 3D (n: 42). Resultados: 83.3% (n=35) presentó NT clásica y 16.7% (n = 7) idiopática. La mayoría con afectación del lado derecho 59.5% (n = 25) y el dolor paroxístico con 81% (n = 34). La compresión de origen arterial representó 76.2% (n: 32) de los casos, la arteria cerebelosa superior representó la primera causa de compresión neurovascular (CNV) en un 52.4% (n:22) en la zona de salida del nervio trigémino. Se analizó la validez del protocolo de resonancia magnética (RM) seleccionado para esta serie; evidenciando una alta sensibilidad de la RM con 97%, y una especificidad del 86%. Conclusión: Se demostró la sensibilidad y especificidad de los estudios de resonancia magnética (RM) de alta definición y con protocolos especiales para la evaluación de la NT, como paraclínico estándar de oro. La DNV ofreció resultados seguros, un alto porcentaje de los pacientes se calificaron como exitosos. El registro 3D permitió analizar en retrospectiva con una visión idéntica a la del cirujano durante el intraoperatorio, el tipo de CNV.

Proximal trigeminal nerve atrophy is associated with favourable outcomes and persistent facial numbness following percutaneous balloon compression for primary trigeminal neuralgia.

OBJECTIVE: Whether nerve atrophy can affect the prognosis of primary trigeminal neuralgia (PTN) patients undergoing percutaneous balloon compression (PBC) remains unclear. This study aimed to determine the association between nerve characteristics observed on preoperative magnetic resonance imaging (MRI) and PBC outcomes. METHODS: Between January 2019 and December 2022, a cohort of 58 patients with unilateral PTN treated with PBC were analysed retrospectively and included in this study. The relationship between MRI findings, including the proximal and distal nerve cross-sectional areas (CSAs), and favourable pain outcomes (BNI Grades I-III) was analysed through Kaplan‒Meier analysis. RESULTS: After a mean follow-up period of 23.8 ± 13.0 months (range, 6-50 months), 48 (82.8%) patients with PTN were pain free with or without medication. A smaller proximal CSA ratio (proximal CSA of the affected nerve/proximal CSA of the unaffected nerve) was significantly associated with favourable outcomes. The Kaplan-Meier survival analysis showed that patients with proximal nerve atrophy (proximal CSA ratio ≤ 87% after receiver operating characteristic curve analysis) had a higher estimated 4-year probability of maintaining a favourable outcome than those without nerve atrophy (94.4% vs. 30.8%, p = 0.005). In addition, patients with proximal nerve atrophy were more likely to suffer from postoperative persistent facial numbness. CONCLUSIONS: Proximal nerve atrophy is correlated with both favourable outcomes and persistent facial numbness following PBC. Prospective studies are required to determine the optimal duration and pressure of balloon compression in relation to the proximal CSA ratio to achieve better pain outcomes and less facial numbness.

[Concomitant, asynchronous and refractory trigeminal and glossopharyngeal neuralgia. Good response to surgical approach in one time]. / Neuralgia del trigémino y del glosofaríngeo concomitantes, asíncronas y refractarias. Buena respuesta al abordaje quirúrgico en un tiempo.

INTRODUCTION: Microvascular decompression (MVD) surgery is the first choice treatment for refractory cranial neuralgia secondary to vascular compression. Simultaneous neuralgia of two cranial nerves is extremely rare. We describe a case of concomitant refractory trigeminal (TN) and glossopharyngeal (GN) neuralgia secondary to neurovascular crossover, treated surgically at the same time. CASE REPORT: 65-year-old woman with right TN (initially V2-V3) since 2004 with regular control with carboxamides. Seventeen years later, paroxysms worsened in V2-V3, also appearing in V1 and in the territory of the right glossopharyngeal nerve (right ear and tonsillar fossa when speaking and swallowing). Cerebral MRI showed significant arterial contact between the superior cerebellar artery (SCA) with the origin of the right V cranial nerve and the antero-inferior cerebellar artery (AICA) with the origin of the right lower CCNN. MVD of both cranial nerves was performed at the same surgical time by means of retrosigmoid craniectomy, releasing the V cranial nerve, in intimate contact with the SCA, and the IX cranial nerve in contact with the right AICA, interposing teflon between them. The patient had an immediate resolution of the trigeminal paroxysms and a dramatic improvement in intensity and frequency of glossopharyngeal paroxysms. Two years after the intervention, de-escalation of neuromodulator treatment continues with good response. CONCLUSION: MVD in simultaneous TN and GN is feasible and can offer a good post-surgical outcome.

TITLE: Neuralgia del trigémino y del glosofaríngeo concomitantes, asíncronas y refractarias. Buena respuesta al abordaje quirúrgico en un tiempo.Introducción. La cirugía de descompresión microvascular (DMV) es el tratamiento de elección de una neuralgia craneal refractaria secundaria a compresión vascular. Las neuralgias simultáneas de dos pares craneales son extremadamente infrecuentes. Describimos un caso con neuralgia concomitante del trigémino (NT) y glosofaríngeo (NG) refractarias y secundarias a cruce neurovascular abordadas quirúrgicamente en un mismo tiempo. Caso clínico. Mujer de 65 años con NT derecho (inicialmente en V2-V3) desde 2004 con control regular con carboxamidas. Diecisiete años después empeoraron los paroxismos en V2-V3, aparecieron también en V1 y en el territorio del nervio glosofaríngeo derecho (oído derecho y fosa amigdalar al hablar y deglutir). La resonancia magnética cerebral mostró contacto arterial significativo entre arteria cerebelosa superior (ACS) con origen del V par craneal derecho y de la arteria cerebelosa antero-inferior (AICA) con el origen de pares craneales bajos derechos. Se realizó DMV de ambos pares craneales en un mismo tiempo quirúrgico mediante craniectomía retrosigmoidea, y se procedió a la liberación del V par craneal, en contacto íntimo con la ACS, y del IX par craneal en contacto con la AICA derecha, para lo que se puso teflón entre ellas. La paciente tuvo una resolución inmediata de los paroxismos trigeminales y una mejoría considerable en intensidad y frecuencia de los glosofaríngeos. A los 2 años de la intervención continúa la desescalada de tratamiento neuromodulador con buena respuesta. Conclusión. La DMV en la NT y NG simultáneas es factible y puede ofrecer un buen resultado posquirúrgico.

Nomogram Model for Predicting the Risk of Recurrence after Surgery of the V3 Branch of the Trigeminal Nerve.

BACKGROUND: Factors influencing recurrence after V3 trigeminal nerve surgery remain unknown. OBJECTIVES: To analyze the risk factors affecting recurrence after trigeminal nerve branch V3 surgery, construct a nomogram prediction model, and verify the predictive efficacy of the model. STUDY DESIGN: A retrospective study. SETTING: This study was performed at the Affiliated Hospital of Jiaxing University, China. METHODS: Patients with mandibular nerve pain of the V3 branch of the trigeminal nerve treated with percutaneous puncture foramen ovale trigeminal mandibular nerve radiofrequency or trigeminal semilunar nerve microballoon compression at the Pain Department of the Affiliated Hospital of Jiaxing College, between January 2016 and April 2021, were enrolled and randomly divided into the training group (n = 108) and the test group (n = 47) according to the ratio of 7:3. The feasibility of the nomogram prediction model was further explored using multifactor logistic regression analysis based on the screening of independent predictors by the least absolute shrinkage and selection operator (LASSO) regression analysis using recurrence in one year after surgery as the outcome variable, and was assessed by the validation group. Finally, the discriminatory power, accuracy, and clinical utility of the prediction model were assessed using the area under the receiver operating characteristic curve (AUC), calibration curve, and decision curve analysis (DCA), respectively. RESULTS: Among the 155 patients with trigeminal V3 pain, 128 had no recurrence and 27 had recurrence one year after surgery. LASSO regression combined with multifactorial logistic regression analysis showed that age, procedure, and duration were factors influencing recurrence one year after surgery (P < 0.05). A nomogram prediction model was developed using the above variables. The AUC of the nomogram prediction model was 0.749 (95% CI [0.618, 0.879]) in the training group and 0.793 (95% CI [0.584, 0.980]) in the test group for postoperative recurrence of V3. The DCA showed that the net benefit of using the nomogram prediction model to predict the risk of postoperative recurrence of the V3 branch of the trigeminal nerve was higher when patients had a threshold probability of 0 to 0.486. LIMITATIONS: This was a single-center study. CONCLUSIONS: This study successfully developed and validated a highly accurate nomogram prediction model (with age, procedure, and duration as predictive variables), which can improve the early identification and screening of patients at high risk of recurrence after trigeminal nerve V3 branch surgery. KEY WORDS: Trigeminal neuralgia, mandibular nerve, risk factors, prediction model.

Postoperative trigeminal neuropathy outcomes following surgery for tumors involving the trigeminal nerve.

OBJECTIVE: To observe the evolution and outcomes of postoperative trigeminal neuropathy following surgery of tumor involving the trigeminal nerve. METHODS: A prospective observational study was conducted between October 2018 and February 2019 involving 25 patients with tumors confirmed to involve the trigeminal nerve during surgery by senior author. Pre- and postoperative trigeminal nerve function status and clinical data were recorded. RESULTS: This study included 18 cases of meningioma and seven of trigeminal schwannoma. Among the meningioma cases, 55.6% of the patients reported facial sensory dysfunction before surgery, 33.3% presented ocular discomfort, and 5.6% had masticatory muscle atrophy. Postoperatively, all patients experienced facial paresthesia, 94.4% complained of eye dryness, and one (5.56%) exhibited keratitis. Additionally, one patient (5.56%) showed new-onset masticatory weakness. During follow-up, 50.0% of patients reported improvement in facial paresthesia, and one (5.56%) experienced deterioration. Eye dryness resolved in 35.3% of patients, and keratitis remission was observed in one patient. However, one patient (5.56%) developed neurotrophic keratitis. Overall, 55.6% of patients displayed mild masticatory weakness without muscle atrophy. In the cases of schwannoma, 28.6% of patients had facial paresthesia before surgery, 42.9% showed ocular discomfort, and one (14.3%) complained of masticatory dysfunction. Postoperatively, 85.7% of patients reported facial paresthesia and eye dryness, with one patient (16.7%) experiencing keratitis. During follow-up, 66.7% of patients demonstrated improvement in facial paresthesia, 28.6% showed eye dryness remission, and one patient (16.7%) recovered from keratitis. However, one patient (16.7%) developed new-onset neurotrophic keratitis. One patient (16.7%) experienced relief of masticatory dysfunction, but 42.9% reported mild deterioration. Another patient (14.3%) had facial anesthesia that had not improved. CONCLUSION: Postoperative trigeminal neuropathy is a common complication with a high incidence rate and poor recovery outcomes after surgery for tumors involving the trigeminal nerve. When trigeminal nerve damage is unavoidable, it is essential to provide a multidisciplinary and careful follow-up, along with active management strategy, to mitigate the more severe effects of postoperative trigeminal neuropathy.

Peritrigeminal Safe Entry Zone Access to Anterolateral Pons Using the Presigmoid Retrolabyrinthine Suprameatal Approach: A Cadaveric Morphometric Study.

BACKGROUND AND OBJECTIVES: Access to the anterolateral pontine lesions can be achieved through the peritrigeminal and supratrigeminal safe entry zones using Kawase, retrosigmoid, or translabyrinthine approaches. However, these approaches entail shallow extensive dissection, tangential access, and compromise vestibulocochlear function. We aimed to investigate infratentorial presigmoid retrolabyrinthine approach to access pontine lesions through the peritrigeminal zone. METHODS: We performed 10 presigmoid retrolabyrinthine suprameatal approach dissections in 5 cadaveric heads. Anatomic-radiological characteristics and variations were evaluated. Six morphometric parameters were measured and analyzed to predict surgical accessibility. RESULTS: The pontine infratrigeminal area was accessible in all patients. The mean exposed area of the anterolateral pontine surface was 98.95 cm 2 (±38.11 cm 2 ). The mean length of the exposed trigeminal nerve was 7.9 cm (±2.9 cm). Preoperative anatomic-radiological parameters may allow to select patients with favorable anatomy that offers appropriate surgical accessibility to the anterior pontine cavernoma through a presigmoid retrolabyrinthine corridor. CONCLUSION: Anterolateral pontine lesions can be accessed through a minimally invasive infratentorial presigmoid retrolabyrinthine approach by targeting the infratrigeminal safe entry zone. Further clinical studies should be conducted to evaluate the viability of this technique for treating these complex pathologies in real clinical settings.