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Background: The anatomy and spatial relationships of the dural sac comprising the Meckel cave (MC) and its ensheathed trigeminal ganglion (TG) are exceedingly intricate and complex. There are conflicting accounts in the literature regarding the dural configuration of the MC around the ganglion and the dual embryology of the MC and TG is still unclear., Methods: A combined systematic and narrative literature review was conducted to collate articles addressing MC and TG anatomy, in addition to their embryology, role in tumor spread, somatotopy, and association with trigeminal neuralgia., Results: Three key anatomic models by Paturet (1964), Lazorthes (1973), and Lang and Ferner (1983) have been put forward to show the arrangement of the MC around the TG. The TG is formed from both neural crest and placodal cells and drags the enveloping dura caudally to form the MC prolongation during development. Both a mediolateral and dorsoventral somatotopic arrangement of neurons exists in the TG, which corresponds to the 3 nerve divisions, of which V2 and V3 are prone to perineural tumor spread along their course., Conclusions: Sound knowledge concerning the dural arrangement of the MC and the trigeminal divisions will be invaluable in optimally treating cancers in this region, and understanding TG somatotopy will immensely improve treatment of trigeminal neuralgia in terms of specificity, efficacy, and positive patient outcomes., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Tumors of the middle fossa or cavernous sinus (CS), or intraorbital tumors, can penetrate each other through the superior orbital fissure (SOF) or neighboring tissue. These complicated pathologies are often treated with highly invasive surgical procedures. In this article, we demonstrate surgical anatomic dissections of the CS, SOF, orbital apex (OA), and dura mater extending to the periorbita from the middle fossa, by performing an epidural dissection via a lateral orbitotomy approach, and discuss findings that may provide guidance during surgery in these regions., Methods: Lateral orbitotomy was performed on latex-injected cadaver heads by making a 2-cm skin incision lateral to the lateral canthus, drilling the lesser and greater sphenoid wings that form the SOF borders, and removing the bone section between the middle fossa and orbit. Dura mater from the middle fossa to the periorbita was exposed to perform anterior clinoidectomy. Meningeal dura was dissected from the endosteal dura, which forms the lateral wall of the CS, to expose the CS, SOF, and OA for dissections., Results: Changing the orientation of the microscope from posterior to anterior enabled regional control for dissection from the Gasserian ganglion to the OA. Cranial nerves that pass through the CS, SOF, and OA were dissected and exposed. The annular tendon was opened, revealing the oculomotor nerves and its branches, as well as the abducens and nasociliary nerves, which pass through the oculomotor foramen and course within the OA and orbit., Conclusions: This approach causes less tissue damage; provides control of the surgical area in spheno-orbital tumors invading the fissure and foramen by changing the orientation of the microscope toward the orbit, OA, SOF, CS, and middle fossa; and expands the indication criteria for lateral orbitotomy surgery. This approach, therefore, represents an alternative surgical method for excising complicated tumors in these regions.

Objective: Percutaneous treatments for trigeminal neuralgia are safe, simple, and effective for achieving good pain control. Procedural risks could be minimized by using noninvasive imaging techniques to improve the placement of the radiofrequency thermocoagulation probe into the trigeminal ganglion. Positioning of a probe is crucial to maximize pain relief and to minimize unwanted side effects, such as denervation in unaffected areas. This investigation examined the use of laser speckle imaging during probe placement in an animal model., Methods: This preclinical safety study used nonhuman primates, Macaca nemestrina (pigtail monkeys), to examine whether real-time imaging of blood flow in the face during the positioning of a coagulation probe could monitor the location and guide the positioning of the probe within the trigeminal ganglion., Results: Data from 6 experiments in 3 pigtail monkeys support the hypothesis that laser imaging is safe and improves the accuracy of probe placement., Conclusions: Noninvasive laser speckle imaging can be performed safely in nonhuman primates. Because improved probe placement may reduce morbidity associated with percutaneous rhizotomies, efficacy trials of laser speckle imaging should be conducted in humans.

Background: Percutaneous trigeminal rhizotomy (PTR) uses fluoroscopic guidance to cannulate the foramen ovale for the treatment of trigeminal neuralgia., Objective: To describe the use of a high-resolution biplane neuroangiosuite for PTR and retrospectively to assess the performance of this technique., Methods: From 1990 through 2010, 67 PTRs were performed in 51 patients at our institution; 47 used the c-arm in the operating room (OR) and 20 used the biplane angiosuite. Hospital charts were reviewed for demographics, symptomatology, operative time, number of cannulation attempts, fluoroscopy time and pain outcome. Two-tailed univariate analyses were performed to compare the OR and angiosuite groups., Results: In 20 of 67 PTRs, biplane fluoroscopic guidance in the angiosuite was used. Variations in type of PTR, fluoroscopy technique and follow-up time barred meaningful comparison of these variables between OR and biplane groups. However, the biplane group had significantly fewer mean cannulation attempts (1 vs 2.2, p<0.001)., Conclusions: High-resolution biplane neuroangiosuites offer a readily available alternative to ORs for PTR in the treatment of trigeminal neuralgia. Use of the biplane fluoroscopy machine was practical, safe and at least as effective as the use of the c-arm. It may also offer the advantages of a reduced number of cannulation attempts., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)

Objectives: The objective of this case is to report the rare complication of a meningitis after an invasive treatment of the trigeminal ganglion., Methods: In this case report, two cases of meningitis due to oral streptococci are reported and a review of literature is presented., Results and Discussion: This complication should be recognized as early as possible to prevent deterioration of the situation. Meningitis must be suspected when a patient reports headache and fever within days after an invasive treatment of the trigeminal ganglion.

Objectives: There are controversies about the use of local anesthetics during balloon compression for trigeminal neuralgia (TN) as a protective factor for cardiovascular events. The objective of this study was to investigate cardiovascular parameters (blood pressure and heart rate [HR]) of patients that underwent trigeminal balloon compression with local anesthetics compared to a control group (placebo)., Methods: This is a randomized controlled study; 55 patients were randomized into two groups: study (deep sedation and trigeminal block with 0.8-mL lidocaine 2%) and control group (deep sedation and trigeminal injection of 0.8-mL saline). Blood pressure and HR were measured in five distinct moments: preoperative, during puncture for local anesthesia/placebo, during puncture with the catheter, during balloon compression, and final evaluation. Statistical analysis was performed with Pearson's chi (2) and McNemar tests and the analysis of variance for repetitive measures., Results: The means of systolic and diastolic blood pressures (SBP and DBP, respectively) were higher in the control group when compared to the study group at the evaluation during puncture with the catheter (p < 0.001) and balloon compression (p < 0.001 and p = 0.018 for DBP and SBP, respectively). There was an increase in the HR in the control group during the procedure (p = 0.017)., Conclusion: The use of local anesthetics during the trigeminal balloon compression for TN can have a preventive role for the risk of cardiovascular events.

We report the case of a woman with short-lasting unilateral, neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) whose severe headache attacks ceased after percutaneous balloon compression of the Gasserian ganglion. The patient remains pain free after 10-year follow-up. This may be the first literature report of SUNCT in Chile.

Objective: To introduce a novel surgical technique for the dissection of the greater superficial petrosal nerve (GSPN) in the middle fossa approach., Methods: Interdural temporal elevation was performed with a front-to-back technique to preserve the GSPN in 12 sides of 6 injected cadaveric heads dissected through a middle fossa approach., Results: The GSPN emerged from the facial hiatus in a shallow bony groove proximally, ran into a deeper sphenopetrosal groove, and eventually reached the mandibular nerve. With front-to-back dissection, this nerve was easily identified at the posterior border of the mandibular nerve. Dissection from front to back minimized the retraction force applied to the proximal part of the GSPN, which was preserved in all specimens., Conclusion: The temporal dura can be elevated safely with a front-to-back technique to preserve the GSPN and to help maintain the physiological integrity of the facial nerve.

Background: The purpose of this study was to call attention to the subtemporal approach directed through the petrous apex to the IAM. We studied the microsurgical anatomy of the middle floor to delineate a reliable angle between the GSPN and the IAM to precisely localize and expose the IAM from above. A new technique for the elevation of middle fossa floor in an anterior-to-posterior direction has also been examined in cadaveric dissections and performed in surgery., Methods: The microsurgical anatomy of the middle fossa floor was studied in 10 adult cadaveric heads (20 sides) after meatal drilling on the middle fossa. Five latex-injected specimens were dissected in a stepwise manner to further define the microsurgical anatomy of the middle fossa approach. The middle fossa approach is illustrated in a patient for the decompression of the facial nerve to demonstrate the surgical technique and limitations of bone removal., Results: Elevation of middle fossa dura in an anterior-to-posterior direction leads to early identification of the GSPN, where the nerve passes under V3. The most reliable and easily appreciated angle to be used in localizing the IAM is between the IAM and the long axis of the GSPN, which is approximately 61 degrees . Beginning drilling the meatus medially at the petrous ridge is safer than beginning laterally, where the facial and vestibulocochlear nerves become more superficial. The cochlea anteromedially, vestibule posterolaterally, and superior semicircular canal posteriorly significantly limit the bone removal at the lateral part of the IAM., Conclusions: The surgical technique for the middle fossa approach which includes an anterior-to-posterior elevation of middle fossa dura starting from the foramen ovale and uses the angle between the IAM and the long axis of the GSPN to localize the meatus from above may be an alternative to previously proposed surgical methods.

Background: Conventional percutaneous thermocoagulation of postgasserian fibers has shown high success rates, with significant residual morbidity., Methods: This communication summarizes conclusions of multiple publications on our computerized mapping method and technique, and presents new data on short- and long-term results on trigeminal pain, including an actuarial analysis, complications., Results: In TTN, 97.4% of 75 procedures produced initial pain relief without medication. In all, 84.7% of appropriate verbal responses were achieved by proper location of the needle at the chosen target, requiring an average of 1.45 tracts per procedure. Needle tip was located between 1 and 15 mm below the sellar floor in 97.0% of procedures and in an angle of 40 degrees to 80 degrees regarding the clivus profile projection in 99.1%. A 93% reduction of corneal analgesia and a 100% suppression of major dysesthesias and cranial nerve palsies were found., Conclusion: We have shown a significant reduction of morbidity from percutaneous thermocoagulation of postgasserian fibers with similar short- and long-term results as those shown in 11 recently selected series. Strict adherence to all details of our new method and technique is essential. Future multiinstitutional studies are needed to confirm and enrich this small series.

The authors present a retrospective study of 121 patients treated with balloon compression of the rootlets behind the Gasser ganglion from 1995 to 2007. The inclusion criteria were drug-resistant idiopathic trigeminal neuralgia. The authors described the surgical technique and compared their results with results from the literature. The following parameters were compared: technical success, pain relief and recurrence, and complications. Balloon compression is considered in the literature to be a safer procedure than other percutaneous surgeries, especially for postoperative sensitive disorders. The best indications seem to be trigeminal neuralgia in older patients or pain due to multiple sclerosis and neuralgia involving the V1 territory. These conclusions should be confirmed by larger series, a longer follow-up (> 5 years) and statistically better analysis.

Background: Percutaneous balloon compression of the gasserian ganglion is an effective management of trigeminal neuralgia and is the only percutaneous procedure that preferentially may be performed under general anesthesia. However, the anatomy of Meckle's cave dictates the degree of compression, and if capacious, the usual smaller balloons may fail to adequately compress the ganglion., Methods: We designed a series of larger cannulas, placed over a guidewire technique for using larger balloons, or even multiple balloons, to increase the applicability of this technique in these patients., Results: In select cases, where smaller balloons fail to distort and deform the ganglion, with resultant poor clinical results, larger or multiple balloons may produce the desired response of pain relief., Conclusion: This technique is an added resource in managing this condition.

Objective: Balloon compression of the rootlets behind the trigeminal ganglion for the treatment of trigeminal neuralgia has become an increasingly popular method among neurosurgeons. However, the method has recognized complications, including double vision. Although occurring infrequently, diplopia may cause the patient significant disability. To minimize the risk for this complication, we analyzed our patients with respect to the surgical technique., Methods: We reviewed our joint consecutive series of 193 patients with trigeminal neuralgia treated with balloon compression. The medical records and the intraoperative x-ray images were analyzed., Results: We identified six patients with double vision postoperatively. In analyzing these occurrences, we found that the balloon was inflated outside Meckel's cave in four patients, the balloon was initially inflated too deeply in one patient, and the anatomy of Meckel's cave was probably aberrant in one patient. In five of the six patients, the symptoms resolved within 5 months., Conclusion: By meticulous surgical technique with close attention to the anatomic position and the shape of the inflated balloon, most cases of postcompression diplopia should be avoided.

Background: The history of the development of current available techniques to treat TN was reviewed., Methods: The largest peer-reviewed publications on the surgical treatment of refractory TN were analyzed, considering the pros and cons of each technique. Results of modern peer-reviewed radiosurgery series were presented, taking into consideration the approach of each research article. Radiation doses and targets for radiosurgery were discussed to maximize the understanding of this technique., Results: It is concluded that radiosurgery is the least invasive modality with the fewest side effects, although, to match the results of the competing techniques, a substantial number of patients still need some medication intake., Conclusion: Further studies determining the ideal target and radiation dose may bring radiosurgery results to the level of the ones achieved with microvascular decompression, currently considered the gold-standard method.

Background: Trigeminal neuralgia is a common cause of facial pain, characterized by shock-like pain affecting one or more branches of the trigeminal nerve. When conservative treatment fails and microdecompression is not indicated, percutaneous procedures are helpful. This percutaneous approach is done by a puncture up to the Gasserian ganglion, through the foramen ovale. Although simple and safe, this puncture demands some expertise from neurosurgeons. For that, a partnership between neurosurgeons and bio-engineers has developed a model for foramen ovale puncture, allowing practice for residents and young neurosurgeons., Method: A model for foramen ovale puncture has been created by interposition of synthetic materials over a skull, simulating the human face., Findings: This model has shown great similarity with that found in conventional surgeries, even upon repeated testing by experienced functional neurosurgeons and young residents., Conclusion: This model for foramen ovale puncture training has demonstrated valuable help for initial practicing of this common neurosurgical procedure, particularly in centers where there are not many cadavers available for training.