Meckel's Cave Research Articles

Comparative Analysis of Surgical Working Corridors for Meckel Cave Trigeminal Schwannomas: A Quantitative Anatomic Study.

Volumetric analysis of the working corridors of the interdural approach to the Meckel cave may lead to a selection of routes which are anatomically more advantageous for trigeminal schwannoma resection. The herein-reported anatomic study quantitively compares the infratrochlear (IT) transcavernous, anteromedial (AM), and anterolateral (AL) corridors, highlighting their feasibility, indications, advantages, and limitations. Anatomic boundaries and depth of Meckel cave, porus trigeminus, IT transcavernous, AM, and AL corridors were identified in 20 formalin-fixed latex-injected cadaveric heads and were subsequently measured. The corridor areas and volumes were derived accordingly. Each opening angle was also calculated. Angles and volumes were compared using analysis of variance. Statistical significance was set at a P -value <.05. The IT transcavernous corridor volume was greater than that of the AM and AL. The opening angle of the AM middle fossa triangle was wider than the other 2. The IT corridor can be advantageous for Meckel cave schwannomas invading the cavernous sinus and those with a notable extension into the posterior fossa because the transcavernous approach maximizes the working space into the retrosellar area. The AM middle fossa corridor is strategic in schwannomas confined to the Meckel cave with a minor extension into the posterior fossa. It raises the chance of total resection with a single approach involving the porus trigeminus opening.

A New Perspective on the Cavernous Sinus as Seen through Multiple Surgical Corridors: Anatomical Study Comparing the Transorbital, Endonasal, and Transcranial Routes and the Relative Coterminous Spatial Regions.

Background: The cavernous sinus (CS) is a highly vulnerable anatomical space, mainly due to the neurovascular structures that it contains; therefore, a detailed knowledge of its anatomy is mandatory for surgical unlocking. In this study, we compared the anatomy of this region from different endoscopic and microsurgical operative corridors, further focusing on the corresponding anatomic landmarks encountered along these routes. Furthermore, we tried to define the safe entry zones to this venous space from these three different operative corridors, and to provide indications regarding the optimal approach according to the lesion's location. Methods: Five embalmed and injected adult cadaveric specimens (10 sides) separately underwent dissection and exposure of the CS via superior eyelid endoscopic transorbital (SETOA), extended endoscopic endonasal transsphenoidal-transethmoidal (EEEA), and microsurgical transcranial fronto-temporo-orbito-zygomatic (FTOZ) approaches. The anatomical landmarks and the content of this venous space were described and compared from these surgical perspectives. Results: The oculomotor triangle can be clearly exposed only by the FTOZ approach. Unlike EEEA, for the exposure of the clinoid triangle content, the anterior clinoid process removal is required for FTOZ and SETOA. The supra- and infratrochlear as well as the anteromedial and anterolateral triangles can be exposed by all three corridors. The most recently introduced SETOA allowed for the exposure of the entire lateral wall of the CS without entering its neurovascular structures and part of the posterior wall; furthermore, thanks to its anteroposterior trajectory, it allowed for the disclosure of the posterior ascending segment of the cavernous ICA with the related sympathetic plexus through the Mullan's triangle, in a minimally invasive fashion. Through the anterolateral triangle, the transorbital corridor allowed us to expose the lateral 180 degrees of the Vidian nerve and artery in the homonymous canal, the anterolateral aspect of the lacerum segment of the ICA at the transition zone from the petrous horizontal to the ascending posterior cavernous segment, surrounded by the carotid sympathetic plexus, and the medial Meckel's cave. Conclusions: Different regions of the cavernous sinus are better exposed by different surgical corridors. The relationship of the tumor with cranial nerves in the lateral wall guides the selection of the approach to cavernous sinus lesions. The transorbital endoscopic approach can be considered to be a safe and minimally invasive complementary surgical corridor to the well-established transcranial and endoscopic endonasal routes for the exposure of selected lesions of the cavernous sinus. Nevertheless, peer knowledge of the anatomy and a surgical learning curve are required.

The Consistency Between the Preoperative 3D-Reconstructed Meckel's Cave and the Intraoperative Balloon Results in Percutaneous Balloon Compression.

To predict the volume and shape of the balloon before PBC by reconstructing the Meckel's cave (MC) and establishing a volumetric measurement model, supporting preoperative preparation and intraoperative decisions. The clinical data of 31 patients with good therapeutic effects who underwent PBC are retrospectively collected, including preoperative MRI, the volume of contrast agent injected into the balloon, and intraoperative lateral X-ray images. The MC on the affected side of the 31 patients is reconstructed based on MRI using 3D Slicer, while the volume of the MC is calculated to compare with the volume of contrast agent. The width (W) and length (L) of the model of the MC in lateral view are measured and used to classify the shape of the MC based on W/L. The consistency between the W/L of the model of the MC and the W/L of the intraoperative balloon is evaluated. For volume, the mean value of the models of the MC (V1) in 31 patients is 399.77±155.13 mm³, while the mean value of the contrast agent injected during PBC (V2) is 539.03±111.93 mm³. The formula obtained by linear regression is V2= 392.1 + 0.3676×V1. Based on the value of W/L, the shape of the MC is classified into thin "pear" in 5 patients (16.13%), standard "pear" in 22 patients (70.97%), and square "pear" in 4 patients (12.90%). There is no significant difference in W/L between the models of the MC and the intraoperative balloons in 31 patients (P=0.221). In 31 patients with good efficacy, it is verified that the prediction of the MC before PBC by 3D Slicer is consistent with the actual situation of the intraoperative balloon. This method can provide certain basis for preoperative preparation and intraoperative judgment.

The Value of a Headless Pear Shape in Percutaneous Balloon Compression for Trigeminal Neuralgia.

Percutaneous balloon compression (PBC) has been regarded as a simple and effective remedy for trigeminal neuralgia. This study aims to retrospectively analyze the correlation between intraoperative balloon shapes and postoperative outcomes. Those consecutive PBC cases performed in our department between 2019 and 2022 were reviewed. According to the intraoperative balloon figures, they were cataloged as headless pear, slim pear, bottle gourd, and winter melon groups. The degree of pain or numbness was quantified using the visual analog scale. Those pain-free or pain score <3 and satisfied by the patient were called effective, and those numb score >3 were taken into account of numbness incidence. Except for missing cases, 160 were finally recruited in this study with a mean follow-up for 23.6 ± 12.8 months. Postoperatively, the pain score plunged from 8.8 ± 1.0 to 0.8 ± 2.0 immediately, which rose slightly over time and maintained at 2.4 ± 3.1. The maximal pain score drop occurred in the headless pear group ( P < .001) and the minimal in the winter melon group ( P < .001). The early efficacy of PBC was 100%, 84.1%, 91.4%, and 50.0%, respectively. However, the long-term efficacy was 88.2%, 75.0%, 82.1% and 25.0%. The ipsilateral numbness occurred in most of the cases immediately after PBC with a score of 3.5 ± 2.3, which decreased significantly within 3 months to 2.3 ± 2.0 and turned to 1.7 ± 1.8 finally ( P < .05). The highest and lowest numb score appeared in bottle gourd and winter melon groups, respectively ( P < .05). A headless pear shape emerged in lateral fluoroscopy as the balloon was fully inflated indicates that the entire Meckel cave is suffused, and hence, the anterior semilunar ganglion has been solidly compressed, which may lead to a successful outcome.

Endoscopic Lateral and Superior Cerebellar Keyhole Approach to the Anterior and Middle Incisural Space and Meckel Cave: An Anatomic Study

We sought to assess the feasibility of endoscopic lateral and superior cerebellar keyhole approach for exposure of the anterior and middle incisural space and Meckel cave. The endoscopic lateral and superior cerebellar keyhole approach was performed in 6 cadaveric heads (12 sides) using 0- and 30-degree endoscopes, respectively. The anatomic structures for this approach to the anterior and middle incisural space and Meckel cave were observed. By grinding out the suprameatal tubercle and petrous apex and incising the tentorium, the anatomic structures in the anterior incisural space were visualized. The mean area exposed with a 0-degree endoscope in the anterior incisural space was 212.50 ± 6.04 mm2, significantly less than that exposed with a 30-degree endoscope (233.83 ± 8.72 mm2) (P < 0.05). The anatomic distance of the Meckel cave in the depth was the same between a 0-degree endoscope and a 30-degree endoscope; however, the distance in the width was 9.48 and 12.32 mm, respectively (P < 0.01). The area of petrous window grinded by a 30-degree endoscope was only increased by 5.83 mm2, compared with a 0-degree endoscope (P > 0.05). This approach provides access to the anterior and middle incisural space and Meckel cave, which is feasible to clearly expose the anatomic structures in those regions with minimal invasiveness. Additionally, better visualization and surgical space can be achieved under a 30-degree endoscope.

How to understand an enlarged Meckel's cave? An anatomical study.

Dilatation of the trigeminal cavum, or Meckel's cave (MC), is usually considered a radiological sign of idiopathic intracranial hypertension. However, the normal size of the trigeminal cavum is poorly characterized. In this study, we describe the anatomy of this meningeal structure. We dissected 18 MCs and measured the length and width of the arachnoid web and its extension along the trigeminal nerve. Arachnoid cysts were clearly attached to the ophthalmic (V1) and maxillary (V2) branches until they entered the cavernous sinus and foramen rotundum, respectively, without extension to the skull base. Arachnoid cysts were close to the mandibular branch toward the foramen ovale, with a median anteromedial extension of 2.5 [2.0-3.0] mm, lateral extension of 4.5 [3.0-6.0] mm, and posterior extension of 4.0 [3.2-6.0] mm. The trigeminal cavum arachnoid had a total width of 20.0 [17.5-25.0] mm and length of 24.5 [22.5-29.0] mm. Our anatomical study revealed variable arachnoid extension, which may explain the variability in size of the trigeminal cavum in images and calls into question the value of this structure as a sign of idiopathic intracranial hypertension. The arachnoid web extends beyond the limits described previously, reaching almost double the radiological size of the cavum, particularly at the level of V3 afference of the trigeminal nerve. It is possible that strong adhesion of the arachnoid to the nerve elements prevents the formation of a true subarachnoid space that can be visualized by magnetic resonance imaging.

Pre-operative MRI measurement of the Meckel's cave volume in percutaneous balloon compression of the trigeminal nerve.

To explore the feasibility of measuring the volume of Meckel's cave by MRI before operation and its value in guiding percutaneous balloon compression (PBC) of trigeminal nerve (TN). The pre-operative MRI and operative data of 31 patients, who underwent PBC of TN, were analyzed retrospectively. Axial scanning was performed using T2 weighted three-dimensional high-resolution MRI, and then coronal and sagittal images were reconstructed. Volumes of Meckel's cave were measured by two radiologists, and their consistence was assessed using intraclass correlation coefficient. Pearson and Spearman analyses were used to assess the correlations of the volumes of Meckel's cave among coronal, sagittal, and axial MRI images, and between that measured by MRI and the filling volume of operative balloon, respectively. Bland-Altman plot was used to assess their agreements. There was high consistency in volumes of Meckel's cave between the two radiologists with intraclass correlation coefficient from 0.921 to 0.962. High correlations and good agreements in volumes of Meckel's cave were obtained from the three orientations, with Pearson coefficients and differences of 0.96 and 0.01 ml (coronal vs sagittal), 0.95 and 0.01 ml (coronal vs axial), and 0.95 and 0.00 ml (sagittal vs axial), respectively. The moderate correlation and good agreements were also obtained between MRI and operative balloon volume (ρ = 0.448, p < 0.05; difference, 0.02 ml). It is feasible to measure the volume of Meckel's cave by MRI before operation, and it is of guiding significance for the individual selection of balloon filling volume in PBC of TN. This is the first study to investigate the relationships between the three-dimensional high resolution MRI images and the clinical volume of Meckel's cave. The high-resolution MRI method can help guide PBC of TN.

Simplified anterior transpetrosal approach without superior petrosal sinus and tentorial incision for lesions centered in Meckel's cave.

The anterior transpetrosal approach (ATPA) is an effective method to reach lesions in the petroclival region. This approach involves many steps, including superior petrosal sinus (SPS) ligation and tentorial cutting. It is sometimes unnecessary to perform all procedures in the ATPA for certain lesions, especially those centered in the Meckel's cave. Here, we present a simplified anterior transpetrosal approach (SATPA) without superior petrosal sinus and tentorial incision for lesions centered in the Meckel's cave as a modified ATPA. This study included 13 patients treated with SATPA. The initial steps of SATPA are similar to ATPA, excluding a middle cranial fossa dural incision, SPS dissection, or tentorial incision. Histological examination was performed to understand the membrane structure of the trigeminal nerve, which runs through the Meckel's cave. Pathology revealed trigeminal schwannoma (n=11), extraventricular central neurocytoma (n=1), and a metastatic tumor (n=1). The average tumor size was 2.4 cm. The total removal rate was 76.9% (10/13). Permanent complications included trigeminal neuropathy in four cases and cerebrospinal fluid leakage in one case. Histological examination revealed the trigeminal nerve traverses the subarachnoid space from the posterior fossa subdural space to the Meckel's cave and is covered with the epineurium in the inner reticular layer. We used SATPA for lesions located in the Meckel's cave identified using histological examination. This approach may be considered for small- to medium-sized lesions centered in the Meckel space. None.

Comparative Anatomic Study Between Intradural Suboccipital Retrosigmoid and Extradural Transzygomatic Middle Fossa Approaches to Expose the Trigeminal Nerve

Meckel cave tumors are relatively rare, especially trigeminal nerve (TN) schwannomas. These tumors frequently project through the trigeminal pore, occupying the middle and posterior fossae. The most used routes to this region are the suboccipital retrosigmoid intradural approach (SORSA) and the transzygomatic middle fossa approach (TZMFA). Both approaches allow further exposure by adding intraoperative techniques, such as removing the suprameatal tubercle (retrosigmoid intradural suprameatal approach [RISA]) and the petrous apex (TZMFA-PA), respectively. This study aims to understand how TN exposure differs between both surgical approaches and how it increases by adding specific surgical maneuvers to these techniques. Five formalin-fixed adult cadaver heads were submitted to high-resolution computed tomography and their images were loaded into the neuronavigation device. Anatomic key points were defined along the outline of the TN, and their three-dimensional spatial locations were collected following each surgical approach. This process allowed the calculation of the TN exposed area obtained through each technique. The mean areas of exposure of the TN were 125.9 mm2 with SORSA and 208.9 mm2 with RISA, which represents an additional mean gain of 61.92% (P= 0.047). Using TZMFA, a mean exposure of 419.24 mm2 was obtained. When TZMFA-PA was used, the mean exposed area was 486.03 mm2, representing a mean gain in the exposure area of 16.81% (P= 0.072). Our study suggests that TZMFA allows better exposure of TN ganglionic and postganglionic segments, and the removal of the PA adds the preganglionic segment visualization, although with less TN exposed area compared with RISA. With SORSA, the additional suprameatal tubercle removal shows the trigeminal pore and the medial margin of the central portion of the TN ganglionic segment, making it possible to expose the mouth of the Meckel cave and part of its contents.

Robot-Assisted Percutaneous Balloon Compression in Elderly Patients with Trigeminal Neuralgia.

To investigate the clinical effects of percutaneous balloon compression (PBC) for trigeminal neuralgia in elderly patients with the assistance of a neurosurgical navigation and positioning planning system (referred to hereafter as the robot). We performed a retrospective analysis of 11 patients with trigeminal neuralgia. Preoperative TOF MRA, T2WI-SPACE, and thin-slice CT scans were performed, and the volume of Meckel's Cave was calculated by multi-modal image fusion on a workstation. Surgical planning involved two paths. Path A was the actual puncture path, the target point was the anterior inner quadrant of the inner opening of the foramen ovale; Path B represented a virtual path for measurement, and was used to plan the depth of balloon placement. The foramen ovale puncture for path A was completed under the guidance of a robotic arm adapter, while path B was completed under lateral X-ray fluoroscopy with a DSA machine. The balloon was placed at a predetermined depth, and filled to a "pear" shape to complete the operation. Preliminary follow-up results were obtained by considering VAS score and BNI classification. The foramen ovale was successfully punctured in all 11 patients and entered Meckel's Cave, the balloon was then filled to create a "pear shape". Immediate complete healing was achieved in 10 patients and delayed healing was achieved in one patient by the 5th postoperative day. No serious complications were identified that were related to surgery, and over a follow-up time of 1-12 months, there was no recurrence of pain, and a BNI numbness grade of 2-3 points. The appropriate ratio of the balloon inflated volume to the preoperative Meckel's Cave volume was approximately 1.7. Preliminary clinical application and short-term follow-up showed that robot-assisted PBC surgery is a safe and effective surgical method for elderly patients with trigeminal neuralgia.

Endoscopic Transnasal Transpterygoid Biopsy of the Trigeminal Nerve

Metastatic involvement of the trigeminal nerve is a rare manifestation of malignant neoplasms. Squamous cell carcinoma of the head and neck, lymphoma, and lung and colon cancers are reported to affect Meckel's cave. Little is known to why tumors may metastasize and involve some branches of the trigeminal nerve. In case of suspicious lesions, an endoscopic transnasal biopsy approach into the pterygopalatine and the infratemporal fossa is an option. An endoscopic transnasal transpterygoid approach to the Meckel's cave and middle cranial fossa is described in our case. Neurosurgical literature reports that open approaches to this area subject the brain parenchyma to stretch forces that render gaining full access somewhat challenging. The choice of approach should be tailored to the case and the size of the tumor and the prognosis of the patient. In our reported case, the biopsy was performed in the described technique without complications or a major cerebrospinal fluid leak.

Endoscopic transorbital approach for skull base lesions: a report of 16 clinical cases.

Due to the deep location, complex anatomy, and adjacent vital neurovascular structures, skull base surgery is challenging and requires specific approaches. The emerging endoscopic transorbital approach (eTOA) technique provides a new approach to the orbital content, spheno-orbital region, lateral cavernous sinus, and Meckel's cave. In this study, the clinical utility and effectiveness of the eTOA are reported. Sixteen cases who underwent the eTOA were included in the current study. The patients were divided into 3 groups according to tumor location: Group A (intraorbital, 6 cases), group B (spheno-orbital, 7 cases), and group C (cavernous sinus, and Meckel's cave, 3 cases). The clinical data and surgical results were analyzed. Eight meningiomas, 2 hemangiomas, 1 low-grade glioma, 1 instance of inflammatory hyperplasia tissue, 1 Langerhans cell histiocytosis, 1 epidermoid cyst, 1 trigeminal schwannoma, and 1 bone fibrosis hyperplasia were observed. The mean tumor diameter was 2.4cm. A single case in Group A and Group C underwent biopsy (12.5%), and 1 case of fibrous dysplasia in Group B underwent sufficient orbit decompression (6.25%). The remaining 13 cases underwent gross total tumor resection (81.25%). No cerebral-spinal fluid leak or infection occurred. And no cosmetic problems or significant complications were observed during the follow-up. As a minimally invasive technique, the eTOA has unique advantages for carefully selected skull base lesions because of its direct route, short working distance, and distinct attack angle.

A Nod for Meckel: A Novel Surgical Position Utilizing Meckel's Cave Anatomy for Percutaneous Glycerol Rhizotomy in Trigeminal Neuralgia.

Objective We aim to describe a novel positioning technique using a specific surgical table to achieve the optimal angle during percutaneous glycerol rhizotomy (PGR) for trigeminal neuralgia (TN). Design This is a descriptive and photographic analysis of successful cases for future implementation. Setting This study was conducted at a single-institution, academic center. Participants The participants were adult patients with TN who underwent PGR and provided consent for publication. Main Outcome Measures Primary outcomes of this study were TN symptomatic relief and surgical complications. Results The use of a beach chair sliding headboard surgical table for PGR is plausible and ensures precise and immobile head flexion for 1 hour postglycerol injection. There were no intraoperative or postoperative complications. All patients achieved successful reduction of TN symptoms. Conclusions Utilizing this new method of intraoperative navigation with a unique surgical table in the upright position, surgeons may achieve precise head adjustments post-PGR. Head flexion has been postulated as a means of ensuring glycerol containment in Meckel's cave. This method can help standardize this procedure for future systematic studies on the importance of head positioning post-PGR.

Correlation between balloon volume and Meckel's cave size and its influence of percutaneous microballoon compression for trigeminal neuralgia

Objective: To investigate the correlation between balloon volume and Meckel's cave size during percutaneous puncture microballoon compression (PMC) for trigeminal neuralgia and the influence of the compression coefficient (the ratio of balloon volume/Meckel's cave size) on the prognosis. Methods: Seventy-two patients (28 males and 44 females) aged (62±11) years who underwent PMC under general anesthesia for trigeminal neuralgia in the First Affiliated Hospital of Zhengzhou University from February 2018 to October 2020 were retrospectively collected. All patients underwent preoperative cranial magnetic resonance imaging (MRI) to measure Meckel's cave size, intraoperative balloon volume was recorded, and the compression coefficient was calculated. Follow-up visits were performed preoperatively (T0) and 1 d (T1), 1 month (T2), 3 months (T3), and 6 months (T4) postoperatively, either in the outpatient clinic or by telephone, and the Barrow Neurological Institute pain scale (BNI-P) score, the Barrow Neurological Institute facial numbness (BNI-N) score and the occurrence of complications were recorded and compared at each time point. Patients were divided into 3 groups according to different prognoses: patients in group A (n=48) were with no recurrence of pain and mild facial numbness, patients in group B (n=19) were with no recurrence of pain but severe facial numbness, while those in group C (n=5) had recurrence of pain. The differences in balloon volume, Meckel's cave size, and compression coefficient were compared among the three groups, and the correlation between balloon volume and Meckel's cave size in each group was analyzed by Pearson correlation. Results: The effective rate of PMC for trigeminal neuralgia was 93.1% (67/72). At time points from T0 to T4, patients had BNI-P scores [M (Q1, Q3)] of 4.5 (4.0, 5.0), 1.0 (1.0, 1.0), 1.0 (1.0, 1.0), 1.0 (1.0, 1.0) and 1.0 (1.0, 1.0), and BNI-N scores [M (Q1, Q3)] of 1.0 (1.0, 1.0), 4.0 (3.0, 4.0), 3.0 (3.0, 4.0), 3.0 (2.0, 4.0) and 2.0 (2.0, 3.0), respectively. Compared with those at T0, patients had lower BNI-P scores and higher BNI-N scores from T1 to T4 (all P<0.05). In all patients, group A, group B, and group C, the balloon volume was (0.65±0.15), (0.67±0.15), (0.59±0.15) and (0.67±0.17) cm3, respectively, with no statistically significant difference (P>0.05), while the Meckel's cave size was (0.42±0.12), (0.44±0.11), (0.32±0.07), and (0.57±0.11) cm3, with a statistically significant difference (P<0.001). The balloon volumes and Meckel's cave sizes were all linearly and positively correlated (r=0.852, 0.924, 0.937 and 0.969, all P<0.05). The compression coefficient in group A, B and C was (1.54±0.14), (1.84±0.18) and (1.18±0.10), respectively, with a statistically significant difference (P<0.001). There were no serious intraoperative complications such as death, diplopia, arteriovenous fistula, cerebrospinal fluid leak, and subarachnoid hemorrhage. Conclusions: Intraoperative balloon volume during PMC for trigeminal neuralgia is linearly and positively correlated with the volume of the patient's Meckel's cave. The compression coefficient varies among patients with different prognoses and the compression coefficient may be a factor affecting the patient's prognosis.

Microanatomical study of arachnoid granulations and meningeal architecture around Meckel’s cave

Although the microanatomy of Meckel’s cave (MC) has been well studied, there are still controversies regarding the meningeal architecture of the space. Moreover, there are only general mentions of the arachnoid granulations near MC in just a few sources. This study is aimed at determining the frequency, location, and anatomical variability of the main clusters of arachnoid granulations around MC. The dissection involved 26 isolated specimens of MC fixed in formalin (neutral buffered, 10%). This number included five freshly harvested specimens examined histologically. Additional paraffin block with MC horizontal section was taken from our neuroanatomical collection. Carefully selected anatomical and histological techniques were applied to assess the complex relationships between the arachnoid granulations and adjacent structures. Arachnoid granulations were found around MC in all specimens with different anatomical variations. The main clusters of arachnoid granulations were close to the trigeminal ganglion and its divisions. The dorsolateral wall of MC was a thick layer formed by interweaving bundles of collagen fibers arranged in various directions. The entire MC was surrounded by a dural sleeve (envelope). This sleeve separated MC from the lateral sellar compartment. At its anterior (rostral) end, it formed a cribriform area pierced by individual fascicles of the trigeminal nerve’s primary divisions. The connective tissue forming the sleeve was not only continuous with the epineurium but also shifted to the perineuria surrounding individual nerve fascicles. The meningeal architecture around MC has a complex and multilayer arrangement with a collagenous sleeve closely related to the trigeminal ganglion. Arachnoid granulations are typically found around MC.

Refining the Anatomy of Percutaneous Trigeminal Rhizotomy: A Cadaveric, Radiological, and Surgical Study.

Percutaneous trigeminal rhizotomy (PTR) is a widely used procedure for trigeminal neuralgia. However, comprehensive analyses that combine anatomic, radiological, and surgical considerations are rare. To present high-quality anatomic dissections and radiological studies that highlight the technical nuances of this procedure. Six silicon-injected postmortem heads underwent PTR. The surgical corridors were dissected, and the neurovascular relationships were studied. In addition, 20 dried human skulls and 50 computed tomography angiography and MRI scans were collected to study the anatomic relationships for a customized puncture corridor. The PTR corridor was divided into 3 segments: the buccal segment (length, 34.76 ± 7.20 mm), the inferior temporal fossa segment (length, 42.06 ± 6.92 mm), and the Meckel cave segment (length, 24.75 ± 3.34 mm). The puncture sagittal (α) and axial (β) angles measured in this study were 38.32° ± 4.62° and 19.13° ± 2.82°, respectively. The precondylar reference line coincided with the foramen ovale in 75% of the computed tomography angiography scans, and the postcondylar line coincided with the carotid canal in 70% of the computed tomography angiography scans; these lines serve as the intraoperative landmarks for PTR. The ovale-carotid-pterygoid triangle, delineated by drawing a line from the foramen ovale to the carotid canal and the lateral pterygoid plate, is a distinguished landmark to use for avoiding neurovascular injury during fluoroscopy. Knowledge of the anatomic and radiological features of PTR is essential for a successful surgery, and a customized technical flow is a safe and effective way to access the foramen ovale.

Trigeminal Schwannoma - Case Report of a Rare Tumour.

Schwannomas are benign nerve tumours arising from the Schwann cells. Approximately 25-45% of schwannomas occurs in the head and neck region. Majority of schwannomas in the head and neck region arise from the vagus nerve. Trigeminal schwannomas account for about 0.2% of all intracranial tumours. Trigeminal schwannomas can originate from any section of the fifth cranial nerve, from the root to the distal extracranial branches, but majority develops from the Gasserian ganglion, usually growing in the middle cranium. Most common presenting symptom is facial pain. MRI is the imaging modality of choice and CT scan usually serves as a supplementary imaging especially for skull base tumours. 47 year old male patient presented to the outpatient department with complains of swelling over the left side of palate. Contrast enhanced CT scan demonstrated a large bilobed heterogeneously enhancing soft tissue lesion in the left infratemporal fossa with widened foramen ovale and extension of lesion into the Meckel's cave, larger contiguous component extending into ramus of mandible. MRI scan showed a large lobulated mass in the left masticator space with intracranial extension. Biopsy of the lesion was suggestive of schwannoma. The patient underwent left composite resection with dural repair and free flap reconstruction. Post operatively, on day 5 he developed features of meningitis for which he was treated conservatively and later discharged in stable condition. Trigeminal schwannomas are rare tumours with very low chance of malignant transformation which commonly presents with facial pain. MRI is the imaging modality of choice. Complete surgical excision is the treatment of choice.

Mandibular Fossa Approach to Petroclival and Anterior Pontine Lesions.

Objective To describe the anatomy related to a novel approach to the petroclival region through the mandibular fossa for the treatment of petroclival and anterior pontine lesions. Design Five dry skulls were examined for surgical approach. Three adult cadaveric heads underwent bilateral dissection. One cadaveric head was evaluated with computed tomography after dissection. Setting This study was performed in an academic medical center. Participants Neurosurgical anatomy researchers performed this study using dry skulls and cadaveric heads. Main Outcome Measurements This was a proof-of-concept anatomical study. Results The mandibular fossa approach uses a vertical preauricular incision above the facial nerve branches. Removal of the temporomandibular joint exposes the mandibular fossa. The anterior boundary is the mandibular nerve at the foramen ovale, and the posterior boundary is the jugular foramen. The chorda tympani, eustachian tube, and tensor tympani muscle are sectioned. The carotid artery is transposed out of the petrous canal, and a petrosectomy is performed from Meckel's cave to the foramen magnum and anterior occipital condyle. Dural opening exposes the anterior pons, vertebrobasilar junction, bilateral vertebral arteries, and the ipsilateral anterior and posterior inferior cerebellar arteries. At completion, the temporomandibular joint is reconstructed with a prosthetic joint utilizing a second incision along the mandible. Conclusions The mandibular fossa approach is a new trajectory to the petroclival region and the anterior pons. It combines the more anterior angle of endoscopic approaches along with the enhanced control of open approaches. Further study is necessary before this approach is used clinically.

Neurovascular Structures at Risk During Surgical Access to Trigeminal Ganglion and Meckel's Cave - An Anatomical Study.

It is difficult to approach the Trigeminal Ganglion (TG) and Meckel's cave (MC) during surgeries. Therefore, the exact knowledge of the relationship of surgical landmarks to related anatomical structures is vital to reduce the associated postoperative morbidity. The aim of the present study was to enhance the knowledge of the surgical anatomy of structures that are present in the conduit of all surgical approaches to TG and MC, their distances from surrounding neurovascular structures, and their variations. The study was carried out on 40 embalmed cadavers (Eight Female) of the anatomy department of a teaching hospital in Central India. Meticulous dissection of cranial fossae was done to locate TG, MC, and related anatomical structures. All distances from TG and MC were measured using an electronic digital calliper. Length, width, and thickness of TG were 15.39 mm, 4.39 mm, and 2.54 mm, respectively. The distance from zygomatic arch, the lateral end of the petrous ridge, arcuate eminence, foramen ovale, and foramen spinosum to MC was 26.10 mm and 37.94 mm, 16.46 mm, 4.54 mm, and 11.23 mm, respectively. The sixth, fourth, and third cranial nerves were 6.26 mm, 4.94 mm, and 2.53 mm from MC, respectively. The MC was 42.72 mm and 33.87 mm anteromedial from posterior and anterior limits of the sigmoid sinus. Findings of the present study will aid surgical planning and decide the approach to TG and MC and avoid surgical complications.

The Key to a Successful PBC in Treatment of Trigeminal Neuralgia.

As a minimally invasive treatment of trigeminal neuralgia, percutaneous balloon compression (PBC) has become increasingly popular worldwide. Because it is simple and straightforward, it does not need a complicated apparatus only a fluoroscope plus an operator's experience. Therefore, the surgical technique seems to be essential and worth further addressing. The paper stresses that the target of PBC should be the semilunar ganglion (the soma of neurons) rather than the rootlets (axons) because the latter is renewable. To obtain a sufficient pressure against the ganglion, Meckel's cave should be covered utterly by an inflating balloon, which fluoroscopically appears in a pear shape. To attain a proper balloon position, it is suggested to make a tunnel with a blunt stylet in a proper penetrative angle before inserting a soft catheter. Too large a pear is unnecessary, hence injecting should be stopped when growth becomes apparently slow. To avoid an unacceptable postoperative paresthesia, a prolonged compression is not encouraged.