Absence of the torcular, review of venous sinus anatomy, and the simplified dural sinus classification.

BACKGROUND: Classically, the torcular Herophili is described as the symmetric junction between the superior sagittal sinus (SSS), transverse sinuses (TSs), and straight sinus (SS). However, finding this pattern in practice is not standard. Anatomical variations are common, and different drainage patterns should be expected. Existing literature proposes highly detailed descriptions and classifications of this region. Still, a simplified and practical categorization is not available. METHODS: We present an anatomical finding of the torcular Herophili discovered on a cadaveric dissection. Then, we conducted a retrospective study examining the 100 most recent cranial magnetic resonance venographies (MRVs) from the Mayo Clinic, labeling them with a new proposed dural sinus classification system. Images were initially classified by two authors and further validated by a board-certified neurosurgeon and a board-certified neuroradiologist from our institution. To measure consistency in image identification, two additional international neurosurgeons were asked to classify a subset of the same MRV images, and their answers were compared. RESULTS: Of the MRV cohort, 33 patients were male and 67 were female. Their ages ranged from 18 to 86 years, with a mean of 47.35 years and a median of 49 years. Upon examination, 53 patients presented as confluent (53%), 9 as SSS divergent (9%), 25 as SS divergent (25%), 11 as circular (11%), and 2 as trifurcated (2%). The inter-rater reliability ranked very good; agreement between the two neurosurgeons was 83% (κ = 0.830, p < 0.0005). CONCLUSION: The confluence of the venous sinuses is a highly variable anatomical area that is rarely evaluated with neuroimaging before surgery. The classic textbook configuration is not the rule. Using a simplified classification system may increase awareness and hopefully patient safety by preparing the physician for anatomical variations that they will encounter in a surgical or clinical scenario.

Trigeminal Neuralgia Secondary to Meckel's Cave Meningoencephaloceles: A Systematic Review and Illustrative Case.

Background: The culprit of trigeminal neuralgia (TGN) may occur at any point between the nerve's root entry zone (REZ) and Meckel's cave. Meckel's cave meningoencephaloceles are rare middle cranial fossa defects that usually remain asymptomatic but may contain prolapsed trigeminal nerve rootlets and result in TGN. Their management and surgical outcomes remain poorly understood. Objectives: To perform a systematic review of clinical presentation and surgical outcomes of middle fossa defects presenting with trigeminal nerve-related symptoms. Materials and Methods: A systematic review was conducted in accordance with the PRISMA guidelines for all reports of middle cranial fossa defects causing trigeminal nerve-related symptoms. The pathophysiology, presentation, surgical management, and outcomes are discussed and illustrated with a case. Results: Initial search from inception to March 2021 identified 33 articles for screening. After applying inclusion and exclusion criteria, 6 articles were included representing a total of 8 cases in addition to our case (n = 9). All 9 patients were females and 33.3% (n = 3) presented with classic trigeminal neuralgia. "Empty sella" syndrome and radiologic signs of intracranial hypertension were present in 40%-62%. No patient presented with cerebrospinal fluid leak. The preferred treatment modality was surgical with subtemporal extradural repairs using combinations of autologous fat and muscle grafts and synthetic dura. Postoperative outcomes were only available in 55.5% (n = 5) of the cases, and nearly all reported complete symptom resolution, except for one case in which the meningoencephalocele wall was incised, along with trigeminal rootlets adhered to it. Our patient had immediate and durable symptom relief after a 4-year follow-up. Conclusions: MEC containing prolapsed trigeminal nerve rootlets can cause typical trigeminal neuralgia from chronic pulsatile stress. This supports the hypothesis that the compressive or demyelinating culprit can locate more ventrally on the course of the trigeminal nerve. Subtemporal extradural surgical repairs can be safe, effective, and durable. Incising the MEC wall should be avoided as it may have trigeminal rootlets adhered to it.

The Middle Meningeal Artery: Branches, Dangerous Anastomoses, and Implications in Neurosurgery and Neuroendovascular Surgery.

The middle meningeal artery (MMA) has always been the workhorse corridor for devascularization of dural-based intracranial lesions and, more recently, has been established as a target for the endovascular management of chronic subdural hematomas. The MMA anatomy is complex and deceitful, and its territory of irrigation (including cranial nerves) is poorly understood. Furthermore, MMA variations and anastomoses are more frequent than expected, which may predispose to procedure-related morbidity. A literature search was conducted in electronic databases per PRISMA guidelines for studies describing normal and abnormal MMA anatomy including variations in MMA origin and dangerous anastomoses. Our institutional case series of greater than 100 MMA embolizations for management of chronic subdural hematomas were reviewed for abnormal MMA anatomy, and clinically relevant case examples are presented. In this article, we provide a comprehensive review of the MMA to provide a better understanding and appreciation of this artery, including pearls and pitfalls, that we hope will aid the neurosurgeon and neurointerventionalist in safely tackling these lesions.

Ultrasonic spine surgery for every thoracic disc herniation: a 43-patient case series and technical note demonstrating safety and efficacy using a partial transpedicular thoracic discectomy with ultrasonic aspiration and ultrasound guidance.

OBJECTIVE: Thoracic disc herniations (TDHs) are a challenging pathology. A variety of surgical techniques have been used to achieve spinal cord decompression. This series elucidates the versatility, efficacy, and safety of the partial transpedicular approach with the use of intraoperative ultrasound and ultrasonic aspiration for resection of TDHs of various sizes, locations, and consistencies. This technique can be deployed to safely remove all TDHs. METHODS: A retrospective review was performed of patients who underwent a thoracic discectomy via the partial transpedicular approach between January 2014 and December 2020 by a single surgeon. Variables reviewed included demographics, perioperative imaging, and functional outcome scores. RESULTS: A total of 43 patients (53.5% female) underwent 54 discectomies. The most common presenting symptoms were myelopathy (86%), motor weakness (72%), and sensory deficit (65%) with a symptom duration of 10.4 ± 11.6 months. A total of 21 (38.9%) discs were fully calcified on imaging and 15 (27.8%) were partially calcified. A total of 36 (66.7%) were giant TDHs (> 40% canal compromise). The average operative time was 197.2 ± 77.1 minutes with an average blood loss of 238.8 ± 250 ml. Six patients required ICU stays. Hospital length of stay was 4.40 ± 3.4 days. Of patients with follow-up MRI, 38 of 40 (95%) disc levels demonstrated < 20% residual disc. Postoperative Frankel scores (> 3 months) were maintained or improved for all patients, with 28 (65.1%) patients having an increase of 1 grade or more on their Frankel score. Six (14%) patients required repeat surgery, 2 of which were due to reherniation, 2 were from adjacent-level herniation, and 2 others were from wound problems. Patients with calcified TDHs had similar improvement in Frankel grade compared to patients without calcified TDH. Additionally, improvement in intraoperative neuromonitoring was associated with a greater improvement in Frankel grade. CONCLUSIONS: The authors demonstrate a minimally disruptive, posterior approach that uses intraoperative ultrasound and ultrasonic aspiration with excellent outcomes and a complication profile similar to or better than other reported case series. This posterior approach is a valuable complement to the spine surgeon's arsenal for the confident tackling of all TDHs.

Creation of a Proof-of-Concept 3D-Printed Spinal Lateral Access Simulator.

Background Minimally invasive lateral lumbar interbody fusion (LLIF) offers advantages over traditional approaches, providing indirect decompression of neural elements and deformity correction while avoiding many challenges and risks of anterior and posterior approaches. Mastering this technique requires a specialized team, advanced equipment, and sufficient case exposure. Current training is limited to the classic educational model, and alternative training methods such as cadaver labs can be inconvenient, inaccessible, expensive, and incompatible with intraoperative neuromonitoring (IONM) systems. Objective The aim of this study was to create a proof-of-concept, low-cost, fully synthetic lateral lumbar surgical simulator and to increase awareness of the lack of current training alternatives. Methods Standard engineering design and expert interviews of attending neurosurgeons, nurses, engineers, and medical device representatives (n=20) were utilized to determine key elements for the simulator, physical characteristics of the components, and translational strategy. Physical and radiographic testing was performed on multiple thermoplastics to determine appropriateness for inclusion in the simulator. For evaluation of the concept, a descriptive slide deck and questionnaire were sent to 15 U.S. and 15 international surgeons who perform LLIF. Results The lateral access training model (LATM) features the following three components: torso casing, spine module, and IONM feature. This model utilizes operable ABS (acrylonitrile butadiene styrene) 3D-printed lumbar vertebrae, verified for anatomical accuracy and compatibility with fluoroscopy. Additionally, a novel neuromonitoring simulation algorithm was developed to train junior residents on neurological complications. To further highlight the need for lateral training models, 30/30 polled surgeons felt that this simulator has value for the field, 29/30 noted that they would have used the LATM if they had access during training, and 30/30 responded that they would encourage trainees to practice on the LATM. Conclusion The LATM is a first step to provide reliable and inexpensive basic lateral lumbar spine training. While this model is lacking some anatomical features, our simulator offers novel training elements for lateral lumbar transpsoas approaches, which lay the foundation for future models to be built. The need for this training exists, and current gaps in the approach to learning these complex techniques need to be filled due to the inconvenience, cost, and impracticability of standard cadaveric models.

Cerebral venous thrombosis during the COVID-19 Pandemic: A multi-center experience.

OBJECTIVE: To describe the clinical characteristics and outcomes of CVT in patients with history of recent COVID-19 infection or vaccination. METHODS: We reviewed demographic, clinical, and radiographic characteristics of non-pyrogenic, non-traumatic CVT cases at our multi-center institution between March 2020 and December 2021. Patients were grouped according to their history of recent COVID-19 infection or vaccination into group-I (+COVID-19 association) and group-II (-COVID-19 association). RESULTS: Fifty-one patients with CVT were included, of which 14 (27.4%) had a positive COVID-19 association: 10 with infection and 4 with mRNA-COVID-vaccine. Nine patients in group-I had COVID-19 infection or vaccine within 30 days of CVT diagnosis, including 3 patients with active infection at the time of CVT diagnosis. Half of the patients in group-I (n = 7,50.0%) and 32.4% (n = 12) of group-II were male, and mean age was 52.6 years in group-I and 51.4 years in group-II. Fever at presentation was noted in one patient who had active COVID infection (I=1 (7.1%), II= 0 (0%)). Higher rates of comorbidities were observed in group-II: hypertension (I= 2 (14.3%), II= 13 (35.1%)), deep venous thrombosis(I=1(7.1%), II= 10 (27.0%)), pulmonary emboli (I=1(7.1%), II= 8(21.6%)), or stroke(I=0(0%), II= 6(16.4%)). Three patients had thrombocytopenia at the time of CVT diagnosis (5.4%) and most patients (n = 37, 72.5%) were treated medically with anticoagulation. Complication rate during hospitalization was 17.6% (n = 6), and no mortality was noted. CONCLUSION: Twenty-seven percent of CVT patients were associated with COVID-19 infection or vaccination, and the majority presented within 30 days of infection/vaccination.

The Wandering Nerve: Positional Variations of the Cervical Vagus Nerve and Neurosurgical Implications.

BACKGROUND: The vagus ("wandering") nerve is the longest cranial nerve with the largest territory of innervation in the human body. Injury during various operative procedures involving the anterior or lateral neck may lead to serious complications. Per "textbook" descriptions, the cervical vagus nerve (CVN) commonly locates within the carotid sheath, in between the common carotid artery (CCA) and internal jugular vein (IJV). However, anatomic variations in its positioning may occur more often than expected and intraoperative identification may anticipate potential surgical pitfalls. METHODS: A literature review was conducted per PRISMA guidelines for all studies describing positional variations of the CVN within the carotid sheath. A rare and potentially dangerous variation, occurring in only 0.7% of all reported cases, is illustrated with a cadaveric case. RESULTS: Overall, 10 anatomic CVN variations have been described across 971 specimens. The non-textbook variations (26.5%) consist of: lateral (4.7%), anterolateral (8.7%), posteromedial (0.2%), posterior (5.8%), anterior (3.1%), medial (0.7%), and anteromedial (0.4%) to the CCA, as well as posterolateral (0.3%) and posterior (2.6%) to IJV. The "textbook" anatomic location is posterolateral to CCA (73.5%). Moreover, an increase in variability is reported on the left side (17.1%) compared with the right (11.3%). Our cadaveric dissection revealed a right-sided CVN directly medial to the CCA. CONCLUSIONS: Positional variations of the CVN occur in over 26% of patients and may add difficulty to an array of surgical procedures. Knowledge of these variations and their prevalence may aid the surgeon in conducting a more precise dissection possibly preventing significant potential adverse sequelae.

Retrosigmoid Craniectomy and Suprameatal Drilling-3-Dimensionally Printed Microneurosurgical Simulation: 2-Dimensional Operative Video.

Neurosurgical training is being challenged by rigorous work-hour restrictions and the COVID-19 pandemic.1 Now, more than ever, surgical simulation plays a pivotal role in resident education and psychomotor skill development. Three-dimensional (3D) printing technologies enable the construction of inexpensive, patient-specific, anatomically accurate physical models for a more convenient and realistic simulation of complex skull base approaches in a safe environment.2 All stages of the surgical procedure can be simulated, from positioning and exposure to deep microdissection, which has an unparalleled educational value. The complex approach-specific anatomy, narrow working angles, and pathoanatomic relationships can be readily explored from the surgeon's perspective or point of view.2,3 Furthermore, different thermoplastic polymers can be utilized to replicate the visual and tactile feedback of bone (cortical/cancellous), neurological, and vascular tissues.4 Retrosigmoid craniectomies are widely used in neurosurgery with various applications, including microvascular decompressions in patients with trigeminal neuralgia.5-7 Removal of the suprameatal tubercle (SMT) extends the retrosigmoid approach superiorly to the middle fossa and Meckel's cave, and anteriorly to the clivus.8,9 This maneuver may be necessary in patients with prominent SMTs obstructing the view of the trigeminal nerve and in patients with a more anterosuperior neurovascular conflict. This video illustrates a microsurgical training tool for learning and honing the technique of retrosigmoid craniectomy and suprameatal drilling using an affordable (29.00 USD) biomimetic 3D-printed simulator that closely recapitulates not only the anatomy but also the tactile feedback of drilling and manipulating neurological tissues (see Table and Graph 1; minute 07:11) as it happens at the time of surgery.

Cerebral aneurysm debuting as rupture during diagnostic CT angiography: An unexpected worst-case scenario.

Previously-asymptomatic intracranial aneurysm rupture during cerebral angiography is an extremely rare phenomenon. There is a small risk of rupture of these aneurysms during digital subtraction angiography (DSA), but no case of spontaneous rupture during computed tomographic angiography (CTA) has been reported. A concise case of a 40-year-old woman referred for workup of an asymptomatic intracranial aneurysm who experienced acute rupture at the time of identification of a second aneurysm is described. This case highlights the potential for rupture at the time of scan acquisition and the importance of maintaining a high level of suspicion in the setting of neurological deterioration, as well as the potential need by all medical imaging professionals to identify an emergency and activate an urgent response.

Surgical Strategies for Acutely Ruptured Arteriovenous Malformations.

Brain arteriovenous malformations (AVMs) are focal neurovascular lesions consisting of abnormal fistulous connections between the arterial and venous systems with no interposed capillaries. This arrangement creates a high-flow circulatory shunt with hemorrhagic risk and hemodynamic abnormalities. While most AVMs are asymptomatic, they may cause severe neurological complications and death. Each AVM carries an annual rupture risk of 2-4%. Intracranial hemorrhage due to AVM rupture is the most common initial manifestation (up to 70% of presentations), and it carries significant morbidity and mortality. This complication is particularly important in the young and otherwise healthy population, in whom AVMs cause up to one-third of all hemorrhagic strokes. A previous rupture is the single most important independent predictor of future hemorrhage. Current treatment modalities for AVM are microsurgery, endovascular embolization, and radiosurgery. In acutely ruptured AVMs, early microsurgical excision is usually avoided. The standard is to wait at least 4 weeks to allow for patient recovery, hematoma liquefaction, and inflammatory reactions to subside. Exceptions to this rule are small, superficial, low-grade AVMs with elucidated angioarchitecture, for which early simultaneous hematoma evacuation and AVM excision is feasible. Emergent hematoma evacuation with delayed AVM excision (unless, as mentioned, the AVM is low grade) is recommended in patients with a decreased level of consciousness due to intracranial hemorrhage, posterior fossa or temporal lobe hematoma of >30 ml, or hemispheric hematoma of >60 ml. The applicability of endovascular techniques for acutely ruptured AVMs is not clear, but feasible options, until a definitive treatment is determined, include occluding intranidal and distal flow-related aneurysms and 'sealing' any rupture site or focal angioarchitectural weakness when one can be clearly identified and safely accessed. Radiosurgery is not performed in acutely ruptured AVMs because its therapeutic effects occur in a delayed fashion.

Neurosurgical management of a giant colloid cyst with atypical clinical and radiological presentation.

The finding of a colloid cyst on neuroimaging is often incidental. These lesions are usually located at the foramen of Monro, are hyperdense on CT scans, and generally demonstrate signal intensity of water on MR images, although this depends on their content. When symptomatic, they frequently present with headaches and nausea due to an obstructive hydrocephalus. The authors describe a case of a giant colloid cyst in a patient presenting with complete left-sided vision loss and progressive memory loss, two very atypical findings in colloid cyst presentation. Imaging findings were also atypical, and this case proved to be a diagnostic dilemma because of its clinical and radiological presentation. Histopathological investigation was of utmost importance in the final diagnosis of a colloid cyst. To the authors' knowledge this colloid cyst is larger than any other described in the literature.