Link, Michael J.

AbstractThe 3D stereoscopic technique consists in providing the illusional perception of depth of a given object using two different images mimicking how the right and left eyes capture the object. Both images are slightly different and when overlapped gives a three‐dimensional (3D) experience. Considering the limitations for establishing surgical laboratories and dissections courses in some educational institutions, techniques such as stereoscopy and photogrammetry seem to play an important role in neuroanatomy and neurosurgical education. The aim of this study was to describe how to combine and set up realistic models acquired with photogrammetry scans in 3D stereoscopic projections. Three donors, one dry skull, embalmed brain and head, were scanned using photogrammetry. The software used for displaying the final realistic 3D models (Blender, Amsterdam, the Netherlands) is a free software and allows stereoscopic projection without compromising the interactivity of each model. By default, the model was exported and immediately displayed as a red cyan 3D mode. The 3D projector used in the manuscript required a side‐by‐side 3D mode which was set up with simple commands on the software. The final stereoscopy projection offered depth perception and a visualization in 360° of each donor; this perception was noted especially when visualizing donors with different cavities and fossae. The combination of 3D techniques is of paramount importance for neuroanatomy education. Stereoscopic projections could provide a valuable tool for neuroanatomy instruction directed at clinical trainees and could be especially useful when access to laboratory‐based learning is limited.

OBJECTIVE Petroclival meningiomas (PCMs) are challenging lesions to treat because of their deep location and proximity to critical neurovascular structures. Patients with these lesions commonly present because of local mass effect. A symptom that proves challenging to definitively manage is trigeminal neuralgia (TN), which occurs in approximately 5% of PCM cases. To date, there is no consensus on whether microsurgical resection or stereotactic radiosurgery (SRS) leads to better outcomes in the treatment of TN secondary to PCM. In this systematic review and meta-analysis, the authors aimed to evaluate the available literature on the efficacy of microsurgical resection versus SRS for controlling TN secondary to PCM. METHODS The Embase, MEDLINE, Scopus, and Cochrane databases were queried from database inception to May 17, 2022, using the search terms “(petroclival AND meningioma) AND (trigeminal AND neuralgia).” Study inclusion criteria were as follows: 1) reports on patients aged ≥ 18 years and diagnosed with TN secondary to PCM, 2) cases treated with microsurgical resection or SRS, 3) cases with at least one posttreatment follow-up report of TN pain, 4) cases with at least one outcome of tumor control, and 5) publications describing randomized controlled trials, comparative or single-arm observational studies, case reports, or case series. Exclusion criteria were 1) literature reviews, technical notes, conference abstracts, or autopsy reports; 2) publications that did not clearly differentiate data on patients with PCMs from data on patients with different tumors or with meningiomas in different locations (other intracranial or spinal meningiomas); 3) publications that contained insufficient data on treatments and outcomes; and 4) publications not written in the English language. References of eligible studies were screened to retrieve additional relevant studies. Data on pain and tumor outcomes were compared between the microsurgical resection and SRS treatment groups. The DerSimonian-Laird random-effects model with Hartung-Knapp-Sidik-Jonkman variance correction was used to pool estimates from the included studies. RESULTS Two comparative observational studies and 6 single-arm observational studies describing outcomes after primary intervention were included in the analyses (138 patients). Fifty-seven patients underwent microsurgical resection and 81 underwent SRS for the management of TN secondary to PCM. By the last follow-up (mean 71 months, range 24–149 months), the resection group had significantly higher rates of pain resolution than the SRS group (82%, 95% CI 50%–100% vs 31%, 95% CI 18%–45%, respectively; p = 0.004). There was also a significantly longer median time to tumor recurrence following resection (43.75 vs 16.7 months, p < 0.01). The resection group showed lower rates of pain persistence (0%, 95% CI 0%–6% vs 25%, 95% CI 13%–39%, p = 0.001) and pain exacerbation (0% vs 12%, 95% CI 3%–23%, p = 0.001). The most common postintervention Barrow Neurological Institute pain score in the surgical group was I (66.7%) compared with III (27.2%) in the SRS group. Surgical reintervention was less frequently required following primary resection (1.8%, 95% CI 0%–37% vs 19%, 95% CI 1%–48%, p < 0.01). CONCLUSIONS Microsurgical resection is associated with higher rates of TN pain resolution and lower rates of pain persistence and exacerbation than SRS in the treatment of PCM. SRS with further TN management is a viable alternative in patients who are not good candidates for microsurgical resection.

Objective Compare cochlear implant (CI) performance between patients with ipsilateral sporadic vestibular schwannoma (VS) and NF2-related schwannomatosis (NF2). Compare CI performance according to VS management modality. Study Design Historical cohort. Setting Tertiary academic center. Patients Forty-nine patients (52 ears) undergoing cochlear implantation in the setting of ipsilateral sporadic (n = 21) or NF2-associated VS (n = 28). Interventions CI ipsilateral to VS. Main Outcome Measures Auditory thresholds, consonant–nucleus–consonant (CNC) word scores, and AzBio sentences in quiet scores. Results Among all patients, median post-CI pure tone average was 28 dB HL (interquartile range [IQR], 21–38), CNC word score was 39% (IQR, 6–62), and AzBio sentences in quiet score was 60% (IQR, 11–83) at a median of 12.5 months postimplantation. Despite the NF2 cohort having larger tumors, when comparing patients with sporadic versus NF2-associated VS, there were no statistically significant differences in CNC word (49% [30–70] vs. 31% [0–52]) or AzBio sentences in quiet (66% [28–80] vs. 57% [5–83]) scores. Regardless of NF2 status, all patients managed with observation, and radiosurgery achieved open-set speech. In patients who underwent microsurgery, 6 (46%) of 13 with NF2 achieved open-set speech recognition compared with 4 (67%) of 6 with sporadic disease. Conclusion Select patients with VS achieve successful hearing rehabilitation with a CI. In this cohort, tumor management strategy significantly influenced CI performance, whereas differences in NF2 status exhibited less effect. Specifically, all patients managed with observation or radiosurgery achieved open-set speech perception, whereas approximately half of people with NF2-related VS and two-thirds of people with sporadic VS achieved this outcome after tumor microsurgery. When disease permits, observation and radiosurgery should be considered in patients who may later pursue a CI.

This Viewpoint discusses how recent discoveries surrounding the natural history of sporadic vestibular schwannoma provide data to support a shift in current management paradigms.

Objective In certain cases, clinicians may consider continued observation of a vestibular schwannoma after initial growth is detected. The aim of the current work was to determine if patients with growing sporadic vestibular schwannomas could be stratified by the likelihood of subsequent growth based on initial growth behavior. Study Design Slice-by-slice volumetric tumor measurements from 3,505 serial magnetic resonance imaging studies were analyzed from 952 consecutively treated patients. Setting Three tertiary-referral centers. Patients Adults with sporadic vestibular schwannoma. Interventions Wait-and-scan. Main Outcome Measures Composite end point of subsequent growth- or treatment-free survival rates, where growth is defined as an additional increase of at least 20% in tumor volume from the volume at the time of initial growth. Results Among 405 patients who elected continued observation despite documented growth, stratification, of volumetric growth rate into less than 25% (reference: n = 107), 25 to less than 50% (hazard ratio [HR], 1.39; p = 0.06; n = 96), 50 to less than 100% (HR, 1.71; p = 0.002; n = 112), and at least 100% (HR, 2.01; p < 0.001; n = 90) change per year predicted the likelihood of future growth or treatment. Subsequent growth- or treatment-free survival rates (95% confidence interval) at year 5 after detection of initial growth were 31% (21–44%) for those with less than 25% growth per year, 18% (10–32%) for those with 25 to less than 50%, 15% (9–26%) for those with 50 to less than 100%, and 6% (2–16%) for those with at least 100%. Neither patient age (p = 0.15) nor tumor volume at diagnosis (p = 0.95) significantly differed across stratification groups. Conclusions At the time of diagnosis, clinical features cannot consistently predict which tumors will ultimately display aggressive behavior. Stratification by volumetric growth rate at the time of initial growth results in a stepwise progression of increasing likelihood of subsequent growth. When considering continued observation after initial growth detection, almost 95% of patients who have tumors that double in volume between diagnosis and the first detection of growth demonstrate further tumor growth or undergo treatment if observed to 5 years.

OBJECTIVE Chordomas are rare tumors from notochordal remnants and account for 1%–4% of all primary bone malignancies, often arising from the clivus and sacrum. Despite margin-negative resection and postoperative radiotherapy, chordomas often recur. Further, immunohistochemical (IHC) markers have not been assessed as predictive of chordoma recurrence. The authors aimed to identify the IHC markers that are predictive of postoperative long-term (≥ 1 year) chordoma recurrence by using trained multiple tree-based machine learning (ML) algorithms. METHODS The authors reviewed the records of patients who had undergone treatment for clival and spinal chordomas between January 2017 and June 2021 across the Mayo Clinic enterprise (Minnesota, Florida, and Arizona). Demographics, type of treatment, histopathology, and other relevant clinical factors were abstracted from each patient record. Decision tree and random forest classifiers were trained and tested to predict long-term recurrence based on unseen data using an 80/20 split. RESULTS One hundred fifty-one patients diagnosed and treated for chordomas were identified: 58 chordomas of the clivus, 48 chordomas of the mobile spine, and 45 chordomas sacrococcygeal in origin. Patients diagnosed with cervical chordomas were the oldest among all groups (58 ± 14 years, p = 0.009). Most patients were male (n = 91, 60.3%) and White (n = 139, 92.1%). Most patients underwent resection with or without radiation therapy (n = 129, 85.4%). Subtotal resection followed by radiation therapy (n = 51, 33.8%) was the most common treatment modality, followed by gross-total resection then radiation therapy (n = 43, 28.5%). Multivariate analysis showed that S100 and pan-cytokeratin are more likely to predict the increase in the risk of postoperative recurrence (OR 3.67, 95% CI 1.09–12.42, p= 0.03; and OR 3.74, 95% CI 0.05–2.21, p = 0.02, respectively). In the decision tree analysis, a clinical follow-up > 1897 days was found in 37% of encounters and a 90% chance of being classified for recurrence (accuracy = 77%). Random forest analysis (n = 500 trees) showed that patient age, type of surgical treatment, location of tumor, S100, pan-cytokeratin, and EMA are the factors predicting long-term recurrence. CONCLUSIONS The IHC and clinicopathological variables combined with tree-based ML tools successfully demonstrated a high capacity to identify recurrence patterns with an accuracy of 77%. S100, pan-cytokeratin, and EMA were the IHC drivers of recurrence. This shows the power of ML algorithms in analyzing and predicting outcomes of rare conditions of a small sample size.

Abstract Introduction Although many neuroanatomic atlases have been published, few have detailed complex cranial approaches and pertinent anatomic considerations in a stepwise fashion intended for rapid comprehension by neurosurgery students, residents, and fellows. Methods Five sides of formalin-fixed latex-injected specimens were dissected under microscopic magnification. The frontotemporal and orbitozygomatic approaches were performed by neurosurgical residents and fellows at different training levels with limited previous experience in anatomical dissection mentored by the senior authors (M.P.C. and M.J.L.). Meticulous surgical anatomic dissections were performed until sufficient visual and technical completion was attained, with parameters of effectively demonstrating key surgical steps for educational training purposes. Following the completion of dissection and three-dimensional photography, illustrative case examples were reviewed to demonstrate the relative benefits and optimal applications of each approach. Results The frontotemporal and orbitozygomatic approaches afford excellent access to anterior and middle skull base pathologies, as well as the exposure of the infratemporal fossa. Key considerations include head positioning, skin incision, scalp retraction, fat pad dissection and facial nerve protection, true or false MacCarty keyhole fashioning, sphenoid wing drilling and anterior clinoidectomy, completion of the craniotomy and accessory orbital osteotomy cuts, dural opening, and intradural neurovascular access. Conclusion The frontotemporal and orbitozygomatic approaches are core craniotomies that offer distinct advantages for complex cranial operations. Learning and internalizing their key steps and nuanced applications in a clinical context is critical for trainees of many levels. The orbitozygomatic craniotomy in particular is a versatile but challenging approach; operative-style laboratory dissection is an essential component of its mastery and one that will be powerfully enhanced by the current work.