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Experience and modification of skull base reconstruction results in lower complications rates

Objectives To investigate the efficacy of nasal septum bone flap combined with vascularized pedicle nasoseptal flap (VPNSF) in the treatment of high-flow cerebrospinal fluid (CSF) leakage in the endonasal endoscopic skull base surgery.

Methods A total of 156 patients in group A used a multi-layer skull base reconstruction method of fat-absorbable artificial dura mater- fascia lata-VP-NSF, and were treated with drainage of the lumbar cistern after surgery, in addition, a total of 94 patients in group B used a multi-layer skull base reconstruction method of fat-absorbable artificial dura mater-nasal septal bone flap-VP-NSF, and no lumbar cistern drainage was performed after surgery. Analyzed and compared the differences of postoperative cerebrospinal fluid rhinorrhea, intracranial infection, re-repair, average bed rest time, pulmonary infection and deep venous thrombosis of lower extremities were analyzed and compared in the two groups.

Results In group A, 11 cases of cerebrospinal fluid rhinorrhea occurred after operation. In addition, 15 cases developed intracranial infection. During this period, there were 20 cases of pulmonary infection and 3 cases of deep venous thrombosis of lower extremities. In group B, there were 1 case of cerebrospinal fluid rhinorrhea (P < 0.05), 2 cases of intracranial infection (P < 0.05), 2 cases of pulmonary infection (P < 0.05), and 0 case of deep venous thrombosis of lower extremities (P > 0.05).

Conclusion Nasal septum bone flap combined with VP-NSF is effective in the treatment of high-flow CSF leaks in the endonasal endoscopic skull base surgery, which can avoid postoperative lumbar cistern drainage and is worth popularizing.

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Retrolabyrinthine transsigmoid approach to complex parabrainstem tumors in the posterior fossa

J Neurosurg 136:1097–1102, 2022

The surgical management of large and complex tumors of the posterior fossa poses a formidable challenge in neurosurgery. The standard retrosigmoid craniotomy approach has been performed at most neurosurgical centers; however, the retrosigmoid approach may not provide enough working space without significant retraction of the cerebellum. The transsigmoid approach provides wider and shallower surgical fields; however, there have been few clinical and no cadaveric studies on its usefulness. In the present study, the authors describe the transsigmoid approach in clinical cases and cadaveric specimens.

METHODS For the clinical study, the authors retrospectively reviewed the medical records and operative charts of patients who had been surgically treated for parabrainstem tumors using the transsigmoid approach between 1997 and 2019. They analyzed patient demographic and clinical data, as well as surgical and clinical outcomes. In the cadaveric study, they compared the surgical views obtained in different approaches (retrosigmoid, presigmoid, retrolabyrinthine, and transsigmoid) and measured the sigmoid sinus width at the level of the endolymphatic sac and the distance between the anterior edge of the sigmoid sinus and the endolymphatic sac on 35 sides in 19 cadaveric specimens.

RESULTS A total of 21 patients (6 males and 15 females) with a mean age of 42.2 (range 15–67) years were included in the clinical study. Eleven patients had meningioma, 7 had vestibular schwannoma, 2 had hemangioblastoma, and 1 had epidermoid cyst. Gross-total, near-total, and subtotal removal were achieved in 7 (33.3%), 3 (14.3%), and 11 (52.4%) patients, respectively. In the cadaveric study, 19 cadaveric specimens were used. The sigmoid sinus was cut in the middle, and the incision was extended from the retrosigmoid to the presigmoid dura. The dura was then retracted upward and downward like opening a door. The results indicated that this technique can widen the operative field anteriorly by approximately 2 cm as compared to the retrosigmoid approach and provides a better view anterior to the brainstem.

CONCLUSIONS The transsigmoid approach is useful for complex parabrainstem tumors in the posterior fossa because it provides a wider and shallower operative view with less retraction of the cerebellum. This enables safer tumor removal with less damage to important structures in the posterior fossa, resulting in better operative and clinical outcomes.

 

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Double pedicled nasoseptal flap for skull base repair after endoscopic expanded endonasal approach

Acta Neurochirurgica (2022) 164:1111–1114

Expanded endonasal approach offers a spectacular corridor for skull base tumour resection but requires reliable multilayer reconstruction techniques with a vascularized nasoseptal flap.

Method On the basis on our substantial experience of 136 patients operated on between January 2008 and January 2020, the double pedicled nasoseptal flap technique was developed for skull base repair. The technique is finely detailed. The nasal floor mucosa was preserved. CSF leakage occurred in 4% of patients.

Conclusion Double pedicled nasoseptal flap is a reproducible and efficient technique for skull base reconstruction after expanded endonasal approach and is associated with limited rhinological complications.

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Risk of tract recurrence with stereotactic biopsy of brain metastases

J Neurosurg 136:1045–1051, 2022

Stereotactic biopsy is increasingly performed on brain metastases (BrMs) as improving cancer outcomes drive aggressive multimodality treatment, including laser interstitial thermal therapy (LITT). However, the tract recurrence (TR) risk is poorly defined in an era defined by focused-irradiation paradigms. As such, the authors aimed to define indications and adjuvant therapies for this procedure and evaluate the BrM-biopsy TR rate.

METHODS In a single-center retrospective review, the authors identified stereotactic BrM biopsies performed from 2002 to 2020. Surgical indications, radiographic characteristics, stereotactic planning, dosimetry, pre- and postoperative CNS-directed and systemic treatments, and clinical courses were collected. Recurrence was evaluated using RANO-BM (Response Assessment in Neuro-Oncology Brain Metastases) criteria.

RESULTS In total, 499 patients underwent stereotactic intracranial biopsy for any diagnosis, of whom 25 patients (5.0%) underwent biopsy for pathologically confirmed viable BrM, a proportion that increased over the time period studied. Twelve of the 25 BrM patients had ≥ 3 months of radiographic follow-up, of whom 6 patients (50%) developed new metastatic growth along the tract at a median of 5.0 months post-biopsy (range 2.3–17.1 months). All of the TR cases had undergone pre- or early post-biopsy stereotactic radiosurgery (SRS), and 3 had also undergone LITT at the time of initial biopsy. TRs were treated with resection, reirradiation, or observation/systemic therapy.

CONCLUSIONS In this study the authors identified a nontrivial, higher than previously described rate of BrM-biopsy tract recurrence, which often required additional surgery or radiation and justified close radiographic surveillance. As BrMs are commonly treated with SRS limited to enhancing tumor margins, consideration should be made, in cases lacking CNS-active systemic treatments, to include biopsy tracts in adjuvant radiation plans where feasible.

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The influence of aneurysm morphology on the volume of hemorrhage after rupture

J Neurosurg 136:1015–1023, 2022

Factors determining the risk of rupture of intracranial aneurysms have been extensively studied; however, little attention is paid to variables influencing the volume of bleeding after rupture. In this study the authors aimed to evaluate the impact of aneurysm morphological variables on the amount of hemorrhage.

METHODS This was a retrospective cohort analysis of a prospectively collected data set of 116 patients presenting at a single center with subarachnoid hemorrhage due to aneurysmal rupture. A volumetric assessment of the total hemorrhage volume was performed from the initial noncontrast CT. Aneurysms were segmented and reproduced from the initial CT angiography study, and morphology indexes were calculated with a computer-assisted approach. Clinical and demographic characteristics of the patients were included in the study. Factors influencing the volume of hemorrhage were explored with univariate correlations, multiple linear regression analysis, and graphical probabilistic modeling.

RESULTS The univariate analysis demonstrated that several of the morphological variables but only the patient’s age from the clinical-demographic variables correlated (p < 0.05) with the volume of bleeding. Nine morphological variables correlated positively (absolute height, perpendicular height, maximum width, sac surface area, sac volume, size ratio, bottleneck factor, neck-to-vessel ratio, and width-to-vessel ratio) and two correlated negatively (parent vessel average diameter and the aneurysm angle). After multivariate analysis, only the aneurysm size ratio (p < 0.001) and the patient’s age (p = 0.023) remained statistically significant. The graphical probabilistic model confirmed the size ratio and the patient’s age as the variables most related to the total hemorrhage volume.

CONCLUSIONS A greater aneurysm size ratio and an older patient age are likely to entail a greater volume of bleeding after subarachnoid hemorrhage.

 

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Intervention for unruptured high-grade intracranial dural arteriovenous fistulas: a multicenter study

J Neurosurg 136:962–970, 2022

The risk-to-benefit profile of treating an unruptured high-grade dural arteriovenous fistula (dAVF) is not clearly defined. The aim of this multicenter retrospective cohort study was to compare the outcomes of different interventions with observation for unruptured high-grade dAVFs.

METHODS The authors retrospectively reviewed dAVF patients from 12 institutions participating in the Consortium for Dural Arteriovenous Fistula Outcomes Research (CONDOR). Patients with unruptured high-grade (Borden type II or III) dAVFs were included and categorized into four groups (observation, embolization, surgery, and stereotactic radiosurgery [SRS]) based on the initial management. The primary outcome was defined as the modified Rankin Scale (mRS) score at final follow-up. Secondary outcomes were good outcome (mRS scores 0–2) at final follow-up, symptomatic improvement, all-cause mortality, and dAVF obliteration. The outcomes of each intervention group were compared against those of the observation group as a reference, with adjustment for differences in baseline characteristics.

RESULTS The study included 415 dAVF patients, accounting for 29, 324, 43, and 19 in the observation, embolization, surgery, and SRS groups, respectively. The mean radiological and clinical follow-up durations were 21 and 25 months, respectively. Functional outcomes were similar for embolization, surgery, and SRS compared with observation. With observation as a reference, obliteration rates were higher after embolization (adjusted OR [aOR] 7.147, p = 0.010) and surgery (aOR 33.803, p < 0.001) and all-cause mortality was lower after embolization (imputed, aOR 0.171, p = 0.040). Hemorrhage rates per 1000 patient-years were 101 for observation versus 9, 22, and 0 for embolization (p = 0.022), surgery (p = 0.245), and SRS (p = 0.077), respectively. Nonhemorrhagic neurological deficit rates were similar between each intervention group versus observation.

CONCLUSIONS Embolization and surgery for unruptured high-grade dAVFs afforded a greater likelihood of obliteration than did observation. Embolization also reduced the risk of death and dAVF-associated hemorrhage compared with conservative management over a modest follow-up period. These findings support embolization as the first-line treatment of choice for appropriately selected unruptured Borden type II and III dAVFs.

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Recovery of Supraspinal Microstructural Integrity and Connectivity in Patients Undergoing Surgery for Degenerative Cervical Myelopathy

Neurosurgery 90:447–456, 2022

It remains unknown if the progressive loss of axonal conduction along sensorimotor tracts can be recovered after surgery in patients with degenerative cervical myelopathy (DCM) and if subsequent adaptive microstructural changes are associated with the neurological improvement.

OBJECTIVE: To investigate the upstream recovery of microstructural integrity and reorganization of microstructural connectivity that occurs in patients with DCM after surgical decompression.

METHODS: Preoperative and postoperative cerebral diffusion tensor imaging and diffusion spectrum imaging data were collected for 22 patients with DCM (age = 56.9 ± 9.1 years). Paired t-tests were used to identify significant microstructural changes within cohorts, and correlation analysis was used to identify whether those changes are associated with neurological improvement.

RESULTS: Before surgery, higher structural connectivity (SC) was observed in the prefrontal/ frontal lobes, anterior cingulate, the internal and external capsules, and the anterior, posterior, and superior regions of the corona radiata fibers. Following surgery, an increased modified Japanese Orthopaedic Association score was associated with increased SC from the primary sensorimotor regions to the posterior cingulate and precuneus; increased SC between the cerebellum and the bilateral lingual gyri; and decreased SC from areas of the limbic system to the basal ganglia and the frontal lobe. In addition, increased fractional anisotropy and normalized quantitative anisotropy values along white matter fibers responsible for conveying sensory information and motor coordination and planning were associated with neurological improvement of patients with DCM after surgery.

CONCLUSION: Recovery of microstructural integrity along the corticospinal tract and other sensorimotor pathways, together with supraspinal reorganization of microstructural connectivity within sensory and motor-related regions, was associated with neurological improvement after surgical decompression.

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Extending the multistage surgical strategy for recurrent initially low-grade gliomas: functional and oncological outcomes in 31 consecutive patients who underwent a third resection under awake mapping

J Neurosurg 136:1035–1044, 2022

Maximal safe resection is the first treatment in diffuse low-grade glioma (DLGG). Due to frequent tumor recurrence, a second surgery has already been reported, with favorable results. This study assesses the feasibility and functional and oncological outcomes of a third surgery in recurrent DLGG.

METHODS Patients with DLGG who underwent a third functional-based resection using awake mapping were consecutively selected. They were classified into group 1 in cases of slow tumor regrowth or group 2 if a radiological enhancement occurred during follow-up. All data regarding clinicoradiological features, histomolecular results, oncological treatment, and survival were collected.

RESULTS Thirty-one patients were included, with a median age of 32 years. There were 20 astrocytomas and 11 oligodendrogliomas in these patients. Twenty-one patients had medical oncological treatment before the third surgery, consisting of chemotherapy in 19 cases and radiotherapy in 8 cases. No neurological deficit persisted after the third resection except mild missing words in 1 patient, with 84.6% of the patients returning to work. The median follow-up duration was 13.1 ± 3.4 years since diagnosis, and 3.1 ± 2.9 years since the third surgery. The survival rates at 7 and 10 years were 100% and 89.7%, respectively, with an estimated median overall survival of 17.8 years since diagnosis. A comparison between the groups showed that the Karnofsky Performance Scale score dropped below 80 earlier in group 2 (14.3 vs 17.1 years, p = 0.01). Median residual tumor volume at the third surgery was smaller (2.8 vs 14.4 cm 3 , p = 0.003) with a greater extent of resection (89% vs 70%, p = 0.003) in group 1.

CONCLUSIONS This is the first consecutive series showing evidence that, in select patients with progressive DLGG, a third functional-based surgery can be achieved using awake mapping with low neurological risk and a high rate of total resection, especially when reoperation is performed before malignant transformation.

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Awake craniotomy with transcortical motor evoked potential monitoring for resection of gliomas within or close to motor-related areas

J Neurosurg 136:1052–1061, 2022

The authors previously showed that combined evaluation of changes in intraoperative voluntary movement (IVM) during awake craniotomy and transcortical motor evoked potentials (MEPs) was useful for predicting postoperative motor function in 30 patients with precentral gyrus glioma. However, the validity of the previous report is limited to precentral gyrus gliomas. Therefore, the current study aimed to validate whether the combined findings of IVM during awake craniotomy and transcortical MEPs were useful for predicting postoperative motor function of patients with a glioma within or close to motor-related areas and not limited to the precentral gyrus.

METHODS The authors included 95 patients with gliomas within or close to motor-related areas who were treated between April 2000 and May 2020. All tumors were resected with IVM monitoring during awake craniotomy and transcortical MEP monitoring. Postoperative motor function was classified into four categories: “no change” or “declined,” the latter of which was further categorization as “mild,” “moderate,” or “severe.” The authors defined moderate and severe deficits as those that impact daily life.

RESULTS Motor function 6 months after surgery was classified as no change in 71 patients, mild in 18, moderate in 5, and severe in 1. Motor function at 6 months after surgery significantly correlated with IVM (p < 0.0001), transcortical MEPs (decline ≤ or > 50%) (p < 0.0001), age, preoperative motor dysfunction, extent of resection, and ischemic change on postoperative MRI. Thirty-two patients with no change in IVM showed no change in motor function at 6 months after surgery. Five of 34 patients (15%) with a decline in IVM and a decline in MEPs ≤ 50% had motor dysfunction with mild deficits 6 months after surgery. Furthermore, 19 of 23 patients (83%) with a decline in IVM and decline in MEPs > 50% had a decline in motor function, including 13 patients with mild, 5 with moderate, and 1 with severe deficits. Six patients with moderate or severe deficits had the lowest MEP values, at < 100 μV.

CONCLUSIONS This study validated the utility of combined application of IVM during awake craniotomy and transcortical MEP monitoring to predict motor function at 6 months after surgery in patients with a glioma within or close to motorrelated areas, not limited to the precentral gyrus. The authors also validated the usefulness of the cutoff value, 100 μV, in MEP monitoring.

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Gut‑disc axis: A cause of intervertebral disc degeneration and low back pain?

European Spine Journal (2022) 31:917–925

Low back pain (LBP), a widely prevalent and costly disease around the world, is mainly caused by intervertebral disc (IVD) degeneration (IDD). Although numerous factors may trigger this degenerative process, microbiome dysbiosis has recently been implicated as one of the likely causes. However, the exact relationship between the microbiome and IDD is not well understood. This review summarizes the potential mechanisms and discusses microbiome dysbiosis’s possible influence on IDD and LBP.

Methods Prospective literature review.

Results Alterations in microbiome composition and host responses to the microbiota causing pathological bone development and involution, led to the concept of gut-bone marrow axis and gut-bone axis. Moreover, the concept of the gut-disc axis was also proposed to explain the microbiome’s role in IDD and LBP. According to the existing evidence, the microbiome could be an important factor for inducing and aggravating IDD through changing or regulating the outside and inside microenvironment of the IVD. Three potential mechanisms by which the gut microbiota can induce IVD and cause LBP are: (1) translocation of the bacteria across the gut epithelial barrier and into the IVD, (2) regulation of the mucosal and systemic immune system, and (3) regulation of nutrient absorption and metabolites formation at the gut epithelium and its diffusion into the IVD. Furthermore, to investigate whether IVD is initiated by pathogenic bacteria and establish the correlation between the presence of certain microbial groups with the disease in question, microbiome diversity analysis based on16S rRNA data can be used to characterise stool/blood microbiota from IVD patients.

Conclusion Future studies on microbiome, fungi and viruses in IDD is necessary to revolutionize our thinking about their possible role in the development of IVD diseases. Furthermore, we believe that inflammation inhibition and interruption of amplification of cascade reaction in IVD by targeting the gut and IVD microbiome is worthwhile for the treatment of IDD and LBP.

Level of Evidence I Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

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The precuneal interhemispheric, trans‑tentorial corridor to the pineal region and brainstem, surgical anatomy, and case illustration

Acta Neurochirurgica (2022) 164:1095–1103

The pineal region and dorsal midbrain are among the most challenging surgical targets. To approach lesions in this region that harbor a superior to inferior long axis, we describe the basic steps of the precuneal, interhemispheric, transtentorial approach and illustrate anatomical landmarks of this established, but not so popular, surgical trajectory.

Method To study the anatomical landmarks and safety of this approach, the neurovascular anatomy was studied on 22 sides of 11 formalin-fixed latex-injected anatomical specimens. A step-by-step dissection of the precuneal interhemispheric trans-tentorial approach and study of the key anatomical landmarks was performed. An illustrative clinical case of a pontomesencephalic cavernous malformation (CM) resected through this approach is also detailed.

Results The mean distance from the transverse sinus to the most posterior cortical vein draining into the superior sagittal sinus was 6.4 cm. The mean distance from the calcarine sulcus to the most posterior cortical vein was 5.3 cm. Key steps of the dissection are as follows: craniotomy exposing the posterior aspect of the superior sagittal sinus (SSS), durotomy and gentle retraction of the SSS edge, dissection of the interhemispheric fissure, linear incision of the tentorium that extends anteriorly to the incisura and lateral reflection of the tentorium, and arachnoidal dissection and exposure of the cerebellomesencephalic fissure.

Conclusion The precuneal, interhemispheric, trans-tentorial approach affords excellent access to the falcotentorial junction, splenium, pineal region, quadrigeminal cistern, and dorsal pons once the cerebellomesencephalic fissure has been dissected.

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Natural History of Spinal Cord Cavernous Malformations

Neurosurgery 90:390–398, 2022

The natural history of spinal cord cavernous malformations (SCCMs) remains relatively unclear.

OBJECTIVE: To investigate the natural history for hemorrhagic risks and neurological outcomes, as well as relevant predicting factors, of SCCMs.

METHODS: All patients between 2002 and 2019 with diagnosis of SCCMs were identified retrospectively. An observational study of patients with conservative management was performed to reveal the natural history of SCCMs.

RESULTS: We identified 305 patients in the full cohort, including 126 patients who were conservatively treated for at least 6 months (median observational period, 24.0 months). Forty-five hemorrhage events occurred during 527 person-years of follow-up, yielding an annual hemorrhage rate of 8.5% per person-year. The 1-, 2-, and 5-year cumulative risks of hemorrhage were 13.9%, 26.1%, and 35.1%, respectively. Prior hemorrhage (hazard ratio [HR] = 12.948, P = .012) and pediatric patients (HR = 2.841, P = .031) were independent predictors of hemorrhage in the long-term follow-up. Familial form (adjusted odds ratio [OR] = 30.695, P = .010) and subsequent hemorrhage events (adjusted OR = 16.333, P = .000) were independent risk factors for worsening of neurological function, and baseline neurological status (adjusted OR = 78.984, P = .000) and presence of subsequent hemorrhage (adjusted OR = 9.611, P = .001) were significantly associated with neurological outcomes.

CONCLUSION: The natural history of SCCMs varies. Baseline characteristics, such as pediatric patients, familial form, and baseline neurological status, as well as prior and subsequent hemorrhagic events, significantly affect the natural history of the SCCMs, which prompts a differentiated treatment strategy.

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Tractography-Based Surgical Targeting for Thalamic Deep Brain Stimulation: A Comparison of Probabilistic vs Deterministic Fiber Tracking of the Dentato-Rubro-Thalamic Tract

Neurosurgery 90:419–425, 2022

The ventral intermediate (VIM) thalamic nucleus is the main target for the surgical treatment of refractory tremor. Initial targeting traditionally relies on atlas-based stereotactic targeting formulas, which only minimally account for individual anatomy. Al- ternative approaches have been proposed, including direct targeting of the dentato-rubro- thalamic tract (DRTT), which, in clinical settings, is generally reconstructed with deterministic tracking. Whether more advanced probabilistic techniques are feasible on clinical-grade magnetic resonance acquisitions and lead to enhanced reconstructions is poorly understood.

OBJECTIVE: To compare DRTT reconstructed with deterministic vs probabilistic tracking. METHODS: Thisisaretrospectivestudyof19patientswithessentialtremorwhounderwentdeep brain stimulation (DBS) with intraoperative neurophysiology and stimulation testing. We assessed the proximity of the DRTT to the DBS lead and to the active contact chosen based on clinical response.

RESULTS: In the commissural plane, the deterministic DRTT was anterior (P<104)and  < 104) to the DBS lead. By contrast, although the probabilistic DRTT was also anterior to the lead (P < 104), there was no difference in the mediolateral dimension (P = .5). Moreover, the 3- dimensional Euclidean distance from the active contact to the probabilistic DRTT was smaller vs the distance to the deterministic DRTT (3.32 ± 1.70 mm vs 5.01 ± 2.12 mm; P < 104).

CONCLUSION: DRTT reconstructed with probabilistic fiber tracking was superior in spatial proximity to the physiology-guided DBS lead and to the empirically chosen active contact. These data inform strategies for surgical targeting of the VIM.

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The mini-combined transpetrosal approach: an anatomical study and comparison with the combined transpetrosal approach

Acta Neurochirurgica (2022) 164:1079–1093

The combined transpetrosal approach (CTPA) is a versatile technique suitable for challenging skull base pathologies. Despite the advantages provided by a wide surgical exposure, the soft tissue trauma, complex and time-consuming bony work, and cosmetic issues make it far from patient expectations. In this study, the authors describe a less invasive modification of the CTPA, the mini-combined transpetrosal approach (mini-CTPA), and perform a quantitative comparison between these two approaches.

Methods Five human specimens were used for this study. CTPA was performed on one side and mini-CTPA on the opposite side. The surgical freedom, petroclival and brainstem area of exposure, and maneuverability for 6 anatomical targets, provided by the CTPA and mini-CTPA, were calculated and statistically compared. The bony volumes corresponding to each anterior petrosectomy were also measured and compared. Three clinical cases with an operative video are also reported to illustrate the effectiveness of the approach.

Results The question-mark skin incision done along the muscle attachments permits an optimal cosmetic result. Even though the limited incision, the smaller craniotomy, and the less extensive bone drilling of mini-CTPA provide a smaller area of surgical freedom, the areas of exposure of petroclival region and brainstem were not statistically different between the two approaches. The antero-posterior maneuverability for the oculomotor foramen (OF), Meckel’s cave (MC) and the REZ of trigeminal nerve, and the supero-inferior maneuverability for OF, MC, Dorello’s canal, and REZ of CN VII are significantly reduced by the smaller opening. The bony volume of anterior petrosectomy resulted similar among the approaches.

Conclusions The mini-CTPA is an interesting alternative to the CTPA, providing comparable surgical exposure both for petroclival region and for brainstem. Although the lesser soft tissue dissection and bony opening decrease the surgical maneuverability, the mini-CTPA may reduce surgical time, potential approach-related morbidities, and improve cosmetic and functional outcomes for the patients.

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Real‐time augmented reality application in presurgical planning and lesion scalp localization by a smartphone

Acta Neurochirurgica (2022) 164:1069–1078

Objective A smartphone augmented reality (AR) application (app) was explored for clinical use in presurgical planning and lesion scalp localization.

Methods We programmed an AR App on a smartphone. The accuracy of the AR app was tested on a 3D-printed head model, using the Euclidean distance of displacement of virtual objects. For clinical validation, 14 patients with brain tumors were included in the study. Preoperative MRI images were used to generate 3D models for AR contents. The 3D models were then transferred to the smartphone AR app. Tumor scalp localization was marked, and a surgical corridor was planned on the patient’s head by viewing AR images on the smartphone screen. Standard neuronavigation was applied to evaluate the accuracy of the smartphone. Max-margin distance (MMD) and area overlap ratio (AOR) were measured to quantitatively validate the clinical accuracy of the smartphone AR technique.

Results In model validation, the total mean Euclidean distance of virtual object displacement using the smartphone AR app was 4.7 ± 2.3 mm. In clinical validation, the mean duration of AR app usage was 168.5 ± 73.9 s. The total mean MMD was 6.7 ± 3.7 mm, and total mean AOR was 79%.

Conclusions The smartphone AR app provides a new way of experience to observe intracranial anatomy in situ, and it makes surgical planning more intuitive and efficient. Localization accuracy is satisfactory with lesions larger than 15 mm.

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Prediction of Shunt Responsiveness in Suspected Patients With Normal Pressure Hydrocephalus Using the Lumbar Infusion Test: A Machine Learning Approach

Neurosurgery 90:407–418, 2022

Machine learning (ML) approaches can significantly improve the classical Rout -based evaluation of the lumbar infusion test (LIT) and the clinical management of the normal pressure hydrocephalus.

OBJECTIVE: To develop a ML model that accurately identifies patients as candidates for permanent cerebral spinal fluid shunt implantation using only intracranial pressure and electrocardiogram signals recorded throughout LIT.

METHODS: This was a single-center cohort study of prospectively collected data of 96 patients who underwent LIT and 5-day external lumbar cerebral spinal fluid drainage (external lumbar drainage) as a reference diagnostic method. A set of selected 48 intracranial pressure/ electrocardiogram complex signal waveform features describing nonlinear behavior, wavelet transform spectral signatures, or recurrent map patterns were calculated for each patient. After applying a leave-one-out cross-validation training–testing split of the data set, we trained and evaluated the performance of various state-of-the-art ML algorithms.

RESULTS: The highest performing ML algorithm was the eXtreme Gradient Boosting. This model showed a good calibration and discrimination on the testing data, with an area under the receiver operating characteristic curve of 0.891 (accuracy: 82.3%, sensitivity: 86.1%, and specificity: 73.9%) obtained for 8 selected features. Our ML model clearly outperforms the classical Rout based manual classification commonly used in clinical practice with an accuracy of 62.5%.

CONCLUSION: This study successfully used the ML approach to predict the outcome of a 5-day external lumbar drainage and hence which patients are likely to benefit from permanent shunt implantation. Our automated ML model thus enhances the diagnostic utility ofLIT in management.

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Customized cost‑effective polymethylmethacrylate cranioplasty: a cosmetic comparison with other low‑cost methods of cranioplasty

Acta Neurochirurgica (2022) 164:655–667

Intraoperative hand-moulded cranioplasty and polymethylmethacrylate (PMMA) prostheses made from bone impressions are economical but the cosmetic results are less than satisfactory. Commercially available customized prostheses perform better but are prohibitively expensive. We evaluate the performance of a locally developed, low-cost customized PMMA cranioplasty prosthesis.

Objective To compare the cosmetic outcome of 3 types of PMMA cranioplasty as well as with objective measurements on postoperative CT scans

Methods This study includes 70 patients who underwent cranioplasty between March 2016 and June 2020. In this period, patients had their cranioplasty prostheses made by intra-operative hand moulding (HM), by using the removed bone as a template and making a bone impression (BI) or by 3D printing the prosthesis based on a CT scan. Cosmetic outcomes were assessed by the patient and the operating surgeon on an 8-point scale. The degree of measured anthropometric asymmetry was measured on a postoperative CT scan and correlated with the cosmetic outcome.

Results Our locally produced 3D-printed cranioplasty prostheses showed a statistically better performance in cosmetic scores when compared to the HM and BI (p value < 0.001). CT anthropometric measurements significantly correlated with cosmetic outcome (p value 0.01)

Conclusion Our 3D cranioplasty prostheses had better cosmetic outcomes than HM and BI prostheses, and our technique is able to produce them at 10% of the cost of the currently available commercial customized prostheses.

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The Evolution of 5-Aminolevulinic Acid Fluorescence Visualization: Time for a Headlamp/Loupe Combination

The use of 5-aminolevulinic acid (5-ALA) for intraoperative protoporphyrin IX fluorescent imaging in the resection of malignant gliomas has been demonstrated to improve tumor visualization, increase the extent of resection, and extend progression-free survival. The current technique for visualization of 5-ALA consists of excitation and emission filters built into the operating microscope. However, there are notable limitations to this process, including low quantum yield, expense, and masking of surrounding anatomy.

METHODS: We present 3 cases in which 3 separate methods were employed for visualizing fluorescence. The devices reported are 1) a low-cost blue light flashlight, 2) a low-cost headlamp, and 3) the first reported case of the new Designs for Vision REVEAL Fluorescence-Guided Surgery (FGS) 5-ALA fluorescent headlight and loupes. The aim of the study is to provide confirmation that tumor fluorescence can be observed using commercially available products other than the microscope.

RESULTS: We demonstrate through 3 intraoperative cases that a variety of devices can produce visible fluorescence of the high-grade tumor and allow for simultaneous real-time visualization of the adjacent brain parenchyma and vasculature. The REVEAL FGS system appears to offer increased fluorescence emission compared with all other methods, including the microscope. –

CONCLUSIONS: Our study demonstrates the feasibility of using blue/ultraviolet light supplied by a commercially available, inexpensive flashlight or headlamp to visualize 5-ALA fluorescence in high-grade gliomas. We also provide the first documentation of the intraoperative use of the new Designs for Vision REVEAL FGS 5-ALA fluorescent headlight and loupes and report on the experience. Lack of an operative microscope capable of fluorescent illumination should not be a limiting factor in performing fluorescent guided glioma resection

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Single position lumbar fusion: a systematic review and meta-analysis

The Spine Journal 22 (2022) 429−443

Recently, a single position lumbar fusion has been described in which both the anterior or lateral interbody fusion as well as posterior percutaneous pedicle screw fixation are performed in a single position.

PURPOSE: The purpose of this study was to present and analyze the current evidence for single position lumbar fusion.

STUDY DESIGN/SETTING: This is a systematic review and meta-analysis.

PATIENT SAMPLE: Prospective or retrospective studies published in English that assessed outcomes of single position lumbar fusion surgery for patients with lumbar degenerative disease, spondylolisthesis, or radiculopathy were included.

OUTCOME MEASURES: Outcome measures included operative time, estimated blood loss, hospital length of stay, X-Ray exposure time, and postoperative outcomes including leg numbness or pain, leg weakness, lumbar lordosis, and segmental lordosis.

METHODS: This systematic review was performed in accordance with PRISMA guidelines. Two separate meta-analyses were performed. The first compared single position (SP) surgery, both lateral and prone, to dual position or flipped (F) surgery. The second meta-analysis compared lateral single position (LSP) surgery to prone single position (PSP) surgery. Variables were included if (1) they were a mean with a reported standard deviation or (2) if they were a categorical variable. For calculating standard error of the mean, we used sample size, mean, and standard deviation. A random effects model was used. The heterogeneity among studies was assessed with a significance level of <0.05.

RESULTS: Twenty-one articles were included for analysis. Three studies were prospective nonrandomized studies, while 18 were retrospective. Seven articles studied lateral single position only, 10 articles compared lateral single position to traditional repositioning surgery, three articles studied prone single position surgery, and one article compared prone single position surgery to traditional repositioning surgery. A detailed review is provided for all 21 articles. Seventeen studies were included for meta-analysis comparing the SP versus F groups, for a total of 942 patients in the SP group and 254 in the F group. Mean operative time was significantly less for the SP group compared with the F group (SP: 127.5§7.9, F: 188.7§15.5, p<.001). Average hospital length of stay was 2.87§0.3 days in the SP group and 6.63§0.6 days in the F group (p<.001). Complication rates did not significantly differ between groups. Pedicle screws placed in the lateral position had a higher rate of complication as compared with those placed in a prone position (L: 10.2§2%, P: 1.6§1%, p=.015). Seventeen studies were included in the LSP versus PSP analysis, including 13 in the LSP group and four in the PSP group, with a total of 785 patients in the LSP group and 85 patients in the PSP group. Operative time and X-Ray exposure was significantly less in the LSP compared with the PSP group (117.1§5.5 minutes vs. 166.9§21.9 minutes, p<.001; 43.7§15.5 minutes vs. 171.0§25.8 minutes, p<.001). Postoperative segmental lordosis was greater in the prone single position group (p<.001).

CONCLUSIONS: Single position surgery decreases operative times and hospital length of stay, while maintaining similar complication rates and radiographic outcomes. PSP surgery was found to be longer in duration and have increased radiation exposure time compared with LSP, while increasing postoperative segmental lordosis.

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Endplate defects, not the severity of spinal stenosis, contribute to low back pain in patients with lumbar spinal stenosis

The Spine Journal 22 (2022) 370−378

It is controversial whether lumbar spinal stenosis (LSS) itself contributes to low back pain (LBP). Lower truncal skeletal muscle mass, spinopelvic malalignment, intervertebral disc degeneration, and endplate abnormalities are thought to be related to LBP. However, whether these factors cause LBP in patients with LSS is unclear.PURPOSE: To identify factors associated with LBP in patients with LSS.

STUDY DESIGN/SETTING: Cross-sectional design.

PATIENT SAMPLE: A total of 260 patients (119 men and 141 women, average age 72.8 years) with neurogenic claudication caused by LSS, as confirmed by magnetic resonance imaging (MRI).

OUTCOME MEASURES: Ratings of LBP, buttock and leg pain, and numbness on a numerical rating scale (NRS), 36-Item Short Form Survey (SF-36) scores, muscle mass measured by bioelectrical impedance analysis, and radiographic measurements including slippage and lumbopelvic alignment. The severity of LSS, endplate defects, Modic endplate changes, intervertebral disc degeneration, and facet joint osteoarthritis were assessed on MRI.

METHODS: The presence of LBP was defined as an NRS score ≥3. The demographic data, patient-reported outcomes, and radiological and MRI findings were compared between patients with and without LBP. Multivariate logistic regression analysis was used to identify the factors that were independently associated with the presence of LBP.

RESULTS: There were significant differences between patients with and without LBP for buttock and leg pain and numbness on the NRS, general health on the SF-36, presence of endplate defects, presence of Modic changes, disc degeneration grading, and disc height grading (all p < .05). Multivariate logistic regression analysis showed significant associations between LBP and diabetes (OR 2.43; 95% CI 1.07−5.53), buttock and leg numbness on the NRS (OR 1.34; 95% CI 1.17−1.52), general health on the SF-36 (OR 0.97; 95% CI 0.95−0.99), and the presence of erosive endplate defects (OR 3.04; 95% CI 1.51−6.11) (all p < .05).

CONCLUSIONS: These results suggest that LBP in patients with LSS should be carefully assessed not only for spinal stenosis but also clinical factors and endplate defects.

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