Author: cba

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Prediction of Diffuse High-Grade Glioma Survival Outcomes Using Preoperative Whole-Brain Tractography–Based Resectability Metrics

Neurosurgery 98:836–847, 2026

This study presents novel whole-brain tractography (WBT)–derived resectability metrics—resectability index (RI) and unresectable tumor volume (UTV), plus modified versions mRI and mUTV—calculated from preoperative diffusion imaging to estimate how much of diffuse high-grade gliomas (HGG) can be safely resected. Metrics are derived by quantifying tumor overlap with critical white-matter tracts and deep structures, and compared with conventional postoperative measures.

Using retrospective data from 146 tumors (84 with WBT), mRI and mUTV strongly predicted biopsy versus resection and correlated with extent of resection, residual tumor, and overall survival. Accelerated failure time models incorporating mUTV/mRI provided accurate preoperative survival predictions, outperforming conventional metrics in postoperative models.

Problem: Extent of resection (EOR) predicts survival in diffuse high-grade glioma but is only measurable postoperatively, limiting preoperative decision-making.

Approach: Preoperative whole-brain tractography (WBT) was used to quantify tumor overlap with eloquent tracts and deep structures to estimate resectability before surgery.

Metrics: Unresectable tumor volume (UTV) = tumor overlap with eloquent tracts + deep structures; Resectability index (RI) = (preop tumor volume − UTV) / preop tumor volume.

Modified metrics: mUTV/mRI focused only on corticospinal tract and left arcuate fasciculus, and performed better than unmodified metrics in several analyses.

Surgical decision prediction: mRI (AUROC 0.953) and mUTV (AUROC 0.854) accurately predicted biopsy vs resection, with optimal cutoffs mRI 0.75 and mUTV 2.5 cm³.

Survival separation: Tumors with mRI > 0.65 vs ≤ 0.65 showed the largest median overall survival difference (not reached vs 82 days, P < .0001).

Best preop survival model: A log-logistic accelerated failure time (AFT) model using only preoperative covariates achieved validated C-index 0.788, with mUTV an independent predictor of overall survival (P = .008).

Overall conclusion: Preoperative WBT-based resectability metrics approximate postoperative EOR/residual tumor volume and can strongly predict survival outcomes after biopsy or resection.

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Global economic differences in modern glioblastoma care – a systematic review

Acta Neurochirurgica (2026) 168:89

This systematic review quantifies global cost and cost-effectiveness differences in contemporary glioblastoma (GBM) care, analyzing 21 studies standardized to 2024 USD. It reports extreme heterogeneity in direct medical costs—from about $18,908 in India to $356,481 in the United States—and identifies inpatient care and adjuvant therapies as primary cost drivers in high-income settings.

Economic models reveal that the full Stupp protocol often exceeds willingness-to-pay thresholds in middle- and low-income countries, while surgical resection and 5‑ALA fluorescence-guided surgery show relatively favorable cost-effectiveness. The authors call for standardized cost reporting and inclusion of societal perspectives to improve cross-country comparisons and policy decisions.

Purpose Quantified global differences in costs and cost-effectiveness of modern Stupp-protocol–based glioblastoma care via a systematic review.

Methods Searched PubMed/MEDLINE/Cochrane to Dec 1, 2025 using (Glioblastoma OR GBM) AND (costs OR cost-effectiveness OR economic burden); included studies with quantifiable economic outcomes from 2005 onward, yielding 21 eligible studies.

Standardization Converted all reported costs to 2024 USD by inflating with country-specific CPI to 2024 and converting using 2024 PPP rates.

Direct costs range Direct medical costs were highly heterogeneous, from about $356,481 (United States) to about $18,908 (India), across 15,547 real-world patients.

Cost drivers (Western systems) Adjuvant treatment and inpatient care were major contributors to direct medical costs in western countries (with inpatient care and radiotherapy prominent in US analyses).

Stupp protocol affordability The Stupp protocol exceeded willingness-to-pay thresholds in middle-income/resource-limited settings, indicating substantial financial burden in those contexts.

TTF cost-effectiveness variability Tumor treating fields (TTF) showed very high ICERs in France (≈ $862k–$940k per LYG) and $252,590 per LYG in the US, but a more favorable estimate of $45,813.91 per QALY in China.

Key implication Uniform, standardized cost reporting is needed to better compare cost-effectiveness across countries; economic findings also underscore the role of surgery as a cost-effective component of modern GBM management.

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Low Posterior Electromyographic Threshold and Functional Outcomes After L4-5 Lateral Lumbar Interbody Fusion

Operative Neurosurgery 30:566–570, 2026

This single-institution retrospective study evaluates whether low posterior electromyography (EMG) stimulation thresholds during lateral L4-5 lumbar interbody fusion (LLIF) correlate with postoperative femoral nerve motor or sensory neurapraxia. Forty-two lateral-position single-level L4-5 LLIFs with neuromonitoring data showed no significant association between posterior EMG threshold or retractor time and transient postoperative anterior thigh numbness or weakness.

The cohort experienced transient sensory neurapraxia in 38% at six weeks that resolved by six months; only one patient had temporary motor neurapraxia. Limitations include small sample size, retrospective design, and short follow-up, leading authors to conclude no demonstrable link between posterior EMG threshold and plexus injury in this series.

Context: In L4-5 transpsoas LLIF, the retractor is placed near the lumbar plexus; directional EMG stimulation thresholds are used intraoperatively to estimate nerve proximity and potentially reduce injury risk.

Objective: Assessed whether posterior EMG stimulation threshold was associated with lumbar plexus injury/neurapraxia after single-level L4-5 LLIF performed in the lateral position.

Design/criteria: Retrospective, single-institution review of single-level L4-5 LLIF (Jan 2019–May 2022) with available neuromonitoring thresholds and retractor time; excluded cases with additional levels or missing monitoring data.

Cohort/intraop metrics: 42 patients (mean age 66 years); mean retractor time 12.4 minutes; mean posterior EMG threshold 10.4 mA.

Neurologic outcomes: Femoral motor neurapraxia occurred in 1 patient (2%); sensory neurapraxia (anterior thigh numbness) occurred in 16 patients (38%) at 6 weeks and resolved to 0% by 6 months.

Main finding: Posterior EMG threshold was not associated with postoperative motor neurapraxia or sensory neurapraxia at 6 weeks (including logistic regression showing OR 1.00; P=.98 for thigh numbness).

Other associations: No significant correlation between posterior EMG threshold and retractor time (Spearman ρ=0.11; P=.50) or postoperative ODI (ρ=0.17; P=.33).

Notable case/interpretation: The single motor neurapraxia case had 27-minute retractor time with posterior EMG 5 mA and recovered by 6 months; median retractor time in the cohort was low (10.8 minutes), limiting conclusions about longer retraction durations.

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When the saline hits your brain: effects of standard irrigation solutions on neural function

J Neurosurg 144:995–1002, 2026

This report examines the physiological consequences of commonly used neurosurgical irrigation fluids, highlighting effects on synaptic transmission, vascular responses, spreading depolarization, and long-term cellular toxicity. Preclinical brain-slice and animal models demonstrate that normal saline, lactated Ringer’s, and PlasmaLyte can impair neuronal function, alter electrolytes and pH, and worsen recovery compared with artificial cerebrospinal fluid (aCSF).

Clinical observations and preliminary trials mirror experimental findings: aCSF associates with improved postoperative neurophysiology, reduced chronic subdural hematoma recurrence, and better outcomes after aneurysm surgery. The authors advocate prioritizing physiologically matched irrigation solutions and propose targeted clinical trials to evaluate aCSF or electrolyte-optimized fluids across neurosurgical and ICU applications.

Risk premise Nonphysiological neurosurgical irrigation solutions may be an underrecognized contributor to impaired neurological recovery and potentially long-term impairment.

High-volume exposure Irrigation volumes commonly exceed 1 L intraoperatively, and ICU intraventricular irrigation around 60 mL/hr can total ~1.5 L/day for multiple days—large relative to ~125 mL total CSF volume and ~500 mL/day CSF production.

Composition mismatch Commonly available fluids (normal saline, lactated Ringer’s, PlasmaLyte) are roughly iso-osmolar to CSF but differ substantially from CSF in pH and key ions/metabolites (e.g., NS lacks bicarbonate, Ca²⁺, Mg²⁺ and is acidic; LR lacks Mg²⁺ and is acidic).

Synaptic suppression (NS) Superfusion with normal saline rapidly abolishes excitatory postsynaptic potentials; adding Ca²⁺ only partially restores activity, implying multiple missing factors beyond Ca²⁺.

Mechanisms (pH/Mg²⁺ effects) Low pH in NS and LR can depress AMPA/NMDA receptor currents, while LR’s lack of Mg²⁺ can cause transient hyperexcitability followed by loss of synaptic transmission with continued exposure.

Spreading depolarization vulnerability After a spreading depolarization, tissue recovers fully in aCSF but shows profound, persistent suppression of synaptic transmission in LR (even with glucose/oxygen supplementation), with LR also prolonging the depolarization signal.

Preclinical harms In animal and cell models, NS and LR are associated with worse edema/cellular damage than aCSF, and ventriculocisternal NS infusion in rats caused seizures, death, and cortical/CA1 cell death not seen with aCSF.

Clinical signals favor aCSF In endoscopic and other neurosurgical contexts, NS irrigation has been linked to CSF acidification and decreases in glucose/calcium, and comparative studies/meta-analyses report better outcomes with aCSF (e.g., reduced chronic subdural hematoma recurrence; improved early recovery after aneurysm clipping; faster BAEP recovery in microvascular decompression).

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Outpatient minimally invasive transforaminal lumbar interbody fusion performed at a single ambulatory surgery center: the Semmes Murphey Clinic experience

Neurosurg Focus 60(4):E5, 2026

This study reports outcomes from 179 patients undergoing single-level minimally invasive transforaminal lumbar interbody fusion (miTLIF) at a single ambulatory surgery center (ASC) between 2012–2024. It presents demographics, surgical details, complications, and validated patient-reported outcomes with 2-year follow-up showing sustained pain reduction, functional improvement, and high satisfaction.

The authors detail selection criteria, perioperative technique using tubular retractors and percutaneous pedicle screws, low complication and 90-day readmission/reoperation rates, and discuss economic and policy implications for ASC-based lumbar fusion care.

Objective Report 2-year outcomes for outpatient minimally invasive TLIF (miTLIF) performed at a single ambulatory surgery center (ASC).

Cohort 485 single-level miTLIFs were performed at the ASC (2012–2024); 179 registry-enrolled patients were analyzed (mean age 54; BMI mean 31).

Selection ASC eligibility exclusions included BMI > 50, weight > 350 lb, cardiac disease not cleared “low risk,” ASA class IIIb or above, family history of malignant hyperthermia, or inability to ambulate; Medicare primary insurance was also excluded for reimbursement reasons.

Disposition 98.3% were discharged within a few hours; 1.1% observed < 23 hours for pain control; 0.56% required hospital transfer for new-onset atrial fibrillation (treated and discharged within 23 hours).

Patient-reported outcomes Mean scores improved from baseline to 3 months and remained improved through 2 years (e.g., back pain NRS 6.98→2.40 at 3 months and 2.86 at 2 years; ODI 44.14→19.37 at 3 months and 13.87 at 2 years; EQ-5D 0.56→0.81 at 3 months and 0.82 at 2 years).

Complications Durotomy occurred in 1.7% (treated with fibrin glue, discharged within hours); superficial surgical site infection 0.56% (oral antibiotics only); postoperative hematoma 0.56%; urinary tract infection 0.56%.

Readmissions/reoperations (90-day) 2.2% readmissions and 1.1% reoperations within 90 days (including hardware failure and delayed hematoma).

Conclusion For carefully selected patients, ASC-based miTLIF showed significant, durable PROM improvement with acceptably low complications, readmissions, and reoperations.

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Impact of lateral plate and screw fixation on long-term radiographic subsidence in lateral lumbar interbody fusion

J Neurosurg Spine 44:493–497, 2026

This clinical study evaluates long-term radiographic subsidence after lateral lumbar interbody fusion (LLIF), comparing stand-alone procedures with those augmented by lateral plate and screw fixation. Retrospective analysis of 146 patients (219 levels) with ≥1-year CT follow-up shows lateral plating significantly reduced subsidence odds, while 3D-printed porous titanium cages trended toward lower subsidence than PEEK.

Results note similar reoperation rates between groups, no grade III subsidence, and rare adverse events including one delayed vertebral fracture with plating; methodology included multivariate logistic regression and Marchi subsidence grading. Conclusions support lateral plate and screw fixation, particularly with porous titanium cages, as protective against severe radiographic subsidence.

Objective Assess whether adding lateral plate and screw fixation changes the long-term rate/grade of radiographic cage subsidence after LLIF (excluding posterior instrumented fusion).

Design/Population Retrospective review (2014–2022) of degenerative lumbar spondylosis LLIF cases at two centers; required ≥1-year postoperative CT; 146 patients/219 levels (45% plated, 55% stand-alone).

Subsidence grading Long-term imaging graded by Marchi criteria (grade 0: 0%–24% disc height loss; I: 25%–49%; II: 50%–74%; III: 75%–100%); no intraoperative subsidence included.

Main finding (plating effect) Lateral plate + screws was significantly associated with reduced long-term radiographic subsidence (multivariable OR 0.484, p = 0.006).

Severity pattern All grade II (severe) subsidence cases occurred in the stand-alone LLIF group (4 patients); no grade III subsidence observed.

Cage material trend 3D-printed porous titanium cages trended toward lower subsidence versus PEEK but did not reach statistical significance (OR 0.401, p = 0.071).

Reoperation/fusion No significant difference in reoperation rate between plated and stand-alone groups; radiographic fusion rates were similar (83.1% plated vs 86.4% stand-alone; p = 0.58).

Noted complications/implant details One lateral-plate patient had a delayed vertebral body fracture; plated cases used 18-mm-wide cages, while nearly all stand-alone cases used 22-mm-wide cages.

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Quantitative MRI Tractography of White Matter Tracts After Tumor Craniotomy Surgery: Comparative Analysis Between Tubular Retractor and Open Craniotomy Surgery

Operative Neurosurgery 30:525–532, 2026

This study compares quantitative diffusion MRI tractography outcomes after deep-seated brain tumor resections using tubular retraction (TR) versus open craniotomy (OC) with spatula/cottonoid retraction. In a matched cohort of 20 patients, TR achieved comparable extent of resection with improved postoperative fractional and geodesic anisotropy metrics and a greater mean increase in Karnofsky Performance Score.

Methods include pre/postoperative 1.5T DTI, autosegmented tractography of ipsilateral tracts, and statistical comparison of FA, GA, diffusivity metrics, and tract volume. Results suggest TR reduces certain retraction-related white matter distortion without worsening diffusivity markers, supporting TR as a viable technique for deep subcortical lesions with potential functional benefit.

Goal Quantitatively compare cerebral retraction–related white matter tract changes after deep-seated tumor surgery using tubular retraction (TR) vs open craniotomy (OC) with spatula retraction via diffusion MRI tractography metrics.

Design Retrospective matched-pair analysis of 20 patients (10 TR vs 10 OC), matched by tumor size, depth, and age; all surgeries performed by a single surgeon.

Tractography process/metrics Pre- and postoperative DTI tractography (1.5T MRI) autosegmented ipsilateral supratentorial tracts; quantified FA, GA, MD, RD, AD, and tract volume across specified tracts (e.g., corticospinal, arcuate/SLF, ILF, IFOF, fornix, uncinate, optic radiations).

Extent of resection Resection was comparable between groups (TR 90.4% vs OC 94.8%, P = .395).

Functional outcome Change in Karnofsky Performance Score (KPS) favored TR (mean +11 points) vs OC (no change), P = .035.

Key quantitative findings Postoperative FA and GA differed significantly in favor of TR (FA 0.322 TR vs 0.029 OC, P = .011; GA increased in TR 0.441 vs decreased in OC 0.411, P = .012).

Other imaging metrics Postoperative tract volume was higher in TR than OC (14.9 cm³ vs 10.6 cm³, P = .036), while diffusivity metrics (MD, RD, AD) were broadly comparable between cohorts.

Conclusion TR offers a viable approach for deep-seated tumors with similar resection extent while mitigating some components of retraction injury as reflected by quantitative tractography changes and improved KPS.

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Stereotactic Radiosurgery Versus Observation in Small- and Medium-Sized Vestibular Schwannoma Patients With Normal Hearing: A Retrospective International Multicenter Study

Neurosurgery 98:887–894, 2026

This multicenter retrospective study compares stereotactic radiosurgery (SRS) with observation (OBS) for small-to-medium vestibular schwannomas (Koos I–II) in patients presenting with normal (AAO‑HNS class A) hearing. Propensity-score–matched cohorts (57 SRS, 57 OBS) were analyzed for serviceable hearing preservation (SHP), tumor control (TC), and cranial nerve outcomes over median follow-ups of 49 and 37 months.

Results show SRS achieved markedly superior tumor control (≈98% at 5–10 years) while producing noninferior hearing outcomes versus observation (5‑year SHP: SRS 76.2% vs OBS 56.1%; difference not statistically significant). The authors conclude SRS is preferable for TC without compromising hearing, emphasizing individualized decision-making given study limitations.

Clinical question Comparison of stereotactic radiosurgery (SRS) vs observation (OBS) for small/medium Koos I–II vestibular schwannomas in patients with AAO-HNS class A (normal) hearing at presentation, focusing on hearing preservation and tumor control

Design Retrospective international multicenter study with propensity score matching (age, sex, tumor volume, PTA, SDS) yielding 57 SRS vs 57 OBS matched patients

Serviceable hearing preservation No statistically significant difference in long-term serviceable hearing preservation between SRS and OBS in the matched analysis (log-rank P = .17), despite numerically higher SRS rates

Hearing rates over time Matched-cohort 5-/9-year serviceable hearing preservation: SRS 76.2% / 42.4% vs OBS 56.1% / 16.8%

Class A hearing Class A preservation was similar: 57.9% (SRS) vs 52.6% (OBS) (P = .70)

Tumor control SRS achieved markedly superior tumor control (log-rank P < .0001); 5-/10-year tumor control: SRS 97.9% / 97.9% vs OBS 40.9% / 15.1%

Other clinical outcomes No significant matched-cohort differences in cranial nerve deficits, vestibulopathy, or composite CN/tinnitus worsening; tinnitus worsening trended higher with OBS (21.1% vs 8.8%) but was not significant (P = .066)

Overall conclusion SRS provided noninferior hearing outcomes while being significantly better for tumor control, supporting SRS as a favored option while still emphasizing individualized decision-making

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Long-term tumor control after Gamma Knife radiosurgery for sporadic vestibular schwannoma

J Neurosurg 144:965–971, 2026

This clinical study evaluates long-term tumor control after single-fraction Gamma Knife stereotactic radiosurgery (SRS) for sporadic vestibular schwannoma in 749 adults treated from 2000–2022, reporting Kaplan–Meier control rates of 100%, 98%, 96%, 92%, and 91% at 1, 3, 5, 10, and 15 years respectively. Patient demographics, SRS dosing, and complication rates—including low persistent facial paresis—are summarized with statistical analysis and clear definitions for growth, pseudoprogression, and salvage.

The authors detail three post-SRS tumor behavior patterns, finding 13% pseudoprogression (mostly within 5 years) and 42 salvage treatments (median 3.7 years), and conclude that SRS offers durable control while emphasizing the need for prolonged surveillance and nuanced clinical decision-making about retreatment.

Objective Assess long-term efficacy of single-fraction stereotactic radiosurgery (SRS) as primary treatment for adult, treatment-naïve sporadic vestibular schwannoma (Gamma Knife), treated from 2000–2022.

Cohort 749 adults included; 76% had tumors extending into the cerebellopontine angle (CPA) at SRS; median age 62; 50% women; 99% had House-Brackmann (HB) grade I facial nerve function at SRS.

Long-term tumor control Tumor control after SRS remained high: 100% (1 yr), 98% (3 yr), 96% (5 yr), 92% (10 yr), and 91% (15 yr).

Radiosurgical failure/salvage 42 patients required salvage (35 microsurgery, 7 repeat SRS), median 3.7 years post-SRS; 3 salvage treatments occurred >10 years after SRS, indicating late failures can occur.

Risk factors Age, macrocystic tumor presence, and treated tumor volume were not significantly associated with risk of salvage in univariable analysis.

Post-SRS tumor patterns Three post-SRS behaviors were observed: (1) stability/shrinkage, (2) pseudoprogression (growth then stability/shrinkage), and (3) continued growth without stability at last follow-up.

Pseudoprogression timing 13% experienced pseudoprogression; all but 4 showed it by year 5 post-SRS, though some initial growth occurred later (e.g., 5.1–8.6 years) with subsequent stability on follow-up imaging.

Conclusion/implication SRS provides durable control through 15 years for most patients (91%), but ongoing long-term surveillance is needed because failures may occur even beyond 10 years and pseudoprogression can be seen out to ≥5 years.

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Clinical Significance and Utility of Early Postoperative Computed Tomography Scan Head after Brain Surgery

Neurosurgery 98:810–817, 2026

This prospective single-center study assesses the clinical value of routine early (within 6 hours) postoperative CT scans in 339 adults after intracranial surgery, correlating immediate neurological status with CT findings and resulting management changes. Results show 97.3% had only expected postoperative changes, 2.7% had hematoma without mass effect, and none required surgical intervention; only six patients had medical management altered.

The authors conclude that routine early CT provides minimal benefit for extubated, neurologically stable or expected-deficit patients and advocate selective imaging for clinical deterioration or unreliable examinations, highlighting cost, radiation, and logistical considerations particularly relevant to resource-limited settings.

Aim Evaluate whether an early postoperative head CT within 6 hours after intracranial surgery changes patient management and assess its clinical utility.

Design/setting Single-center prospective cohort of 339 intracranial surgery patients; all received CT within 6 hours and were grouped clinically as no deficit, expected deficit, or unexpected deficit.

CT classification Imaging findings were categorized as postoperative changes only, operative site hematoma without mass effect, or hematoma with mass effect (with management options: no change, medical change, or surgery).

Key findings (imaging) 97.3% (330/339) showed postoperative changes only; 2.7% (9/339) had operative site hematoma without mass effect; 0% had hematoma with mass effect.

Key findings (management impact) 98.2% (333/339) had no change in management based on early CT; 1.8% (6/339) had a change in medical management; 0% required surgical intervention.

Neurological status distribution Postoperatively, 90.9% had no fresh deficit, 7.1% had an expected deficit, and 2.1% had an unexpected deficit.

Association signal Patients with unexpected neurological deficits were more likely to have abnormal CT findings (reported OR 6.22, wide CI, P = .193, not statistically significant).

Bottom line Early postoperative CT offers minimal benefit for extubated patients with no or expected deficits; CT should be reserved for clinical deterioration or unreliable neurological examination.

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Neuropsychological profile and risk factors for poor cognitive outcomes in survivors of aneurysmal subarachnoid hemorrhage

J Neurosurg 144:517–525, 2026

This clinical study characterizes long-term neuropsychological outcomes in 156 survivors of aneurysmal subarachnoid hemorrhage (aSAH), using MoCA-22, digit span, and verbal fluency tests. Findings show that 34% scored below the 25th percentile despite largely favorable functional recovery, with deficits concentrated in executive function, working memory, and language.

Multivariable analysis identified modified Fisher grade 4 on admission and new radiological infarction during hospitalization as independent predictors of poor cognitive outcomes. Secondary assessments revealed frequent depressive symptoms and acquired personality disturbances, implicating impacts on work productivity and social relationships.

Objective Characterize neuropsychological deficits in aneurysmal subarachnoid hemorrhage (aSAH) survivors and identify clinical variables linked to poor cognitive outcomes.

Design/assessments Retrospective cohort (2009–2024) with cognitive testing ≥6 months post-aSAH using MoCA-22, Digit Span Forward/Backward, and Verbal Fluency; poor outcome defined as MoCA-22 <25th percentile (norm-adjusted).

Prevalence 34% (53/156) had MoCA-22 <25th percentile despite most having good functional recovery at discharge (mRS ≤2 in 79% of those with poor MoCA-22).

Cognitive profile Moderate/severe deficits (z-score >1 SD below norms) occurred in 11% on DST-F, 27% on DST-B, and 9% on VFT, highlighting prominent working-memory/executive-function vulnerability.

Key risk factors Modified Fisher grade 4 on admission and new radiological infarction during hospitalization were independently associated with poor MoCA-22 outcomes (aOR 2.43 and 2.71, respectively).

Quality of life impact Radiological infarction was associated with worse work productivity (OR 0.69) and social relationships (OR 0.72).

Behavioral sequelae Among those assessed, 27% reported at least mild depressive symptoms and 64% showed acquired personality disturbance.

Bottom line Cognitive/behavioral deficits can persist long after aSAH even with favorable mRS; higher hemorrhage burden (modified Fisher 4) and in-hospital infarction signal higher risk.

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Historical evolution of microvascular decompression after Jannetta’s establishment: Anatomical maps and physiological compasses—a narrative review

Acta Neurochirurgica (2026) 168:74

This narrative review chronicles five decades of refinement in microvascular decompression (MVD) for trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia, tracing developments from Jannetta’s microsurgical breakthrough to contemporary practice. It emphasizes evolving microsurgical anatomy, tailored craniotomies, endoscopic/exoscopic visualization, and nuanced decompression techniques such as noncompressive transposition versus prosthetic interposition.

The article also highlights operative support advances—high-resolution MRI/MRA, virtual simulation, and intraoperative neuromonitoring (BAEP, LSR)—as physiological “compasses” that improve safety and outcome durability. Together, anatomical “maps” and physiological feedback frame current standards and ongoing challenges in achieving long-term, biologically harmonious decompression.

Microvascular Decompression (MVD) Evolution: MVD has developed from Jannetta’s original microsurgical demonstration of vascular compression into a safe, durable, and standardized surgical treatment for neurovascular compression syndromes, especially trigeminal neuralgia (TN), hemifacial spasm (HFS), and glossopharyngeal neuralgia (GPN).

Anatomical Foundations: Detailed microsurgical anatomy, including the “Rule of Three” for the cerebellopontine angle (CPA), enables tailored, minimally invasive approaches and underpins the understanding of neurovascular conflicts and surgical route selection.

Tailored Surgical Approaches: Three individualized approaches—lateral supracerebellar-infratentorial for TN, infrafloccular for HFS, and transcondylar fossa for GPN—minimize cerebellar retraction and optimize decompression, improving safety and efficacy.

Decompression Strategies: Techniques have shifted from prosthetic interposition (placing a material between vessel and nerve) to noncompressive transposition (mobilizing and securing the vessel away from the nerve), with evidence supporting better long-term outcomes for transposition.

Visualization and Simulation Advances: The integration of endoscopic/exoscopic systems, neuronavigation, and virtual simulation has enhanced visualization, surgical precision, and education, extending the original ethos of microscopic surgery.

Intraoperative Monitoring: Real-time monitoring using brainstem auditory evoked potentials (BAEPs) and lateral spread response (LSR) on facial EMG helps avoid complications and assess decompression adequacy, significantly reducing postoperative morbidity.

Role of Imaging: High-resolution MRI and MRA now routinely identify neurovascular compression preoperatively, though imaging findings are considered supportive rather than diagnostic due to limited specificity in low-grade conflicts.

Sustained First-Line Role: Despite advances in radiosurgery and pharmacotherapy, MVD remains the first-line surgical option for appropriately selected patients, due to its proven long-term efficacy and safety.

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Complications associated with anterior cervical spine surgery: A systematic review of literature

Brain and Spine 6 (2026) 105897

This systematic review examines complications following anterior cervical spine surgery, quantifying incidence rates across studies and identifying major risks such as dysphagia, adjacent segment disease, recurrent laryngeal nerve palsy, infection, pseudarthrosis, esophageal perforation, hematoma, and vertebral artery injury. It synthesizes data from 116 studies (1989–2024) and assesses study quality using the Newcastle–Ottawa Scale.

The review highlights key risk factors—multilevel procedures, revision surgery, OPLL, smoking, older age, and surgeon experience—and emphasizes the importance of preoperative planning, patient selection, standardized prospective monitoring, and timely management to minimize morbidity and guide informed consent and long-term surveillance.

Aim Quantify frequency, causes, and outcomes of complications associated with anterior cervical spine surgery.

Methods Systematic review following PRISMA; searched CINAHL Plus, MEDLINE, PubMed, Scopus, and EMBASE for English-language studies (1989–2024) in adults; quality assessed with the Newcastle Ottawa Scale.

Evidence base 326 records screened; 116 studies included; study quality ranged from 3/9 to 9/9 on NOS, with frequent weaknesses in external control selection and cohort comparability.

Most common complication (dysphagia) Reported incidence varied widely (2.3%–87.5%); overall rate across all included dysphagia studies was 13%, with higher pooled incidence in prospective vs retrospective cohorts (53.7% vs 12.7%).

Other key complications (ranges) Adjacent segment disease 0.4%–32%; recurrent laryngeal nerve palsy 0.1%–9%; infection 0.39%–8.5%; pseudarthrosis 0.25%–31%; esophageal perforation 0.1%–0.45%; vertebral artery injury 0.3%–7.7%; Horner’s syndrome 0.06%–0.45%; graft failure 2.7%–35.5%; CSF leak 0%–1%; postoperative hematoma 0.21%–7%; new/worsening neurological deficits 0.37%–3.3.

Risk factors (higher complication rates) Multilevel disease, revision surgery, and ossification of the posterior longitudinal ligament (OPLL) were associated with increased complications.

Volume–outcome effect Greater surgeon experience and higher case volume were consistently associated with lower complication rates.

Prevention emphasis Reducing complications depends on thorough preoperative planning, careful patient selection, and proper surgical technique.

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Predictors of shunt responsiveness and outcomes in idiopathic normal pressure hydrocephalus: a retrospective cohort study

Acta Neurochirurgica (2026) 168:80

This retrospective cohort study from Tel-Aviv Medical Center evaluates predictors of clinical benefit following shunt placement in idiopathic normal pressure hydrocephalus (iNPH). Among 167 patients undergoing high-volume lumbar puncture, 62 (37%) were LP responders and 38 proceeded to shunting; 21 of 38 (55%) experienced favorable outcomes at one year, with gait disturbance the commonest presenting symptom.

Key associations with LP responsiveness and positive one‑year shunt outcome included lower CSF total tau, lower CSF protein, younger age at symptom onset, pronounced immediate gait improvement after CSF drainage, and the presence of a disproportionately enlarged subarachnoid-space hydrocephalus (DESH) imaging pattern. The authors recommend a multimodal approach combining clinical response, imaging, and fluid biomarkers to refine patient selection for shunting.

Aim Identify clinical, imaging, and CSF biomarkers linked to LP responsiveness and 1-year shunt outcomes in suspected idiopathic normal pressure hydrocephalus (iNPH).

Cohort & pathway 183 evaluated (2020–2022); 167 underwent high-volume LP (≥30 mL removed); LP responders were referred for shunting and outcomes assessed at 1 year.

LP response rate 62/167 (37%) improved after CSF drainage and were referred; 38/62 (61%) ultimately received a shunt (others mainly declined surgery).

Clinical predictors (LP response) Gait disturbance was the most common initial symptom (68%) and was more frequent in LP responders, while cognitive symptoms were more common as the first symptom among non-responders.

CSF biomarkers (LP response) LP responders had lower CSF total tau (t-tau) and protein than non-responders.

Imaging predictor (LP response) DESH pattern was more common in LP responders (73% vs 46%).

Shunt effectiveness Among shunted patients, 21/38 (55%) had a favorable clinical outcome at 1 year.

Outcome predictors (post-shunt) Favorable 1-year outcomes were associated with more frequent DESH and a trend toward lower t-tau.

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Perimesencephalic hemorrhage: a proposed explanation of its cause and clinical manifestations

J Neurosurg 144:740–746, 2026

This neurosurgical forum article analyzes perimesencephalic hemorrhage (PMH), proposing that small dural arterial variants—particularly the artery of Wollschlaeger and Wollschlaeger (AWW) arising from the superior cerebellar artery—can undergo distraction-avulsion and explain PMH’s characteristic cisternal distribution and benign clinical course. The authors present a surgical case with intraoperative identification of an SCA-derived dural branch and perform detailed anatomical correlation.

The paper contrasts venous and arterial hypotheses, reviews perimesencephalic cisternal anatomy and tentorial blood supply, and argues that spontaneous tearing of a tethered intradural dural branch best accounts for imaging, pathophysiology, and low recurrence of PMH, while acknowledging limits of confirmatory testing.

PMH profile Nonaneurysmal perimesencephalic hemorrhage (PMH) is ~10%–15% of spontaneous cisternal SAH, with CT blood confined around the midbrain and typically a benign course with complete recovery and rare recurrence.

Unknown etiology Despite decades of imaging/anatomical work, the cause often remains unidentified on initial and follow-up angiography, leading to the concept of “SAH of unknown cause,” especially when bleeding is perimesencephalic-only.

Index case A 54-year-old woman with SAH had angiography showing a dural arteriovenous fistula (DAVF) fed by the meningohypophyseal trunk and draining via the superior petrosal vein; surgery disconnected the fistula with good outcome.

Unexpected anatomy Intraoperatively, a dural branch from the superior cerebellar artery (SCA) was found bridging the ambient cistern to the undersurface of the tentorium (the artery of Wollschlaeger and Wollschlaeger, AWW) and was sacrificed; it had not been seen on preop angiography and was not the hemorrhage source in that case.

Key anatomical concept The perimesencephalic cistern system (interpeduncular, ambient, quadrigeminal) surrounds the midbrain at the tentorial incisura; vessels can traverse cisternal spaces and arachnoid septations, influencing where blood can collect.

Tentorial dural supply variants The medial tentorium can be supplied by the marginal tentorial artery from the meningohypophyseal trunk, plus intradural-origin dural branches from the PCA (artery of Davidoff and Schechter, ADS) and from the SCA (AWW) that course within the ambient cistern before entering tentorium.

Competing sources considered Two structures fit many PMH constraints: the basal vein of Rosenthal (BVR) (venous, tethered to vein of Galen) and the ADS/AWW (arterial dural branches tethered to the medial tentorial edge).

Proposed mechanism for PMH Spontaneous distraction-avulsion of the AWW from its fragile tentorial attachment during everyday Valsalva/exertion could cause focal cisternal bleeding that self-limits as pressure equalizes in the confined cistern; this is proposed to explain PMH distribution, negative angiography, generally mild course, low hydrocephalus/vasospasm, and rare rebleed.

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The Helsinki Unruptured Intracranial Aneurysm Quality of Care study: a prospective observational study

J Neurosurg 144:507–516, 2026

This prospective single-center study evaluates the safety of unruptured intracranial aneurysm (UIA) treatments by prospectively measuring postprocedural diffusion-weighted MRI (DWI) lesions and correlating them with clinical outcomes at 3 months. Among 169 consecutive patients, 63% developed new DWI lesions, with endovascular cases showing more multiple lesions and surgical cases showing larger lesions.

Despite excellent functional outcomes by modified Rankin Scale (98% mRS 0–1) and high return-to-work rates, DWI lesions were associated with increased neurological symptoms, longer hospital stays, and worse outcomes when ≥10 mm. The authors argue that routine DWI should complement mRS to better capture ischemic burden and guide quality assessment and follow-up.

Objective Evaluate safety of unruptured intracranial aneurysm (UIA) treatment by measuring postprocedural ischemic lesions on MRI diffusion-weighted imaging (DWI) and correlating them with clinical outcomes.

Design Prospective, investigator-initiated, single-center observational cohort of consecutive UIA patients treated at Helsinki University Hospital (Dec 2022–Aug 2024) with brain MRI within 3 days and 3-month follow-up (mRS, neurological symptoms, return to work).

Cohort 169 patients: 120 (71%) endovascular and 49 (29%) surgical; aneurysm location distribution differed (most surgical cases were MCA aneurysms).

DWI incidence New DWI lesions occurred in 63% overall, with no difference between endovascular and surgical treatment (63% vs 63%).

Lesion patterns by modality Endovascular treatment more often produced high lesion counts (≥6 lesions: 14% vs 0%), while surgery more often produced larger lesions (≥10 mm: 20% vs 8%).

Symptoms association Most DWI lesions were asymptomatic (85%), but having any DWI lesion increased risk of new neurological symptoms (15% vs 2%), with 59% of symptoms transient.

mRS association Any DWI lesion was not associated with mRS outcomes, but lesions ≥10 mm were linked to poorer mRS status (mRS 0–1: 84% vs 99%) and higher risk of mRS worsening (21% vs 1%).

Return to work & conclusion 97% of previously working patients returned to work within 3 months; DWI lesions are common despite excellent mRS outcomes, and DWI may add information that mRS alone misses when assessing quality of care.

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Machine learning models for predicting patient satisfaction after adult spinal deformity surgery

J Neurosurg Spine 44:457–468, 2026

This clinical study develops and internally validates machine learning–guided logistic regression models to predict patient satisfaction 24 months after adult spinal deformity (ASD) surgery, using 213 patients and three feature-selection methods. Nine routinely measurable predictors—including postoperative WOMAC function, frailty, pelvic compensation, imaging MCID achievement, rFCSA, and SVA—were identified and ranked by SHAP for their influence on satisfaction.

The model showed strong discrimination (AUROC 0.846) and calibration, yielded a nomogram for individualized prognostication, and emphasizes modifiable targets for perioperative care and rehabilitation. Limitations include single-center retrospective design, modest sample size, and inclusion of postoperative variables limiting preoperative decision use.

Goal Develop and internally validate models to predict patient satisfaction 24 months after adult spinal deformity (ASD) surgery, using SRS-22r satisfaction (high satisfaction defined as score ≥ 4.5).

Cohort 213 ASD patients met criteria; 128 (60%) used for training and 85 (40%) for internal test validation.

Pipeline Used three ML feature-selection methods—LASSO, recursive feature elimination (RFE), and Boruta—and retained variables consistently selected by all three.

Final predictors Nine key indicators were retained: rFCSA, fatty infiltration, frailty, pelvic compensation, postoperative SVA, imaging MCID achievement, postoperative subtotal score, postoperative WOMAC function, and change in WOMAC function.

Model Built an interpretable logistic regression model from these predictors; binary cutoff optimized via ROC/Youden index, with SHAP used to rank feature importance.

Performance In the test set, the model achieved AUROC 0.846 and accuracy 0.812 (also reported AUPRC 0.894 and Brier score 0.153).

Top drivers (SHAP order) Higher postoperative WOMAC function, absence of frailty, imaging MCID achieved, larger WOMAC function improvement, higher rFCSA, higher postoperative subtotal, lower postoperative SVA, successful pelvic compensation, and lower fatty infiltration increased satisfaction likelihood.

Implication/limitation Intended mainly to identify modifiable factors to guide postoperative rehabilitation; practical preoperative counseling is limited because key inputs include postoperative variables, and external multicenter validation is still needed.

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Three-dimensional microsurgical anatomy of the basal aspect of the cerebrum: a fiber dissection study

J Neurosurg 144:690–702, 2026

This study presents a three-dimensional microsurgical fiber-dissection analysis of the basal aspect of the human cerebrum, detailing the spatial organization of commissural, projection, and association fibers and their relationships with subcortical nuclei, ventricles, and cortical landmarks. Using 10 formalin-fixed brains with layer-by-layer dissection and stereoscopic photography, the authors map tracts such as the ILF, UF, SS, cingulum, fornix, and connections around the amygdala and nucleus accumbens.

The findings emphasize surgical implications by clarifying trajectories and landmarks relevant to approaches like STIO and SCTT, illustrating a clinical case of hippocampal glioma resection with optic-radiation preservation, and proposing that 3D anatomical insight enhances safe, precise planning for medial temporal and basal lesions.

Objective Limited surgical exposure of the cerebral base makes basal fiber-tract injury a key risk; detailed 3D tract anatomy is needed to plan safer resections and support brain-function research.

Aim Mapped the topography of basal white-matter tracts and subcortical gray matter (including hippocampus, amygdala, and nucleus accumbens) and their relationships to cortex, ventricles, and nuclei.

Methods Performed Klingler-style layer-by-layer fiber dissection on 10 formalin-fixed human brains under ×6–×40 magnification, documenting each stage with stereoscopic 3D photography.

Key anatomy (basal tracts) Sequential basal dissection exposed U fibers, inferior cingulum (lower part), Li-Am fasciculus, SRF, and ILF; removing Li-Am/ILF revealed the temporal horn with the hippocampus medially.

Sagittal stratum layering The lateral wall of the atrium is layered (medial→lateral): ependyma, tapetum, IC-SL, optic radiations, posterior AC extension, IFOF, MdLF, posterior SLF/AF, U fibers, cortex—together forming the sagittal stratum.

ILF clarification The ILF was identified as a long association tract connecting the base of the temporal pole to the occipital base, located above the fusiform gyrus and beneath the sagittal stratum; “merging fibers” in lateral occipital base were distinguished from the temporal portion of the AF.

Amygdala connectivity The amygdala links to septal nuclei/hypothalamus/thalamus via the stria terminalis, projects to cortical regions via the uncinate fasciculus, and connects via additional pathways including amygdalofugal routes and the anterior commissure.

Surgical application (STIO case) A right hippocampal WHO grade 2 glioma was resected via a supratentorial-infraoccipital (STIO) approach; the fusiform gyrus was incised anterior to the basal turning point of the optic radiation to reach the lateral ventricle, and postoperative DTI confirmed optic-radiation preservation.

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Suprasellar Versus Third Ventricular Cysts: Anatomic and Surgical Considerations

Operative Neurosurgery 30:468–471, 2026

This surgical case instruction contrasts suprasellar arachnoid cysts (SACs) and third ventricular cysts (3VCs), emphasizing their distinct imaging features, clinical presentations, and risks of obstructive hydrocephalus. It summarizes patient examples, MRI findings, and outcomes after endoscopic cyst fenestration, demonstrating restoration of cerebrospinal fluid flow and symptom resolution.

The article details stepwise endoscopic techniques—cyst plane development, wall reduction, excision, and membrane management—highlighting anatomical cues that guide whether endoscopic third ventriculostomy is necessary. Practical tips on preserving hypothalamic structures, restoring aqueduct patency, and minimizing reaccumulation are provided for neurosurgical practice.

Prevalence Intracranial arachnoid cysts occur in ~2.6% of children and ~1.4% of adults; suprasellar arachnoid cysts (SACs) comprise ~9%–21% of pediatric arachnoid cysts and can be confused with rarer third ventricular cysts (3VCs).

Presentation SACs and 3VCs often enlarge and cause obstructive hydrocephalus with symptoms of increased intracranial pressure, prompting urgent treatment to restore CSF circulation.

Imaging differences (SAC) SACs elevate the third ventricular floor, displace mammillary bodies superiorly/posteriorly, and elongate/stretch the midbrain and aqueduct, with aqueduct occlusion from distortion and the posterior cyst wall.

Imaging differences (3VC) 3VCs displace the third ventricular floor and mammillary bodies inferiorly with midbrain compaction; the aqueduct is obstructed by midbrain distortion and the inferoposterior cyst wall.

Treatment rationale A shunt without cyst fenestration can lead to asymmetric hydrocephalus and/or continued cyst enlargement due to cyst-related occlusion of the foramina of Monro; neuroendoscopy enables cyst fenestration with low morbidity risk at experienced centers.

Endoscopic steps A stepwise intraventricular endoscopic approach includes: developing the cyst/ventricle plane; reducing cyst wall size (coagulation); excising roof/lateral/medial walls (with caution laterally in SACs due to hypothalamic fusion); removing/reducing floating membranes (especially posteriorly) to open access to the aqueduct.

Inferior wall strategy In SACs, inferior membrane fenestration may be unnecessary because the prepontine cistern is already exposed/communicates with the third ventricle; in 3VCs, the inferior aspect is the third ventricular floor, and endoscopic third ventriculostomy (ETV) is an option.

ETV decision point If posterior membrane resection fully restores aqueduct patency, ETV may not be necessary; reducing expansile membranes is pursued to lower risk of reaccumulation from scarring.

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Utilization of robotic pars repair for early return to activity in adolescents with symptomatic spondylolysis

J Neurosurg Spine 44:349–354, 2026

This case series from a tertiary academic spine center reports outcomes of robot-assisted percutaneous pars repair in nine adolescents with symptomatic lumbar spondylolysis who failed conservative management. The authors describe a single–midline incision technique using CT-based robotic guidance and a single lagged transdefect screw, detailing operative workflow, implant sizes, and a standardized postoperative rehabilitation protocol.

Results show most patients returned to preinjury or higher activity within months, with low complication rates and radiographic evidence of union in those who obtained CT follow-up. The authors conclude that minimally invasive robotic pars repair is a viable option after failed nonoperative care and advocate timely surgical consultation to potentially accelerate return to sport and avoid progressive spondylolisthesis.

Clinical problem Symptomatic lumbar pars interarticularis fractures (spondylolysis) are a common cause of adolescent low-back pain; nonoperative care with activity modification is standard first-line treatment.

Nonunion risk Despite conservative management, about 20% of patients may progress to symptomatic nonunion, and some can later develop spondylolisthesis that may require fusion.

Study aim Robotic surgical guidance was used to enable percutaneous pars screw placement; the series reports the largest cohort of adolescents treated with robot-assisted pars repair to date.

Design & cohort Retrospective review of a prospectively collected database identified 9 adolescents/young adults (13–25 years) treated with a single-screw pars repair technique.

Technique Using Excelsius robotic planning/registration and intraoperative 3D imaging, bilateral screw trajectories were planned to converge so bilateral pars screws could be placed through a single 1–2 cm midline incision; compression was achieved via a “lag-by-technique” preparation without direct pars visualization/grafting.

Postop protocol Patients walked only for 2 weeks, then added stationary biking for 2 weeks, followed by 4 weeks of sport-directed physical therapy; if tolerated symptom-free, they were cleared for activity (cleared to begin return-to-sport training at 4 weeks).

Outcomes Mean preop activity cessation at consultation was 8.6 ± 10.6 months; at mean follow-up 11.4 ± 9.1 months, 78% had returned to baseline activity or were cleared to return to sport.

Safety/efficacy conclusion Robot-assisted pars repair was reported as a safe, effective option after failed nonoperative care, enabling return to activity in as little as 8 weeks; a single lag-style screw may be clinically effective compared with prior open debridement/bone-grafting approaches.

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