This Week in Neurosurgery — May 14, 2026

Welcome to This Week in Neurosurgery. This week we're covering 8 notable papers spanning refining diagnostics and prognostics, optimizing surgical and procedural performance, and a look at the future of neurosurgical training and circuit-level technology. Let's dive in.

Our first theme is the refinement of diagnostic and prognostic tools, where we have three papers that provide a new imaging sign, validate an old one, and cast serious doubt on an emerging clinical syndrome.

Let's start with a common diagnostic challenge: distinguishing primary central nervous system lymphoma, or PCNSL, from glioblastoma on preoperative imaging. A study in *Neurosurgery* introduces a novel imaging biomarker that may prove exceptionally useful. Investigators reviewed images from 61 patients with PCNSL and 65 with glioblastoma [3]. They identified what they call the "cortical diffusion-enhancement mismatch sign." This is defined as a lesion with high signal on diffusion-weighted imaging that involves both the gray and white matter, but where the gadolinium enhancement is confined only to the subcortical white matter. This sign was found in over half of the superficially located PCNSL cases. Critically, it was not seen in a single case of glioblastoma, giving it a specificity of 100%. While the sensitivity was modest at about 54%, its perfect specificity suggests that when you see this sign, you can be highly confident in a diagnosis of PCNSL, which could significantly alter management by prioritizing stereotactic biopsy over a more aggressive resection.

Moving from tumor diagnosis to hydrocephalus, a paper in *Acta Neurochirurgica* provides an important external validation for a key prognostic score in idiopathic normal pressure hydrocephalus, or iNPH [6]. Previous work suggested the DESH score—which stands for Disproportionally Enlarged Subarachnoid-space Hydrocephalus—could predict response to shunting. This new study retrospectively analyzed 127 shunt-operated iNPH patients in Denmark with a longer mean follow-up of over 7 months. The results confirmed the original findings: a higher DESH score was significantly associated with a better objective response to shunt surgery. An equally important secondary finding was that there was no significant difference in DESH score assessments between CT and MRI. This practical point increases the utility of the score, as it suggests clinicians can reliably use the more readily available CT scan for prognostication, though the authors note that formal equivalence studies are still needed.

Rounding out our diagnostics section is a crucial, cautionary paper from *Nature Medicine* that challenges the clinical criteria for Traumatic Encephalopathy Syndrome, or TES, the proposed clinical correlate for Chronic Traumatic Encephalopathy, or CTE [1]. Since CTE can only be diagnosed on postmortem pathology, the TES criteria were developed to identify it in living individuals. This study examined the records of over 1,000 individuals from a brain bank. Of the 25 cases that met clinical criteria for TES, only 6 actually had CTE pathology at autopsy. This yields a positive predictive value of just 24%. In other words, for every four people diagnosed with TES based on these criteria, three did not have CTE. The study found that the diagnostic accuracy was driven almost entirely by a history of repetitive head impacts, not by the specific clinical features themselves. This poor performance raises substantial concerns about the potential for misdiagnosis and the associated psychological burden on athletes and others with a history of head trauma.

Our next theme is the optimization of surgical and procedural performance, featuring papers on moyamoya, craniopharyngioma, and AI assistance in the angio suite.

First, in cerebrovascular surgery, a study in *Neurosurgery* addresses a key question in the management of bilateral moyamoya disease: is staged bilateral bypass always necessary? [2]. Investigators in this retrospective study looked at 151 adult patients with bilateral disease who underwent a unilateral combined bypass. At 6-month follow-up using SPECT imaging, they found that not only did cerebral blood flow and cerebrovascular reserve improve on the operated hemisphere, but basal cerebral blood flow also significantly increased in several territories of the *contralateral*, unoperated hemisphere. This finding suggests that unilateral revascularization can, in some cases, improve bilateral hemodynamics. The clinical implication is that surgeons should consider a more selective approach, reserving intervention for the hemisphere with clear symptomatic and hemodynamic instability, rather than reflexively planning a staged bilateral operation in all cases.

Next, in the realm of quality improvement and skull base surgery, a paper from *Operative Neurosurgery* provides much-needed benchmarks for endoscopic transnasal resection of craniopharyngiomas [8]. Using the RAPID consortium database, which includes data from 14 academic centers across the United States, the authors analyzed outcomes for 318 adult patients. They stratified patients into low- and high-risk cohorts based on factors like age, tumor size, and intraventricular extension. For low-risk patients, for example, benchmark performance, defined as the 50th to 75th percentile, included a gross total resection rate between 50 and 61 percent, a postoperative CSF leak rate under 15 percent, and new permanent diabetes insipidus rates between 33 and 50 percent. Establishing these risk-stratified benchmarks provides a powerful framework for institutions to assess their own performance, counsel patients more accurately on expected outcomes, and identify areas for quality improvement.

Finally, a third paper from *Neurosurgery* this week explores the utility of artificial intelligence in the neuroendovascular suite [4]. This study retrospectively analyzed 130 procedures where a real-time AI guidance system was used. The system provided automated notifications if a guidewire or guiding catheter exited the fluoroscopic field. The key finding was that these notifications were significantly more frequent and more often "clinically useful"—meaning the operator repositioned the device within 10 seconds—during emergency procedures compared to elective ones. The rate of useful notifications was twice as high in the emergency group. This makes sense, as emergency procedures were more often performed by less-experienced operators. The study suggests that real-time AI guidance can serve as a valuable safety net, particularly in high-acuity settings where less experienced physicians may be operating under pressure.

Our final section looks to the future, with one paper on how we train neurosurgeons and another offering a glimpse into the future of circuit-level neuromodulation.

First, a study in *World Neurosurgery* provides clear evidence for optimizing our training curricula [7]. The study compared three training models for pterional and retrosigmoid approaches: simulator-only, body donor-only, and a hybrid model where participants used a simulator before moving to a body donor. The primary outcome was the number of anatomical structures correctly identified during the cadaveric dissection. The results were clear: the hybrid group significantly outperformed the body donor-only group, identifying more key structures in both approaches. This suggests that simulation serves as an effective preparatory tool, priming trainees to learn more effectively when they get to the invaluable, but limited, resource of body-donor dissection. This finding has direct implications for residency program directors looking to maximize the educational yield of their labs.

Lastly, a basic science report in *Nature* introduces a powerful new tool for editing brain circuits with remarkable precision [5]. Researchers engineered an electrical synapse using two connexin proteins from a fish. The key innovation is that these engineered proteins were designed to connect with each other, but not with the native connexins found in the mammalian brain. This allows for the creation of a new, artificial electrical synapse exclusively between two specific, targeted cell populations. The authors call the technique "LinCx," for Long-term integration of circuits using connexins. They demonstrated in both worms and mice that this tool can be used to strengthen communication across specific neural circuits and modify behavior accordingly. While still in the preclinical phase, LinCx represents a major step forward in precision circuit editing, opening the door for future research and potentially, one day, novel therapies for neurological and psychiatric disorders.

If you only have time for one paper this week, make it the study from *Nature Medicine* on the performance of Traumatic Encephalopathy Syndrome criteria [1]. Its finding that the clinical criteria have a positive predictive value of only 24% for actual CTE pathology is a critical, practice-changing piece of information. It demands that we be far more cautious and nuanced when counseling patients with a history of head trauma about their risk of a progressive neurodegenerative disease.

Here are the key takeaways from this week in Neurosurgery.

First: A new imaging finding called the "cortical diffusion-enhancement mismatch sign" appears to be 100% specific for primary CNS lymphoma versus glioblastoma, offering a powerful non-invasive diagnostic clue [3].

Second: Be extremely cautious when applying the clinical criteria for Traumatic Encephalopathy Syndrome, or TES. A major new study shows these criteria have a very poor positive predictive value of only 24% for underlying CTE pathology, meaning most patients who meet criteria will not have the disease [1].

Third: In patients with bilateral moyamoya disease, a unilateral bypass can improve blood flow on the unoperated side, suggesting that routine staged bilateral surgery may not always be necessary and a more selective approach is warranted [2].

Fourth: For training residents, a hybrid model that incorporates simulation practice *before* cadaveric dissection is superior to cadaveric dissection alone for learning key surgical anatomy [7].

Fifth: New risk-stratified, multi-center benchmarks for endoscopic craniopharyngioma resection are now available, allowing you to compare your institutional outcomes for metrics like GTR and CSF leak against national data [8].

That's your roundup for This Week in Neurosurgery. The full transcript and references are available on the episode page in your AudioScholar library. This is an AI-curated summary — for clinical decisions, always consult primary sources and current guidelines. See you next week.

This is an automated summary generated by artificial intelligence, which can make mistakes. Always review the original source materials.