Letter to the Editor. Clinical Rating Scale for Tremor: a needed clarification
Can Sarica, Anton Fomenko, Christian Iorio-Morin, Ajmal Zemmar, Kazuaki Yamamoto, Artur Vetkas, Andres M. Lozano, and Alfonso Fasano
Computational modeling of whole-brain dynamics: a review of neurosurgical applications
Stefan Lang, Davide Momi, Artur Vetkas, Brendan Santyr, Andrew Z. Yang, Suneil K. Kalia, John D. Griffiths, and Andres Lozano
A major goal of modern neurosurgery is the personalization of treatment to optimize or predict individual outcomes. One strategy in this regard has been to create whole-brain models of individual patients. Whole-brain modeling is a subfield of computational neuroscience that focuses on simulations of large-scale neural activity patterns across distributed brain networks. Recent advances allow for the personalization of these models by incorporating distinct connectivity architecture obtained from noninvasive neuroimaging of individual patients. Local dynamics of each brain region are simulated with neural mass models and subsequently coupled together, considering the subject’s empirical structural connectome. The parameters of the model can be optimized by comparing model-generated and empirical data. The resulting personalized whole-brain models have translational potential in neurosurgery, allowing investigators to simulate the effects of virtual therapies (such as resections or brain stimulations), assess the effect of brain pathology on network dynamics, or discern epileptic networks and predict seizure propagation in silico. The information gained from these simulations can be used as clinical decision support, guiding patient-specific treatment plans. Here the authors provide an overview of the rapidly advancing field of whole-brain modeling and review the literature on neurosurgical applications of this technology.
Use of cortical volume to predict response to temporary CSF drainage in patients with idiopathic normal pressure hydrocephalus
Stefan Lang, Dennis Dimond, Albert M. Isaacs, Jarred Dronyk, Artur Vetkas, Christopher R. Conner, Jurgen Germann, Alfonso Fasano, Suneil Kalia, Andres Lozano, and Mark G. Hamilton
Temporary drainage of CSF with lumbar puncture or lumbar drainage has a high predictive value for identifying patients with suspected idiopathic normal pressure hydrocephalus (iNPH) who may benefit from ventriculoperitoneal shunt insertion. However, it is unclear what differentiates responders from nonresponders. The authors hypothesized that nonresponders to temporary CSF drainage would have patterns of reduced regional gray matter volume (GMV) as compared with those of responders. The objective of the current investigation was to compare regional GMV between temporary CSF drainage responders and nonresponders. Machine learning using extracted GMV was then used to predict outcomes.
This retrospective cohort study included 132 patients with iNPH who underwent temporary CSF drainage and structural MRI. Demographic and clinical variables were examined between groups. Voxel-based morphometry was used to calculate GMV across the brain. Group differences in regional GMV were assessed and correlated with change in results on the Montreal Cognitive Assessment (MoCA) and gait velocity. A support vector machine (SVM) model that used extracted GMV values and was validated with leave-one-out cross-validation was used to predict clinical outcome.
There were 87 responders and 45 nonresponders. There were no group differences in terms of age, sex, baseline MoCA score, Evans index, presence of disproportionately enlarged subarachnoid space hydrocephalus, baseline total CSF volume, or baseline white matter T2-weighted hyperintensity volume (p > 0.05). Nonresponders demonstrated decreased GMV in the right supplementary motor area (SMA) and right posterior parietal cortex as compared with responders (p < 0.001, p < 0.05 with false discovery rate cluster correction). GMV in the posterior parietal cortex was associated with change in MoCA (r2 = 0.075, p < 0.05) and gait velocity (r2 = 0.076, p < 0.05). Response status was classified by the SVM with 75.8% accuracy.
Decreased GMV in the SMA and posterior parietal cortex may help identify patients with iNPH who are unlikely to benefit from temporary CSF drainage. These patients may have limited capacity for recovery due to atrophy in these regions that are known to be important for motor and cognitive integration. This study represents an important step toward improving patient selection and predicting clinical outcomes in the treatment of iNPH.
Clinical outcomes and complications of peripheral nerve field stimulation in the management of refractory trigeminal pain: a systematic review and meta-analysis
Can Sarica, Christian Iorio-Morin, David H. Aguirre-Padilla, Michelle Paff, Samuelle-Arianne Villeneuve, Artur Vetkas, Kazuaki Yamamoto, Nardin Samuel, Vanessa Milano, Aaron Loh, Brendan Santyr, Ajmal Zemmar, Andres M. Lozano, and Mojgan Hodaie
Peripheral nerve field stimulation (PNFS) is a tool in the armamentarium of treatment options for trigeminal pain. The efficacy of this modality in mitigating trigeminal pain remains unclear. The aim of this study was to examine the existing literature on PNFS and elucidate pain score outcomes associated with its use in patients with trigeminal pain.
A systematic review and meta-analysis was performed in accordance with the PRISMA framework. The PubMed, Web of Science, and Scopus databases were queried on June 10, 2020. Studies reporting pain outcomes in more than 5 adult patients treated with PNFS for facial pain were included. The primary outcome of the study was the mean difference in the visual analog scale (VAS) score from the last follow-up to baseline, and it was analyzed by an inverse-variance, random-effect model. The risk of bias was assessed using the Newcastle-Ottawa Scale and a funnel plot.
Of the 4597 studies screened for inclusion, 46 relevant full-text articles were assessed for eligibility. Eleven observational cohort studies from the 46 articles were found to be eligible, and reported on a total of 109 patients. In 86% (94/109) of cases, trial stimulation was successful and followed by a permanent system implantation. VAS scores improved by 75% (mean difference 6.32/10 points, 95% CI 5.38–7.27 points) compared to baseline. Seventy-six percent (42/55) of patients became medication free or required lower doses of medications. The complication rate necessitating surgical revision was estimated at 32% per procedure.
These findings support the belief that PNFS provides effective, long-term pain control for trigeminal pain. Statistical heterogeneity was considerable across all studies. Future work should be aimed at conducting double-blind randomized controlled trials to determine the utility of PNFS for treating various forms of trigeminal pain for which limited therapeutic options exist.
Successful magnetic resonance–guided focused ultrasound treatment of tremor in patients with a skull density ratio of 0.4 or less
Artur Vetkas, Alexandre Boutet, Can Sarica, Jurgen Germann, Dave Gwun, Kazuaki Yamamoto, Hyun Ho Jung, Afnan Alkhotani, Nardin Samuel, Stefan Lang, Christopher R. Conner, Gavin J. B. Elias, Cletus Cheyuo, Clement Chow, Brendan Santyr, Christian Iorio-Morin, Andrew Z. Yang, Carolina Candeias da Silva, Alfonso Fasano, Suneil K. Kalia, and Andres M. Lozano
The use of magnetic resonance–guided focused ultrasound (MRgFUS) for the treatment of tremor-related disorders and other novel indications has been limited by guidelines advocating treatment of patients with a skull density ratio (SDR) above 0.45 ± 0.05 despite reports of successful outcomes in patients with a low SDR (LSDR). The authors’ goal was to retrospectively analyze the sonication strategies, adverse effects, and clinical and imaging outcomes in patients with SDR ≤ 0.4 treated for tremor using MRgFUS.
Clinical outcomes and adverse effects were assessed at 3 and 12 months after MRgFUS. Outcomes and lesion location, volume, and shape characteristics (elongation and eccentricity) were compared between the SDR groups.
A total of 102 consecutive patients were included in the analysis, of whom 39 had SDRs ≤ 0.4. No patient was excluded from treatment because of an LSDR, with the lowest being 0.22. Lesioning temperatures (> 52°C) and therapeutic ablations were achieved in all patients. There were no significant differences in clinical outcome, adverse effects, lesion location, and volume between the high SDR group and the LSDR group. SDR was significantly associated with total energy (rho = −0.459, p < 0.001), heating efficiency (rho = 0.605, p < 0.001), and peak temperature (rho = 0.222, p = 0.025).
The authors’ results show that treatment of tremor in patients with an LSDR using MRgFUS is technically possible, leading to a safe and lasting therapeutic effect. Limiting the number of sonications and adjusting the energy and duration to achieve the required temperature early during the treatment are suitable strategies in LSDR patients.