Middlebrooks, Erik H

OBJECTIVE Stereotactic radiosurgery (SRS) is an effective treatment for refractory tremor. However, the lack of reliable patient-specific targeting biomarkers leads to varying outcomes. Although connectomic-based targeting is commonly used in deep brain stimulation, its application in SRS is limited. This study aimed to develop a new targeting approach by using patient-specific structural connectivity to improve outcomes after SRS. METHODS The authors performed a retrospective study of patients in a prospective trial for frameless virtual-cone SRS on a linear accelerator for essential tremor or tremor-dominant Parkinson disease. The primary endpoint was percentage improvement in Fahn-Tolosa-Marin tremor rating scale scores contralateral to the treatment side. Probabilistic tractography assessed connectivity from each thalamic voxel to the primary motor cortex (M1), primary sensory cortex (S1), and supplemental motor area/premotor cortex (SMA/PMC). Group-level comparisons were conducted to evaluate the relationship between the sweet spot for maximum contralateral tremor improvement and areas maximally connected to M1, S1, and SMA/PMC. Multiple regression analysis assessed the relationship between the lesion centerpoint coordinates and the maximally connected voxel to M1, S1, and SMA/PMC at the individual level. RESULTS The analysis included 27 patients with a mean follow-up of 17.9 ± 11.1 months. The sweet spot for maximal contralateral tremor improvement at the group level was in the region most connected to M1 cortex. Smaller y-distances (anterior-posterior) from the lesion center to the M1 maximally connected voxel significantly correlated with tremor improvement at the single-subject level (p < 0.001). However, the authors found no significant correlation between the lesion y-coordinate and the maximally connected voxel to SMA/PMC and S1, nor between the x-distances from the lesions to the SMA/PMC, M1, and S1 voxels (p > 0.07). CONCLUSIONS This study demonstrates that patient-specific connectivity between the treatment target and M1 correlates with treatment outcomes. The authors’ approach provides a practical targeting method for SRS thalamotomy for tremor.

Diagnosis of motor neuron diseases and other corticospinal tractopathies requires a comprehensive approach that integrates clinical symptoms and laboratory findings with findings from conventional MRI and advanced neuroimaging.

Abstract BACKGROUND Yttrium-90 (Y90) microsphere treatment is an FDA-approved endovascular radiotherapy for Hepatocellular Carcinoma; however, extra-hepatic experience is limited. The FRONTIER trial (NCT05303467) is a first-in-human study conducted under an IDE from the FDA evaluating the safety and feasibility of intra-arterial Y90 endovascular radiotherapy in patients with recurrent glioblastoma (rGBM). METHODS The primary endpoint is the incidence of treatment-related limiting toxicities through 30 days, in 12 patients with rGBM. Eight subjects (50% male) with non-dominant hemisphere rGBM have been enrolled to date, with 6 patients reported herein. The treatment region, encompassing the recurrent lesion, excluding eloquent regions, and defined using cerebral angiography-MRI fusion, was selectively targeted with 40±4Gy. Immediate post-treatment imaging included MRI to evaluate acute treatment-related effects and Y90-PET to evaluate the absorbed dose distribution. Neurological assessments were performed pre- and post-treatment. Analysis of post-contrast T1w enhancing tissue volume (T1wvol) inside and outside the treated region was performed longitudinally. RESULTS All patients tolerated the procedure well and were discharged the following day. No decrease in neurological function and no limiting toxicities were reported through 30 days. Post-treatment MRI revealed no device-related acute ischemia or hemorrhage. Mean absorbed dose to the treatment region was 42.1±2.4Gy, within 3% of the targeted value, suggesting technical feasibility. Mean tumor absorbed dose within the treatment region was 65.1±22.6Gy most likely due to increased tumor perfusion in the treatment region. A reduction in T1wvol at 2m was observed in 4/6 patients, with the remaining 2 patients showing increased T1wvol. Disease progression by T1wvol occurred more rapidly outside the treatment region than within. All patients received subsequent therapy, with 2 patients receiving surgery 82 and 120 days post Y90 treatment. CONCLUSION Interim results in this first-in-human feasibility study demonstrated technical feasibility and no limiting toxicities through 30 days. Enrollment is ongoing. These data warrant additional investigation.

AbstractQuantitative susceptibility mapping (QSM) is a tool for mapping tissue susceptibility. Using QSM for functional brain mapping, it is possible to directly quantify blood‐oxygen‐level‐dependent (BOLD) susceptibility changes. This study presents a submillimeter functional QSM (fQSM) approach compared to BOLD fMRI from data acquired with 3D gradient‐echo echo planar imaging (EPI) at ultra‐high field. Complex EPI data were acquired in nine healthy subjects with varying temporal and spatial resolutions and used for BOLD fMRI and for fQSM. Right‐hand finger tapping experiments were performed as well as one measurement with intentional subject movement. Susceptibility maps were computed using 3D path‐based unwrapping, the variable‐kernel sophisticated harmonic artifact reduction for phase data, and the streaking artifact reduction for QSM algorithm. Functional data analysis included general linear modeling and computation of z‐scores. Submillimeter data were denoised using NOise reduction with DIstribution Corrected (NORDIC), which improved z‐scores in the motor cortex for fQSM and fMRI. An expected increase in BOLD fMRI signal and corresponding decrease in magnetic susceptibility was observed in sensorimotor areas during active periods. For all experiments, fQSM showed smaller activation regions compared with fMRI. The percentage of high negative t‐values localized in the cortex was higher for fQSM (52%) than for positive or negative t‐values for fMRI (45%). For the scans with intentional motion, movement exceeded the size of a voxel, but paradigm dependent signal evolution could be recovered using motion correction. In conclusion, this study demonstrates the feasibility of submillimeter whole‐brain fQSM with voxel volume of 0.53 μL. In comparison to traditional BOLD fMRI, fQSM provided improved localization of brain activation within the cortex, especially in submillimeter 3D EPI sequences.

AbstractObjectiveNeuromodulation is a viable option for patients with drug‐resistant epilepsies. We reviewed the management of patients with two deep brain neurostimulators. In addition, patients implanted with a device targeting the centromedian‐parafascicular (CM‐Pf) nuclear complex supplements this report to provide an illustrative case to implantation and programming a patient with three active devices.MethodsA narrative review using PubMed and Embase identified patients with drug‐resistant epilepsy implanted with more than one neurostimulator was performed. Combinations of vagus nerve stimulation (VNS), deep brain stimulation (DBS), and responsive neurostimulation (RNS) were identified. We provide a background of a newly reported case of an adult with a triple implant eventually responding to CM‐Pf DBS as the third implant following suboptimal benefit from VNS and RNS.ResultsIn review of the literature, dual‐device therapy is increasing in reports of use with combinations of VNS, RNS, and DBS to treat patients with drug‐resistant epilepsy. We review dual‐device implants with thalamic DBS device combinations, functional neural networks, and programming patients with dual devices. CM‐Pf is a new target for DBS and has shown a variable response in focal epilepsy. We report the unique case of 28‐year‐old male with drug‐resistant focal epilepsy who experienced a 75% seizure reduction with CM‐Pf DBS as his third device after suboptimal responses to VNS and RNS. After 9 months, he also experienced seizure freedom from recurrent focal to bilateral tonic–clonic seizures. No medical or surgical complications or safety issues were encountered.ConclusionWe demonstrate safety and feasibility in an adult combining active VNS, RNS, and CM‐Pf DBS. Patients with dual‐device therapy who experience a suboptimal response to initial device use at optimized settings should not be considered a neuromodulation “failure.” Strategies to combine devices require a working knowledge of brain networks.

Objectives: To evaluate the relationship between Framingham Stroke Risk Profile (FSRP) score and rate of white matter hyperintensity (WMH) progression and cognition. Methods: Consecutive patients enrolled in the Mayo Clinic Florida Familial Cerebrovascular Diseases Registry (2011-2020) with 2 brain-MRI scans at least 1 year apart were included. The primary outcome was annual change in WMH volume (cm3/year) stratified as fast versus slow (above vs. below median). Cognition was assessed using a Mini-Mental State Exam (MMSE, 0-30). FSRP score (0 to 8) was calculated by summing the presence of age 65 years or older, smoking, systolic blood pressure greater than 130 mmHg, diabetes, coronary disease, atrial fibrillation, left ventricular hypertrophy, and antihypertensive medication use. Linear and logistic regression analyses were performed to examine the association between FSRP and WMH progression, and cognition. Results: In all, 207 patients were included, with a mean age of 60±16 y and 54.6% female. FSRP scores risk distribution was: 31.9% scored 0 to 1, 36.7% scored 2 to 3, and 31.4% scored ≥4. The baseline WMH volume was 9.6 cm3 (IQR: 3.3-28.4 cm3), and the annual rate of WMH progression was 0.9 cm3/year (IQR: 0.1 to 3.1 cm3/year). A higher FSRP score was associated with fast WMH progression (odds ratio, 1.45; 95% CI: 1.22-1.72; P<0.001) and a lower MMSE score (23.6 vs. 27.1; P<0.001). There was a dose-dependent relationship between higher FSRP score and fast WMH progression (odds ratios, 2.20, 4.64, 7.86, 8.03 for FSRP scores 1, 2, 3, and ≥4, respectively; trend P<0.001). Conclusions: This study demonstrated an association between higher FSRP scores and accelerated WMH progression, as well as lower cognition.

OBJECTIVE The term "sagittal stratum" was coined by Heinrich Sachs in 1892 to define a parasagittally oriented white matter layer at the temporo-occipital cortex. Although this term has been widely used for more than 100 years, the description, classification, borders, and involved fibers of the structure vary among authors and remain imprecise. Through fiber microdissection and tractography, the authors aimed to define the sagittal stratum and resolve the uncertainty by revealing the relationship of this structure to other cerebral white matter pathways and the orientation of fibers in it. METHODS Twenty postmortem human cerebral hemispheres were prepared according to Klingler’s method. Fiber dissections were performed under a surgical microscope and with microsurgical techniques. The results of dissection at each step were photographed with 2D and 3D imaging techniques, and 3D photogrammetry techniques were used to create a 360° model. Diffusion tensor imaging and 7T high-resolution MRI were used to confirm the findings. RESULTS This study revisited the 3D organization of white matter tracts in the sagittal stratum through fiber microdissection and tractography. The microneuroanatomical structure of the sagittal stratum and its special organization with fibers from all three fiber systems are demonstrated. The authors’ findings revealed that the sagittal stratum has two layers consisting of four different fiber tracts. Its external layer consists of a long association fiber and a commissural fiber, while its internal layer consists of intertwined projection fibers, including temporo-parieto-occipitopontine fibers and the posterior thalamic peduncle. Detailed microdissection also showed the location of the posterior thalamic peduncle in the most medial site of all posterior hemispheric projection fibers. CONCLUSIONS The structure of the sagittal stratum is distinctive in that it contains all three main fiber systems: association, commissural, and projection. Because of its expansive location in the temporal and occipital lobes, it can be damaged by most neurosurgical pathologies and procedures. The authors emphasize the significance of preserving the sagittal stratum during surgical interventions while also challenging the notion of a "silent" brain, suggesting that the current inability to fully comprehend cerebral function contributes to this misconception. Detailed knowledge of the complex white matter anatomy of the sagittal stratum can guide neurosurgeons in surgical planning and the selection of appropriate surgical approaches with intraoperative orientation for safe surgery and less comorbidity.