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Introduction: Anterior nucleus of the thalamus (ANT) deep brain stimulation (DBS) is an increasingly promising treatment option for refractory epilepsy. Optimal therapeutic benefit has been associated with stimulation at the junction of ANT and the mammillothalamic tract (mtt), but electrophysiologic markers of this target are lacking. The present study examined microelectrode recordings (MER) during DBS to identify unique electrophysiologic characteristics of ANT and the ANT-mtt junction., Methods: Ten patients with medically refractory epilepsy underwent MER during ANT-DBS implantation under general anesthesia. MER locations were determined based on coregistration of preoperative MRI, postoperative CT, and a stereotactic atlas of the thalamus (Morel atlas). Several neurophysiological parameters including single unit spiking rate, bursting properties, theta and alpha power and cerebrospinal fluid (CSF)-normalized root mean square (NRMS) of multiunit activity were characterized at recording depths and compared to anatomic boundaries., Results: From sixteen hemispheres, 485 recordings locations were collected from a mean of 30.3 (15.64 ± 5.0 mm) recording spans. Three-hundred and ninety-four of these recording locations were utilized further for analysis of spiking and bursting rates, after excluding recordings that were more than 8 mm above the putative ventral ANT border. The ANT region exhibited discernible features including: (1) mean spiking rate (7.52 Hz ± 6.9 Hz; one-way analysis of variance test, p = 0.014 when compared to mediodorsal nucleus of the thalamus [MD], mtt, and CSF), (2) the presence of bursting activity with 40% of ANT locations (N = 59) exhibited bursting versus 24% the mtt (χ2; p < 0.001), and 32% in the MD (p = 0.38), (3) CSF-NRMS, a proxy for neuronal density, exhibited well demarcated changes near the entry and exit of ANT (linear regression, R = -0.33, p < 0.001). Finally, in the ANT, both theta (4-8 Hz) and alpha band power (9-12 Hz) were negatively correlated with distance to the ventral ANT border (linear regression, p < 0.001 for both). The proportion of recordings with spiking and bursting activity was consistently highest 0-2 mm above the ventral ANT border with the mtt., Conclusion: We observed several electrophysiological markers demarcating the ANT superior and inferior borders including multiple single cell and local field potential features. A local maximum in neural activity just above the ANT-mtt junction was consistent with the previously described optimal target for seizure reduction. These features may be useful for successful targeting of ANT-DBS for epilepsy., (© 2024 S. Karger AG, Basel.)

Introduction: Deep brain stimulation of the zona incerta is effective at treating tremor and other forms of parkinsonism. However, the structure is not well visualized with standard MRI protocols making direct surgical targeting unfeasible and contributing to inconsistent clinical outcomes. In this study, we applied coronal gradient echo MRI to directly visualize the rostral zona incerta in Parkinson's disease patients to improve targeting for deep brain stimulation., Methods: We conducted a prospective study to optimize and evaluate an MRI sequence to visualize the rostral zona incerta in patients with Parkinson's disease (n = 31) and other movement disorders (n = 13). We performed a contrast-to-noise ratio analysis of specific regions of interest to quantitatively assess visual discrimination of relevant deep brain structures in the optimized MRI sequence. Regions of interest were independently assessed by 2 neuroradiologists, and interrater reliability was assessed., Results: Rostral zona incerta and subthalamic nucleus were well delineated in our 5.5-min MRI sequence, indicated by excellent interrater agreement between neuroradiologists for region-of-interest measurements (>0.90 intraclass coefficient). Mean contrast-to-noise ratio was high for both rostral zona incerta (6.39 ± 3.37) and subthalamic nucleus (17.27 ± 5.61) relative to adjacent white matter. There was no significant difference between mean signal intensities or contrast-to-noise ratio for Parkinson's and non-Parkinson's patients for either structure., Discussion/conclusion: Our optimized coronal gradient echo MRI sequence delineates subcortical structures relevant to traditional and novel deep brain stimulation targets, including the zona incerta, with high contrast-to-noise. Future studies will prospectively apply this sequence to surgical planning and postimplantation outcomes., (© 2021 S. Karger AG, Basel.)

Background/aims: Laser interstitial thermal therapy (LITT) has become an alternative to open-resective surgery for refractory mesial temporal lobe epilepsy (MTLE). Occurrence of visual field defects (VFDs) following open surgery for MTLE is reported at 52-100%. We examined the rate of VFDs following LITT for amygdalohippocampectomy (AHE) and correlated the occurrence of VFDs with damage to the optic radiations, assessed by diffusion tensor tractography (DTI)., Methods: We performed a retrospective analysis of 5 patients who underwent LITT-AHE for medically refractory MTLE. We examined the association between VFDs and optic radiation damage by correlating postprocedural visual field testing with qualitative assessment of optic radiation fiber tracts., Results: Postoperative assessments showed that 4 patients had normal visual field testing, and 1 had a right superior quadrantanopsia (20%). We performed 3-dimensional reconstruction of the optic radiation, laser probe trajectory, and ablation volume. Damage to Meyer's loop was determined consistent with the VFD., Conclusions: Short-term follow-up in our series suggests that laser ablation AHE may be associated with a lower rate of VFD than has been reported for open AHE. Our results suggest that incorporating optic radiation mapping through DTI may preoperatively help to minimize the risk of VFD following laser ablation AHE., (© 2017 S. Karger AG, Basel.)

Objective: The success of deep brain stimulation (DBS) of the internal segment of the globus pallidus (GPi) depends on accurately placing the electrode into the GPi motor territory. Direct targeting can be difficult as GPi laminar borders are not always clearly identifiable on MRI. Here, we report a method for using the putamen (PUT) as a surrogate anatomical marker to target the GPi., Methods: We developed a PUT-based GPi targeting using the FGATIR (fast gray matter acquisition T1-weighted inversion recovery) MRI sequence and compared it with consensus coordinate-based indirect targeting. Stereotactic target coordinates were obtained and analyzed., Results: In our GPi DBS case sequences, GPi borders were unresolvable on T2-weighted MRI. However, in all cases, application of the PUT-based method resulted in consistently localized GPi targets, which were confirmed by merging the T2-weighted MRI with the FGATIR MRI. Significant differences were noted in the target coordinates between the PUT-based method and indirect targeting based on both the distance from the anterior commissure and the distance from the intercommissural plane. The mean differences for mediolateral distance and anteroposterior distance were 1.4 and 1.42 mm, respectively. In addition, the PUT-based method estimated a target that was closer to the nearest implanted electrode., Conclusion: Our PUT-based method allows consistent and precise patient-specific GPi targeting. Further study is planned to correlate PUT-based GPi targeting with microelectrode recording, location of active contact of the DBS electrode and clinical outcome., (© 2017 S. Karger AG, Basel.)