Miller, Kai

BACKGROUND Laser interstitial thermal therapy is a minimally invasive surgical technique commonly used for treating epileptogenic foci in patients with drug-resistant epilepsy. Densely calcified lesions pose a challenge because they prevent the placement of a laser cannula within them and act as a heat shield. A 22-year-old male presented with intractable epilepsy with imaging demonstrating a densely calcified lesion in the right medial occipitotemporal gyrus radiographically consistent with a polymorphous low-grade neuroepithelial tumor of the young. OBSERVATIONS Two laser cannulas were stereotactically positioned to flank the centrally calcified portion of the lesion at its anterior and posterior aspects. Intraoperative MR thermography during each ablation showed that the dense calcification shielded ablative heating from spreading to the other side of the lesion. The sum of the thermal ablation zones covered the entirety of the lesion. Postprocedure MRI demonstrated overlapping peripherally enhancing ablation zones, which subsumed the entirety of the calcified mass. The patient tolerated the procedure well and remained seizure free at the 14-month follow-up. LESSONS Using multiple stereotactically placed laser filaments to flank epileptogenic lesions that are densely calcified is a strategy to effectively encompass the entirety of the lesion within the combined ablation zones. https://thejns.org/doi/10.3171/CASE26184

OBJECTIVE Electrical stimulation mapping is a widely used technique to determine functional localization for medically refractory epilepsy. Sites where stimulation interferes with naming are often focal regions of the frontal and temporal cortex. The extent to which these crucial sites remain in the same location over time in an individual adult patient has not yet been established. The aim of this study was to determine whether cortical naming sites identified using stimulation mapping are stable in their anatomical location over time in adult patients with medically refractory epilepsy. METHODS Twenty-two patients who underwent electrical stimulation mapping for medically refractory epilepsy during surgical interventions separated by more than 1 year between 1967 and 2005 were included. A median of 8.35 years elapsed between mappings. The mean age at the first operation was 27.7 (range 10–39) years. Fourteen patients were female. Mapping occurred under two different conditions: intraoperatively in procedures conducted under local anesthesia or extraoperatively through implanted grid electrodes. A Bayesian hierarchical model of language site locations across repeated interventions was used to assess the stability of locations of stimulation-evoked interference in language naming. RESULTS Sites where electrical stimulation interferes with language naming were separated by a median of 0.6 cm between the 2 mappings. Eighty-six percent of the mapped sites related to language naming at the second operation were within 1.5 cm of a site identified at the first operation, 61% within 1 cm, and 36% within 0.5 cm. However, in 2 patients, none of the identified language naming sites at the second operation were within 1.5 cm of the sites from the first operation. CONCLUSIONS This unique, long-term series of neurosurgical mappings reveals that language naming sites in the cortex of adult patients with epilepsy show substantial long-term stability over many years. However, rare relocation of these sites does occur in some patients over many years.

Understanding motor representation in the human brain requires mapping beyond the primary motor cortex, into the distributed networks that coordinate complex movements. The insular cortex, a multifunctional hub buried within the Sylvian fissure, has been implicated in motor control through clinical observations and neuroimaging. Yet its precise relation to primary sensorimotor processing remains one of the least understood aspects of motor neurophysiology. To address this gap, we quantified electrophysiological changes from implanted depth electrodes in patients performing simple movement tasks combined with single-pulse electrical stimulation (SPES) to map effective connectivity. The movement data reveal somatotopically specific representation bilaterally, as well as intereffector regions that are active for different movement types. Hand representation is centered along the contralateral ventral aspect of the middle and posterior short gyri bilaterally, while tongue/mouth tuned sites cluster in the dorsal posterior short gyrus and the dorsal long gyri. Insular activity temporally follows the primary motor cortex (M1) and precedes movement onset. SPES revealed somatotopically specific connectivity between corresponding sites in M1 and insula (hand-to-hand, tongue-to-tongue) and between bilateral insulae. These observations establish that somatotopy is a conserved property of distributed motor control incorporating the insular representations and connectivity.

ABSTRACT Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) can reduce seizures in patients with drug-resistant epilepsy. However, seizure freedom is rare, and there is no early response biomarker to predict long-term seizure suppression. To evaluate a short-term biomarker of therapeutic response to DBS, we studied 18-minute trials of ANT stimulation in patients with drug-resistant epilepsy undergoing intracranial electroencephalography. We compared a standard high-frequency periodic versus a non-periodic pulse pattern. We found that short-term ANT stimulation within the clinically used amplitude range preferentially altered the first 150 ms of anterograde ANT to anterior cingulate and superior frontal connectivity. Non-periodic ANT stimulation selectively modified early cortico-cortical evoked potentials more than periodic stimulation, and these changes were driven by the response phase. These pattern-specific changes in connectivity between the ANT and spatially restricted cortical areas suggest differing mechanisms and are a promising biomarker for patients being treated with ANT-DBS.

Miller et al. maintain that thalamic SEEG can now be considered a cornerstone of standard clinical practice in individualized epilepsy care, helping to define seizure onset and spread, assess therapeutic stimulation, map connectivity, and identify target-specific biomarkers for responsive neurostimulation.

Abstract Deep brain stimulation (DBS) of the subthalamic nucleus improves motor symptoms in patients with Parkinson’s disease. Using functional MRI, optimal DBS response networks have been characterized. However, neural activity associated with Parkinsonian symptoms is magnitudes faster than what can be resolved by this method. Although both spatial and temporal domains of these networks appear crucial, no single study has yet investigated both domains simultaneously. Here, we aimed at closing this gap by analysing electrophysiological data from a total of n = 127 hemispheres. Using subthalamic local field potentials that were recorded concurrently alongside whole-brain magnetoencephalography in a multi-centre cohort of patients who underwent subthalamic DBS for the treatment of Parkinson’s disease (n = 100 hemispheres), we analysed the DBS response network in both spatial and temporal domains. In every cortical vertex, cortico-subthalamic coupling was correlated with stimulation outcomes. This network spatially resembled functional MRI-based findings (R = 0.40, P = 0.039) and explained significant amounts of variance in clinical outcomes (βstd = 0.30, P = 0.002), whereas theta–alpha and low beta coupling did not show significant associations with DBS response (theta–alpha: βstd = −0.02, P = 0.805; low beta: βstd = −0.08, P = 0.426). The ‘optimal’ high beta coupling map was robust when subjected to various cross-validation designs (10-fold cross-validation: R = 0.29, P = 0.009; split-half design: R = 0.31, P = 0.026) and was able to predict outcomes across DBS centres [R = 0.74; P(1) = 8.9 × 10−5]. We identified a DBS response network that resembles the previously defined MRI network and operates in the high beta band. Maximal connectivity to this network was associated with optimal DBS outcomes and was able to cross-predict clinical improvements across DBS surgeons and centres.