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Kai J. Miller, Taylor J. Abel, Adam O. Hebb, and Jeffrey G. Ojemann

Object

Emerging research in evoked broadband electrocorticographic (ECoG) measurement from the cortical surface suggests that it might cleanly delineate the functional organization of cortex. The authors sought to demonstrate whether this could be done in a same-session, online manner to identify receptive and expressive language areas.

Methods

The authors assessed the efficacy of simple integration of “χ-band” (76–200 Hz) change in the ECoG signal by implementing a simple band-pass filter to estimate broadband spectral change. Following a brief (less than 10-second) period to characterize baseline activity, χ-band activity was integrated while 7 epileptic patients with implanted ECoG electrodes performed a verb-generation task.

Results

While the patients were performing verb-generation or noun-reading tasks, cortical activation was consistently identified in primary mouth motor area, superior temporal gyrus, and Broca and Wernicke association areas. Maps were robust after a mean time of 47seconds (using an “activation overlap” measure). Correlation with electrocortical stimulation was not complete and was stronger for noun reading than verb generation.

Conclusions

Broadband ECoG changes can be captured online to identify eloquent cortex. This demonstrates the existence of a powerful new tool for functional mapping in the operative and chronic implant setting.

Free access

Kai J. Miller, Dora Hermes, and Nathan P. Staff

Brain–computer interfaces (BCIs) provide a way for the brain to interface directly with a computer. Many different brain signals can be used to control a device, varying in ease of recording, reliability, stability, temporal and spatial resolution, and noise. Electrocorticography (ECoG) electrodes provide a highly reliable signal from the human brain surface, and these signals have been used to decode movements, vision, and speech. ECoG-based BCIs are being developed to provide increased options for treatment and assistive devices for patients who have functional limitations. Decoding ECoG signals in real time provides direct feedback to the patient and can be used to control a cursor on a computer or an exoskeleton. In this review, the authors describe the current state of ECoG-based BCIs that are approaching clinical viability for restoring lost communication and motor function in patients with amyotrophic lateral sclerosis or tetraplegia. These studies provide a proof of principle and the possibility that ECoG-based BCI technology may also be useful in the future for assisting in the cortical rehabilitation of patients who have suffered a stroke.

Open access

Timothy J. Kaufmann, Vance T. Lehman, Lily C. Wong-Kisiel, Panagiotis Kerezoudis, and Kai J. Miller

BACKGROUND

Open surgical treatment of insular epilepsy holds particular risk of injury to middle cerebral artery branches, the operculum (through retraction), and adjacent language-related white matter tracts in the language-dominant hemisphere. Magnetic resonance imaging (MRI)-guided laser interstitial thermal therapy (LITT) is a surgical alternative that allows precise lesioning with potentially less operative risk. The authors presented the case of a 13-year-old girl with intractable, MRI-negative, left (dominant hemisphere) insular epilepsy that was treated with LITT. Diffusion tensor imaging (DTI) tractography was used to aid full posterior insular lesioning in the region of stereo electroencephalography–determined seizure onset while avoiding thermal injury to the language-related superior longitudinal fasciculus (SLF)/arcuate fasciculus (AF) and inferior fronto-occipital fasciculus (IFOF).

OBSERVATIONS

DTI tractography was used successfully in planning insular LITT and facilitated a robust insular ablation with sharp margins at the interfaces with the SLF/AF and IFOF. These tracts were spared, and no neurological deficits were induced through LITT.

LESSONS

Although it is technically demanding and has important limitations that must be understood, clinically available DTI tractography adds precision and confidence to insular laser ablation when used to protect important language-related white matter tracts.

Free access

Kai J. Miller, Nader Pouratian, Jin Woo Chang, and Kendall H. Lee

Restricted access

Panagiotis Kerezoudis, Rohin Singh, Anshit Goyal, Gregory A. Worrell, W. Richard Marsh, Jamie J. Van Gompel, and Kai J. Miller

OBJECTIVE

Insular lobe epilepsy is a challenging condition to diagnose and treat. Due to anatomical intricacy and proximity to eloquent brain regions, resection of epileptic foci in that region can be associated with significant postoperative morbidity. The aim of this study was to review available evidence on postoperative outcomes following insular epilepsy surgery.

METHODS

A comprehensive literature search (PubMed/MEDLINE, Scopus, Cochrane) was conducted for studies investigating the postoperative outcomes for seizures originating in the insula. Seizure freedom at last follow-up (at least 12 months) comprised the primary endpoint. The authors also present their institutional experience with 8 patients (4 pediatric, 4 adult).

RESULTS

A total of 19 studies with 204 cases (90 pediatric, 114 adult) were identified. The median age at surgery was 23 years, and 48% were males. The median epilepsy duration was 8 years, and 17% of patients had undergone prior epilepsy surgery. Epilepsy was lesional in 67%. The most common approach was transsylvian (60%). The most commonly resected area was the anterior insular region (n = 42, 21%), whereas radical insulectomy was performed in 13% of cases (n = 27). The most common pathology was cortical dysplasia (n = 68, 51%), followed by low-grade neoplasm (n = 16, 12%). In the literature, seizure freedom was noted in 60% of pediatric and 69% of adult patients at a median follow-up of 29 months (75% and 50%, respectively, in the current series). A neurological deficit occurred in 43% of cases (10% permanent), with extremity paresis comprising the most common deficit (n = 35, 21%), followed by facial paresis (n = 32, 19%). Language deficits were more common in left-sided approaches (24% vs 2%, p < 0.001). Univariate analysis for seizure freedom revealed a significantly higher proportion of patients with lesional epilepsy among those with at least 12 months of follow-up (77% vs 59%, p = 0.032).

CONCLUSIONS

These findings may serve as a benchmark when tailoring decision-making for insular epilepsy, and may assist surgeons in their preoperative discussions with patients. Although seizure freedom rates are quite high with insular epilepsy treatment, the associated morbidity needs to be weighed against the potential for seizure freedom.

Restricted access

Panagiotis Kerezoudis, Rohin Singh, Veronica Parisi, Gregory A. Worrell, Kai J. Miller, W. Richard Marsh, and Jamie J. Van Gompel

OBJECTIVE

The prevalence of epilepsy in the older adult population is increasing. While surgical intervention in younger patients is supported by level I evidence, the safety and efficacy of epilepsy surgery in older individuals is less well established. The aim of this study was to evaluate seizure freedom rates and surgical outcomes in older epilepsy patients.

METHODS

The authors’ institutional electronic database was queried for patients older than 50 who had undergone epilepsy surgery during 2002–2018. Cases were grouped into 50–59, 60–69, and 70+ years old. Seizure freedom at the last follow-up constituted the primary outcome of interest. The institutional analysis was supplemented by a literature review and meta-analysis (random effects model) of all published studies on this topic as well as by an analysis of complication rates, mortality rates, and cost data from a nationwide administrative database (Vizient Inc., years 2016–2019).

RESULTS

A total of 73 patients (n = 16 for 50–59 years, n = 47 for 60–69, and n = 10 for 70+) were treated at the authors’ institution. The median age was 63 years, and 66% of the patients were female. At a median follow-up of 24 months, seizure freedom was 73% for the overall cohort, 63% for the 50–59 group, 77% for the 60–69 group, and 70% for the 70+ group. The literature search identified 15 additional retrospective studies (474 cases). Temporal lobectomy was the most commonly performed procedure (73%), and mesial temporal sclerosis was the most common pathology (52%), followed by nonspecific gliosis (19%). The pooled mean follow-up was 39 months (range 6–114.8 months) with a pooled seizure freedom rate of 65% (95% CI 59%–72%). On multivariable meta-regression analysis, an older mean age at surgery (coefficient [coeff] 2.1, 95% CI 1.1–3.1, p < 0.001) and the presence of mesial temporal sclerosis (coeff 0.3, 95% CI 0.1–0.6, p = 0.015) were the most important predictors of seizure freedom. Finally, analysis of the Vizient database revealed mortality rates of 0.5%, 1.1%, and 9.6%; complication rates of 7.1%, 10.1%, and 17.3%; and mean hospital costs of $31,977, $34,586, and $40,153 for patients aged 50–59, 60–69, and 70+ years, respectively.

CONCLUSIONS

While seizure-free outcomes of epilepsy surgery are excellent, there is an expected increase in morbidity and mortality with increasing age. Findings in this study on the safety and efficacy of epilepsy surgery in the older population may serve as a useful guide during preoperative decision-making and patient counseling.

Restricted access

Mohammed Ali Alvi, Archis R. Bhandarkar, David J. Daniels, Kai J. Miller, and Edward S. Ahn

OBJECTIVE

CSF shunt insertion is the most commonly performed neurosurgical procedure for pediatric patients with hydrocephalus, and complications including infections and catheter obstruction are common. The rate of readmission in the first 30 days after surgery has been used across surgical disciplines to determine healthcare quality. In the current study, the authors sought to assess factors associated with early shunt revision within 30 days using real-world data.

METHODS

Targeted shunt data set participant user files of the National Surgical Quality Improvement Program (NSQIP) from 2016 to 2019 were queried for patients undergoing a shunt procedure. A multivariable logistic regression model was performed to assess the impact of demographics, etiologies, comorbidities, congenital malformations, and shunt adjuncts on shunt revision within 30 days, as well as shunt revision due to infection within 30 days.

RESULTS

A total of 3919 primary pediatric shunt insertions were identified in the NSQIP database, with a mean (± SD) patient age of 26.3 ± 51.6 months. There were a total of 285 (7.3%) unplanned shunt revisions within 30 days, with a mean duration of 14.9 ± 8.5 days to first intervention. The most common reason for intervention was mechanical shunt failure (32.6% of revision, 2.4% overall, n = 93), followed by infection (31.2% of all interventions, 2.3% overall, n = 89) and wound disruption or CSF leak (22.1% of all interventions, 1.6% overall, n = 63). Patients younger than 6 months of age had the highest overall unplanned 30-day revision rate (8.5%, 203/2402) as well as the highest 30-day shunt infection rate (3%, 72/2402). Patients who required a revision were also more likely to have a cardiac risk factor (34.7%, n = 99, vs 29.2%, n = 1061; p = 0.048). Multivariable logistic regression revealed that compared to patients 9–18 years old, those aged 2–9 years had significantly lower odds of repeat shunt intervention (p = 0.047), while certain etiologies including congenital hydrocephalus (p = 0.0127), intraventricular hemorrhage (IVH) of prematurity (p = 0.0173), neoplasm (p = 0.0005), infection (p = 0.0004), and syndromic etiology (p = 0.0136), as well as presence of ostomy (p = 0.0095), were associated with higher odds of repeat intervention. For shunt infection, IVH of prematurity was found to be associated with significantly higher odds (p = 0.0427) of shunt infection within 30 days, while use of intraventricular antibiotics was associated with significantly lower odds (p = 0.0085).

CONCLUSIONS

In this study of outcomes after pediatric shunt placement using a nationally derived cohort, early shunt failure and infection within 30 days were found to remain as considerable risks. The analysis of this national surgical quality registry confirms that, in accordance with other multicenter studies, hydrocephalus etiology, age, and presence of ostomy are important predictors of the need for early shunt revision. IVH of prematurity is associated with early infections while intraventricular antibiotics may be protective. These findings could be used for benchmarking in hospital efforts to improve quality of care for pediatric patients with hydrocephalus.

Full access

Reinhold Scherer, Stavros P. Zanos, Kai J. Miller, Rajesh P. N. Rao, and Jeffrey G. Ojemann

Electrocorticography (ECoG) offers a powerful and versatile platform for developing brain-computer interfaces; it avoids the risks of brain-invasive methods such as intracortical implants while providing significantly higher signal-to-noise ratio than noninvasive techniques such as electroencephalography. The authors demonstrate that both contra- and ipsilateral finger movements can be discriminated from ECoG signals recorded from a single brain hemisphere. The ECoG activation patterns over sensorimotor areas for contra- and ipsilateral movements were found to overlap to a large degree in the recorded hemisphere. Ipsilateral movements, however, produced less pronounced activity compared with contralateral movements. The authors also found that single-trial classification of movements could be improved by selecting patient-specific frequency components in high-frequency bands (> 50 Hz). Their discovery that ipsilateral hand movements can be discriminated from ECoG signals from a single hemisphere has important implications for neurorehabilitation, suggesting in particular the possibility of regaining ipsilateral movement control using signals from an intact hemisphere after damage to the other hemisphere.

Full access

Tim Blakely, Kai J. Miller, Stavros P. Zanos, Rajesh P. N. Rao, and Jeffrey G. Ojemann

All previous multiple-day brain-computer interface (BCI) experiments have dynamically adjusted the parameterization between the signals measured from the brain and the features used to control the interface. The authors present the results of a multiple-day electrocorticographic (ECoG) BCI experiment.

A patient with a subdural electrode array implanted for seizure localization performed tongue motor tasks. After an initial screening and feature selection on the 1st day, 5 consecutive days of cursor-based feedback were performed with a fixed parameterization. Control of the interface was robust throughout all days, with performance increasing to a stable state in which high-frequency ECoG signal could immediately be translated into cursor control.

These findings demonstrate that ECoG-based BCIs can be implemented for multiple-day control without the necessity for sophisticated retraining and adaptation.

Full access

Kai J. Miller, Casey H. Halpern, Mark F. Sedrak, John A. Duncan III, and Gerald A. Grant

OBJECTIVE

Stereotactic laser ablation and neurostimulator placement represent an evolution in staged surgical intervention for epilepsy. As this practice evolves, optimal targeting will require standardized outcome measures that compare electrode lead or laser source with postprocedural changes in seizure frequency. The authors propose and present a novel stereotactic coordinate system based on mesial temporal anatomical landmarks to facilitate the planning and delineation of outcomes based on extent of ablation or region of stimulation within mesial temporal structures.

METHODS

The body of the hippocampus contains a natural axis, approximated by the interface of cornu ammonis area 4 and the dentate gyrus. The uncal recess of the lateral ventricle acts as a landmark to characterize the anterior-posterior extent of this axis. Several volumetric rotations are quantified for alignment with the mesial temporal coordinate system. First, the brain volume is rotated to align with standard anterior commissure–posterior commissure (AC-PC) space. Then, it is rotated through the axial and sagittal angles that the hippocampal axis makes with the AC-PC line.

RESULTS

Using this coordinate system, customized MATLAB software was developed to allow for intuitive standardization of targeting and interpretation. The angle between the AC-PC line and the hippocampal axis was found to be approximately 20°–30° when viewed sagittally and approximately 5°–10° when viewed axially. Implanted electrodes can then be identified from CT in this space, and laser tip position and burn geometry can be calculated based on the intraoperative and postoperative MRI.

CONCLUSIONS

With the advent of stereotactic surgery for mesial temporal targets, a mesial temporal stereotactic system is introduced that may facilitate operative planning, improve surgical outcomes, and standardize outcome assessment.