The ongoing pilot clinical trial of the BrainGate neural interface system aims in part to assess the feasibility of using neural activity obtained from a small-scale, chronically implanted, intracortical microelectrode array to provide control signals for a neural prosthesis system. Critical questions include how long implanted microelectrodes will record useful neural signals, how reliably those signals can be acquired and decoded, and how effectively they can be used to control various assistive technologies such as computers and robotic assistive devices, or to enable functional electrical stimulation of paralyzed muscles. Here we examined these questions by assessing neural cursor control and BrainGate system characteristics on five consecutive days 1000 days after implant of a 4 × 4 mm array of 100 microelectrodes in the motor cortex of a human with longstanding tetraplegia subsequent to a brainstem stroke. On each of five prospectively-selected days we performed time-amplitude sorting of neuronal spiking activity, trained a population-based Kalman velocity decoding filter combined with a linear discriminant click state classifier, and then assessed closed-loop point-and-click cursor control. The participant performed both an eight-target center-out task and a random target Fitts metric task which was adapted from a human-computer interaction ISO standard used to quantify performance of computer input devices. The neural interface system was further characterized by daily measurement of electrode impedances, unit waveforms and local field potentials. Across the five days, spiking signals were obtained from 41 of 96 electrodes and were successfully decoded to provide neural cursor point-and-click control with a mean task performance of 91.3% ± 0.1% (mean ± s.d.) correct target acquisition. Results across five consecutive days demonstrate that a neural interface system based on an intracortical microelectrode array can provide repeatable, accurate point-and-click control of a computer interface to an individual with tetraplegia 1000 days after implantation of this sensor.

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Neural control of cursor trajectory and click by a human with tetraplegia 1000 days after implant of an intracortical microelectrode array

BACKGROUND Stereoelectroencephalography (SEEG) methodology, originally developed by Talairach and Bancaud, is progressively gaining popularity for the presurgical invasive evaluation of drug-resistant epilepsies. OBJECTIVE To describe recent SEEG methodological implementations carried out in our center, to evaluate safety, and to analyze in vivo application accuracy in a consecutive series of 500 procedures with a total of 6496 implanted electrodes. METHODS Four hundred nineteen procedures were performed with the traditional 2-step surgical workflow, which was modified for the subsequent 81 procedures. The new workflow entailed acquisition of brain 3-dimensional angiography and magnetic resonance imaging in frameless and markerless conditions, advanced multimodal planning, and robot-assisted implantation. Quantitative analysis for in vivo entry point and target point localization error was performed on a sub--data set of 118 procedures (1567 electrodes). RESULTS The methodology allowed successful implantation in all cases. Major complication rate was 12 of 500 (2.4%), including 1 death for indirect morbidity. Median entry point localization error was 1.43 mm (interquartile range, 0.91-2.21 mm) with the traditional workflow and 0.78 mm (interquartile range, 0.49-1.08 mm) with the new one (P < 2.2 × 10). Median target point localization errors were 2.69 mm (interquartile range, 1.89-3.67 mm) and 1.77 mm (interquartile range, 1.25-2.51 mm; P < 2.2 × 10), respectively. CONCLUSION SEEG is a safe and accurate procedure for the invasive assessment of the epileptogenic zone. Traditional Talairach methodology, implemented by multimodal planning and robot-assisted surgery, allows direct electrical recording from superficial and deep-seated brain structures, providing essential information in the most complex cases of drug-resistant epilepsy.

Stereoelectroencephalography: surgical methodology, safety, and stereotactic application accuracy in 500 procedures.

Epilepsy surgery is the most effective way to control seizures in patients with drug-resistant focal epilepsy, often leading to improvements in cognition, behaviour, and quality of life. Risks of serious adverse events and deterioration of clinical status can be minimised in carefully selected patients. Accordingly, guidelines recommend earlier and more systematic assessment of patients' eligibility for surgery than is seen at present. The effectiveness of surgical treatment depends on epilepsy type, underlying pathology, and accurate localisation of the epileptogenic brain region by various clinical, neuroimaging, and neurophysiological investigations. Substantial progress has been made in the methods of presurgical assessment, particularly in patients with normal features on MRI, but evidence is scarce for the indication and effect of most presurgical investigations, with no biomarker precisely delineating the epileptogenic zone. A priority for the development of epilepsy surgery is the generation of high-level evidence to promote the harmonisation and dissemination of best practices.

https://www.thelancet.com/pdfs/journals/laneur/PIIS1474-4422(14)70156-5.pdf

Epilepsy surgery in children and adults

Summary
Purpose

Implantation of subdural grids and invasive electroencephalography (EEG) monitoring is important to define the ictal-onset zone and eloquent cortex in selected patients with medically refractory epilepsy. The objective of this systematic review is to summarize data about adverse events related to this procedure.



Methods

English-language studies published up to July 2012, reporting such adverse events were reviewed. Outcome measures included demographic variables; surgical protocol including number of subdural electrodes implanted per patient, duration of monitoring, antibiotic, and steroid prophylaxis; and adverse events.



Key Findings

Twenty-one studies were identified including a total of 2,542 patients. The reported mean number of electrodes per patient and duration of monitoring varied from 52 to 95 and 5 to 17 days, respectively. There is a trend toward more uniform use of antibiotics and steroids in the perioperative period. Neurologic infections (pooled prevalence 2.3%, 95% confidence interval 1.5–3.1), superficial infections (3.0%, 1.9–4.1), intracranial hemorrhage (4.0%, 3.2–4.8), and elevated intracranial pressure (2.4%, 1.5–3.3) were found to be the most common adverse events. Up to 3.5% of patients required additional surgical procedure(s) for management of these adverse events. Increased number of electrodes (≥67) was found to be independently associated with increased incidence of adverse events.



Significance

Although providing critical information for patients with medically refractory epilepsy, subdural grids implantation and invasive EEG monitoring entails risks of infection, hemorrhage, and elevated intracranial pressure. The prevalence estimates, likely to be conservative due to selective reporting, are expected to be helpful in counseling patients.

Adverse events related to extraoperative invasive EEG monitoring with subdural grid electrodes: a systematic review and meta-analysis.

Recording and analysis techniques for high-frequency oscillations

Partial seizure disorders account for the majority of epilepsy (Sander et al., 1990). In one tertiary center cohort of 2,200 patients, partial epilepsy was more than twice as common as symptomatic, cryptogenic, and idiopathic generalized epilepsies combined. Moreover, in that study, two-thirds of the partial seizure disorders localized to the temporal lobe (Semah et al., 1998). Unfortunately, despite optimal medical therapy, approximately 30% of patients continue to experience recurrent seizures (Sander et al., 1990 Wiebe, et al. 2001). In a recent well-designed trial studying patients who failed initial medication trials, seizure freedom was achieved in only 8% of patients with continued medical therapy compared to 58% of patients undergoing anterior temporal lobectomy (Wiebe, et al. 2001).

However, physicians may be reluctant to consider surgery for temporal lobe epilepsy when structural neuroimaging appears normal. Temporal lobectomy has been shown to render about 80% of patients seizure-free in the setting of a magnetic resonance imaging (MRI)–apparent structural abnormality concordant to the seizure onset zone, such as mesial temporal sclerosis (MTS) (Cascino, 2004). On the other hand, patients with temporal lobe epilepsy and normal MRI have received less attention. In order to demonstrate the absence of a potentially epileptogenic structural lesion, it is critical that patients have high-resolution seizure protocol MRI with both T1- and T2-weighted images (Jack, 1996; Cascino, 2004). There are relatively few studies examining temporal lobectomy in patients with normal modern seizure protocol MRI. Existing research suggests significantly disparate rates of successful surgery in patients with nonlesional MRI, ranging from 18–63% of patients becoming seizure-free (Berkovic et al., 1995; Theodore et al., 1997; Sylaja et al., 2004; Cohen-Gadol et al., 2005; Jeha et al., 2006). Many of these studies were conducted during the 1980s and early 1990s (Berkovic et al., 1995; Radhakrishnan et al., 1998; McIntosh et al., 2004), prior to the widespread use of epilepsy neuroimaging protocols that are more sensitive for detecting MTS (Jack, 1996; Jack et al., 1996). Some of these studies used pathologic findings to categorize patients (McIntosh et al., 2004; Cohen-Gadol et al., 2006), information that is not available preoperatively for clinical prognostication. Other studies include heterogeneous patient populations and only small numbers of patients with nonlesional MRI (Holmes et al., 2000; Sylaja et al., 2004; Cohen-Gadol et al., 2005). Therefore, we sought to examine the efficacy of epilepsy surgery and noninvasive predictors of favorable outcome for patients with medically refractory temporal lobe epilepsy and a nonlesional high-resolution seizure protocol MRI.

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Epilepsy surgery outcomes in temporal lobe epilepsy with a normal MRI.

Objective Intracranial subdural grid monitoring is a useful diagnostic technique for surgical localization in patients with intractable partial epilepsy. The rationale for the present study was to assess the morbidity of intracranial recordings and the surgical outcomes. Methods We retrospectively reviewed the clinical data for 189 unique patients undergoing 198 intracranial subdural grid monitoring sessions between 1996 and 2004 at a tertiary epilepsy center. Results The mean age of patients undergoing monitoring was 28 +/- 14 years. An average of 63 +/- 23 electrodes were inserted. The mean duration of monitoring was 8 +/- 4 days. Localization of an epileptogenic zone occurred in 156 sessions (79%) resulting in 136 resections (69%). There were 13 major complications (6.6%), including five infections and six hematomas. Three patients (1.5%) developed permanent deficits related to implantation. Sixty-two (47%) of 136 patients undergoing resection were seizure-free after resection. An additional 38 patients (28%) had a significant reduction in seizures. The mean follow-up was 51 +/- 30 months. The duration of monitoring, bone flap replacement, number of electrodes, and perioperative corticosteroids were not associated with infection or complication. Conclusion Subdural grid monitoring for identification an epileptogenic focus is high yield, revealing a focus in 79% of monitoring sessions. Complications rarely result in permanent morbidity (1.5%). Surgical outcome indicated that 74% of patients experienced a favorable reduction in seizure tendency.

Intracranial electroencephalography with subdural grid electrodes: techniques, complications, and outcomes.

A 52-year-old man acutely developed delirium and seizures associated with hypertension. MRI showed left hemispheric and brainstem lesions (figure). Profound agitation precluded visualization of the fundi, however an acute hypertensive …

The triumvirate of acute hypertension.

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Michael L. Bell

Papers

Epilepsy surgery outcomes in temporal lobe epilepsy with a normal MRI.

Intracranial electroencephalography with subdural grid electrodes: techniques, complications, and outcomes.

The triumvirate of acute hypertension.

32-year-old man with episodic weakness.