A method for the assessment of time-varying brain shift during navigated epilepsy surgery

Image guidance is widely used in neurosurgery. Tracking systems (neuronavigators) allow registering the preoperative image space to the surgical space. The localization accuracy is influenced by technical and clinical factors, such as brain shift. This paper aims at providing quantitative measure of the time-varying brain shift during open epilepsy surgery, and at measuring the pattern of brain deformation with respect to three potentially meaningful parameters: craniotomy area, craniotomy orientation and gravity vector direction in the images reference frame

Reducing the False-Positive Rate for Isovalerylcarnitine in Expanded Newborn Screening: The Application of a Second-Tier Test

Abstract The isodecyl neopentanoate is an ingredient used in the cosmetic industry to prepare a nipple fissure balm. We report on 12 newborns that showed elevated C5-acylcarnitine levels upon newborn screening following treatment with balm. The first 3 neonates were immediately recalled for confirmatory tests and resulted negative for both isovaleric acidemia and short/branched chain acyl-CoA dehydrogenase deficiency. In the other 9 cases, the immediate recall was avoided by applying a new second-tier test able to confirm the presence of pivaloylcarnitine. The concentration of C5-acylcarnitine was measured in the days following the suspension of balm application. Abnormal concentrations of C5-acylcarnitine did not seem to be associated with free carnitine deficiency, probably due to the short time of exposure. A direct correlation between balm ingestion and the elevation in pivaloylcarnitine has been demonstrated in 10 adult volunteers. The commercial balm containing a pivalic acid derivative is causal of false-positive results during newborn screening, and it could have the potential to cause secondary carnitine deficiency when used chronically

Thalamic and neocortical differences in the relationship between the time course of delta and sigma power during NREM sleep in humans

Sleep spindles and slow waves are the hallmarks of non-rapid eye movement (NREM) sleep and are produced by the dynamic interplay between thalamic and cortical regions. Several studies in both human and animal models have focused their attention on the relationship between electroencephalographic (EEG) spindles and slow waves during NREM, using the power in the sigma and delta bands as a surrogate for the production of spindles and slow waves. A typical report is an overall inverse relationship between the time course of sigma and delta power as measured by a single correlation coefficient both within and across NREM episodes. Here we analysed stereotactically implanted intracerebral electrode (Stereo-EEG [SEEG]) recordings during NREM simultaneously acquired from thalamic and from several neocortical sites in six neurosurgical patients. We investigated the relationship between the time course of delta and sigma power and found that, although at the cortical level it shows the expected inverse relationship, these two frequency bands follow a parallel time course at the thalamic level. Both these observations were consistent across patients and across different cortical as well as thalamic regions. These different temporal dynamics at the neocortical and thalamic level are discussed, considering classical as well as more recent interpretations of the neurophysiological determinants of sleep spindles and slow waves. These findings may also help understanding the regulatory mechanisms of these fundamental sleep EEG graphoelements across different brain compartments

Experience-based SEEG planning: From retrospective data to automated electrode trajectories suggestions

StereoElectroEncephaloGraphy (SEEG) is a minimally invasive technique that consists of the insertion of multiple intracranial electrodes to precisely identify the epileptogenic focus. The planning of electrode trajectories is a cumbersome and time-consuming task. Current approaches to support the planning focus on electrode trajectory optimisation based on geometrical constraints but are not helpful to produce an initial electrode set to begin with the planning procedure. In this work, the authors propose a methodology that analyses retrospective planning data and builds a set of average trajectories, representing the practice of a clinical centre, which can be mapped to a new patient to initialise planning procedure. They collected and analysed the data from 75 anonymised patients, obtaining 30 exploratory patterns and 61 mean trajectories in an average brain space. A preliminary validation on a test set showed that they were able to correctly map 90% of those trajectories and, after optimisation, they have comparable or better values than manual trajectories in terms of distance from vessels and insertion angle. Finally, by detecting and analysing similar plans, they were able to identify eight planning strategies, which represent the main tailored sets of trajectories that neurosurgeons used to deal with the different patient cases

Features of somatosensory manifestations induced by intracranial electrical stimulations of the human insula.

Objective: To study the clinical manifestations induced by intracranial electrical stimulation of the insular cortex in epileptic patients submitted to invasive stereo-electroencephalography (SEEG) recordings. Methods: We retrospectively studied the clinical manifestations induced by intracerebral electrical stimulations of the insular cortex in 96 patients. In order to precisely localize the position of the electrodes a postoperative 3D CT-scan or a 3D MRI was obtained and then the images were merged with the preoperative MRI in the same stereotactic referenced system. Results: A total of 341 electrical bipolar stimulations were performed. The most frequently induced symptom was a somatosensory manifestation (70%), mainly tingling and electric sensation involving the contralateral face and arm. Motor responses represented the 8% of the total amount, as well as auditory phenomena. Language dysfunction accounted for 2% of responses. Autonomic and gustatory phenomena represented respectively 1% of responses. Conclusion: we found a great prevalence of somatosensory manifestations whereas other types of clinical modifications were extremely infrequent. Significance: Our data support a prominent somatosensory role of the human insular cortex and provide a precise characterization of the different types of sensory manifestations induced by intracranial electrical stimulation of the human insula

Stereo-EEG in children

Background: Stereotactic placement of intracerebral multilead electrodes for chronic EEG recording of seizures or stereoelectroencephalography (SEEG) was introduced 50 years ago at Saint Anne Hospital in Paris, France for the presurgical evaluation of patients with drug-resistant focal epilepsy. SEEG explorations are indicated whenever the noninvasive tests fail to adequately localize the epileptogenic zone (EZ). Indications: Currently, approximately 35% of our operated-on children require a SEEG evaluation. Arrangement of electrodes is individualized according to the peculiar needs of each child, to verify a predetermined hypothesis of localization of the EZ based on pre-SEEG anatomo-electro-clinical findings. Multilead intracerebral electrodes are designed to sample cortical structures on the lateral, intermediate, and mesial aspect of the hemisphere, as well as deep-seated lesions. Stereotactic stereoscopic teleangiograms and coregistered 3-D MRI are employed to plan avascular trajectories and to accurately target the desired structures. Pre-SEEG stereotactic neuroradiology and electrode implantation are usually performed in separate procedures. Electrodes are removed once video-SEEG monitoring is completed. Intracerebral electrical stimulations: Intracerebral electrical stimulations are used to better define the EZ and to obtain a detailed functional mapping of critical cortical and subcortical regions. Morbidity: Surgical morbidity of SEEG is definitely low in children. SEEG-guided resective surgery: In 90% of evaluated children, SEEG provides a guide for extratemporal or multilobar resections. SEEG-guided resective surgery may yield excellent results on seizures with 60% of patients in Engel's Class I. \ua9 Springer-Verlag 2006

Intracranial electrical stimulations of human insular cortex: A stereo-EEG study in patients with drug-resistant focal epilepsy

The insular lobe is the less known of human cerebral lobes and few researches have been performed in order to comprehend its function. Lesional and functional neuroimaging studies were initially performed suggesting different roles of the insular lobe. More recently intracranial stimulation studies had contributed to understand the functions of the human insula. We studied the clinical manifestations induced by intracerebral electrical stimulations performed during the pre-surgical work-out in 96 epileptic patients submitted to SEEG, with at least one electrode exploring the insular cortex. In order to precisely localize the position of the electrodes we carried out a postoperative 3D CT-scan or a 3D MRI, and then we fused the images with the preoperative MRI in the same stereotactic referenced system. Electrical bipolar stimulations were carried out at low frequency and high frequency. The most frequent induced symptom was a somatosensory manifestation (72%), mainly paresthesic sensation involving the contralateral face and upper limb, while other types of clinical modification were extremely infrequent. Our data provide evidence of a prominent somatosensory role of the human insular cortex. The fusion imaging methodology enabled us to precisely localize the stimulated contacts, excluding those that were not located into the insular cortex, probably explaining the higher amount of sensory manifestations respect to previous articles

Features of somatosensory manifestations induced by intracranial electrical stimulations of the human insula

Objective: To study the clinical manifestations induced by intracranial electrical stimulation of the insular cortex in epileptic patients submitted to invasive stereo-electroencephalography (SEEG) recordings. Methods: We retrospectively studied the clinical manifestations induced by intracerebral electrical stimulations of the insular cortex in 96 patients. In order to precisely localize the position of the electrodes a postoperative 3D CT scan or a 3D MRI was obtained and then the images were merged with the preoperative MRI in the same stereotactic referenced system. Results: A total of 341 electrical bipolar stimulations were performed. The most frequently induced symptom was a somatosensory manifestation (70%), mainly tingling and electric sensation involving the contralateral face and arm. Motor responses represented the 8% of the total amount, as well as auditory phenomena. Language dysfunction accounted for 2% of responses. Autonomic and gustatory phenomena represented respectively 1% of responses. Conclusions: We found a great prevalence of somatosensory manifestations whereas other types of clinical modifications were extremely infrequent. Significance: Our data support a prominent somatosensory role of the human insular cortex and provide a precise characterization of the different types of sensory manifestations induced by intracranial electrical stimulation of the human insula. \ua9 2011 International Federation of Clinical Neurophysiology