Daniel San-Juan

Propofol and the electroencephalogram

Propofol is an emulsion formulation of 2,6 diisopropylphenol developed in 1975. Widely recognized, it offers beneficial effects compared with other sedative drugs. Propofol is used in several clinical situations including multiple surgical procedures and critical-care medical conditions. Since technological advances over recent years have allowed an ever-increasing number of patients undergoing propofol therapy to be monitored by using continuous digital EEG, it is important to have a complete understanding of the effects of propofol on EEG in diverse clinical scenarios. This paper presents a review of the effects of propofol in electroencephalograms and discusses proconvulsive, anticonvulsive proprieties and the EEG findings in different medical conditions.

Transcranial direct current stimulation in adolescent and adult Rasmussen's encephalitis

Rasmussens encephalitis is a rare, progressive inflammatory disease that typically affects one cerebral hemisphere and causes intractable partial-onset seizures. Currently, the only effective therapy is hemispherectomy; however, this procedure is associated with irreversible neurological deficits. Novel therapeutic approaches to this condition are therefore necessary. One possible option that has not yet been extensively studied is electrical cathodal transcranial direct current stimulation (cTDCS). We describe the cases of two patients with atypical-onset Rasmussens encephalitis who underwent cTDCS at 1- and 2-mA intensity for 60 minutes in four sessions (on days 0, 7, 30, and 60). No complications were recorded during their therapy. At follow-up evaluations 6 and 12 months later, one patient had a significant reduction in seizure frequency and one was seizure free. Additionally, both patients had improved levels of alertness and language. This is the first time that cTDCS has been applied in serial sessions to treat Rasmussens encephalitis to avoid or delay surgical treatment.

The prognostic role of electrocorticography in tailored temporal lobe surgery

UNLABELLED Intraoperative electrocorticography (ECoG) has been in clinical use for many decades, yet the validity of this procedure in guiding resective surgery for temporal lobe epilepsy (TLE) is still uncertain, especially in tailored temporal lobectomies in cases of TLE with hippocampal sclerosis. METHODOLOGY Using a case-control design combined with descriptive and comparative analyses we retrospectively evaluated two groups of patients: patients (n=20) who had tailored temporal lobectomies guided by intraoperative ECoG and patients (n=19) who had standard temporal lobectomies without ECoG. Clinical and neuroimaging data, pre- and post-resection ECoG recordings, and seizure-free outcomes were reviewed. RESULTS Of the 20 patients who underwent epilepsy surgery guided by ECoG, pre-resection ECoG studies found spikes both in mesial temporal lobe (MTL) and lateral temporal lobe (LTL) in 10 patients, and restricted to the LTL or MTL in 7 and 3 patients respectively. Postsurgical ECoG captured residual epileptiform activity in only 3 patients, all of whom had MTL and LTL spikes prior to surgery. Postsurgical follow-up at 16.3 (±6.7) months found 15 (75%) patients were seizure free (1A), while 5 (25%) had other outcomes. Analysis found no difference in the proportion of seizure-free outcomes between patients with residual epileptiform activity compared to those without residual epileptiform activity, or between patients who had a tailored resection guided by ECoG and patients who had standard resections without ECoG monitoring. CONCLUSION The patients who underwent tailored temporal lobe epilepsy surgery guided by ECoG had similar outcome compared with the patients with epilepsy surgery not guided by ECoG.

Transcranial Direct Current Stimulation in Mesial Temporal Lobe Epilepsy and Hippocampal Sclerosis

BACKGROUND Transcranial direct current stimulation (tDCS) has been evaluated in medication refractory epilepsy patients. The results have been inconclusive and protocols have varied between studies. OBJECTIVE To evaluate the safety and efficacy of two protocols of tDCS in adult patients with mesial temporal lobe epilepsy and hippocampal sclerosis (MTLE-HS). METHODS This is a randomized placebo-controlled, double-blinded clinical trial, with 3 arms, 3 sessions, 5 sessions and placebo stimulation. Frequency of seizures (SZs), interictal epileptiform discharges (IEDs) and adverse effects (AEs) were registered before and after treatment, and at 30 and 60 days follow-up. Descriptive statistics, k-related samples, Friedmans test, and relative risk (RR) estimation were used for analysis. RESULTS We included twenty-eight subjects (3d n = 12, 5d n = 8, placebo n = 8), 16/28 (57%) men, age 37.8(±10.9) years old. There was a significant reduction of the frequency of SZs at one (p = 0.001) and two (p = 0.0001) months following cathodal tDCS compared to baseline in the 3 arms (p = 0.0001). The mean reduction of SZ frequency at two months in both active groups was significantly higher than placebo (-48% vs. -6.25%, p < 0.008). At 3 days (-43.4% vs. -6.25%, p < 0.007) and 5 days (-54.6% vs. -6.25%, p < 0.010) individual groups showed a greater reduction of SZs. A significant IED reduction effect was found between baseline and immediately after interventions (p = 0.041) in all groups. Side effects were minor. CONCLUSIONS Cathodal tDCS technique of 3 and 5 sessions decreased the frequency of SZs and IEDs (between baseline and immediately post-tDCS) in adult patients with MTLE-HS compared to placebo tDCS.

Diffusion tensor imaging in radiosurgical callosotomy

Callosotomy by radioneurosurgery induces slow and progressive axonal degeneration of white matter fibers, a key consequence of neuronal or axonal injury (radionecrosis). However, the acute effects are not apparent when using conventional MRI techniques. Diffusion tensor imaging (DTI) during the first week following radioneurosurgical callosotomy allowed evaluation of these microstructural changes. The present report details that the use of sequential DTI to evaluate axonal degeneration following radioneurosurgical callosotomy in a patient normalized with the data of six healthy subjects. We describe a 25-year old woman with symptomatic generalized epilepsy who underwent a radioneurosurgical callosotomy using LINAC (Novalis® BrainLAB). DTI was acquired at the baseline, 3 and 9 months and showed a progressive decrease of the fractional anisotropy values in the irradiated areas compared to the controls that could be interpreted as a progressive disconnection of callosal fibers related to the outcome.

Visual intraoperative monitoring of occipital arteriovenous malformation surgery

1. IntroductionVisual evoked potentials (VEPs) are a useful technique forinvestigating the physiology and pathophysiology of the humanvisual system, however, visual functional mapping is not routinelyemployed during surgical procedures [1]. Visual intraoperativemonitoring (VIOM) has been utilized successfully to guide neuro-logical procedures where the optic nerve or tract is involved [1]. Toour knowledge only Curatolo et al., has used VIOM of cortical VEPsto guided occipital cortical dysplasia resections on two patientswith refractory epilepsy [2]. We report the first case of VIOM usingcortical VEPs in a patient undergoing occipital arteriovenous mal-formation (OAVM) resection.2. Case reportA 41-year-old generally healthy woman presented with a 15-year history of right pulsatile hemicranial cephalea of moderateintensity (5/10) lasting 30min two to three times per weekpreceded by an aura characterized by phosphenes, sometimesassociated with nausea and diaphoresis. Two months before her

Intraoperative monitoring of the abducens nerve in extended endonasal endoscopic approach: a pilot study technical report.

BACKGROUND To determine the reliability and usefulness of intraoperative monitoring of the abducens nerve during extended endonasal endoscopic skull base tumor resection. METHODS We performed abducens nerve intraoperative monitoring in 8 patients with giant clival lesions recording with needle electrodes sutured directly into the lateral rectus muscles of the eye to evaluate spontaneous electromyographic activity and triggered responses following stimulation of the abducens nerves. RESULTS A total of 16 abducens nerves were successfully recorded during endoscopic endonasal skull base surgeries. Neurotonic discharges were seen in two patients (12% [2/16] abducens nerves). Compound muscle action potentials of the abducens nerves were evoked with 0.1-4mA and maintained without changes during the neurosurgical procedures. No patient had new neurological deficits or ophthalmological complications post-surgery. CONCLUSIONS Intraoperative monitoring of the abducens nerve during the extended endonasal endoscopic approach to skull base tumors appears to be a safe method with the potential to prevent neural injury through the evaluation of neurotonic discharges and triggered responses.

Dynamic changes of the intraocular pressure and the pressure of cerebrospinal fluid in nonglaucomatous neurological patients

To describe the dynamic changes of the intraocular pressure (IOP) and intracranial pressure (ICP) with normal or pathological values (intracranial hypertension) in nonglaucomatous neurological patients during lumbar punction (LP).

Long-term surgical results of supplementary motor area epilepsy surgery

OBJECTIVE Supplementary motor area (SMA) epilepsy is a well-known clinical condition; however, long-term surgical outcome reports are scarce and correspond to small series or isolated case reports. The aim of this study is to present the surgical results of SMA epilepsy patients treated at 2 reference centers in Mexico City. METHODS For this retrospective descriptive study (1999-2014), 52 patients underwent lesionectomy and/or corticectomy of the SMA that was guided by electrocorticography (ECoG). The clinical, neurophysiological, neuroimaging, and pathological findings are described. The Engel scale was used to classify surgical outcome. Descriptive statistics, Student t-test, and Friedman, Kruskal-Wallis, and chi-square tests were used. RESULTS Of these 52 patients, the mean age at epilepsy onset was 26.3 years, and the mean preoperative seizure frequency was 14 seizures per month. Etiologies included low-grade tumors in 28 (53.8%) patients, cortical dysplasia in 17 (32.7%) patients, and cavernomas in 7 (13.5%) patients. At a mean follow-up of 5.7 years (range 1-10 years), 32 patients (61%) were classified as Engel Class I, 16 patients (31%) were classified as Engel Class II, and 4 (8%) patients were classified as Engel Class III. Overall seizure reduction was significant (p = 0.001). The absence of early postsurgical seizures and lesional etiology were associated with the outcome of Engel Class I (p = 0.05). Twenty-six (50%) patients had complications in the immediate postoperative period, all of which resolved completely with no residual neurological deficits. CONCLUSIONS Surgery for SMA epilepsy guided by ECoG using a multidisciplinary and multimodality approach is a safe, feasible procedure that shows good seizure control, moderate morbidity, and no mortality.

Correlation Between Bispectral Index and Electrocorticographic Features During Epilepsy Surgery

Surgical resection guided by intraoperative electrocorticography (iECoG) has been in clinical use for many decades. The use of the bispectral index (BIS) for monitoring depth of anesthesia during different types of surgery, including epilepsy surgery, is increasing nowadays. The BIS is an EEG-derived variable indicating cortical electrical activity. However, the correlation between the BIS score and the iECoG score, with the purpose of optimizing the quality and time of the iECoG recordings in epilepsy surgery is unknown. The goal of this study was to evaluate the correlation between BIS values and iECoG parameters during the epilepsy surgery under anesthesia with propofol and fentanyl. This is a prospective study that included patients with epilepsy who underwent epilepsy surgery guided by BIS and iECoG (September 2008 to October 2013). Clinical, physiological, and sociodemographic characteristics are shown. We correlated the iECoG parameters (presence of burst suppressions [BS], suppression time [seconds], background frequency [Hz], and type of iECoG score by Mathern et al) with BIS values. We included 28 patients, 15/28 (53.5%) female, general mean age of 30.5 years (range 13-56 years). Patients underwent epilepsy surgery: 22/28 (79%) temporal and 6/28 (21%) extratemporal. We found a nonlinear polynomial cubic relationship between the mentioned variables noting that a BIS range of 40 to 60 gave the following results: iECoG BS periods <5 seconds, background frequency 10 to 17 Hz, and iECoG score 2 characterized by lack of >20-Hz background frequencies. No BS were observed with a BIS > 60. In conclusion BIS values and iECoG parameters during the epilepsy surgery under anesthesia with propofol and fentanyl have a nonlinear correlation. BS patterns were not found with a BIS > 60. These findings show that BIS is a nonlinear multidimensional measure, which possesses high variability with the iECoG parameters. BS patterns are not found with BIS > 60.