SEARCH · PubMed Health

Results for “ECOG”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources

PubMed2000

Evaluation of three intraoperative auditory monitoring techniques in acoustic neuroma surgery.

OBJECTIVE: To assess the efficacy of three intraoperative auditory monitoring techniques: auditory brainstem response (ABR), electrocochleography (ECoG), and direct eight nerve monitoring (DENM). STUDY DESIGN: A retrospective review of the intraoperative recordings of ABR, ECoG, and DENM was performed. SETTING: A private, neurotologic practice. PATIENTS: Sixty-six patients with usable preoperative hearing underwent intraoperative auditory monitoring with ABR, ECoG, or DENM. INTERVENTIONS: Intraoperative auditory monitoring. MAIN OUTCOME MEASURES: Postoperative pure-tone hearing threshold and word recognition scores. RESULTS: Of the 66 patients, 16 (24%) had postoperative serviceable hearing. Five (18%) of the 28 with ABR monitoring, 3 (17%) of the 18 with ECoG monitoring, and 8 (40%) of the 20 with DENM monitoring had serviceable hearing after surgery. CONCLUSIONS: This study suggests that DENM may be more effective than ABR or ECoG, although the differences in hearing preservation rates are not statistically significant.

Adult↗

PubMed2000

Extratympanic electrocochleography: diagnostic and predictive value.

OBJECTIVE: To define the clinical value of extratympanic electrocochleography (ECoG) in the diagnosis of Meniere's disease. STUDY DESIGN: Retrospective case review. SETTING: An otology/neurotology referral center. PATIENTS: A group of 252 patients with symptoms consistent with Meniere's disease and 20 normal-hearing control subjects. INTERVENTION: All patients underwent audiologic testing and extratympanic ECoG at the time of initial evaluation and, when possible, following treatment. MAIN OUTCOME MEASURES: Audiologic thresholds and summating and action potential ratios (SP:AP). RESULTS: Patients were classified into definite, probable, possible, and bilateral Meniere's disease groups according to American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) guidelines. The definite Meniere's group demonstrated an elevated SP:AP ratio in 74% of cases, the possible Meniere's group in 64%, and the bilateral group demonstrated elevated ratios in both ears in 66%. Contralateral ears produced elevated ratios in 42% for unilateral cases, whereas 40% of these ears reported at least one contralateral symptom. All 40 control ears were normal (SP:AP > or = 0.50). Results statistically correlated (p = 0.004) with the Meniere's staging system set forth in the 1995 AAO-HNS guidelines. No correlation was found between ECoG results and disease duration. Although 72% of the 86 follow-up patients reported complete or substantial vertigo control, changes from initial ECoG results did not specifically correlate to vertigo, tinnitus, or aural fullness improvement. CONCLUSIONS: Extratympanic ECoG can be useful in the diagnosis of Meniere's disease, lending promise to possible cases where objective audiologic data are lacking. Each testing center should study its own results to establish meaningful parameters and confidence levels.

Adolescent↗

PubMed1997

Induction of burst-suppression and activation of epileptiform activity after methohexital and selective amygdalo-hippocampectomy.

Electrocorticography (ECOG) compared the effects of methohexital (MTH) and selective amygdalo-hippocampectomy (selAH) upon lateral temporal neocortical epileptiform activity (EA) in 31 patients with mesial temporal epilepsy. Pre-excision ECOG showed independent neocortical EA before MTH in 12/31 and after MTH in 18/31. MTH (20-50 mg) activated neocortical EA in 12 cases and induced burst-suppression (BS) over temporal neocortex in 14/31. Post-excision ECOG showed neocortical EA in 21/31 and BS in 27/31: compared with pre-excision ECOG before MTH, selAH activated neocortical EA in 15 cases. Significant correlations were found between presence of pre-excisional neocortical EA and presence of post-excisional neocortical EA (P < 0.001) and between activation of pre-excisional neocortical EA by MTH and activation of (post-excisional) neocortical EA by selAH (P < 0.006). Presence or severity of BS in the post-excision ECOG was not correlated with presence, absence or activation of post-excisional EA. Presence of neocortical EA was significantly correlated with a higher pre-operative seizure frequency (P < 0.001) but not with duration of epilepsy nor surgical outcome. Both MTH and selAH can induce neocortical BS, likely through chemical and surgical disconnection of cortex, respectively. Unrelated to induction of BS, MTH and selAH appear to decrease threshold for expression of neocortical EA in a similar fashion.

Adolescent↗

PubMed1997

APH, an N-methyl-D-aspartate receptor antagonist, blocks the metaphit-induced audiogenic seizures in rats.

The effect of the competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, (+/-)2-amino-7-phosphonoheptanoic acid (APH) on electrocorticographic (ECoG) activity and behavior was studied in the model of epilepsy induced by systemic application of metaphit (1-(1-(3-isothiocyanatophenyl)-cyclohexyl)-piperidine). Male Wistar rats were injected with metaphit intraperitoneally (10 mg/kg, i.p.), and exposed to intense audio stimulation (electric bell generating 100 +/- 3 dB at animal level for 60 s) 1 h after administration and at 1-h intervals thereafter. ECoG tracings showed appearance of paroxysmal activity in form of spikes, spike-wave complexes and ECoG seizures. Audiogenic seizures consisted of wild running followed by clonic and tonic convulsions. Each behavioral seizure response had a characteristic ECoG correlate. The incidence and severity of seizures increased with time, reaching a peak 8-12 h after metaphit administration, and then gradually decreased until 31 h, when no animal responded to sound stimulation. APH was injected intracerebroventricularly (0.005, 0.01, 0.02, 0.03 and 0.05 mumol icv in 5 microL of sterile saline) after the 8th hour of audiogenic testing (AGS). APH inhibited seizures in a dose-dependent manner. The minimum dose which blocked seizures in all animals was 0.03 mumol. However, ECoG signs of seizure susceptibility were not suppressed by APH. After varying periods of time, behavioral seizures reappeared. It seems that APH blocks epileptiform propagation, but has less influence on the epileptogenic activity caused by metaphit.

2-Amino-5-phosphonovalerate↗

PubMed1997

Morphofunctional effects of moderate forebrain ischemia combined with short-term hypoxia in rats--protective effects of Cerebrolysin.

Morphofunctional effects of combined moderate forebrain ischemia due to permanent bilateral carotid artery ligation and short-term systemic hypoxia in rats were investigated. Moreover, a putative effect of brain protection by Cerebrolysin (Cerebrolysin, EBEWE, Austria), a brain tissue hydrolysate containing a mixture of 85% free amino acids and 15% small peptides (MW < 10,000), was studied. Eighty-seven adult Wistar rats (24 Cerebrolysin treated and 63 controls) were subjected to chronic moderate forebrain ischemia by permanent bilateral carotid artery ligation for 7 days. Twenty-four hours after the onset of ischemia, 56 of them underwent an additional hypoxic hypoxia (FiO2 = 0.08) of 15 min. A first group (19 out of 56 animals) received Cerebrolysin (every dose 2.5 ml/kg body weight s.c.) after ligation, after hypoxia and then daily. A second group (6 out of 56 animals) received an equal volume of physiological saline after ligation and Cerebrolysin the first time after hypoxia and then once a day. An untreated control group (31 out 56 animals) received physiological saline. Changes in behavior were scored and electrophysiological activity was quantified by spectral ECoG analysis before carotid artery ligation, before and after hypoxia, and once a day during the following 7 days. On the 7th day after hypoxia, the animals were sacrificed and the grade of histological damage was quantified by morphometry. After permanent carotid artery ligation, 20 out of 63 (31.7%) untreated control animals died within 24 h but only 4 out of 20 (16.7%) Cerebrolysin treated animals. However, Cerebrolysin had not detectable effect on mortality after the additional acute hypoxia. Within 24 h after hypoxia, ECoG power of the higher frequency ranges remained low (p < 0.05). Surviving animals showed a significantly higher ECoG power during and 15 min after hypoxia than those animals that died within 48 h after hypoxia (p < 0.05). All animals showed reduced behavioral activity (p < 0.01) 20 min after hypoxia, however, basal reflex responses were not altered. The major patterns of neuronal damage were coagulation necrosis and general sponginess of the neuropil which is a sign of brain edema. These changes occurred predominantly within the superolateral convexities of the parietal cortex, in the entorhinal and in the piriform cortex as well as in the CA1 and CA4 region and in the dentate gyrus of the hippocampus. The striatum and the origin nuclei of the brain nerves were also affected. We did not observe a relationship between behavior, ECoG depression and the extent of morphological damage after hypoxia nor did we find any protective effects of Cerebrolysin on these parameters. Rather it is suggested that the degree of ECoG depression immediately after hypoxic hypoxia could be a predictor for prognosis of animal survival. Cerebrolysin reduced the amount of early mortality which was caused by moderate global forebrain ischemia. However, no protective influences of the amount of brain tissue damage could be shown.

Amino Acids↗

PubMed2003

Intraoperative electrocorticography in epilepsy surgery: useful or not?

Intraoperative electrocorticography (ECoG) has been traditionally used in the surgical management of medically refractory partial epilepsies to identify the location and limits of the epileptogenic area, to guide the extent of resection, and to assess its completeness. Although in clinical use for many years, the basic questions regarding indications and limitations of this method has remained unanswered. ECoG plays a major role in tailored temporal lobectomies, whereas, it serves no practical purpose in standard resection of medial temporal lobe epilepsy (TLE) with magnetic resonance imaging (MRI) evidence of mesial temporal sclerosis (MTS). Residual hippocampal spikes, unaltered by resection, correlate with a greater proportion of seizure recurrence. Intraoperative hippocampal ECoG can allow sparing of functionally important hippocampus, thus minimising postoperative memory decline. ECoG eminently aids removal of developmental malformations of brain, and most importantly, the excision of highly epileptogenic cortical dysplasias (CDs) for deciding the extent of resection for best seizure control. The ECoG can be a valuable tool during multiple subpial transections (MST).

Anesthesia↗

PubMed1997

Welfare implications of gas stunning pigs: 3. The time to loss of somatosensory evoked potentials and spontaneous electrocorticogram of pigs during exposure to gases.

Changes in the spontaneous electrocorticogram (ECoG) and somatosensory evoked potentials (SEPs) were recorded in 12 pigs in each of three gas killing treatments. The treatments were 90% argon in air with 2% residual oxygen; a mixture of 30% carbon dioxide and 60% argon in air with 2% residual oxygen; or 80-90% carbon dioxide in air. The mean times to loss of SEPs were 15, 17 and 21 s, respectively. The mean time to loss of SEPs recorded during killing with a high concentration of carbon dioxide was significantly longer than those recorded for the other two gas killing treatments (P < 0.05). Slow waves (high amplitude and low frequency) appeared on average 15 s after exposure to argon. In some pigs killed with the carbon dioxide-argon mixture, a decrease in the frequency of electrical activity was apparent, although slow waves did not appear during killing with a higher concentration of carbon dioxide. A suppressed ECoG (reduction in amplitude of signals) was recorded at 22 and 20 s respectively, during exposure to the carbon dioxide-argon mixture and 80-90% carbon dioxide in air, but the onset of ECoG suppression could not be determined exactly during exposure to 90% argon in air. The time to onset of an isoelectric ECoG was 54, 39d and 32 s after exposure to argon, carbon dioxide-argon mixture and a high concentration of carbon dioxide, respectively. The mean time to the onset of an isoelectric ECoG during exposure to argon was significantly longer than that recorded for the other two gas killing treatments (P < 0.05). Based on the time to loss of SEPs, it is concluded that during killing with a high concentration of carbon dioxide, pigs would have to endure a moderate to severe respiratory distress induced with this gas for a considerable period of time prior to the loss of brain responsiveness. Argon-induced anoxia appears to be the first choice from a welfare point of view for killing pigs, based on its lack of aversive properties and its effectiveness in rapidly abolishing brain responsiveness. A mixture of 30% carbon dioxide and 60% argon in air is considered to be more humane than using a high concentration of carbon dioxide, as the time to loss of brain responsiveness is similar to that using 90% argon in air.

Animal Welfare↗

PubMed2006

[Chemotherapy and survival in advanced non-small cell lung carcinoma: is pneumologists' skepticism justified?].

OBJECTIVE: Few studies have assessed whether the advantage chemotherapy has been shown to have in treating advanced non-small lung carcinoma in clinical trials is transferrable to normal health care activity. This could explain the skepticism of a large number of pneumologists towards this treatment. The objective of our study was to analyze prognostic factors related to survival and to see whether cytostatic treatment was an independent predictor. PATIENTS AND METHODS: Patients enrolled in the study had been diagnosed with non-small cell carcinoma in stages IV or IIIB with pleural or N2-N3 involvement and with a performance status of 2 or below according to the Eastern Cooperative Oncology Group (ECOG). Survival was analyzed with regard to the following variables: age, sex, comorbidity, weight loss, laboratory test results, histological type, ECOG score, TNM staging, and treatment. The Student t test, the chi(2) test, the Kaplan-Meier method, the log-rank test, and Cox regression analysis were used in the statistical analysis. RESULTS: We enrolled 190 patients (157 men and 33 women) with a mean (SD) age of 61.75 (10.85) years (range, 33-85 years). Of these patients, 144 received cytostatic treatment and 46 palliative treatment. The median survival was 31 weeks and was related to absence of weight loss (hazard ratio [HR], 1.73; 95% confidence interval [CI], 1.26-2.39; P=.001), cytostatic treatment (HR, 1.85; 95% CI, 1.25-2.76; P=.002), and ECOG score of 0 to 1 (HR, 2.84; 95% CI, 1.62-5.00; P=.0001). In patients with ECOG scores of 0 to 1, weight loss and treatment were significant prognostic factors. Survival in the ECOG 2 group was 15 weeks for patients undergoing cytostatic treatment and 11 weeks for patients with symptomatic treatment. CONCLUSIONS: In normal clinical practice, chemotherapy significantly prolongs survival in patients with performance status of less than 2, more time being gained if there is no associated weight loss. We conclude that the reluctance shown by many pneumologists toward using this treatment is not entirely justified.

Aged↗

PubMed1999

Toxicity and feasibility of adjuvant high-dose interferon alpha-2b in patients with melanoma in clinical oncologic practice.

To assess the feasibility and toxicity profile of high-dose interferon alpha-2b (IFN-alpha-2b) in the adjuvant treatment of patients with cutaneous malignant melanoma outside the reference ECOG 1684 clinical trial, we conducted a prospective follow-up in an identical population of patients (cutaneous melanoma, T4 and/or N1) treated by intravenous IFN-alpha-2b:20 MIU m(-2), 5 days a week for 4 weeks; and subcutaneous:10 MIU m(-2), 3 times a week for 11 months. Thirty-six consecutive patients were considered in four different institutions. The frequency and severity of side-effects related to IFN-alpha, as well as the percentage of the planned dose given to patients, were identical to those reported in the initial report by ECOG. Fifty per cent and 47% of patients had a grade 3/4 WHO toxicity in the induction and consolidation phase respectively. A dose modification was necessary for 47.2% and 55.8% of the patients in the induction and consolidation phase respectively. The schedule and dose of high-dose IFN-alpha-2b in the adjuvant treatment of cutaneous malignant melanoma, as reported by ECOG 1684, is feasible. The significant toxicity reported in ECOG 1684 was also seen in our patients. Nevertheless, this protocol will not be a 'standard' treatment until the publication of the ECOG 1690 trial.

Antineoplastic Agents↗

PubMed2000

The effect of propofol on intraoperative electrocorticography and cortical stimulation during awake craniotomies in children.

Propofol has been proposed as a sedative agent during awake craniotomies. However, there are reports of propofol suppressing spontaneous epileptiform electrocorticography (ECoG) activity during seizure surgery, while others describe propofol-induced epileptiform activity. The purpose of this study was to determine if propofol interferes with ECoG and direct cortical stimulation during awake craniotomies in children. Children scheduled for awake craniotomies for resection of epileptic foci or tumours were studied. An intravenous bolus of 1-2 mg.kg-1 followed by infusion of 100-200 microgram.kg-1.min-1 of propofol was administered to induce unconsciousness. Fentanyl (0.5 microgram.kg-1) was administered incrementally to provide analgesia. After the cortex was exposed, the propofol infusion was stopped and the patient permitted to awaken. Cortical electrodes were applied. ECoG was recorded continuously on a Grass polygraph. Motor, sensory, language, and memory testing were done throughout the procedure. The cortex was stimulated with a hand-held electrode using sequential increases in voltage to map the relevant speech and motor areas. We studied 12 children (aged 11-15 years) with intractable seizures. The raw ECoG did not reveal any prolonged beta-waves associated with propofol effect. Electroencephalogram spikes due to spontaneous activity or cortical stimulation were easily detected. Cognitive, memory and speech testing was also successful. We conclude that propofol did not interfere with intraoperative ECoG during awake craniotomies. Using this technique, we were able to fully assess motor, sensory, cognitive, speech and memory function and simultaneously avoid routine airway manipulation.

Adolescent↗

PubMed2001

Inhalant allergy and Meniere's disease: Use of electrocochleography and intranasal allergen challenge as investigational tools.

INTRODUCTION: In an earlier study, we demonstrated the feasibility of using electrocochleography (ECoG) to document changes in inner ear function objectively after intranasal challenge of patients with inhalant allergy (with no prior immunotherapy) and Meniere's disease, using the antigen to which they were most sensitive. OBJECTIVE: We expand on this earlier study and continue to investigate the feasibility of this model in a subset of patients with inhalant allergy and Meniere's disease after immunotherapy. STUDY DESIGN: Prospective study of 11 patients identified with both Meniere's disease and inhalant allergy in the practices of 2 neurotologists at our institution. Patients underwent a baseline ECoG, followed by intranasal challenge with the allergen to which they were most sensitive. This was followed by a second ECoG. RESULTS: Six of 11 patients had at least 1 year of immunotherapy (group 1), and 5 of 11 had had 0 to 6 months of immunotherapy (group 2). Four of 6 group 1 patients had a >15% increase in SP/AP ratio after immunotherapy. In group 2, 2 patients increased the SP/AP in at least 1 ear. No patient with a normal ECoG experienced vestibular symptoms after allergen challenge, whereas 2 of group 1 and 2 of group 2 had vestibular symptoms with abnormal ECoGs. CONCLUSION: This protocol is a useful tool for investigating the relationship of inhalant allergy and Meniere's disease, but needs a larger group of patients and further study to draw valid statistical conclusions.

Allergens↗

PubMed2002

Continuous potential display of ictal electrocorticography.

The objective of this study was to determine whether the animation of electrical activity recorded on ictal electrocorticograms (ECoGs) can demonstrate the propagation of seizure discharges from the epileptogenic zone (EZ) to the surrounding cortical area. A computer program, continuous potential display (CPD), was designed to animate the color-coded potential changes in 5-msec intervals at each recorded site. This program was used to analyze 35 ictal ECoGs recorded by subdural grid electrodes from 11 subjects who underwent epilepsy surgery for intractable partial seizures. Continuous potential display demonstrated recurrent cycles of seizure propagation from the EZ to the surrounding cortical area even when seizure discharges appeared widespread on ECoG. Hence, the EZ could be mapped at any time during the seizure course. The EZ mapped by analyzing a small fraction of ECoG during widespread seizure discharges using CPD only overlapped 69 +/- 24% (mean +/- standard deviation) of the surgical area. The EZ mapped by CPD had 34 +/- 22% false positives and 35 +/- 27% false negatives. Animation of potential changes recorded by ictal ECoG can assist in studying the temporal and spatial patterns of seizure propagation and in mapping the EZ for surgical resection.

Action Potentials↗

PubMed2001

Non-linear changes of electrocortical activity after antenatal betamethasone treatment in fetal sheep.

We determined the effects of betamethasone on the fetal sheep electrocorticogram (ECoG) using linear (power spectral) and non-linear analysis. For non-linear analysis we used an algorithm based on the Wolf algorithm for the estimation of the leading Lyapunov exponent which calculates a prediction error based on the course of the time series in the phase space. A high prediction error stands for low predictibility or low regularity and vice versa. After 48 h of baseline recordings, vehicle (n = 6) or betamethasone (n = 7) at 10 microg h(-1) was infused over 48 h to the sheep fetus at 128 days gestational age (0.87 of gestation). ECoG spectral analysis revealed no difference in power spectrum between vehicle- and betamethasone-treated fetuses. The prediction error of the ECoG during REM sleep was higher than during non-REM or quiet sleep in both groups (P < 0.0001) revealing lower causality of brain activity during REM sleep. During REM sleep, prediction error significantly decreased 18-24 h after onset of betamethasone treatment (P < 0.05) and returned to baseline values within the following 24 h of continued betamethasone treatment. No ECoG changes were found during quiet sleep. Non-linear ECoG changes during metabolically active REM sleep accompanied the previously described decrease in cerebral blood flow. These results suggest that betamethasone in doses used in perinatal medicine acutely alters complex neuronal activity.

Algorithms↗

PubMed1995

GABAergic and glutamatergic effects on behaviour in fetal sheep.

1. Studies were carried out in unanaesthetized fetal sheep at 125-135 days gestation to investigate neurotransmitters involved in behavioural state. 2. Catheters and electrodes were chronically placed to record tracheal and arterial pressure, electrocortical activity (ECoG), nuchal muscle activity and to instill drugs into the cerebrospinal fluid (CSF) of the fourth ventricle. 3. Administration of the N-methyl-D-aspartate receptor antagonists DL-2-amino-5-phosphopentanoic acid (AP5) or (+)-5-methyl-10,11-dihydro-5H-dibenzol[a,d]cyclohepten-5,10- iminemoleate (MK-801) increased the incidence of fetal behaviour characterized by low voltage ECoG, nuchal muscle activity and an increase in mean arterial blood pressure from 4.1 +/- 6 to 60.6 +/- 6.2% (mean +/- S.E.M.) (AP5; P = 0.003) and from 7.6 +/- 3.6 to 50.8 +/- 7.0% (MK-801; P = 0.004; values are expressed as the percentage of each 60 min period in which the state was present). 4. The incidence of fetal breathing during periods of low voltage (LV)-ECoG and nuchal muscle activity was 83.1 +/- 5.6%. The incidence of fetal breathing during LV-ECoG associated with nuchal muscle atonia was 63.1 +/- 5.0% before AP5 or MK-801 and 64.4 +/- 9.8% after instillation of these drugs. The amplitude of fetal breaths increased from 4.0 +/- 0.3 mmHg in low voltage ECoG periods to 6.7 +/- 0.8 mmHg (P = 0.006) during periods of low voltage with nuchal muscle activity. There was no significant change in breath timing during these periods.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Cerebral oxidative metabolism in lambs during perinatal period: relationship to electrocortical state.

Cerebral oxidative metabolism and regional blood flow were studied, with changes in behavioral state over the immediate perinatal period, to determine the change in cerebral metabolism at birth and the relationship to behavioral activity. Nine unanesthetized fetal sheep (139-142 days gestation) were each studied during a period of high-voltage and low-voltage electrocorticogram (ECOG) activity and then again after cesarean delivery at 2 h of age while awake and at 24 h of age while awake and during a period of high-voltage ECOG sleep. Preductal arterial and sagittal vein blood samples were analyzed for O2 content, blood gases, and pH. Blood flow was measured with a radioactive microsphere technique. Cerebral oxidative metabolism showed no significant perinatal change, although a coupling to behavioral state was evident with significant increases during both the perinatal low-voltage ECOG state and the awake state at 24 h. Blood flow to the brain showed a significant perinatal decrease after birth and state-related increases during both the prenatal low-voltage ECOG state and the awake state at 24 h consistent with the tight coupling of flow and/or O2 delivery to metabolic needs reported for normal brain tissue. The cerebral metabolic rate of the prenatal low-voltage ECOG state suggested a level of functional excitation comparable with that of the awake state after birth, supporting the importance of the rapid-eye-movement (REM) state mechanism as a source of endogenous stimulation during the perinatal period of brain growth and development.

Animals↗

PubMed1994

Spontaneous waves of cerebral blood flow associated with a pattern of electrocortical activity.

We examined the relationship between spontaneous changes in regional cerebral blood flow and electrocortical (ECoG) activity in spinalized rats anesthetized with 1.5% isoflurane. Regional cerebral blood flow, measured by laser-Doppler flowmetry, and ECoG activity were measured bilaterally in frontal and parietal cortex. Spontaneous cerebrovascular waves (SCWs) were seen in all (n = 80) rats and consisted of sawtoothed waves with an average amplitude of 20.1 +/- 0.78%, a duration of 11.7 +/- 0.6 s, and a frequency of 6.3 +/- 0.2 min-1. SCWs were always preceded by a high-amplitude burst of ECoG activity (averaging 752.0 +/- 41.8 microV at 5.6 +/- 0.2 Hz) and comparable to the well-recognized burst-suppression/barbiturate-spindle patterns of ECoG activity. The latency between bursts and SCWs averaged 1.71 +/- 0.05 s. The frequency of bursts and SCWs was highly correlated within and between cortical areas bilaterally (r > 0.9) and appeared synchronously across brain. Deepening anesthesia (to 1.75% isoflurane) reduced the frequency of bursts and SCWs by > 30% but not their correlation (r > 0.9) and minimally increased burst-SCW latency. SCWs differed from an uncommon sinusoidal oscillation regional cerebral blood flow triggered by changes in arterial pressure and independent of the ECoG. Bursts and SCWs were not affected by inhibition of nitric oxide synthase. The results indicate that a population of local cortical neurons, probably driven from subcortical pacemakers, when excited, elicits local cerebrovascular vasodilation.

Anesthesia↗

PubMed1990

Catecholamine neurons in fetal brain: effects on breathing movements and electrocorticogram.

We investigated the effect of increasing the synaptic concentration of catecholamines released from central pathways on breathing movements and electrocortical (ECoG) activity in fetal sheep in utero. In 11 trials (9 fetuses) intravenous infusion of the noradrenergic uptake inhibitor desipramine (DMI) resulted in an initial increase in the incidence of breathing movements from 47.8 +/- 2.2%/h to a maximum of 77.9 +/- 5.5%/h (P less than 0.05) followed by a subsequent decrease to 18.8 +/- 2.7%/h (P less than 0.05), which was associated with a decrease in the incidence of low-voltage ECoG activity. Mean breath amplitude also increased after DMI infusion from 5.8 +/- 0.2 mmHg to a peak of 8.9 +/- 0.9 mmHg (P less than 0.05). In five fetuses, intravenous injection of the alpha 1-receptor antagonist prazosin 30 min after the start of the DMI infusion blocked the increase of breath amplitude observed when DMI was given alone. Intracisternal infusion of 6-hydroxydopamine (6-OHDA, which causes an initial displacement of transmitter stores followed by a neurotoxic action) in six fetuses caused an increase in mean breath amplitude from 6.6 +/- 0.3 mmHg (control) to 22.3 +/- 5.5 mmHg (P less than 0.05) and a prolonged episode of breathing movements (168.5 +/- 47.2 min). The incidence of low-voltage ECoG activity was also increased significantly. A second infusion of 6-OHDA, 2 days after the first, had no effect on breathing movements or ECoG activities. The two treatments with 6-OHDA also resulted in a significant reduction in the response to intravenous infusion of DMI, indicating that endogenous release of norepinephrine had been reduced by the neurotoxin. These results suggest that 1) there is normally some tonic release of norepinephrine from central pathways, but this release is insufficient to stimulate sustained fetal breathing, and 2) accumulation in the synaptic cleft of catecholamines from central neurons is able to stimulate fetal breathing and promote low-voltage ECoG activity. Possible mechanisms that normally limit the activity of central catecholamine pathways before birth are discussed.

Animals↗

PubMed1987

Transtragal, transtympanic electrode placement for intraoperative electrocochleographic monitoring.

Transtragal, transtympanic electrode placement was performed for the purpose of intraoperative electrocochleographic (ECoG) monitoring during seven suboccipital acoustic neuroma resections. The promontory, the tragus, and two external sutures stabilized the electrode during surgery. The only noted otologic sequallae of electrode placement were small circular lesions at tympanic membrane puncture sites. Satisfactory ECoG recordings were obtained in five of seven cases. Peak-to-peak N1 amplitudes were (on average) 13.4-fold larger than the corresponding amplitudes of peak I of the surface-recorded brainstem auditory evoked potential (BAEP) recordings. During acoustic neuroma resection, ECoG and BAEP recordings changed relatively independently, which suggests multiple mechanisms and/or sites of injury to the cochlea or cochlear nerve. However, once they had become manifest, none of the observed changes exhibited a tendency to return to preoperative patterns. Hearing was preserved postoperatively in only two of seven patients, one of whom could not be monitored due to technical difficulty. Transtragal, transtympanic electrode placement provided a rapid, stable, and safe method of obtaining intraoperative ECoG recordings. Although combined intraoperative monitoring of ECoG and BAEP responses appeared to provide more precise documentation of injury to the cochlea and/or cochlear nerve, it was probably not influential in preservation of hearing in this series.

Adult↗