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PubMed2000

The use of an implicit standard for measuring discrimination thresholds.

We measured thresholds for comparing the separation between lines, using either the method of constant stimuli (MCS) or the method of single stimuli (MSS). In the MCS an explicit standard is presented on each trial, whereas in the MSS the standard is the mean of the set. The thresholds for the MSS procedure were nearly identical to those with the MCS procedure, whether or not feedback was used. A statistical model is presented showing how the threshold error estimated by MSS varies according to the number of past stimuli used by the observer to calculate the mean of the set. If the model is an accurate representation of human processing, our observers were averaging over the last 10-20 trials to estimate the implicit standard. Our results show that the explicit standard in the MCS procedure is generally superfluous. Provided that the test range is small, and that the observer is given some practice trials, thresholds measured with MSS procedure are just as precise as those measured with the traditional MCS procedure.

Differential Threshold↗
PubMed1985

Importance of the pacing mode in the initiation of ventricular tachyarrhythmia in a canine model of chronic myocardial infarction.

The use of unipolar anodal or bipolar pacing, as compared with unipolar cathodal pacing, purportedly increases the likelihood of inducing inadvertent ventricular fibrillation in susceptible patients. In this study, the ability to initiate sustained ventricular tachycardia or fibrillation with unipolar cathodal, unipolar anodal and bipolar pacing modes was compared using programmed ventricular stimulation at 82 subendocardial periinfarction sites in 11 dogs with chronic myocardial infarction. The late diastolic excitability threshold was significantly higher and the ventricular refractory period was significantly shorter (p less than 0.001) with anodal pacing (mean 0.62 mA, 156 ms, respectively) than with pacing in either the cathodal (0.12 mA, 174 ms) or the bipolar (0.13 mA, 173 ms) mode. At a current intensity twice that of the excitability threshold, the introduction of one or two extrastimuli induced ventricular tachycardia and ventricular fibrillation comparably among the three pacing modes. However, when three extrastimuli were used, ventricular fibrillation was induced with anodal pacing twice as frequently (50 [61%] of 82 sites) as with either of the other two pacing modes (each 23 [28%] of 82 sites, p less than 0.001), whereas the induction of ventricular tachycardia remained comparable with anodal pacing (15 [18%] of 82 sites) and cathodal and bipolar pacing (each 14 [17%] of 82 sites). Furthermore, a similarly high incidence of inducibility of ventricular fibrillation was observed with both cathodal pacing (56 [68%] of 82 sites) and bipolar pacing (40 [49%] of 82 sites) when an increased current equal to twice the anodal excitability threshold (1.23 mA) was used.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Implantation of a unipolar cardioverter/defibrillator system under local anaesthesia.

OBJECTIVE: To evaluate prospectively the safety and feasibility of the implantation of cardioverter/defibrillator systems under local anaesthesia. Conventionally, cardioverter/defibrillator systems are implanted under general anaesthesia. With the development of single-lead transvenous unipolar cardioverter/defibrillator systems for subpectoral implantation a pacemaker-like approach for device implantation appears applicable. METHODS: Implantation of a single-lead transvenous unipolar cardioverter/defibrillator under local anaesthesia with sedation for defibrillation threshold testing was performed in 37 consecutive patients. The presenting arrhythmia was ventricular fibrillation in 13 patients, and monomorphic ventricular tachycardia in 24 patients. A 1% lidocaine solution was used for local anaesthesia, and midazolam was applied for sedation to perform defibrillation threshold testing. Arterial blood pressure, arterial oxygen saturation and heart rate were monitored throughout the procedure. The patient's tolerance of the implantation procedure was evaluated with a standardized questionnaire. RESULTS: The unipolar transvenous cardioverter/defibrillator system was implanted successfully in all patients under local anaesthesia. During defibrillation threshold testing, sufficient sedation was achieved with 12.5 +/- 3.7 mg midazolam. For determination of the defibrillation threshold 5.9 +/- 1.4 episodes of ventricular fibrillation were induced. The mean defibrillation threshold was 13.1 +/- 5.5 J, and the mean duration of the implantation procedure was 68 +/- 30 min. Mean heart rate, mean arterial blood pressure and arterial oxygen saturation were not significantly different before and after defibrillation threshold testing. Twenty-six patients (70%) were symptom-free throughout the implantation procedure; most of the remaining patients reported minor symptoms. There were no complications, and patients were discharged 2.2 +/- 0.7 days after implantation. In 12 patients, post-implant testing of the implantable cardioverter/defibrillators was performed successfully, without sedation, 2.8 +/- 1.4 days after as an outpatient procedure. CONCLUSION: Single-lead unipolar transvenous implantable cardioverter/defibrillator systems can be safely implanted under local anaesthesia with mild sedation for defibrillation threshold testing. The procedure is well tolerated.

Aged↗
PubMed1987

Effect of cross cylinder power on cylinder axis sensitivity.

Astigmatic errors (0.50 D to 1.50 D in 0.25 D steps) were induced in each of 5 subjects, and cylinder axis thresholds were assessed from 12 reversals of a 2.5 degrees stepsize staircase for 0.50 D and 1.00 D cross cylinders (CC). Equivalent power thresholds were 0.077 D (0.05 SD) for the 0.50 D CC and 0.104 D (0.05 SD) for the 1.00 D CC. Findings are significantly different from predictions of a "linear" blur detection model, but are consistent with a model assuming constant blur thresholds and power-dependent distortion thresholds. Our results support the use of minimal CC power in refining cylinder axis.

Adult↗
PubMed1995

The effects of dopamine on the subthreshold electrophysiological responses of rat prefrontal cortex neurons in vitro.

The rat prefrontal cortex is densely innervated by dopaminergic fibres originating in the mesencephalic ventral tegmental area, and dopamine application in vivo has an inhibitory effect. We have studied the effects of dopamine on the persistent sodium current that is present in prefrontal cortex neurons and on the subthreshold electrophysiological responses generated by that current: a slow depolarization and a fast oscillatory activity. Experiments were made in coronal slices of rat frontal cortex (300-400 microns thickness) and intracellular recordings from regularly spiking cells were obtained with 3 M potassium acetate-filled glass microelectrodes (80-150 M omega). Dopamine was applied dissolved in the extracellular medium and, in current-clamp recordings, reversibly inhibited the slow subthreshold depolarization. Dopamine was ineffective when applied after tetrodotoxin (1 microM) had blocked the action potentials. This inhibition was dose-dependent in the range of 0.1-10 microM). Dopamine, applied at 10 microM, decreased the steady-state firing frequency and also inhibited the subthreshold fast oscillatory activity. The currents activated in the subthreshold range were recorded with the single-electrode voltage-clamp technique and a clear persistent, tetrodotoxin-sensitive component was isolated. This component was inhibited by 50% in a reversible way by 20 microM dopamine. These results show that dopamine increases the threshold for spike firing and suggest a mechanism for the inhibitory action of this neurotransmitter in the prefrontal cortex.

Animals↗
PubMed1993

Membrane properties of rat suprachiasmatic nucleus neurons receiving optic nerve input.

1. The electrophysiological properties of suprachiasmatic nucleus (SCN) neurons (n = 33) receiving optic nerve input were studied with intracellular recordings in rat hypothalamic slices maintained in vitro. Our major goal was to provide baseline data concerning the intrinsic membrane properties of these neurons and to test the hypothesis that the neurons are homogeneous electrophysiologically. 2. Action potentials were short in duration and followed by a pronounced hyperpolarizing after-potential. Spike amplitude (58.2 +/- 1.1 mV, mean +/- S.E.M.; measured from threshold), spike duration (0.83 +/- 0.03 ms; measured at half amplitude) and hyperpolarizing after-potential amplitude (23.9 +/- 1.0 mV; measured from threshold) appeared unimodally distributed and did not co-vary. 3. Intracellular injection of depolarizing current pulses evoked spike trains, and spike inactivation, spike broadening and frequency accommodation were always present. An after-hyperpolarization followed the spike train in all but one neuron. 4. Membrane time constant ranged from 7.5 to 21.1 ms (11.4 +/- 0.7 ms, n = 27), and its distribution appeared to be unimodal with the peak at approximately 10 ms. Input resistance ranged from 105 to 626 M omega (301 +/- 23 M omega, n = 33); the distribution also appeared unimodal with its peak at approximately 250 M omega. 5. A subpopulation (16 of 33, 48%) of the neurons exhibited slight (6-29%) time-dependent inward rectification in their voltage responses to hyperpolarizing current injection. Of the neurons lacking the time-dependent rectification, some (n = 5) exhibited time-independent inward rectification of 6-20% and others showed no (or < 3%) such rectification. The degree of inward rectification was correlated with neuronal excitability (r = 0.60, P < 0.002; assessed by measuring the steepness of the primary slope of the frequency-current plot) and with the spontaneous firing rate (r = 0.49, P < 0.007). Furthermore, the neurons with > 6% inward rectification (neurons with time-dependent and -independent rectification were combined) were more excitable (362 +/- 43 Hz/nA (n = 15) vs. 221 +/- 37 Hz/nA (n = 9), P < 0.05) and had a higher spontaneous firing rate (11.1 +/- 1.9 Hz (n = 19) vs. 3.9 +/- 1.5 Hz (n = 11), P < 0.02) than the neurons with no or negligible (i.e. < 3%) inward rectification. The two groups, however, were not significantly different in membrane time constant and input resistance. 6. When adequately hyperpolarized, twelve of seventeen (71%) neurons generated small low-threshold spike (LTS) potentials in response to depolarizing current pulses.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1995

Voltage-dependent calcium currents are enhanced in dorsal root ganglion neurones from the Bio Bred/Worchester diabetic rat.

1. Whole-cell, high-threshold, voltage-dependent calcium currents (ICa) were enhanced in acutely dissociated, capsaicin-sensitive dorsal root ganglion neurones from diabetic Bio Bred/Worchester (BB/W) rats, compared with those from age-matched, non-diabetic controls. The magnitude of the enhancement increased with the duration of diabetes, and reached significance at diabetic durations of 6 months (diabetic: 6.3 +/- 0.4 nA; current density (CD), 157 +/- 12 pA pF-1; means +/- S.E.M., n = 9, P < 0.01; control: 3.9 +/- 0.6 nA; CD, 116 +/- 11 pA pF-1; n = 18) and 8 months (diabetic: 7.6 +/- 0.4 nA; CD, 177 +/- 25 pA pF-1; n = 11, P < 0.005; control: 5.1 +/- 0.5 nA; CD, 111 +/- 26 pA pF-1; n = 15). Low-threshold, voltage-dependent ICa were also enhanced in neurones from animals diabetic for 8 months (diabetic: 2.5 +/- 0.7 nA, n = 4, P < 0.05; control: 0.7 +/- 0.5 nA, n = 6). 2. The ICa enhancement was prevented by long-term treatment of diabetic animals with an aldose reductase inhibitor (ARI; peak ICa at 6 months: 4.41 +/- 0.48 nA, n = 2; at 8 months: 4.32 +/- 0.60 nA, n = 9). 3. The ICa enhancement was not due to a shift in the voltage dependence of either the current-voltage relationship or steady-state inactivation. 4. The L channel antagonist nifedipine and preferential N channel antagonist omega-conotoxin GVIA (omega-CgTX) caused a greater inhibition of high-threshold ICa in diabetic neurones compared with controls (nifedipine: control: 25 +/- 3%, n = 26; diabetic: 36 +/- 7%, n = 11; omega-CgTX: control: 40 +/- 4%, n = 21; diabetic: 50 +/- 7%, n = 7). Diabetic neurones also demonstrated a significantly greater residual current (2.44 +/- 0.34 nA, n = 7) in the presence of both antagonists vs. controls (1.28 +/- 0.30 nA, n = 8, P < 0.05), suggesting that N-, L- and additional non-N-, non-L-type high-threshold ICa were enhanced.

Aldehyde Reductase↗
PubMed2002

Sodium channel function and the excitability of human cutaneous afferents during ischaemia.

The changes in excitability of cutaneous afferents in the median nerve of healthy subjects were compared during 13 min of ischaemia and during 13 min continuous depolarizing DC. In addition, intermittent polarizing currents were used to compensate for or to accentuate the threshold change produced by ischaemia. Measurements were made alternately of the ischaemic (or current-induced) changes in threshold, refractoriness and, in some experiments, supernormality. The strength-duration time constant (tau(SD)) was calculated from the thresholds to test stimuli of different duration. During ischaemia for 13 min, the threshold decreased steadily by 34 % over the initial 8 min, reached a plateau and increased slightly over the final few minutes. However, with continuous depolarizing DC, the threshold decreased linearly with the applied current, by 55 % with strong current ramps. Intermittent injection of hyperpolarizing DC was used to compensate for the ischaemic threshold change, but the compensating current increased progressively and did not reach a plateau as had occurred with the ischaemic threshold change. During ischaemia, tau(SD) increased to a plateau, following the threshold more closely than the current required to compensate for threshold. Refractoriness, on the other hand, increased more steeply than the applied compensating current. There were similar discrepancies in the relationships of tau(SD) and refractoriness to supernormality. The smaller-than-expected threshold change during ischaemia could result from limitations on the change in excitability produced by ischaemic metabolites acting on the gating and/or permeability of Na(+) channels. Intermittent depolarizing DC was applied during the ischaemic depolarization to determine whether it would reduce or accentuate the discrepancies noted during ischaemia alone. The extent of the threshold change was greater than with ischaemia alone, and there was a greater change in tau(SD) and a proportionately smaller change in refractoriness. It is concluded that ischaemia produces factors that can block Na(+) channels and/or alter their gating. Without these processes, the ischaemic change in threshold would be much greater than that actually recorded, probably sufficient to produce prominent ectopic impulse activity.

Differential Threshold↗
PubMed1994

Dysfunction and safety factor strength-duration curves for biphasic defibrillator waveforms.

Newly developed biphasic waveforms significantly lower defibrillation threshold in animal and clinical models. However, underlying mechanisms and optimum waveform shape are unknown. Defibrillation shocks produce dysfunction; safety factor, the ratio of shock intensity inducing dysfunction to that producing stimulation of partially refractory cells, is an important parameter for defibrillator waveforms. We determined dysfunction and safety factor strength-duration curves for symmetric and asymmetric (50% undershoot) monophasic and biphasic rectangular (0%-tilt) waveforms. Dysfunction threshold, defined as the voltage producing a 4-s postshock contractile arrest, was determined for waveforms with total durations from 1 to 40 ms. For all waveforms, dysfunction threshold decreased with waveform duration. At all durations, dysfunction threshold was similar for symmetric monophasic and biphasic waveforms with the same total duration. In contrast, asymmetric biphasic waveforms increased dysfunction threshold 14 +/- 3% (P < 0.005) compared with monophasic control waveforms. Because long-duration, low-tilt, biphasic waveforms improve excitation threshold for refractory cells, they should improve defibrillation threshold. Asymmetric waveforms have the additional advantage of improving safety factor by reducing postshock dysfunction.

Animals↗
PubMed1995

Poly I:C-induced fever elevates threshold for shivering but reduces thermosensitivity in rabbits.

Shivering threshold and thermosensitivity were determined in six conscious rabbits at ambient temperature (Ta) 20 and 10 degrees C before and at six different times after saline injection (0.15 ml iv) and polyriboinosinic-polyribocytidylic acid (poly I:C)-induced fever (5 micrograms/kg iv). Thermosensitivity was calculated by regression of metabolic heat production (M) and hypothalamic temperature (Thypo) during short periods (5-10 min) of square-wave cooling. Heat was extracted with a chronically implanted intravascular heat exchanger. Shivering threshold was calculated as the Thypo at which the thermosensitivity line crossed resting M as measured in afebrile animals at Ta 20 degrees C. There were negligible changes in shivering threshold and thermosensitivity in saline-injected rabbits. In the febrile animals, shivering threshold generally followed the shape of the biphasic fever response. At Ta 20 degrees C, shivering threshold was higher than regulated Thypo during the initial rising phase of fever and was lower during recovery. At Ta 10 degrees C the shivering thresholds were always higher than regulated Thypo except during recovery. Thermosensitivity was reduced by 30-41% during fever.

Animals↗
PubMed1999

Cellular mechanisms contributing to response variability of cortical neurons in vivo.

Cortical neurons recorded in vivo exhibit highly variable responses to the repeated presentation of the same stimulus. To further understand the cellular mechanisms underlying this phenomenon, we performed intracellular recordings from neurons in cat striate cortex in vivo and examined the relationships between spontaneous activity and visually evoked responses. Activity was assessed on a trial-by-trial basis by measuring the membrane potential (Vm) fluctuations and spike activity during brief epochs immediately before and after the onset of an evoked response. We found that the response magnitude, expressed as a change in Vm relative to baseline, was linearly correlated with the preceding spontaneous Vm. This correlation was enhanced when the cells were hyperpolarized to reduce the activation of voltage-gated conductances. The output of the cells, expressed as spike counts and latencies, was only moderately correlated with fluctuations in the preceding spontaneous Vm. Spike-triggered averaging of Vm revealed that visually evoked action potentials arise from transient depolarizations having a rise time of approximately 10 msec. Consistent with this, evoked spike count was found to be linearly correlated with the magnitude of Vm fluctuations in the gamma (20-70 Hz) frequency band. We also found that the threshold of visually evoked action potentials varied over a range of approximately 10 mV. Examination of simultaneously recorded intracellular and extracellular activity revealed a correlation between Vm depolarization and spike discharges in adjacent cells. Together these results demonstrate that response variability is attributable largely to coherent fluctuations in cortical activity preceding the onset of a stimulus, but also to variations in action potential threshold and the magnitude of high-frequency fluctuations evoked by the stimulus.

Action Potentials↗
PubMed1982

[Origin of N1 wave of the cochlear nerve action potential recorded at the bony wall of the cochlea].

As an objective audiometry, the cochlear nerve action potential (AP) evoked by tone stimulation has been clinically utilized. But the origin of AP wave is still obscure. In order to know the origin of the N1 wave of AP, the author intended to compare the AP waves (AP(W)) recorded at the bony wall of the cochlea with action potentials of the individual spiral ganglion cell (spikes) and group of the spiral ganglion cells (AP(R)) in the Rosenthal canal of the guinea pig. Spikes and AP(R) were recorded by glass pipettes filled with 2M NaCl. The results showed that waves of AP(R) demonstrated a wide monophasic negative wave in contrast to diphasic AP(W) wave. The Input-Output Curves (I.O.C.) of the AP(W) and AP(R) were compared in order to ascertain whether both APs were derived from the cochlear nerve or not. The I.O.C. of latency, onset, amplitude, offset and width of both AP(R) and AP(W) N1 waves showed a same pattern with high correlation coefficient. So it was confirmed that both AP(R) and AP(W) N1 waves were the direct and indirect cochlear nerve action potential respectively. The thresholds of both AP(W) and AP(R) at the characteristic frequency of a single ganglion cell showed a high correlation. The time of onset and latency of AP(R) were longer than those of AP(W). Based on anatomy and electrophysiology, it is concluded that AP(W) N1 wave originates from the action potential generated at the habenula perforata, where spikes are first produced. The curves of the AP(R) were flat in respect of frequency-threshold relationship. The threshold was the lowest in the spiral ganglion cell followed by AP(R) and AP(W).

Acoustic Stimulation↗
PubMed1999

Increased concentrations of interleukin 1-beta in whole blood cultures supernatants after 12 weeks of moderate endurance exercise.

The aim of the study was to investigate whether a regular moderate endurance exercise programme influenced the in vitro cytokine synthesis by stimulated whole blood cultures. To this end, eight healthy subjects exercised moderately by running for 3-5 h a week over a period of 12 weeks, whilst seven other healthy subjects served as the control group. The intensity of the exercise was determined by lactic acid concentrations in the blood which were maintained between 1.8 and 2.5 mmol x l(-1). Over the period of training the running velocity producing the 4 mmol x l(-1) lactic acid threshold increased from 2.86 (SD 0.83) m x s(-1) to 3.06+/-0.79 m x s(-1) (P < or = 0.008). Blood samples were taken at rest before and after the training programme. The following blood parameters were determined: leucocyte count, differential leucocyte count, lymphocyte subpopulations [CD14 positive (+)/CD45+, CD4+/ CD25+, CD8+, CD16+/CD122+]. Whole blood cultures were stimulated with lipopolysaccarides [interleukin (IL)-1 beta and IL-6] and staphylococcal enterotoxin B [IL-2, soluble interleukin 2 receptor (sIL2-R) and interferon (IFN)-gamma]. Cytokine concentrations in the supernatants were measured using an enzyme-linked immunosorbent assay. The white blood cell count, differential leucocyte count, lymphocyte subset distribution and the expression of the CD25 and CD122 antigen on lymphocytes were unchanged by training. After the training programme the IL-1 beta production changed significantly [1496 (SD 264) pg ml(-1) before, compared to 2127 (SD 672) pg ml(-1) after training, P < or = 0.008]. In the control group these parameters remained unchanged. With respect to changes in the values in both groups the syntheses of IL-1 beta (P < or = 0.023) and IL-6 (P < or = 0.021) were significantly higher after regular training. The syntheses of IL-2, sIL-2 and INF-gamma were not significantly influenced. Regular endurance exercise influenced the in vitro production of monocyte derived cytokines, while the effect of exercise on the cytokines synthesized by T-cells appeared to be of lesser importance.

Adult↗
PubMed2005

Statistical process control for radiotherapy quality assurance.

Every quality assurance process uncovers random and systematic errors. These errors typically consist of many small random errors and a very few number of large errors that dominate the result. Quality assurance practices in radiotherapy do not adequately differentiate between these two sources of error. The ability to separate these types of errors would allow the dominant source(s) of error to be efficiently detected and addressed. In this work, statistical process control is applied to quality assurance in radiotherapy for the purpose of setting action thresholds that differentiate between random and systematic errors. The theoretical development and implementation of process behavior charts are described. We report on a pilot project is which these techniques are applied to daily output and flatness/symmetry quality assurance for a 10 MV photon beam in our department. This clinical case was followed over 52 days. As part of our investigation, we found that action thresholds set using process behavior charts were able to identify systematic changes in our daily quality assurance process. This is in contrast to action thresholds set using the standard deviation, which did not identify the same systematic changes in the process. The process behavior thresholds calculated from a subset of the data detected a 2% change in the process whereas with a standard deviation calculation, no change was detected. Medical physicists must make decisions on quality assurance data as it is acquired. Process behavior charts help decide when to take action and when to acquire more data before making a change in the process.

Humans↗
PubMed1990

Methylxanthines elevate reinforcement threshold for electrical brain stimulation: role of adenosine receptors and phosphodiesterase inhibition.

Caffeine increases reinforcement threshold in a brain stimulation procedure that allows the rat to self-regulate the intensity of electric current delivered via an electrode in the medial forebrain bundle. In order to determine the generality of that finding, we used this same autotitration procedure to assess the behavioral effects of 5 methylxanthines in addition to caffeine. All of the methylxanthines produced significant dose-dependent elevations of reinforcement threshold with the following order of potency: 7-(beta-chloroethyl)theophylline greater than isobutylmethyl-xanthine greater than 1,7-dimethylxanthine greater than theophylline greater than caffeine greater than 8-chlorotheophylline. This order of potency correlates significantly with the reported order of potency for inhibiting adenosine-stimulated cAMP, an effect mediated by the adenosine A2 receptor. Some of the behavioral effects of methylxanthines have been attributed to antagonism of adenosine receptor binding and inhibition of phosphodiesterase. The nonxanthine phosphodiesterase inhibitors papaverine and Ro 20-1724, had small but significant effects on reinforcement threshold, papaverine increasing it and Ro 20-1724 decreasing it. Thus, as a pharmacologic class, methylxanthines appear to increase reinforcement threshold, an effect which may be mediated via adenosine receptor antagonism but probably not by inhibition of phosphodiesterase.

Animals↗
PubMed1994

Orientation discrimination of motion-defined gratings.

Spatial boundaries can be defined by discontinuities in motion. However, several types of motion contrast exist, each corresponding to the involvement of different spatio-temporal cues. We examined the contribution of two motion cues: a difference in direction of motion (relative motion) and a dynamic occlusion cue. We measured just noticeable differences in the orientation of boundaries defined by one or both of these visual cues. Just noticeable differences in orientation were similar to those reported for luminance gratings, and the presence of two cues in place of one, lowered the thresholds. These results show that relative motion as well as dynamic occlusion can yield precise spatial boundary information.

Adult↗
PubMed2002

Focal cooling suppresses spontaneous epileptiform activity without changing the cortical motor threshold.

PURPOSE: Focal cerebral cooling has been shown to reduce epileptiform activity in animals. There are, however, few reports of this phenomenon in humans. METHODS: Electrocorticography was performed before resection of a right frontal tumor in a patient with partial seizures. Cold saline was applied to the interictal spike focus, and its effect on the epileptiform discharges was observed. RESULTS: Application of cold saline to the spike focus resulted in a transient, complete cessation of spiking. This effect was reproduced with a second application of cold saline. The motor threshold for electrical stimulation remained unchanged during the application of saline. CONCLUSIONS: In this patient with tumor-related epilepsy, focal cooling of the cortex reproducibly abolished interictal epileptiform discharges without changing the motor threshold to electrical stimulation.

Adult↗