Percentage Change In Amplitude Research Articles

A New Diagnostic Medium for Cervical Spondylotic Myelopathy: Dynamic Somatosensory Evoked Potentials

To identify and reveal the sensitivity and efficiency of dynamic somatosensory evoked potentials (DSSEPs) in the diagnosis of cervical spondylotic myelopathy (CSM). This retrospective study included 31 CSM and 15 control patients. All patients received SSEP examination with stimulation of median and ulnar nerves at neutral, flexed, and extended cervical positions; latency and amplitude were recorded at the C2 and C5 spinous processes and in the scalp over the primary sensory area (C3'/4'). The percentage changes in latency and amplitude with dynamic motion were examined for each lead and compared between groups; the diagnostic cutoff values were determined using receiver operating characteristic curve analysis. All the patients with CSM received surgeries and were followed up for 1 year. Amplitude parameters varied with a dynamic position in both groups; all recorded dynamic SSEP indices except right median stimulus recorded at C5 spinous process, right ulnar stimulus recorded at scalp point C3, and right ulnar stimulus recorded at C2 spinous process were significantly different between groups (P < 0.05), but latency was not (P > 0.05). At the neutral position, the amplitude of left media stimulus recorded at C2 spinous process (LMC2) was associated with CSM, but with low diagnostic accuracy (area under the curve= 0.199). At a dynamic position, the percentage change in amplitude of LMC2 and of left ulnar stimulus recorded at C2 spinous process (LUC2) were determined to be diagnostic of CSM (P < 0.05), with areas under the curve of 0.891 and 0.912, respectively. Both records had high sensitivity and specificity in the diagnosis of CSM; the diagnostic cutoff values of LMC2 and LUC2 were calculated as 10.2% and 19.25%, respectively. The percentage change in amplitude was obvious during cervical dynamic motion, with records from LMC2 and LUC2 being predictive of CSM diagnosis; dynamic SSEPs provided a simple, accurate, and noninvasive supplementary test for the diagnosis of complicated CSM.

Effect of Topical Anesthesia Using an Adhesive Patch and Anesthetic Solution.

We analyzed trigeminal somatosensory evoked potentials (TSEP) to the alveolar mucosa to investigate the efficacy of an amide local anesthetic, 2% lidocaine hydrochloride with 12.5 μg/mL epinephrine (Lido treatment) as a topical anesthetic. Eighteen consenting healthy adult volunteers were enrolled. A volume of 0.06 mL of Lido, 0.06 g of 20% benzocaine, or 0.06 mL of physiological saline (control) was instilled onto a hemostatic adhesive patch, which was then applied to the alveolar mucosa at the maxillary right canine for 5 minutes. An electrical stimulus approximately 5 times that of the sensory threshold was applied using a surface stimulation electrode. The trigeminal somatosensory evoked potential was recorded immediately, 5 minutes, and 10 minutes after removal of the patch. Positive P125 and P310 peaks and negative N100 and N340 peaks were observed as a result of the electrical stimulation. A significant decrease in the percentage change in amplitude of N100-P125 was observed in the Lido treatment immediately, 5 minutes, and 10 minutes after patch removal. In the Lido treatment, trigeminal somatosensory evoked potential amplitude at N100-P125 decreased significantly, suggesting that topical anesthesia produced by an amide local anesthetic may have a topical anesthetic effect as potent as that produced by an ester local anesthetic.

Serotonergic modulation of the responses to excitatory amino acids of rat dorsal horn neurons in vitro: implications for somatosensory transmission.

Serotonin (5-HT) is one of the major transmitters involved in supraspinal control of somatic sensation and nociception. The aim of the present study was to investigate if the 5-HT-induced modulation of sensory transmission in the dorsal horn could be due to regulation of neuronal responses to excitatory amino acids. Experiments were performed in an in vitro preparation of the young rat spinal cord. Responses to dorsal root stimulation (DR-EPSP) and to droplet application of N-methyl-D-aspartic acid (NMDA) and alpha-amino-2,3-dihydro-5-methyl-3-oxo-4-isoxazolepropanoic acid (AMPA) were obtained by means of intracellular recordings of dorsal horn neurons. Bath applications of 5-HT (50 microM) generally caused reductions in amplitude and integrated area of DR-EPSPs and of responses to NMDA but the responses to AMPA were unaltered. A linear correlation was found between the effects of 5-HT on the DR-EPSP and on the NMDA response measured as percentage change in amplitude (r2 = 0.45; P < or = 0.01) and integrated area (r2 = 0.77; P < or = 0.001). The NMDA receptor antagonist d-AP5 (50 microM) completely abolished NMDA responses and caused a depression of the DR-EPSP similar to that of 5-HT. The 5-HT1 receptor agonist 5-carboxamidotryptamine (5-CT; 1 microM) mimicked the depressant effects of 5-HT but had a stronger depressant action on the DR-EPSP than 5-HT. The depression of NMDA responses induced by 5-HT and 5-CT was tetrodotoxin (1 microM) resistant. It is concluded that 5-HT-induced depression of NMDA responses explains partially the depressant action of 5-HT on dorsal horn synaptic transmission activating a postsynaptic site sensitive to 5-CT. The possible activation of coadjuvant mechanisms is discussed.

Influence of positive inotropic agents on intracellular calcium transients. Part I. Normal rat heart

This study, which was designed to evaluate the effects of positive inotropic agents on intracellular calcium transients ([Ca 2+]i), is the first to analyze calcium transients in the whole heart. The positive inotropic agents that augment intracellular cyclic adenosine monophosphate (cAMP) (dibutyryl CAMP, amrinone, and isoproterenol) caused an increase in developed pressure and [Ca 2+]i transients and a decrease in diastolic [Ca2+]i. On the other hand, the glycoside digoxin and the a-adrenoceptor agents, phenylephrine and dobutamine, also caused an increase in [Ca 2+]i transients and developed pressure. However, unlike the agents that increase [cAMP]i, they induced an elevation in diastolic [Ca 2+]i. With all the positive inotropic agents, developed pressure increased commensurately with the percentage changes in amplitude of the [Ca 2+]i transients.