Vibratory perception threshold in patients with mild multiple sclerosis

The vibratory perception threshold (VPT) was measured bilaterally on both the upper and lower extremity in 69 patients with mild multiple sclerosis. In the case of the lower extremities the VPT measurements were closely correlated with qualitative vibratory perception measurements performed with a tuning fork; in the upper extremities the association was weak. The VPT was abnormal at least in one extremity in 38% of the patients. Quantitative VPT measurement seem to be a suitable technique for the detection of sensory symptoms of central origin.     

Factor analysis of thermal and vibration thresholds in young patients with Type 1 diabetes mellitus.

AIMS: To identify factors that represent relationships among sets of interrelated thermal and vibration threshold variables and to find clinical correlates that are significantly associated with these factors. METHODS: Thermal and vibration perception thresholds were tested in the hands and feet of Type 1 diabetic patients treated in an outpatient clinic for juvenile-onset diabetes. Factor analysis was used to identify factors that represent relationships among sets of thermal and vibration threshold variables. RESULTS: One hundred and forty-eight patients (47.3% males, median current age 22.3 years and median duration of diabetes 11.4 years) were evaluated. Three factors explained 77% of the total variance: 'hand sensation' factor, underlying cold, warmth and vibration perception thresholds in the hand; 'foot sensation' factor, underlying the same sensory thresholds in the foot; and 'heat-related pain' factor, underlying heat pain perception threshold in both limbs. The 'foot sensation' factor was the only factor that significantly correlated with diabetes-related variables (e.g. duration and cumulative glycaemic control of the disease) and concurrent diabetic microangiopathy. Male sex was associated with higher values of the 'heat-related' factor, while the 'hand sensation' factor did not correlate with any of the study variables. CONCLUSIONS: The distribution of the various thermal and vibration threshold variables according to the three factors may point at length-dependent mechanism of axonal degeneration. Cold, warmth and vibration perception thresholds in the foot may be the only valuable psychophysical parameters in the evaluation of early sensory impairment associated with diabetes.     

定量温度觉阈值检查在糖尿病周围神经病诊断中的应用

目的 探讨定量温度觉阈值检查(QTT)在糖尿病周围神经病诊断中的应用价值.方法 选取有神经系统症状的169例糖尿病患者[根据病程分为≤5年(69例)和>5年(100例)2个亚组;根据神经传导检测(NCS)是否存在异常分为正常组(45例)和异常组(124例)],并选取年龄匹配的53名健康对照,进行手及足背的冷感觉阈值(CT)、热感觉阈值(WT)、冷痛觉阈值(CPT)、热痛觉阈值(WPT)测定.结果 病程≤5年糖尿病组的手及足背CT[分别为(29.6±1.4)、(26.5±4.3)℃]、WT[(35.9±3.0)、(41.3±4.0)℃]高于健康对照组[手背CT(30.2±1.2)℃,足背CT(29.1±1.5)℃;手背WT(35.0±1.9)℃,足背WT(36.5±1.5)℃;t=3.27、6.63、2.80、8.61,均P<0.05],病程>5年糖尿病组[手背CT(28.2±4.0)℃,足背CT(23.1±7.9)℃;手背WT(37.0±4.7)℃,足背WT(42.6±4.2)℃]高于病程≤5年糖尿病组(t=4.09、4.63、2.55、2.68,均P<0.05),NCS正常的糖尿病组[手背CT(29.5±1.8)℃,足背CT(27.0±4.6)℃;手背WT(35.0±1/9)℃,足背WT(40.9±3.8)℃]高于健康对照组(t=3.22、4.17、3.51、9.95,均P<0.01),差异具有统计学意义.糖尿病组QTT的异常率比NCS的异常率更高,病程>5年糖尿病组NCS、QTr的异常率较病程≤5年糖尿病组高;糖尿病组WT异常率(86.4%,146/169)高于CT异常率(68.1%,115/169,x2=15.49,P<0.01),足背刺激QTT的异常率高于手背刺激QTT的异常率.与健康对照组相比,糖尿病患者的痛觉阈值较高.结论 QTT较常规NCS在糖尿病周围神经病诊断中具有更高的灵敏度,可作为常规NCS的必要补充.下肢热感觉阈值检查是诊断糖尿病周围神经病的敏感指标.     

Skin profiles during sinusoidal vibration of the fingerpad

Summary Skin on the fingertips of humans and monkeys was stimulated by a probe vibrating with a sinusoidal displacement. The probe and the skin were illuminated stroboscopically and were viewed through a dissecting microscope. The stroboscope was triggered by the sinusoidal generator via a digital delay, so that the position of both the probe and the skin could be measured at regular intervals during the cycle. Six frequencies and 3 amplitudes of vibration were used. During a portion of the cycle the probe and the skin separated, so that the skin waveform was a clipped sinusoid. An increase in stimulus frequency increased the fraction of the cycle during which the probe and the skin were separated. Adding a static pre-indentation to the vibration reduced this fraction, and for this condition a decrease in vibratory amplitude also decreased the fraction. Thus the skin motion contained harmonics that were not present in the probe motion, and the harmonic content differed for different stimulus conditions.     

Electrochemical Properties of Platinum, Glassy Carbon, and Pyrographite as Stimulating Electrodes

Presently, platinum, platinum-iridium, and carbon (glossy and pyrographite) are the preferred materials to be used as stimulating electrodes. Electrochemical tests revealed higher thresholds with Pt-Ir, which possibly are a result of excessive connective tissue growth. A porous structure appears to be preferred especially if the electrode materials are smooth and activated glassy carbon. When comparing power consumption, glassy carbon was found to be a superior electrode material.     

Six Years' Experience with Atrial Leads

This report describes a six-year experience with atrial leads consisting of 329 unipolar and 12 bipolar leads implanted in 302 patients. A variety of lead types were used: passive fixation with preformed J [including tines or fins in a solid electrode]; porous tip electrodes with small tines, most of which were also preformed; active fixation leads (both straight and preformed); and finally bipolar leads, which were all preformed. No statistical differences were found between the P waves recorded from various unipolar leads. Similarly, there were no statistical differences found between voltage or energy thresholds between the different types of leads. The complication rate included 6.3% of early complications and 4.7% late complications for a total complication rate of 11%. This compares to a complication rate of 2% for ventricular leads. Thus, the complication rate of atrial leads is higher than ventricular leads; this must be considered when selecting a pacemaker system for a given patient.     

Multiple clinical and paraclinical analyses of chronic tension-type headache associated or unassociated with disorder of pericranial muscles

Thirty-two female patients fulfilling the diagnostic criteria of chronic tension-type headache underwent multiple clinical (severity index before and after biofeedback therapy; anxiety score) and paraclinical (pericranial EMG levels and pressure-pain thresholds, temporalis exteroceptive silent period) assessments. Twenty-three patients (72%) had at least one increased EMG level and/or at least one decreased pain threshold and qualified for the subgroup" associated with disorder of pericranial muscles" (code 2.2.1). Nine patients (28%) were within the normal range for both investigations and would have been classified in the subgroup "unassociated with such disorder" (code 2.2.2). No significant differences were found between these two groups of patients for headache severity, anxiety, response to biofeedback therapy or duration of temporalis second exteroceptive silent period. The various clinical and paraclinical parameters were not significantly correlated to each other. It is therefore suggested that the subdivision of chronic tension-type headache in two subgroups based on pericranial EMG levels and/or pain sensitivity might be artificial. Since both of the latter and temporalis silent periods vary independently, they appear complementary in the study of tension-type headache patients and probably represent peripheral abnormalities, which are induced to varying intensities by a common central nervous system dysfunction.     

Clinical Results of Low Energy Unipolar or Bipolar Activated Carbon Tip Leads

Biocompatibility of carbon makes it a good candidate for a pacing electrode. Moreover, activation of the electrode creates microporosity, which increases the surface area and reduces polarization losses. Chronic thresholds noninvasively measured on a large population of patients implanted with vitreous carbon electrodes of one manufacturer are significantly lower than those caused by polished platinum tip electrodes of the same manufacturer with similar electrode design.     

Long-Term Threshold Stability with Porous Tip Electrodes

Experience with 163 unipolar tined porous endocardial electrodes is reported. One patient required repositioning of the electrode because of exit block. There were no other complications in the entire series of patients. All of the patients had low chronic stimulation thresholds. The mean pulse width 24 hours after implantation was 0.0534 ± 0.0128 ms. Seventy-four patients were restudied six months after implantation. The mean pulse width threshold was then 0.07432 ± 0.0775 ms. Fifty-four patients were evaluated one year after lead implantation. The mean pulse width threshold was then 0.0611 ± 0.0230 ms. The pulse generator was reprogrammed to a lower pulse width in all of the patients. This permitted a substantial prolongation of the pulse generator life. The cost effectiveness of the pulse generator was also greatly improved by pacing with reduced pulse widths. In an additional 16 patients, the voltage amplitude was reduced from 5.0 volts to 2.5 volts. This permitted an even greater increase in the pulse generator longevity.