Thy Sheng Lin

Time-course analysis of stretch reflexes in hemiparetic subjects using an on-line spasticity measurement system.

Spasticity after a stroke is usually assessed in a score form by subjectively determining the resistance of a joint to an externally imposed passive movement. This work presents a spasticity measurement system for on-line quantifying the stretch reflex of paretic limbs. Four different constant stretch velocities in a ramp-and-hold mode are used to elicit the stretch reflex of the elbow joint in spastic subjects. The subjects are tested at supine position with the upper limb stretched towards the ground, in contrast with the horizontally stretched movement used in other studies. By subtracting the baseline torque, reflex torque measured at a selected low stretch velocity of 5 deg/sec, the influence of gravity torque and inertial in vertical stretching mode can be minimized. The averaged speed-dependent reflex torque (ASRT), defined as the measured torque deviated from the baseline torque, is used for quantifying the spastic hypertonia. Four subjects having incurred cerebrovascular accident (CVA) are recruited for time-course study in which the measurements are taken at 72 hours, one week, one month, three months, and six months after onset of stroke. During the development of spasticity, the changes of ASRT and velocity sensitivity of ASRT of the involved and the intact elbow joints are discussed.

Epidemiological Study on the Effect of Pre-Hypertension and Family History of Hypertension on Cardiac Autonomic Function

OBJECTIVESnThis study sought to examine the hypothesis that cardiac autonomic function (CAF) is altered in pre-hypertensive subjects and normotensive subjects with a family history of hypertension (FHH).nnnBACKGROUNDnThe findings on the FHH effect in CAF have been inconsistent, and little is known about altered CAF in pre-hypertensive subjects under The Seventh Report of the Joint National Commission on High Blood Pressure criteria of normotension and pre-hypertension.nnnMETHODSnA total of 1,436 community dwellers were classified as having normotension without FHH (NT[-]), normotension with FHH (NT[+]), pre-hypertension, and hypertension. Cardiac autonomic function was determined by standard deviation of RR intervals (SDNN), power spectrum in low frequencies (LF) and high frequencies (HF) and LF/HF ratio in supine position for 5 min, the ratio between the longest RR interval at approximately the 30th beat and the shortest RR interval at approximately the 15th beat after standing (30 max/15 min ratio), and the ratio between the longest RR interval during expiration and the shortest RR interval during inspiration (E/I ratio).nnnRESULTSnThere was a significant difference in all CAF indexes among subjects with NT(-), NT(+), pre-hypertension, and hypertension. Multivariate analyses with an analysis of covariance model showed that 30 max/15 min ratio, E/I ratio, and HF power decreased in subjects with NT(+), pre-hypertension, and hypertension when compared with NT(-) subjects. Pre-hypertensive and hypertensive subjects displayed higher square roots of LF/HF ratios. Only pre-hypertensive subjects had higher LF power.nnnCONCLUSIONSnOur study provides evidence that CAF plays a role in pre-hypertension and that altered autonomic function is already present in subjects with FHH. An autonomic imbalance shifting with augmented sympathetic tone was more enhanced in pre-hypertension.

Altered Cardiac Autonomic Function May Precede Insulin Resistance in Metabolic Syndrome

BACKGROUNDnPrevious studies on the change of cardiac autonomic function and insulin resistance in metabolic syndrome recruited subjects with cardiovascular-related disease and defined metabolic abnormality with a more severe cutoff. We explored the alteration of cardiac autonomic function and insulin resistance in predisease community dwellers with different numbers of metabolic abnormalities.nnnMETHODSnA total of 1298 subjects were classified as none (n=539), one (n=378), 2 (n=218), and 3 or more metabolic abnormalities (n=154). Insulin resistance was calculated by homeostatic model assessment. Cardiac autonomic function included 5-minute standard deviation of R-R interval, low- and high-frequency power spectrum, and low-/high-frequency power spectrum ratio, the ratio of the longest R-R interval around the 30th beat and the shortest R-R interval around the 15th beat after standing, and the ratio of the longest expiratory R-R interval to the shortest inspiratory R-R interval during deep breathing.nnnRESULTSnSubjects with a single metabolic abnormality or more had a lower standard deviation of R-R interval and expiratory/inspiratory ratio than subjects without metabolic abnormality in multivariate analysis. Subjects with 3 or more metabolic abnormalities had a higher low-/high-frequency power spectrum ratio, but a lower high-frequency power. Insulin resistance was higher in groups with 2 metabolic abnormalities or more, but not in the group with one metabolic abnormality, than those without metabolic abnormality.nnnCONCLUSIONSnCardiac autonomic function altered in predisease subjects with one or more metabolic abnormalities, while insulin resistance existed in subjects with 2 or more metabolic abnormalities. Thus, autonomic function change may precede insulin resistance in the initiation of metabolic syndrome.

Delayed neuropathy and myelopathy after organophosphate intoxication.

To the Editor: Massive organophosphorus-compound intoxication is relatively common. Although uncommon, delayed neurotoxicity may also occur in humans.1 Persons with organophosphorus-compound poisoning have acute toxic effects, with a cholinergic crisis due to inhibition of acetylcholinesterase. Some persons subsequently have organophosphate-induced delayed neuropathy, which may be related to the inhibition of neurotoxic esterase.2 Organophosphate-induced delayed neuropathy results in damage to both the peripheral and the central nervous systems.3 The exact sequence of lesions in these systems remains controversial, and few reports have discussed central nervous system neuropathological changes in humans. We describe a patient who had a classic acute cholinergic crisis .xa0.xa0.

Multielectrode surface EMG for noninvasive estimation of motor unit size.

To noninvasively estimate the motor unit size, we present a novel surface electromyographic (EMG) measurement system consisting of a surface multielectrode with four‐pin electrodes and a pair of surface‐disk electrodes. Surface motor unit action potentials (MUAPs) were recorded with the multielectrode, in the so‐called multielectrode surface EMG (MSEMG), which was spatially filtered to localize the sensing area and reduce the noise. In addition, a modified decomposition algorithm, considering the geometrical configuration of the multielectrode, was designed to identify the individual MUAPs in the measured MSEMG. The identified MUAP was subsequently used as the triggering source for the EMG signals recorded by the surface‐disk electrodes. From a pool of 34 subjects with neuromuscular diseases and 14 normal subjects, the median amplitudes of surface‐disk EMG after spike‐triggered averaging, called MSEMG‐MUAP, correlated well (r = 0.82, P < 0.0001) with those of macro EMG. Moreover, the MSEMG‐MUAP recording during a ramp force contraction exhibited the common size principle phenomenon during motor unit recruitment. The results of this study demonstrate that the MSEMG‐MUAP measurement is a feasible approach for estimating the motor unit size from the skin surface.

A retrospective study of catastrophic invasive fungal infections in patients with systemic lupus erythematosus from southern Taiwan

As very few large scale publications of invasive fungal infection (IFI) have been reported in lupus patients from individual medical centers, a retrospective study was performed from 1988 to 2009 in southern Taiwan. Demographic characteristics, clinical and laboratory data, and mycological examinations were analyzed. Twenty cases with IFI were identified in 2397 patients (0.83% incidence). There were 19 females and one male with an average age of 31.8 ± 12.6. Involved sites included eight disseminated cases, six central nervous system, four lungs, one abdomen and one soft tissue. IFI contributed to a high mortality with 10 deaths (50%), and there were no survivors for the disseminated cases and Candida-infected patients. High activity (Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) > 8) was noted in 50% of IFI episodes. The survival from IFI diagnosis to death was only 7.7 ± 4.2 days, all in a rapid course. No statistical difference was found between survivors and non-survivors when comparing their SLEDAI. Eighty-five percent of IFI episodes under high dosages of corticosteroids therapy and 95% of patients had lupus nephritis. There was an increased risk of IFI in the lupus patients receiving high daily dosage of prednisolone therapy. Critical information from analyses of the present large series could be applied into clinical practices to reduce the morbidity and mortality in such patients.

Epidemiological evidence of altered cardiac autonomic function in overweight but not underweight subjects.

Background:Little is known about the altered cardiac autonomic function (CAF) across different levels of body mass index (BMI), including underweight, normal weight, overweight and obesity. This study provides a thorough analysis to clarify the CAF change in subjects with underweight, overweight and obesity.Methods:According to the World Health Organization (WHO) Asia-Pacific BMI cutoffs, a total of 1437 participants were classified as underweight (n=74), normal weight (n=588), overweight (n=313), obesity I (n=390) and obesity II (n=72). CAF was determined by standard deviation of normal-to-normal (SDNN) intervals or RR intervals, power spectrum in low (LF) and high frequency (HF) (LF, 0.04–0.15u2009Hz; HF, 0.15–0.40u2009Hz), and LF/HF ratio at supine for 5u2009min, the ratio between the 30th and the 15th RR interval after standing from the supine position (30/15 ratio) and the average heart-rate change while taking six deep breaths in 1u2009min (HRDB).Results:There were significant differences in age, gender, socioeconomic status, blood pressure, HOMA insulin resistance index, fasting glucose, cholesterol, triglyceride and high-density lipoprotein (HDL)-C, and the prevalence of hypertension, ischemic/left bundle branch block (LBBB) electrocardiography (EKG) pattern, current smoking and alcohol use among subjects with underweight, normal weight, overweight, obesity I and II. Univariate analysis showed that SDNN, HRDB, HF power and the square root of the LF/HF ratio differed among these five groups. Multivariate analysis showed that obesity I and II were inverse correlates of HRDB and HF power. Overweight, obesity I and II were positively associated with the square root of the LF/HF ratio. No BMI status was related to SDNN, 30/15 ratio or LF power. Underweight was not the independent correlate of any CAF indices.Conclusions:The risk for altered CAF is significant in overweight and obese subjects, independent of cardiovascular risk factors. Underweight is not apparently associated with CAF change.

Deficiency of electroneutral K+-Cl- cotransporter 3 causes a disruption in impulse propagation along peripheral nerves.

Nerve conduction requires the fine tuning of ionic currents through delicate interactions between axons and Schwann cells. The K+–Cl− cotransporter (KCC) family includes four isoforms (KCC1–4) that play an important role in the maintenance of cellular osmotic homeostasis via the coupled electroneutral movement of K+ and Cl− with concurrent water flux. Mutation in SLC12A6 gene encoding KCC3 results in an autosomal recessive disease, known as agenesis of the corpus callosum associated with peripheral neuropathy. Nevertheless, the role of KCC3 in nerve function remains a puzzle. In this study, the microscopic examination of KCC isoforms expressed in peripheral nerves showed high expression of KCC2–4 in nodal segments of the axons and in the perinucleus and microvilli of Schwann cells. The KCC inhibitor [[(dihydroindenyl)oxy]alkanoic acid] but not the Na+–K+–2Cl−‐cotransport inhibitor (bumetanide) dose‐dependently suppressed the amplitude and area of compound muscle action potential, indicating the involvement of KCC activity in peripheral nerve conduction. Furthermore, the amplitude and area under the curve were smaller, and the nerve conduction velocity was slower in nerves from KCC3−/− mice than in nerves from wild‐type mice, while the expression pattern of KCC2 and KCC4 was similar in KCC3 kockout and wild‐type strains. KCC3−/− mice also manifested a prominent motor deficit in the beam‐walking test. This is the first study to demonstrate that the K+–Cl− cotransporter activity of KCC3 contributes to the propagation of action potentials along peripheral nerves.

Analysis of motor unit firing patterns in patients with central or peripheral lesions using singular-value decomposition

We applied the singular value decomposition (SVD) method to study single motor unit firing patterns. Two projects were carried out: (1) a computer simulation study to confirm the meanings of two SVD parameters, the eigenvalue corresponding to the positive‐slope eigenvector (PEV) and that corresponding to the negative‐slope eigenvector (NEV); and (2) a clinical study for which electromyographic (EMG) recordings were made from first dorsal interosseous muscle in patients with stroke, myopathies, or neuropathies and in healthy control subjects. Results of computer simulation reveal that the NEV reflects the amount of instantaneous firing variability, whereas the PEV/NEV (P/N) ratio exhibits the relative effect of a trend in the firing pattern. In human studies, the P/N ratio of stroke patients was significantly higher than that of the controls, whereas their NEV was comparable. By contrast, in the myopathy and neuropathy groups, the NEV increased significantly, whereas the P/N ratio did not. These results suggest that the SVD method decomposes the motor unit (MU) firing variation into two components and that the mechanism for increased firing variability is different for supraspinal and spinal–infraspinal lesions.

Value of dermatomal somatosensory evoked potentials in detecting acute nerve root injury: an experimental study with special emphasis on stimulus intensity.

Study Design. Dermatomal somatosensory-evoked potentials (D-SSEPs) in rats were recorded at the spinal level after L2-, L4-, and L5-dermatome stimulation. Pre- and post-transection patterns and rates of change of corresponding nerve roots were compared to determine accuracy. Objective. To investigate characteristics and normal values of D-SSEP elicited from lower limb dermatomes; to determine specificity, sensitivity, and utility of D-SSEP in detecting single-nerve root injury; and to determine optimal stimulation intensity. Summary of Background Data. D-SSEP allows assessment of single nerve root-specific pathways, electrodiagnosis of lumbosacral radiculopathy, and intraoperative neuromonitoring. Unacceptably low sensitivity and specificity make its value suspect. D-SSEP is insufficiently documented. Methods. Eight rats were used to specify a standard D-SSEP waveform and its characteristics, evaluate stimulation sites and strengths, and determine appropriate stimulation and recording techniques. The L4 nerve root was transected in one group of 8 rats and the L5 in another. D-SSEPs were recorded at the thoracolumbar junction following submaximal and supramaximal stimulation at the L2, L4, and L5 dermatomal fields. Potentials recorded before transection, and immediately, 1 hour, and 1 week post-transection were compared. Results. Reproducible spinal responses were obtained in all rats on all tests. Stimulation intensity, but not rates, affected amplitude. Relative amplitude reductions in transected-root D-SSEP were larger using submaximal than supramaximal intensity. D-SSEP elicited by submaximal than supramaximal intensity produced fewer false negatives and false positives. Conclusions. D-SSEP is valuable for detecting acute single nerve root injury. In clinical settings, submaximal dermatomal stimulation identifies conduction abnormalities more consistently and with fewer false negatives and false positives than does supramaximal stimulation. We recommend submaximal stimulation.