Yew ng Lo

The effect of acupuncture on motor cortex excitability and plasticity

Acupuncture has been used extensively in facilitating motor recovery after stroke. Its mechanism of action remains uncertain. In this sham-controlled study, we demonstrate for the first time that acupuncture has a real and enduring effect on motor cortex functional changes, in terms of cortical excitability and output mapping using transcranial magnetic stimulation.

Sensitivities of sensory nerve conduction study parameters in carpal tunnel syndrome.

Summary: It is generally accepted that median sensory nerve conduction studies are more sensitive than motor nerve conduction studies in the electrodiagnostic evidence of carpal tunnel syndrome (CTS). This study was conducted to compare the sensitivities of various parameters of sensory nerve conduction studies in the diagnosis of CTS.This prospective study included 88 consecutive patients (151 hands) with CTS and 106 control subjects. CTS was diagnosed clinically by two neurologists. Median sensory nerve responses with wrist stimulation were determined. The onset and peak latencies, peak-to-peak amplitudes, negative peak duration, and area were measured. The differences between the peak and onset latencies were also calculated as a measure of waveform temporal dispersion. Among each measured parameter, values between the 2.5th and the 97.5th percentile range of the control subjects served as the normal limits.Among the 151 hands with suspected CTS, five (3.3%) had normal electrodiagnostic studies and 146 (96.7%) had at least one abnormal electrodiagnostic study. Among the 146 hands with an abnormality, 138 had abnormal onset latency, 143 had abnormal peak latency, and 88 had abnormal difference between peak and onset latency. In addition, 87 had abnormal amplitude, 70 had abnormal duration, and 59 had abnormal area. The sensitivity was 91.4% for onset latency, 94.7% for peak latency, 58.3% for difference between peak and onset latency, 57.6% for amplitude, 46.4% for duration, and 39.1% for area.Our study shows that in patients with CTS, the most sensitive sensory nerve conduction parameter is the peak latency. Studying various additional sensory nerve conduction parameters did not significantly increase the diagnostic yield.

The lower subscapular nerve conduction studies and utilisation in brachial plexopathy evaluation

OBJECTIVE To define the optimal nerve conduction study (NCS) method of lower subscapular nerve and evaluate its clinical utility. METHODS Thirty healthy adults (8 males) with a mean age of 45.2+/-16.5 (range, 21-75) years were recruited in this study. A total of sixty nerves were studied using the Dantec Counterpoint EMG machine (Dantec, Skovlunde, Denmark). 6 patients with clinical and electrodiagnostic evidence of brachial plexopathy were also evaluated. RESULTS The mean+/-2 standard deviation values of the distal latencies, base-to-peak amplitudes and inter-side amplitude ratio were 2.38+/-0.52 (range, 1.80-2.90) ms, 13.10+/-5.10 (range, 8.70-21.10) mV and 0.93+/-0.12 (range, 0.67-1.00), respectively. There was a significant correlation between the subject age and the base-to-peak amplitudes. All 6 patients with brachial plexopathy had reduced base-to-peak amplitudes as well as inter-side amplitude ratio of less than 0.67 (the normal limits for control). CONCLUSION The lower subscapular NCS were satisfactorily recordable and well tolerated. It was useful in evaluation of patients with brachial plexopathy.

Non-contact parametric estimation and localization of human head for transcranial magnetic stimulation (TMS)

Transcranial magnetic stimulation (TMS) has been gaining popularity in various neurological treatments and an automated platform with better precision is desired. This paper proposes a dexterous articulated robotic arm with TMS coils as the end-effectors. Most robotic arm based positioning systems utilize vision feedback from stationary cameras for dynamic positioning, but these are not suitable for clinics with limited space. In this paper, a compact approach to identify the size, position and orientation of the patients head relative to a robotic arm using a non-vision, range data based system is proposed. An accurate distance measurement sensor is used in tandem with a robotic arm to scan the patients head and produce a growing 3D point cloud. An efficient surface fitting algorithm, taking into consideration the similarity of the human head to an ellipsoid, is presented to simultaneously extract position, orientation and geometrical information of the target head. Simulations and experiments are conducted and promising results are obtained to demonstrate its capability to identify the location and orientation of the patients head.

Cortical Reorganization Is Associated with Surgical Decompression of Cervical Spondylotic Myelopathy

Background. Cervical spondylotic myelopathy (CSM) results in sensorimotor limb deficits, bladder, and bowel dysfunction, but mechanisms underlying motor plasticity changes before and after surgery are unclear. Methods. We studied 24 patients who underwent decompression surgery and 15 healthy controls. Patients with mixed upper and lower limb dysfunction (Group A) and only lower limb dysfunction (Group B) were then analysed separately. Results. The sum amplitude of motor evoked potentials sMEP (p < 0.01) and number of focal points where MEPs were elicited (N) (p < 0.001) were significantly larger in CSM patients compared with controls. For Group A (16 patients), sMEP (p < 0.01) and N (p < 0.001) showed similar findings. However, for Group B (8 patients), only N (p = 0.03) was significantly larger in patients than controls. Group A had significantly increased grip strength (p = 0.02) and reduced sMEP (p = 0.001) and N (p = 0.003) after surgery. Changes in sMEP (cMEP) significantly correlated inversely with improved feeding (p = 0.03) and stacking (p = 0.04) times as was the change in number of focal points (NDiff) with improved writing times (p = 0.03). Group B did not show significant reduction in sMEP or N after surgery, or significant correlation of cMEP or NDiff with all hand function tests. No significant differences in H reflex parameters obtained from the flexor carpi radialis, or central motor conduction time changes, were noted after surgery. Discussion. Compensatory expansion of motor cortical representation occurs largely at cortical rather than spinal levels, with a tendency to normalization after surgery. These mirrored improvements in relevant tasks requiring utilization of intrinsic hand muscles.

A Bayesian framework for calibration and real-time localization of magnetometers using a controllable passive permanent magnet

Magnetic localization systems based on passive permanent magnets (PM) are of great interest due to its ability to provide non-contact sensing and lack of a power requirement of the PM. One sub-problem of particular interest is accurately localizing, in real-time, a single magnetometer with unknown position and orientation, using a passive PM with controllable position and orientation. This is a challenging problem due to the presence of measurement noises and biases, inaccuracy of the magnetic field model, and possible low observability. Bayesian statistical signal processing is a promising approach for this problem, due to its strong mathematical foundation, robustness and suitability for real-time processing. In this work, we develop a Bayesian framework for the individual sensor localization problem which is composed of three parts: magnetic field modeling, sensor calibration, and real-time sensor localization. The effectiveness of the framework is demonstrated using a experimental setup that emulates a possible Transcranial Magnetic Stimulation (TMS) application.

Pregabalin and Radicular Pain Study (PARPS) for Cervical Spondylosis in a Multiracial Asian Population

Background Pain from cervical spondylosis (CS) may result from degenerative spinal canal stenosis (cervical spondylotic myelopathy (CSM)) or lateral recesses compromise, leading to nerve root compression (cervical spondylotic radiculopathy (CSR)). Pregabalin was shown to be effective in randomized, placebo-controlled trials for post-herpetic neuralgia and diabetic neuropathy. We evaluate its efficacy in CS with underlying CSR or CSM in a prospective study comprising Asian patients for the first time. Methods Patients with CS and CSR or CSM (clinical, MRI, or electrophysiological evidence) presenting with neuropathic pain were recruited. We excluded patients with diabetes, underlying neurological disease or who were previously on antiepileptics. Pregabalin 75 mg bd was administered for 4 weeks, after which dosage was increased to 150 mg bd for another 4 weeks if the visual analog scale (VAS) was not reduced by 50%. In addition, we monitored the short form McGill pain questionnaire (SFMPQ) at baseline, 4 weeks and 8 weeks. Mood changes were monitored using the hospital anxiety and depression score (HADS) with an identical timeline. Results We recruited 50 patients, of which 23 completed the trial. Of the 27 who withdrew, 12 (44%) were for somnolence. Thirteen patients’ (54%) dosages remained at 75 mg and 11 patients’ (46%) dosages were escalated to 150 mg bd. There were significantly reducing trends from baseline for VAS (ANOVA, F(1, 21) = 25.4, P < 0.0005), SFMPQ (sensory) (F(1, 22) = 11.2, P = 0.003), and SFMPQ (affective) (F(1, 21) = 10.9, P = 0.008). For VAS, there was significant reduction at 4 weeks (P = 0.001) and 8 weeks (P < 0.0005) compared to baseline. For SFMPQ (sensory), there was significant reduction at 4 weeks (P = 0.01) and 8 weeks (P = 0.006) in scores compared to baselines. For SFMPQ (affective), there was significant reduction at 4 weeks (P = 0.04) and 8 weeks (P = 0.008) in scores compared to baseline. No significant anxiety (F(1, 4) = 1.3, P = 0.32) or depression (F(1, 4) = 0.06, P = 0.82) changes were observed in the HADS. Conclusion Pregabalin is efficacious in alleviation of pain symptoms related to CSR as a first-line single agent, evaluated by quantitative severity and other experiential scales. No significant mood changes reported in other studies were demonstrated. Somnolence was commonest adverse effect leading to high dropout rates, occurring early even at the lowest dose. The findings suggest the need for further studies of efficacy at lower dosages, particularly in the Asian population.

A robust stochastic magnetic field model for sensor network mapping

Magnetic localization systems based on passive permanent magnets (PM) are of great interest due to their ability to provide non-contact sensing and lack of a power requirement of the PM. One sub-problem of particular interest is accurately localizing, in real-time, a single magnetometer with unknown position and orientation, using a passive PM with controllable position and orientation. This is a challenging problem, mainly due to difficulty of designing a magnetic field model that allows high precision localization of a single sensor, but also has other qualities such as low computational complexity and robustness. In this work, we propose a stochastic magnetic field model, based on the dipole model, for the application of mapping a sensor network attached to an object with unknown position and shape. We validate the robustness of the model by testing it with different sensor network mapping configurations.

Superficial Abdominal Reflex

A 59-year-old man presented with a 5-day history of bilateral lower-limb numbness, unsteadiness of gait, and urinary incontinence. A video shows testing for the superficial abdominal reflex.

Predictive Value of Electrophysiology for Presence of Thymic Pathology in Myasthenia Gravis

OBJECTIVE Single fibre electromyography (SFEMG) and repetitive nerve stimulation (RNS) are routinely performed investigations in evaluation of patients with myasthenia gravis (MG). Significant number of MG patients have a thymic pathology. We aimed to explore the relationship between the SFEMG and RNS findings with the presence of thymic pathology. METHODS We studied 159 consecutive patients with MG over a 10 year period. The SFEMG parameters - mean jitter (MJ) and percentage of abnormal fibres (POAF) and the RNS result were correlated with the thymic findings. RESULTS As compared to patients with normal thymus (MJ:58.3 μsec; POAF:63.5%), patients with thymic pathology had a significantly higher MJ (80.9 μsec; p < 0.0005) and POAF (83.5%; p < 0.0005). MG patients with thymic hyperplasia had the highest MJ (87.6 μsec) and POAF (84.4%) followed by patients with thymoma (MJ:78.6 μsec; POAF:83.2%). The MJ and POAF did not correlate with the stage of thymoma. Mean jitter values above 34.9 μsec and POAF above 31% had 100% sensitivity for the presence of thymic pathology. A positive RNS increased the risk of thymic pathology (OR = 3.9, CI = 1.8-8.5) and thymoma. (OR = 3.5; CI = 1.5-8.1). CONCLUSION Electrophysiology could be valuable complimentary tool to identify MG patients at high risk for thymic pathology. However, it does not aid us to identify the exact thymic pathology and does not correlate with the stage of thymoma. All OMG patients with higher MJ and PAOF values should also be screened for thymoma. The results reinforce the immunological role of thymic pathology in neuromuscular transmission interference.