Utility of the cutaneous silent period in the evaluation of carpal tunnel syndrome

Evaluation of the Cutaneous Silent Period in a Healthy Brazilian Population

PURPOSE

To establish cutaneous silent period (CSP) normative values and investigate the variables that may influence them.

METHODS

We tested 41 healthy subjects. All subjects underwent nerve conduction studies, and we evaluated the CSP in both arms.

RESULTS

Four subjects did not have CSP and were excluded. The analyses were performed in the healthy group composed of 23 women and 14 men, with a mean age of 35 (range, 19-64) years. The CSP median duration was 23.2 milliseconds (ms), with 2 to 98th percentile at 11.3 and 48.7 ms. The median onset latency was 87.9 (range, 72.9-109) ms, and the median end latency was 112 (range, 93.8-138) ms. The CSP onset latency positively correlated with height, whereas CSP end latency and duration were weakly but significantly associated with age. Some measurements of ulnar nerve conduction study also correlated with CSP measures. The interrater coefficients for the primary measures of onset and end latency demonstrates the reproducibility of the method.

CONCLUSIONS

The CSP with the fifth digit stimulation and recording from the abductor digiti minimi muscle is a valid diagnostic tool that can be used in clinical practice.

Identification of small diameter nerve fiber damage in hemodialysis patients' hands using the cutaneous silent period

Background

The arteriovenous fistula is the most effective vascular access option for hemodialysis patients. An important and largely unreported concern detected at follow-up is the complaints of tingling or numbness in the hands of those patients. Furthermore, the cutaneous silent period qualifies as a straightforward evaluation of small nerve fiber function. This study aims to evaluate the function of small-diameter nerve fibers in the hands of patients undergoing continuous hemodialysis (HD) on the side with the arteriovenous fistula (AVF) and on the contralateral side.

Results

A cross-sectional study of 40 randomly chosen patients with chronic kidney disease on regular hemodialysis three times weekly the cutaneous silent period (CSP) was recorded on the hand with and without AV fistula. The cutaneous silent period (CSP) CSP was elicited by electrical square pulse stimulation using standard bipolar electrodes. The average cutaneous silent period onset and end latencies demonstrated significant prolongation in the hemodialysis patient group (arteriovenous fistula and non-arteriovenous fistula) compared with the control group. Correlation between cutaneous silent period with hemodialysis duration and adequacy of hemodialysis (KT\V). There was a statistically negative correlation observed between cutaneous silent period onset latency on the arteriovenous side and a positive correlation with KT\V on non-arteriovenous fistula. side.

Conclusions

Hemodialysis patients recommended to undergo regular neurophysiological testing to check for small nerve fiber affection. In particular, measuring the cutaneous Silent period that provides a quick and noninvasive way to rule out small A-delta nerve malfunction. In addition, less nerve injury results from hemodialysis's increased efficiency.

Metabolic syndrome and anthropometric indices in CTS hands: an electrophysiological study

INTRODUCTION

This study aims to evaluate the effect of metabolic syndrome (MetS) and anthropometric indices on carpal tunnel syndrome (CTS).

METHODS

Forty-three healthy controls and 41 CTS patients were enrolled. Complaints of patients were assessed by Boston Questionnaire (BQ). MetS components were investigated. Wrist circumference, wrist depth, wrist width, palm width, and palm length were measured. Routine nerve conduction studies of median and ulnar nerves as well as the "sensitive" comparison tests were performed. Cutaneous silent period (CuSP) was studied by stimulating both second and fifth digital nerves while recording over thenar muscles.

RESULTS

The vast majority of the participants were female and right-handed. CTS was bilateral in 61% of patients. Data of 109 hands were analyzed. MetS was more frequent in CTS patients. BQ scores were not related to MetS. Waist circumference, serum TG, and fasting glucose levels were higher in CTS patients. CTS hands with MetS had lower median CMAP amplitudes and increased sensory thresholds. Sensory thresholds were increased with both median and ulnar nerve stimulations suggesting a wider spread of peripheral nerve excitability changes in MetS presence. CuSPs were recorded from all 109 hands. CuSP latencies and durations were similar between controls and CTS patients. Wrist ratio was the only anthropometric index that was a statistically significant predictor for CTS development.

CONCLUSION

MetS was more prevalent in CTS patients. Some clinical and electrophysiological features (mainly sensory thresholds) may worsen in presence of MetS, but not the wrist ratio.

Utility of shear wave elastography and high-definition color for diagnosing carpal tunnel syndrome

OBJECTIVE

The diagnostic values of measuring median nerve (MN) stiffness and vascularity with shear wave elastography (SWE) and high-definition (HD) color were investigated in carpal tunnel syndrome (CTS).

METHODS

Seventy patients (123 wrists) with CTS and thirty-five healthy volunteers (70 wrists) were enrolled. Based on nerve conduction studies (NCS), the patients were subdivided into NCS-negative, mild-to-moderate, and severe CTS groups. MN and abductor pollicis brevis (APB) SWE and MN HD color were performed on a longitudinal plane.

RESULTS

The mild-to-moderate and severe CTS groups showed increased MN stiffness at the wrist and MN stiffness ratio (wrist-to forearm) compared with the control (p < 0.001). The NCS-negative CTS group showed increased MN stiffness at the wrist (p = 0.022) and MN stiffness ratio (p = 0.032) compared with the control. The severe CTS group showed increased MN stiffness at the wrist compared with the mild-to-moderate CTS group (p = 0.034). The cutoff-values in diagnosing NCS-confirmed CTS were 50.12 kPa for MN stiffness at the wrist, 1.91 for MN stiffness ratio, and grade 1 for HD color.

CONCLUSIONS

SWE and HD color are good supportive tools in diagnosing and assessing severity in CTS.

SIGNIFICANCE

SWE and HD color demonstrated that MN in CTS was associated with increased stiffness and hypervascularity.

Cutaneous silent period in ulnar neuropathy at the elbow

INTRODUCTION/AIMS

The cutaneous silent period (CSP) reflects the function of A-delta sensory fibers. There are few studies on CSP in nerve entrapment syndromes. This study aims to evaluate the neurophysiological abnormalities of small-diameter sensory fibers in ulnar neuropathy at the elbow (UNE) by means of CSP.

METHODS

We consecutively evaluated UNE patients at one electrodiagnostic laboratory. The CSP was obtained upon stimulating the fifth (D5) and third digits, recording from the first dorsal interosseous (FDI) and abductor pollicis brevis (APB) muscles.

RESULTS

We enrolled 37 UNE patients (mean age 55.4 ± 11.2 y) and 30 controls (mean age 51.2 ± 11.1 y). The combinations of the D5-APB and D5-FDI mean onset latencies of CSP were significantly more prolonged in patients (83.7 ± 6.8 and 84.5 ± 8 ms, respectively) than in controls (78.2 ± 8.1 and 79.4 ± 7.6 ms, respectively). The D5-FDI duration of CSP was shorter in patients (52.2 ± 8.3 ms) than in controls (55.8 ± 7 ms). The mean of the onset latencies of D5-FDI and D5-APB was related to the clinical severity (P = .013 and .0025, respectively). D5-APB and D5-FDI onset latencies were more prolonged and the duration was shorter in the UNE group with absent ulnar sensory nerve action potentials (SNAPs) and axonal motor damage than in patients with preserved SNAPs and with demyelinating damage.

DISCUSSION

CSP was able to demonstrate abnormalities of small-diameter myelinated sensory fibers. This damage was directly related to UNE severity and to axonal damage of motor fibers. Absence of a sensory large-diameter fiber response did not exclude preserved residual small fiber conduction.

Modulation of the excitatory phase following the cutaneous silent period by vibration

INTRODUCTION

The post-inhibition excitatory phase (E3) of the cutaneous silent period (CSP) is attributed to the resynchronization of motoneuron activity following the inhibitory period but there is also evidence that a somatosensory startle reflex may contribute to this phase. We hypothesized that the startle reflex component contained in E3 will decrease during vibration.

METHODS

Sixteen healthy individuals were included in the study. CSP was recorded from slightly contracted right thenar muscles after painful index finger stimulation, before, during, and immediately after vibration. The values of the percentage change of E3 relative to pre-stimulus baseline (E3%) were compared before, during, and after vibration for each individual.

RESULTS

There was a reduction in E3% during vibration and the values returned to normal immediately after vibration (153.1 ± 43.5%, 115.2 ± 30.2%, 154.9 ± 68.2%, respectively; p = 0.030).

DISCUSSION

E3 is reduced during vibration in healthy individuals, presumably due to suppression of a reflex component, which is superimposed upon the known resynchronization of motoneurons.

Quantitative evaluation of hand motor function using a gyrosensor in mild and moderate carpal tunnel syndrome

INTRODUCTION

The objective of this study was to determine whether patients with carpal tunnel syndrome (CTS) manifest changes in early-stage motor function and to investigate the utility of a gyrosensor for quantitative evaluation of motor function.

METHODS

Angular velocity signal was measured during finger tapping in 52 patients with mild-to-moderate CTS and 45 controls. Four finger-tapping performance (FTP) values-root-mean-squared (RMS) velocity, RMS angle, peak power, and total power-were derived from the signal.

RESULTS

All FTP values were significantly lower in patients with CTS than in controls (P = 0.001 or P < 0.001). There were no significant differences between the mild and moderate CTS subgroups.

DISCUSSION

FTP measurement with a gyrosensor represents a valuable tool for the evaluation of median nerve motor function in patients with CTS. It facilitates the detection of subclinical motor dysfunction in patients with early stage CTS. Muscle Nerve 59:465-469, 2019.

Scratch Collapse Test for Carpal Tunnel Syndrome: A Systematic Review and Meta-analysis

Background:

Despite the fact that carpal tunnel syndrome (CTS) is the most common entrapment neuropathy, the diagnostic accuracy of clinical screening examinations for CTS is controversial. The scratch collapse test (SCT) is a novel test that may be of diagnostic advantage. The purpose of our study was to determine the diagnostic accuracy of the SCT for CTS.

Methods:

A literature search was performed using PubMed (1966 to April 2018); Ovid MEDLINE (1966 to April 2018); EMBASE (1988 to April 2018); and Cochrane Central Register of Controlled Trials (The Cochrane Library, to April 2018). We examined the studies for the pooled sensitivity, specificity, and likelihood ratios of the SCT. This review has been registered with PROSPERO (CRD42018077115).

Results:

The literature search generated 13 unique articles. Seven articles were included for full text screening and 3 articles met our inclusion criteria, all of which were level II evidence with low risk of bias (165 patients). Pooled sensitivities, specificities, positive likelihood ratio, and negative likelihood ratios were 0.32 [95% CI (0.24–0.41)], 0.62 [95% CI (0.45–0.78)], 0.75 [95% CI (0.33–1.67)], and 1.03 [95% CI (0.61–1.74)], respectively. The calculated area under the summary receiver operating characteristic (AUSROC) curve was 0.25, indicating a low diagnostic accuracy.

Conclusion:

The SCT has poor sensitivity; however, it is moderately specific. Based on the current literature and their variable quality of the evidence, we conclude that the SCT is not an adequate screening test for detecting CTS.

Lengthened Cutaneous Silent Period in Fibromyalgia Suggesting Central Sensitization as a Pathogenesis

The pathogenesis of fibromyalgia (FM) has not been clearly elucidated, but central sensitization, which plays an important role in the development of neuropathic pain, is considered to be the main mechanism. The cutaneous silent period (CSP), which is a spinal reflex mediated by A-delta cutaneous afferents, is useful for the evaluation of sensorimotor integration at the spinal and supraspinal levels. To understand the pathophysiology of FM, we compared CSP patterns between patients with FM and normal healthy subjects. Twenty-four patients with FM diagnosed in accordance with the 1990 American College of Rheumatology classification system and 24 age- and sex-matched healthy volunteers were recruited. The CSP was measured from the abductor pollicis brevis muscle. Demographic data, number of tender points, and visual analog scale and FM impact questionnaire scores were collected. The measured CSP and clinical parameters of the patient and control groups were compared. In addition, possible correlations between the CSP parameters and the other clinical characteristics were analyzed. Mean CSP latencies did not differ between patients (55.50 ± 10.97 ms) and healthy controls (60.23 ± 11.87 ms; p = 0.158), although the mean CSP duration was significantly longer in patients (73.75 ± 15.67 ms) than in controls (63.50 ± 14.05 ms; p = 0.021). CSP variables did not correlate with any clinical variables. The significantly longer CSP duration in FM patients suggests central dysregulation at the spinal and supraspinal levels, rather than peripheral small fiber dysfunction.

Cutaneous silent period recordings in demyelinating and axonal polyneuropathies

OBJECTIVE

To investigate the cutaneous silent period (CSP), a spinal inhibitory reflex mainly mediated by A-delta fibres, in demyelinating and axonal polyneuropathy (PNP) and evaluate whether CSP parameters differ between patients with and without neuropathic pain.

METHODS

Eighty-four patients with demyelinating PNP, 178 patients with axonal PNP and 265 controls underwent clinical examination, DN4 questionnaire, standard nerve conduction study, motor-root stimulation and CSP recordings from abductor digiti minimi. We calculated the afferent conduction time of CSP (a-CSP time) with the formula: CSP latency-root motor evoked potential latency.

RESULTS

In the demyelinating PNP group the a-CSP time was significantly longer; in the axonal PNP group, CSP duration was shorter than the demyelinating group (p=0.010) and controls (p=0.001). CSP parameters were not different between patients with and without neuropathic pain.

CONCLUSIONS

The abnormality of a-CSP time in the demyelinating PNP group suggests the crucial role of A-delta fibres in the mechanism of CSP; the shorter CSP duration in the axonal PNP group supports the strong influence of the number of axons on this parameter. Our study suggests that neuropathic pain could be related to pathophysiological mechanisms differing from mere A-delta fibre loss.

SIGNIFICANCE

CSP evaluation is effective in detecting A-delta fibre dysfunction in axonal as well as demyelinating PNP.

Influence of limb temperature on cutaneous silent periods

OBJECTIVE

The cutaneous silent period (CSP) is a spinal inhibitory reflex mediated by small-diameter afferents (A-delta fibers) and large-diameter efferents (alpha motoneurons). The effect of limb temperature on CSPs has so far not been assessed.

METHODS

In 27 healthy volunteers (11 males; age 22-58 years) we recorded median nerve motor and sensory action potentials, median nerve F-wave and CSPs induced by noxious digit II stimulation in thenar muscles in a baseline condition at room temperature, and after randomly submersing the forearm in 42 °C warm or 15 °C cold water for 20 min each.

RESULTS

In cold limbs, distal and proximal motor and sensory latencies as well as F-wave latencies were prolonged. Motor and sensory nerve conduction velocities were reduced. Compound motor and sensory nerve action potential amplitudes did not differ significantly from baseline. CSP onset and end latencies were more delayed than distal and proximal median nerve motor and sensory latencies, whereas CSP duration was not affected. In warm limbs, opposite but smaller changes were seen in nerve conduction studies and CSPs.

CONCLUSION

The observed CSP shift "en bloc" towards longer latencies without affecting CSP duration during limb cooling concurs with slower conduction velocity in both afferent and efferent fibers. Disparate conduction slowing in afferents and efferents, however, suggests that nociceptive EMG suppression is mediated by fibers of different size in the afferent than in the efferent arm, indirectly supporting the contribution of A-delta fibers as the main afferent input.

SIGNIFICANCE

Limb temperature should be taken into account when testing CSPs in the clinical setting, as different limb temperatures affect CSP latencies more than large-diameter fiber conduction function.

Changes in the cutaneous silent period by paired stimulation

OBJECTIVE

The cutaneous silent period (CSP) corresponds to the inhibition of motor neuronal activity that is induced by electrical cutaneous stimulation. This motor neuronal inhibition might be useful as a therapeutic strategy for modulating the excitability of motor neurons. Therefore, we investigated the CSP changes that can be observed using the paired-stimulation method.

METHODS

Fifteen healthy adults were recruited. The digital cutaneous nerve of the right index finger was stimulated, and the CSP was recorded at the right thenar muscle. During the stimulation, contraction of the opposing right thumb and third finger was maintained at 20% of maximal voluntary contraction. A single stimulation was applied at the right index finger, and the duration and latency of the CSP (CSP1) was recorded. Paired electrical stimulations were then delivered with 60-, 80-, 100-, 120-, 140-, 160-, 180-, and 200-ms interstimulus intervals (ISI), and the latency and duration of a second CSP (CSP2) was measured and compared with that for the single stimulation.

RESULTS

The CSP2 onset latencies were delayed in the 60-, 80-, and 100-ms ISI when compared to CSP1. CSP2 durations were shorter in the 60-, 80-, and 100-ms ISI. No significant differences in the latencies and durations between CSP1 and CSP2 were observed for ISI durations greater than 120 ms.

CONCLUSIONS

We found that repetitive electrical stimulation changed the latency and duration of the CSP. These results suggest that the refractory period of the spinal inhibitory circuit in CSP is less than 100 ms.