Evaluation of Sympathetic Vasomotor Fibres in Carpal Tunnel Syndrome Using Continuous Wave Doppler Ultrasonography

Autonomic Component of Carpal Tunnel Syndrome

Carpal tunnel syndrome (CTS) is the most common compression neuropathy. The median nerve contains sensory, motor, and sympathetic fibers. Involvement of the different fibers of the median nerve in CTS may vary; hence, one of the sensory, motor, or autonomic dysfunctions may be dominant. Autonomic fibers of the median nerve consist of postganglionic sympathetic vasomotor and sudomotor fibers. An incomplete interruption of the axoplasmic flow may provoke a reflex that increases the sympathetic activity, leading to sweating, Raynaud phenomenon, and paleness of fingers. A complete sympathetic axoplasmic flow disruption blocks the sympathetic activity that leads to vasodilation, and the affected area in the hand is believed to be swollen, warmer, pinker, and dryer than the rest of the limb. In advanced and severe autonomic dysfunction, the fingertips may ulcerate, and nail growth changes may occur. Carpal tunnel syndrome diagnosis is a constellation of symptoms and signs; however, there has been limited attention to the autonomic component of CTS. Regeneration and reinnervation capacity of thin unmyelinated sympathetic fibers after compression and axonal degeneration is poor. Ignoring the important role of the autonomic component of CTS may lead to persistent symptoms and unsuccessful CTS surgery. Early carpal tunnel release in patients with autonomic findings is indicated and may provide improved outcomes.

Ultrasonographic measurement of median nerve and wrist skin thickness in patients with carpal tunnel syndrome: relationship with clinical, electrophysiologic and functionality

The study aimed to investigate the relationship between the proximal and distal cross-sectional area (CSA) of the median nerve and wrist skin thickness measured by ultrasound in patients with carpal tunnel syndrome (CTS), demographics, disease characteristics, electrophysiological measurements, symptom severity, functionality, and symptom severity. 98 patients with electrophysiological diagnoses of CTS in the dominant hand were included in the study. Proximal and distal CSAs of the median nerve and wrist skin thickness were measured ultrasonographically. Demographic and disease characteristics of the patients were recorded. Patients were evaluated with the Historical-Objective scale (Hi- Ob) for clinical staging, the Functional status scale (FSS) for functional status, and the Boston symptom severity scale (BSSS) for symptom severity. Ultrasonographic findings were correlated with demographic and disease characteristics, electrophysiological findings, Hi-Ob scala, Functional status scale (FSS), and Boston symptom severity scale (BSSS). Proximal median nerve CSA median was 11.0 (7.0-14.0) mm2, distal median nerve CSA median was 10.5 (5.0-18.0) mm2, and wrist skin thickness was measured 1.10 (0.6-1.40) mm. Median nerve CSAs were positively correlated with the CTS stage and FSS, negatively correlated with the sensory nerve action potential of the median nerve (SNAP) and the compound muscle action potential of the median nerve (CMAP) ( p<0.05). Wrist skin thickness was positively correlated with disease characteristics, including the presence of paresthesia and loss of dexterity and FSS and BSSS levels. Ultrasonographic measurements in CTS are associated with functionality rather than demographics. Especially the increase in wrist skin thickness leads to an increase in symptom severity.

Paradoxical Changes of Cutaneous Microcirculation and Sympathetic Fibers of Rat Hind Limbs after Sciatic Nerve Compression

BACKGROUND

Recent studies show evidence that surgical nerve decompression could improve cutaneous blood flow (CBF), which might benefit ulcer healing. However, the change of CBF and sympathetic fibers after nerve compression is poorly understood. In the current study, a unilateral sciatic nerve compression model was created in Sprague-Dawley rats.

METHODS

A laser Doppler imaging system was applied to assess the CBF of the regions below the ankles. Immunohistochemistry and transmission electron microscopy were used to investigate the histopathologic changes of sympathetic fibers in sciatic nerve samples.

RESULTS

Laser Doppler imaging revealed decreased CBF of both the lesional limb and the contralesional limb, which occurred earlier in the lesional side, indicating an enhanced sympathetic tone on vasomotor function. Intraneural density of sympathetic fibers decreased on both sides and the ultrastructure of unmyelinated fibers of both sides degenerated in a nonsynchronized manner.

CONCLUSIONS

The study revealed nonsynchronized reduced CBF of bilateral hind limbs with paradoxically degenerated and diminished sympathetic fibers in bilateral sciatic nerves after unilateral sciatic nerve compression. These results may validate the importance of and broaden the indications for surgical nerve decompression in preventing or treating foot ulcers.

Infrared thermographic changes after decompression surgery in patients with carpal tunnel syndrome

BACKGROUND

Digital infrared thermal imaging (DITI), which detects infrared rays emitted from body surface to create a body heat map, has been utilized at various musculocutaneous conditions. Notably, DITI can demonstrate autonomic vasomotor activity in the nerve-innervated area, and thus may be of use in carpal tunnel syndrome (CTS). In this study, we compared DITI findings before and after carpal tunnel release (CTR) surgery in patients with unilateral CTS to investigate the corresponding neurophysiological changes.

METHODS

In this retrospective cohort study, DITI parameters such as the temperature differences between the median and ulnar nerve territories and median nerve-innervated digital anisometry were measured. Subjective symptom duration, pain scale, and ultrasonographic findings were also compared before and after CTR. Patients were evaluated before and 6 weeks after CTR, respectively.

RESULTS

A total of 27 patients aged 59.0 ± 11.2 years were finally included. After CTR, median nerve-innervated thermal anisometry was improved (2.55 ± 0.96 °C to 1.64 ± 1.34 °C; p = 0.003). The temperature differences between the median and ulnar nerve territories were not significantly changed. Subjective pain, the Simovic Weinberg Clinical Scale, and palmar bowing of the flexor retinaculum were also significantly improved (p <  0.001 for all comparisons).

CONCLUSIONS

Our results demonstrated that DITI findings could reflect an improvement in autonomic function after CTR. Therefore, DITI can be an objective method to assess pre- and post-operative neurophysiologic changes in CTS.

Brachial arteries sympathetic innervation: A contribution to anatomical knowledge

BACKGROUND

The sympathetic nervous system makes medium and large peripheral arteries smaller to slow the blood flowing through them.

AIM

To observe brachial artery sympathetic innervation.

METHODS

We developed a neurophysiological autonomous test that measured the effects of peripheral sympathetic fibres on peripheral arteries. Our specific objective was to find the sympathetic innervation of the brachial artery. To accomplish this purpose, the brachial artery baseline diameter and flow rate were measured in the right arm of the patients. Afterwards, electrical stimulus was applied to the medial nerve for 5 s. Through electrical sympathetic activation, the vessel diameter and overall flow rate will decrease. After 7 d, a similar experiment was repeated using the ulnar nerve.

RESULTS

The differences in diameter and flow rate of the brachial artery in response to median and ulnar nerve activation were compared. In the total group, no significant difference in diameter was seen between medial and ulnar nerve stimulation (P = 0.648). The difference in absolute slowdown of flow rate between median nerve stimulation and ulnar nerve stimulation was not statistically significant for the entire group (P = 0.733).

CONCLUSION

As a target organ, the brachial artery receives an equal amount of sympathetic innervation from the median and the ulnar nerves.

The impact of cell phone texting on superficial blood flow, touch threshold, and symptoms for individuals with carpal tunnel syndrome

BACKGROUND

It is unclear how individuals with carpal tunnel syndrome (CTS) are affected by texting, or how the texting performance of those with CTS might be impaired or different from individuals without CTS.

OBJECTIVE

The primary purpose of this case-control study was to determine the immediate effects of texting on superficial blood flow, sensory threshold, and symptoms of fatigue, numbness, and pain for individuals with CTS compared to asymptomatic age-matched controls. Another objective was to detect differences in texting performance between the two groups.

METHODS

Superficial blood flow, pain, fatigue, numbness, and touch threshold were measured before, and at three time points following a standardized 15-minute texting task. Overall texting speed was compared between groups.

RESULTS

Changes in red blood cell concentration after the texting task was not significantly different for either the CTS group or controls for any of the measurement time points. Mean touch thresholds at baseline were 4.0 g/mm2 for the CTS group versus 2.6 g/mm2 for healthy controls; a 53%greater touch threshold. Following the texting task, touch threshold did not change for normal controls, but increased to 6.7 g/mm2 for the CTS group, representing a significant increase in touch threshold from baseline. Texting performance was compromised in people with CTS, and symptoms worsened with a short-term controlled texting task.

CONCLUSIONS

Our results suggest that texting performance is limited in individuals with CTS and that texting results in a short term increase in touch threshold values for individuals with CTS. Further study is needed to determine the effect of long term texting on carpal tunnel pressures.

Validation of a novel ultrasound Doppler monitoring device (earlybird) for detection of microvascular circulatory changes

OBJECTIVE

In this proof-of-concept study we aim to validate a novel ultrasound Doppler monitoring device for evaluating microcirculation (earlybird) against LDF and pulsed Doppler.

METHODS

In ten healthy subjects, we measured microcirculatory function at rest and during different autonomic tests (forced respiration, isometric exercise, Valsalva maneuver and cold pressor). Earlybird, LDF and pulsed Doppler were recorded simultaneously. We performed a ZNCC to determine correlation.

RESULTS

The curves for earlybird and LDF or pulsed Doppler correlates visually well. Overall median ZNCC 0.87 (interquartile range 0.77 -0.91) between the LDF and earlybird measurements, and 0.90 (0.82 - 0.95) for pulsed Doppler and earlybird. Median ZNCC for baseline and each provocation test for earlybird against LDF and pulsed Doppler were calculated; baseline: LDF 0.87 (0.73 - 0.97) pulsed Doppler 0.91 (0.81 - 0.94), forced respiration: LDF 0.87 (0.28 - 0.90) pulsed Doppler 0.90 (0.85 - 0.96), isometric exercise: LDF 0.82 (0.59 - 0.90) pulsed Doppler 0.87 (0.68 - 0.94), Valsalva maneuver: LDF 0.88 (0.82 - 0.91) pulsed Doppler 0.94 (0.92 - 0.97) and cold pressor: LDF 0.90 (0.85 - 0.95) pulsed Doppler 0.89 (0.65 - 0.94).

CONCLUSION

Earlybird records vasoconstrictions in healthy subjects as well as LDF and pulsed Doppler.

Color Doppler ultrasound for evaluation of vasomotor activity in patients with carpal tunnel syndrome

BACKGROUND

Patients with carpal tunnel syndrome (CTS) have a variety of vasomotor symptoms. Here, we aimed to study the vasomotor activity of the radialis indicis (RI) artery (median nerve territory) and the radial palmar digital (RPD) artery of the little finger (ulnar nerve territory) before and after sympathetic stimulation in CTS patients using color Doppler ultrasound.

METHODS

We performed a cross-sectional study of 46 consecutive CTS patients plus 36 healthy controls. All patients underwent electromyography studies and were classified into mild and moderate/severe groups according to electrodiagnostic findings. Color Doppler examination of the RI artery and the RPD artery of the little finger were performed with the participants in a relaxed sitting position and after a deep breath followed by a cough (sympathetic stimulation). The pulsatility index (PI) was recorded at the point of maximal change in waveform, before and after this stimulus.

RESULTS

The PI of RI artery was significantly lower (p < 0.01) in CTS patients than healthy controls, both before and after stimulation. The changes in PI of RI artery after stimulation were significantly lower in CTS patients than healthy controls (1.18 ± 0.37 vs. 5.41 ± 0.87; p < 0.001). The same pattern was seen for PI of RI artery when comparing patients with mild vs. moderate/severe CTS. No difference was found in PI of RPD artery of the 5th finger between patients vs. controls and between patients with mild vs. moderate/severe CTS, both before and after stimulation.

CONCLUSIONS

We showed that color Doppler ultrasound can readily determine impaired vasomotor activity in CTS patients.

Pulsed wave Doppler ultrasound is useful to assess vasomotor response in patients with multiple system atrophy and well correlated with tilt table study

The study aim was to assess sympathetic vasomotor response (SVR) by using pulsed wave Doppler (PWD) ultrasound in patients with multiple system atrophy (MSA) and correlate with the tilt table study. We recruited 18 male patients and 10 healthy men as controls. The SVR of the radial artery was evaluated by PWD, using inspiratory cough as a provocative maneuver. The response to head-up tilt was studied by a tilt table with simultaneous heart rate and blood pressure recording. The hemodynamic variables were compared between groups, and were examined by correlation analysis. Regarding SVR, MSA patients exhibited a prolonged latency and less heart rate acceleration following inspiratory cough. Compared with the tilt table test, the elevation of heart rate upon SVR was positively correlated to the increase of heart rate after head-up tilt. The correlation analysis indicated that the magnitude of blood pressure drop from supine to upright was positively associated with the SVR latency but negatively correlated with the heart rate changes upon SVR. The present study demonstrated that blunted heart rate response might explain MSA's vulnerability to postural challenge. PWD may be used to predict cardiovascular response to orthostatic stress upon head-up tilt in MSA patients.

Pulsed wave Doppler ultrasonography for the assessment of peripheral vasomotor response in an elderly population

PURPOSE

To assess sympathetic vasomotor activity and its changes with age, using pulsed wave Doppler ultrasound.

METHODS

We recruited 20 young adults (24-37 years old) and 20 older individuals (60-81 years old). Pulsed wave Doppler ultrasound was applied over the right radial artery to measure blood flow at rest and after a voluntary inspiratory cough eliciting sympathetic activation. The maximal (Vmax), minimal (Vmin), time-averaged (TAMaxV) blood flow velocity, and the pulsatility index (PI) were calculated and compared between groups.

RESULTS

At rest, PI was similar in both groups but Vmax and TAMaxV were higher in the older group (p < 0.05). Vmax, Vmin, and TAMaxV decreased, and PI increased after inspiratory cough in both groups (p ≤ 0.001), but this increase was lower in the older group (p < 0.001). TAMaxV after coughing was higher in the older group (p < 0.05). Heart rate did not differ significantly within or between groups.

CONCLUSIONS

The older group exhibited reduced vasomotor reactivity of the radial artery after sympathetic stimulus. Peripheral vasomotor response should be interpreted with caution in elderly populations.

Application of pulsed-wave Doppler ultrasound to exploration of the peripheral vasomotor response by gender and hand dominance

PURPOSE

Laser Doppler flowmetry measures peripheral vasomotor response but fails to detect changes in vascular diameters, resistance, and heart rates. Because this response contributes to assessing sympathetic disorders and relies on the above variables to be correctly interpreted, we used pulsed-wave Doppler (PWD) ultrasound to evaluate the response and to determine whether it was affected by gender or hand dominance.

METHODS

PWD was applied to bilateral deep palmar branches of the radial arteries of 22 men and 22 women, using post-inspiratory cough as the sympathetic stimulus. Pulsatility index (PI), arterial diameters, heart rates, flow velocity, and blood flow before and after sympathetic stimuli were analyzed for both groups.

RESULTS

Women had a higher PI value of the radial arteries at rest; in contrast, that of men was higher after sympathetic stimuli. Blood flow velocity (V max, V max mean, and V mean) at rest was higher for men than for women. A significant difference was observed in V min after stimulus. Arterial diameters and blood flow before and after stimuli were higher for men than for women. Post-inspiratory cough caused significant diameter reduction in women but heart rate elevation in men. Hand dominance had no effect.

CONCLUSIONS

This study demonstrated the suitability of PWD for detailing peripheral vasomotor response, which was affected by gender but not hand dominance. Our results suggest application of PWD to diseases with unilateral sympathetic impairment, but responses for different sexes should be treated with caution.

A Holistic Evaluation of Risk Factors for Work-Related Musculoskeletal Distress Among Asymptomatic Sonographers Performing Neurosonology

A pilot study was conducted to gather holistic data points on female sonographers who executed neonatal neurosonography over four portable scanning sessions. The hypothesis was that specific risk factors contributed to work-related musculoskeletal distress in the hand and wrist as a result of neonatal neurosonography. A preexperimental pre-post research design was used to gather data on work demands, self-rated physical and mental health, posture/position during scanning, physiologic change, and pain scores. No statistically significant changes were detected between pre-post measures for work demands, physical and mental health, or pain scores as a result of portable scanning sessions. The physiologic changes, between scanning sessions, were recorded with the use of a hand-carried sonographic unit. Sonographic measures were less than the published criteria for carpal tunnel syndrome with a proximal cross-sectional area ≥10 mm 2 and an anterior bulge of the retinaculum of >4 mm. Sonography documented a statistically significant cross-sectional area change, within the median nerve, at the distal radius only after the first scanning session. Power and spectral Doppler was used to document perineural vascular flow within the median nerve, but it was not consistently obtained to allow for a rigorous comparison between pre- and postscanning sessions. This is the first pilot study to explore using a hand-carried sonographic unit to document change in the median nerve for an isolated sonographic examination. The results are only reflective of these particular participants, but much larger N and shorter scanning sessions are needed to confirm the hypothesis proposed.

Sympathetic sweat responses and skin vasomotor reflexes in carpal tunnel syndrome

OBJECTIVE

To investigate cutaneous sympathetic functions in carpal tunnel syndrome (CTS) using sympathetic sweat responses (SSwRs) and skin vasomotor reflexes (SVmRs).

METHODS

In 29 hands (20 patients) with idiopathic CTS, SSwRs were recorded with a sudorometer from the thenar eminence, and SVmRs were used to measure cutaneous blood flow using a Doppler flowmeter placed on the index finger tip. Normal data were obtained from 15 volunteers of similar age.

RESULTS

SSwRs or SVmRs were abnormal in 23 (80%) hands; SSwRs were absent in 38%, whereas SVmRs were abnormally decreased in 59%. Autonomic symptoms were present in 18 (62%) hands; finger edema (38%) and dry hand (35%) were frequent symptoms. Autonomic symptoms, and abnormal SSwRs and SVmRs did not correlate with results of nerve conduction studies.

CONCLUSIONS

Skin sudomotor or vasomotor sympathetic function is frequently impaired in CTS. Susceptibility to compression ischemia may be different in sympathetic unmyelinated and large myelinated fibers.