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Our aim was to explore possible relationships between serum levels of biomarkers in patients with hand-arm vibration injury in relation to the severity of the vascular, i.e., Raynaud's phenomenon (RP), and neurosensory manifestations, the current exposure level, and the duration of exposure. This study was of case series design and involved 92 patients diagnosed with hand-arm vibration injury. Jonckheere's trend test was used to assess any association between serum levels of biomarkers and RP as well as neurosensory manifestations, graded by the International Consensus Criteria. Generalized linear models with adjustment for possible confounders were also used for associations between serum levels of biomarkers and; (1) severity of RP recorded as the extent of finger blanching calculated with Griffin score, (2) vibration perception thresholds, (3) magnitude of current exposure as [A(8); (m/s 2 )] value, and (4) the duration of exposure in years. Serum levels of thrombomodulin, von Willebrand factor, calcitonin gene related peptide (CGRP), heat shock protein 27, and caspase-3 were positively associated with severity of RP. Serum levels of CGRP were positively associated with the neurosensory component. No associations with exposure were shown for these biomarkers. For Intercellular adhesion molecule 1 and monocyte chemoattractant protein 1, no associations were found with neither severity nor exposure. Levels of serum biomarkers associated with endothelial injury or dysfunction, inflammation, vasodilation, neuroprotection, and apoptosis were positively associated with the severity of hand-arm vibration injury., (© 2024. The Author(s).)

Aims: To establish normative values of vibration perception thresholds (VPTs), using multi-frequency vibrometry at finger pulps and at metatarsal heads of the foot in healthy adults. We also aimed to investigate factors that could potentially affect VPTs such as age, sex, height, weight, foot- or handedness and skin temperature., Methods: VPTs were examined in 924 healthy and randomly selected subjects in the southern Sweden (mean 46 years; 628 women and 296 men). Inclusion criterias were adult subjects (>18 years) in considerable health without diabetes mellitus or other nerve affecting disorders. VPTs were measured at the finger pulps of index and little finger, as well as the first and fifth metatarsal heads of the foot, through multi-frequency vibrometry using the VibroSense Meter® I device. Patient characteristics were recorded and skin temperature was measured before assessment of VPTs., Results: We present normative values of VPTs for a large population of both male and female subjects in various ages. VPTs detoriated as age increased (0.09-0.59 dB per year; p<0.001), i.e. progressing with normal aging. Increasing skin temperature affected VPTs in finger pulps, but not at metatarsal heads, with -0.2 to -1.6 dB, i.e. vibration perception improved with higher temperatures. Height was only found to affect the VPTs of metatarsal heads (250 Hz: 0.42 dB per cm). Sex, weight and handedness did not affect the VPTs., Conclusion: We investigated the normative values of VPTs and presented affecting factors as age, skin temperature and height. With these results, VPT testing through multi-frequency vibrometry is enabled to be used in a clinical practice as a diagnostic tool when investigating neuropathy and other neurological disorders., Competing Interests: The authors have declared that no competing interests exist.

Aims: Few studies have examined how improved metabolic control might influence vibration perception thresholds (VPTs). The aim of this study was to evaluate if improved HbA 1c can influence vibration thresholds in adults with type 1 diabetes (T1DM)., Methods: VPTs were investigated at six frequencies (4-125 Hz) using VibroSense Meter in the sole of the foot at two occasions in 159 T1DM patients, at the heads of the first and fifth metatarsal bones, i.e. MTH1 and MTH5, respectively. The participants were divided into three groups: group A: HbA 1c improved by more than 1 mmol/mol (n = 95), group B: HbA 1c deteriorated by more than 1 mmol/mol (n = 48) and group C: HbA 1c unchanged (± 1 mmol/mol) (n = 16) compared to baseline., Results: In group A, the mean z-score, reflecting the combined effect of all VPTs, improved being lower at the follow-up than at the baseline [0.2 (- 0.3 to 1.2) vs. -0.1 (- 0.7 to 0.8), p = 0.00002]. VPTs improved at 4 and 64 Hz at both MTH1 (metatarsal head 1) and MTH5. The VPTs at 125 Hz frequency improved at MTH5, but not at MTH1. No significant differences were seen in group B or group C., Conclusions: Lower HbA 1c and lower VPTs in T1DM patients were associated with improved VPT, suggesting a reversible effect on nerve function by improved metabolic control.

Aims: To investigate practice effects in a test-retest situation, where vibration perception thresholds (VPT) were measured in healthy subjects using a multi-frequency test method., Methods: In eight consecutive tests, VPTs were tested in the pulps of the index and little fingers at seven frequencies (8, 16, 32, 64, 125, 250 and 500 Hz). Subjects were twenty healthy adults aged 26 to 65 years (mean 46.0 ± 11.1 years; 10 male and 10 female). The subjects were examined at six tests with intervals of one month (mean 33 ± 6; time 0 to month 5) and at two additional tests with prolonged intervals (month 12 and 18). Linear mixed model analysis was performed to investigate differences over the subsequent test occasions. To examine where potential practice effects occurred, a pairwise comparison with Bonferroni correction was made., Results: Small decreases in VPTs were found in 8 out of the 14 frequencies (index finger: 8, 16, 32, 250 and 500 Hz; little finger: 16, 250 and 500 Hz) within the test period from time 0 to month 5. In tests at 12 and 18 months, VPTs were increased compared to month 5, but lowered in comparison with time 0. Hence, minor significant decreases were found in three frequencies for the index finger (125, 250 and 500 Hz) and one frequency for the little finger (250 Hz) when examining VPTs with prolonged time intervals., Conclusions: When evaluating vibration perception thresholds in a clinically relevant time period of once or twice a year, no consideration of practice effects is necessary when interpreting the results., Competing Interests: The authors have declared that no competing interests exist.

Objective: To investigate whether multi-frequency vibrometry can identify individuals with elevated vibration perception thresholds (VPTs), reflecting impaired vibrotactile sense, among children and adolescents with type 1 diabetes., Methods: In 72 pediatric patients with type 1 diabetes, VPTs were evaluated for seven frequencies on two sites of the hand, and five frequencies on two sites of the foot. Z-scores, based on previously collected reference data, were calculated. Perception to light touch was investigated using monofilaments. Subjects' characteristics were analyzed in comparison to normal and impaired vibrotactile sense., Results: Subjects' median age, disease duration and age at disease onset were 12.8, 5.3 and 6.9 years, respectively. A total of 13 out of 72 (18%) subjects had impaired vibrotactile sense on at least one foot site. Impaired vibrotactile sense was more common among subjects treated with multiple daily insulin injections (MDI) compared to subjects treated with continuous subcutaneous insulin infusion (CSII) (p = 0.013). Age at disease onset was higher among subjects with impaired vibrotactile sense (p = 0.046). No significant correlations were found with gender, HbA1c or duration of diabetes., Conclusions: Impaired vibrotactile sense, mirroring diabetic peripheral neuropathy, was found in 1/5 of the children and adolescents in the study, and was more common in patients treated with MDI than in subjects treated with CSII.

Aims: To evaluate multi-frequency tactilometry as a method to measure vibrotactile sense in the sole of the foot in subjects with diabetes., Methods: Vibration thresholds were investigated at five frequencies (8, 16, 32, 64 and 125 Hz) at three sites (first and fifth metatarsal heads and heel) in the sole of the foot in subjects with Type 1 and Type 2 diabetes (n = 37). Thresholds were compared with healthy, age- and gender-matched subjects (n = 37) and related to glycaemic levels, subjective estimation of sensation in the feet and to perception of touch., Results: Vibration thresholds were significantly higher in subjects with diabetes compared with healthy subjects at low frequencies (8, 16 and 32 Hz) at all measured sites, and also at 64 Hz for the metatarsal heads. Perception of touch and subjective estimation of sensation were significantly impaired in subjects with diabetes. Glycaemic levels, which were higher in subjects with diabetes, did not correlate with vibration thresholds at 32 Hz (most sensitive to Meissner's corpuscles) or with touch thresholds in subjects with diabetes. Vibration thresholds at 32 Hz correlated significantly with perception of touch (rho = 0.45-0.65; P < 0.01) and with subjective sensation (rho = -0.38 to -0.52; P < 0.001) in subjects with diabetes. Perception of touch and subjective estimation of sensation did also correlate (rho = -0.51 to -0.80; P < 0.002)., Conclusions: Tactilometry is effective in detecting neuropathy in the sole of the foot at low frequencies of mainly 8-32 Hz, indicating that at least Meissner's corpuscles, or their related large nerve fibres, are affected by diabetes., (© 2012 The Authors. Diabetic Medicine © 2012 Diabetes UK.)

Aim: To evaluate vibration perception thresholds of patients with and without diabetes, before and after surgical carpal tunnel release., Methods: In a prospective study, 35 consecutive patients with diabetes and carpal tunnel syndrome were age and gender matched with 31 patients without diabetes having idiopathic carpal tunnel syndrome. Preoperatively, 6, 12 and 52 weeks after surgery, the vibration perception threshold of the index and little finger (median and ulnar nerve, respectively) was measured at seven different frequencies (8, 16, 32, 64, 125, 250 and 500 Hz)., Results: At several frequencies, patients with diabetes and carpal tunnel syndrome demonstrated significantly impaired vibration perception thresholds of both the index and the little finger, before as well as after carpal tunnel release, compared with patients without diabetes with idiopathic carpal tunnel syndrome. After surgery, the overall sensibility index improved for the index finger [patients with diabetes and carpal tunnel syndrome (0.79 to 0.91, P < 0.001), patients without diabetes with idiopathic carpal tunnel syndrome (0.91 to 0.96, P > 0.05)] as well as for the little finger [patients with diabetes and carpal tunnel syndrome (0.82 to 0.90, P < 0.008), patients without diabetes with idiopathic carpal tunnel syndrome (0.95 to 0.99, P < 0.05)]. For the index finger, the sensibility index improved to a significantly higher degree for patients with diabetes and carpal tunnel syndrome not having signs of peripheral neuropathy (0.83 to 0.95, P < 0.001) compared with those with neuropathy (0.74 to 0.84, P < 0.02). Vibration perception threshold correlates with age of both patients with diabetes and carpal tunnel syndrome and patients without diabetes with idiopathic carpal tunnel syndrome, while no relationship was found based on duration of diabetes., Conclusions: Vibrotactile sense is significantly impaired in patients with diabetes before and after carpal tunnel release compared with patients without diabetes. However, patients with diabetes obtained significant recovery of vibration perception threshold, particularly those without peripheral neuropathy., (© 2011 The Authors. Diabetic Medicine © 2011 Diabetes UK.)

A substantial number of people who are exposed to vibrating hand-held tools develop vasospastic and sensorineural symptoms that may seriously affect the ability to work. Apart from the discomfort of the disease itself, this leads to socioeconomic problems for the patients and high costs for the society. The diagnosis of the neurological symptoms is sometimes difficult and may be misinterpreted as a nerve compressive disorder such as carpal tunnel syndrome, which may also develop. This review summarises our available knowledge about the pathophysiology of the neurological dysfunction with reference to hand problems after exposure to vibrating hand-held tools.

Fractionated nerve conduction, vibrotactile sense, and temperature thresholds were studied in 73 symptomatic vibration-exposed male workers. Three symptomatic groups were distinguished: patients with isolated sensorineural symptoms; with isolated vasospastic problems; and with both. Clinical carpal tunnel syndrome occurred in 14 patients and abnormal cold intolerance (without blanching of the fingers) in 23. In the group as a whole, nerve conduction studies were abnormal in the median nerve but not in the ulnar nerve and vibration perception and temperature thresholds were impaired. Of the three symptomatic groups, patients with isolated sensorineural symptoms differed from controls. No differences were seen between patients with and without clinical carpal tunnel syndrome. With severe sensorineural symptoms the vibration perception thresholds, but not the values of the nerve conduction studies, were further impaired. The results indicated two injuries that are easily confused: one at receptor level in the fingertips and one in the carpal tunnel. Careful clinical assessment, neurophysiological testing, and examination of vibrotactile sense are required before carpal tunnel release should be considered in these patients.

Objectives: The purpose of this study was to investigate disturbances of the vibrotactile sense and their relation to clinical symptoms and findings among male symptomatic workers suffering from the hand-arm vibration syndrome., Methods: Ninety-six such patients were interviewed and given a clinical and tactilometric examination. The symptoms were classified according to the Stockholm Workshop Scale. A sensibility index was used to quantify vibrotactile sense in the tactilogram., Results: An abnormal sensibility index (<0.8) was recorded for 57.3% of the patients (mean of 4 fingers), at least 1 finger being abnormal in 72.9% of the patients. The sensibility index did not statistically differ between the patients suffering from sensorineural symptoms and those with vibration white finger. The stages of sensorineural symptoms, according to the Stockholm Workshop Scale, corresponded with the sensibility index, whereas the stages of vibration white finger did not. There were significant differences in the sensibility index between the fingers, between the right and left hands, and between the fingers innervated by the ulnar and median nerves. Bilateral symptoms and cold intolerance were associated with considerable impairment of the vibrotactile sense. Clinical median nerve involvement in the carpal tunnel was not reflected by the sensibility index., Conclusions: There is a considerable degree of neural involvement in all symptomatic vibration-exposed patients irrespective of symptoms. As symptoms progress, the severity of sensorineural symptoms, but not of vibration white finger, is reflected by the sensibility index. Cold intolerance is strongly related to nervous involvement and should be noted in the patient history. Tactilometry should be performed on 1 median and 1 ulnar nerve-innervated finger of both hands, as an examination of 1 finger alone may be misleading.

Objectives: Exposing a hind leg of a rat to vibration induces an injury to the sciatic nerve--a so called conditioning lesion. After such injury induced by vibration the regenerative capacity of the nerve is improved and can be detected as an increased axonal outgrowth from a test crush lesion to the same nerve. The purpose was to study whether the effect of a conditioning lesion induced by vibration can be prevented by local treatment with a Ca2+ channel blocker D600., Methods: D600 (methoxyverapamil) or Ringer's solution was locally applied to the sciatic nerve on one side through a silicone tube connected to a miniosmotic pump, which was implanted subcutaneously. During the same period the hind leg was exposed to vibration (80 Hz; 32 m/s2 root mean squared) for five hours daily for five consecutive days. The other hind leg was not vibrated. After the end of exposure to vibration the sciatic nerves were crushed bilaterally (test crush lesions) and three or six days later the regeneration distances of sensory axons were measured by the pinch reflex test., Results: Nerves in the control animals (without implanted miniosmotic pumps and nerves on to which Ringer's solution was locally applied) that were exposed to vibration showed a significantly increased outgrowth length of sensory axons from the test crush lesion compared with the non-vibrated side. Such an effect of a conditioning lesion from the exposure to vibration was suppressed by local application of D600., Conclusions: Local administration of a Ca2+ channel blocker D600 can prevent the effect of a conditioning lesion-that is, the nerve injury induced by vibration can be inhibited by D600. This may have implications for the treatment of patients with neuropathy of the hand induced by vibration.

Objectives: To analyse the character of morphological changes occurring in a well defined peripheral nerve in humans exposed to vibration from hand held tools., Methods: Biopsies of the dorsal interosseus nerve just proximal to the wrist were taken from 10 men exposed to vibration and from 12 male age matched necropsy controls. The nerve was resected for pain relief either as the sole procedure or in conjunction with carpal tunnel release. All specimens were sectioned and examined by light microscopy in standard sections, thin epon sections, and teasing preparations., Results: The combined results of the analyses showed pathological changes in all 10 patients dominated by breakdown of myelin and by interstitial and perineurial fibrosis. All but one of the 12 controls were normal., Conclusion: These findings often show severe nerve injury previously not described at this level. They indicate that demyelination may be the primary lesion in neuropathy induced by vibration followed by fibrosis associated with incomplete regeneration or with organisation of oedema. Vibration can induce structural changes in peripheral nerves just proximal to the wrist and such changes may constitute a structural component in carpal tunnel syndrome among people exposed to vibration. This may help to explain the poor results achieved by carpal tunnel release in these patients.

We have studied the effects of vibration on the regeneration capacity of the peripheral nerve. A rat model was used where one hind limb was subjected to vibration of defined magnitude and duration while the contralateral hind limb was not exposed to vibration. Seven days later, the sciatic nerves were transected bilaterally and cross-joined giving the following groups: group A, a proximal vibrated nerve end sutured to a non-vibrated distal nerve end; group B, a non-vibrated proximal nerve end sutured to a distal vibrated nerve end, and group C, non-vibrated proximal nerve end sutured to a non-vibrated distal nerve end. The regeneration distances were measured 3, 6 and 8 days after surgery. The control group showed a normal linear outgrowth. The outgrowth in the two experimental groups was initially not different to controls but later became significantly different, indicating a retardation of outgrowth in these groups. It is concluded that short-term exposure to vibration can impair nerve regeneration after transection and nerve repair.

The early skeletal muscle response to vibration stimulus at two different displacement levels was examined. Twelve rats were anaesthetized and the hind limb was exposed to vibration, 80 Hz, 63 micronsrms (root mean square) (group 1) and 40 Hz; 130 micronsrms (group 2) for 5 hours/day for 2 days. Cross-sectional areas of vibrated muscle fibres were significantly larger in group 2. Sizes of different fibre types were differently affected: the slow-twitch type 1 fibres were significantly enlarged in both groups, while the fast-twitch type 2 fibres demonstrated a mixed response pattern. Centrally positioned muscle fibre nuclei increased significantly after vibration in group 2. It is concluded that the level of tissue displacement is a crucial factor for development of vibration-induced muscle injury.

Long-term use of hand-held vibrating tools may induce various types of hand problems. One hundred symptomatic men exposed to vibration from such tools were interviewed and examined with special reference to neurosensory and vasospastic problems. Three distinct symptomatic groups were identified: isolated neurosensory symptoms (48%), isolated vasospastic problems (20%), and combined neurosensory and vasospastic problems (32%). Abnormal cold intolerance (pain and coldness without blanching of the fingers on exposure to cold) occurred in 27% of the patients. Neurosensory problems were more predominant than vasospastic ones, especially during the first 20 years of vibration exposure. Of 80 patients with neurosensory symptoms, only 22 had signs of a carpal tunnel syndrome (CTS). It is concluded that vibration-induced neurosensory and vasospastic symptoms can occur separately or together, and that the neurosensory symptoms are often not due to a CTS.

The effects of controlled vibrations of defined frequency (80 Hz), acceleration (32 m/s2 root mean square), and duration (5 hours daily, 2 or 5 days) induced to the hind limb of rats on the regeneration potential in the sciatic nerve after a test crush lesion were determined. Exposure to vibration induced a marked and significant increase in outgrowth length of axons from the crush injury as evaluated after 3 and 6 days with the pinch reflex test. This effect was still observed 1 month but not 3 months after exposure to vibration. Even such a short duration of vibration exposure as 2 days induced an increased length of outgrowth. Such a conditioning effect may be due to local changes in the environment of the axons or to changes in the nerve cell bodies in the dorsal root ganglion. The results indicate that an alarm reaction exists in the nerve at a time point where no structural changes are observed in the nerve. By inducing such a conditioning lesion to nerve tissue, vibration represents a trauma corresponding to a crush lesion or transection of the nerve.

The hind paws of rats were subjected to vibration at a frequency of 80 Hz., an acceleration of 32 m./s.2 rms (i.e. ah.w approximately 6.3 m./s.2 rms) for five hours daily during five consecutive days. Morphological, histochemical and immunohistochemical analyses of the soleus, extensor digitorum longus and the plantar muscles in the vibrated limb and the contralateral control limb were performed. No changes were seen in the soleus or extensor digitorum longus muscles but different degrees of degeneration of the muscle fibres were seen in the plantar muscle sections as well as signs of regeneration. No changes were observed in the contralateral unexposed limb. It is concluded that it is not only nervous tissue but also muscle tissue that can be affected by vibration. The changes seem to be confined to muscles close to the vibration exciter.

The perception thresholds for vibration stimuli of the hand at seven frequencies (8-500 Hz) were evaluated in 300 patients referred to the Department of Hand Surgery in Malmö during the years 1985-1990 for various types of neuropathy (carpal tunnel syndrome, vibration-induced neuropathy, cervical rhizopathy, brachialgia, ulnar neuropathy, radial tunnel syndrome, and polyneuropathy). A sensibility index was calculated by dividing the integrated area under the obtained vibrogram curve of each object tested (areaT) by that of the corresponding area under a superimposed and age matched reference curve (areaR). Sensibility index of less than 0.8 was regarded as the cut off value. The index and little fingers bilaterally were tested to reflect median and ulnar nerve function. There were considerable variations in patterns of pathology among the various groups of patients. In patients with unilateral carpal tunnel syndrome only 10 patients (23%) had abnormalities limited to one recording, while 21 patients (47%) showed abnormalities in all four recordings. This indicates that an isolated carpal tunnel syndrome may reflect more generalised disease of the peripheral nervous system.

The hind leg of adult rats was exposed to vibrations (82 Hz; amplitude peak-to-peak 0.21 mm) for 4 hours during 5 consecutive days. Light and electron microscopic examination of the plantar and sciatic nerves were done immediately after the exposure period or after a 2- or 4-week recovery period. Light microscopic examination did not reveal any distinct signs of injury. However, ultrastructurally unmyelinated fibers in the plantar nerves showed distinct changes, with deranged axoplasmic structure and/or accumulation of smooth endoplasmatic reticulum. These changes were to a large extent reversible in 2 weeks and appeared normalized after a 4-week recovery period. No ultrastructural changes could be observed in the sciatic nerve. However, when the sciatic nerve was crushed after 5 days of vibration exposure, axonal outgrowth was increased 23% as compared with controls. These findings confirm that vibration induces nerve fiber damage, in this experimental model expressed as a "conditioning effect" contributing to increased regeneration potential of the corresponding neurones.

The hind limbs of anaesthetized rats were exposed to vibration trauma (81 Hz; amplitude peak to peak 0.50 mm) for 4 hours during 2 consecutive days. The animals were examined in groups of 4 immediately after the last exposure, and after 1, 2, 3, 5, 7, 10, 14 and 28 days. The Achilles tendons and the tendons of the anterior tibialis muscles were sampled and processed to demonstrate IGF-I immunoreactivity. In the normal Achilles tendon and in the tendon of the anterior tibial muscle, slight IGF-I immunoreactivity was seen in many of the long slender fibroblasts between the collagen bundles. A strong increase in the IGF-I immunoreactivity appeared in the anterior tibialis muscle tendon 3 days after the last vibration exposure. In addition, the tendon fibroblasts became hypertrophic. A similar but less striking increase in IGF-I immunoreactivity appeared in the Achilles tendon. The peak intensity and frequency of stained cells were achieved after 7 days for both tendons. The intensity then levelled off, and was normalized after 28 days. It is concluded that acute exposure to vibrations induces reactive changes in fibroblasts in tendons, which may reflect a change to a more active synthesising state, as a response to the vibration trauma. The transiently altered expression of IGF-I immunoreactivity forms a link in a chain of events regulating the functional activity level of fibroblasts in response to a trauma.

Peripheral neuropathy represents a well-known complication from long-term exposure to vibration. In the present study an experimental model is presented with the purpose of analyzing the formation of intraneural edema following vibration exposure. Vibration (82 Hz, peak-to-peak amplitude 0.21 mm) was induced in the hind limb of rats by the use of vibrating electric motors during 4 h/d for 5 d. Tracer techniques (with albumin Evans blue and horseradish peroxidase) were used to study the permeability of intraneural microvessels after the vibration exposure on day 5. It was found that the vibration trauma in this model induced epineurial edema in the sciatic nerve. It is hypothesized that the formation of intraneural edema may be an important pathophysiological factor in the occurrence of vibration-induced neuropathy.

Hind legs of adult rats were exposed to vibrations (81 Hz; amplitude 0.50 mm peak to peak) for 4 h during two consecutive days. The sciatic, tibial and plantar nerves were isolated and processed for immunohistochemical demonstration of IGF-I (insulin-like growth factor I; somatomedin C) immunoreactivity at different time intervals after the vibration exposure. In sham-exposed rats the axons in peripheral nerves showed no or faint IGF-I immunoreactivity while most Schwann cells were negative. Exposure of the hind legs to vibrations induced increased IGF-I immunoreactivity in the Schwann cells, demonstrable at the end of the exposure period and reaching maximal intensity 2-3 days after vibration exposure. Several distended axons similarly showed increased staining. The IGF-I immunoreactivity decreased after 7-10 days to almost the level in the control nerves. The most extensive changes were observed in the plantar nerves. The tibial nerves similarly expressed strongly increased IGF-I immunoreactivity in their Schwann cells. The sciatic nerve showed, however, only slightly to moderately increased staining. Cells in the epineurium of the plantar and, to a limited extent, of the tibial nerves expressed concomitantly increased IGF-I immunoreactivity. We conclude that the transiently increased IGF-I immunoreactivity in peripheral nerves reflects reactive changes caused by vibrations and most prominently expressed by the Schwann cells.