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Biomedical subjects

A J Brammer

Publications and source records attributed to A J Brammer.

14 recordsLinked to original sources
PubMed2006

Nerve conduction and sensorineural function in dental hygienists using high frequency ultrasound handpieces.

BACKGROUND: Oscillatory vibration from industrial power tools poses a well-recognized risk of peripheral nerve injury. There have been reports of elevated vibrotactile perception thresholds (VPT) among dentists, dental technicians, and dental hygienists, using rotary devices and ultrasonics. Elevated VPTs are an indicator of small fiber nerve or mechanoreceptor injury, but the high frequencies associated with dental instruments are presumed by the ISO to exceed physiological response upper thresholds. This study examines nerve conduction and sensorineural deficits in dental hygienists. METHODS: A cross-sectional study of 94 experienced dental hygienists was conducted to assess peripheral nerve function and clinical signs and symptoms. Specialized testing included measurement of VPTs for three different categories of mechanoreceptors, sensory nerve conduction tests with fractionated digit and palmar segments, and measurement of calibrated pinch force with force sensitive resistors (FSRs) during a simulated procedure. RESULTS: Chronic hand paresthesias were described by 44.7% of experienced dental hygienists. Sensory nerve conduction velocity (SNCV) across the wrist-palm segment of the median nerve. VPTs were particularly elevated at the FAII mechanoreceptor among experienced dental hygienists. Compared to participants without carpal tunnel syndrome (CTS), as defined by study criteria, 14 experienced hygienists with diagnosed CTS had almost twice the average weekly use of vibratory instruments -8.3 hr versus 4.5 hr, and had SNCV deficits along the digit -47.11 m/sec (+8.70) versus 42.57 m/sec (+8.25), and across the wrist -44.04 m/sec (+7.15) versus 41.36 m/sec (+9.27). There was a distinct subset of dental hygienists (27%) with a combination of low calibrated pinch force in simulations, subjective loss of strength and elevated VPTs, especially in the FAII mechanoreceptor population -110.82 db (+8.57) versus 104.84 db (+6.80) in the rest of the cohort. This subset also had a higher prevalence of paresthesias (67% vs. 39%) and greater cumulative vibration exposure (OR = 1.206 [CI 1.005-1.448]), than other hygienists. CONCLUSIONS: The high levels of paresthesias observed among dental hygienists appear to be attributable to several pathophysiological mechanisms, including, sensory nerve demyelination at the carpal tunnel and intrinsic to the digits, and dysfunction of fingertip mechanoreceptors. A distinct sub-population appears to exhibit a high level of accumulated abnormality.

Adult↗
PubMed2004

Segmental nerve conduction velocity in vibration-exposed shipyard workers.

OBJECTIVES: Segmental sensory nerve conduction velocity (SNCV) was measured from the wrists to the hands and digits of a population of vibration-exposed shipyard workers. This study was designed to investigate whether SNCV was selectively slowed in the fingers and whether a laboratory approach could be adapted for robust field use. METHODS: Wrist-palm, palm-proximal digit, and digital segments were determined from stimulation at the wrist with recording electrodes placed distally and adjusted to individual anatomy. The cohort was selected on the basis of current use of vibratory tools. RESULTS: Wrist-palm and digital segments were slower than palm-proximal digit segments for dominant and non-dominant hands and for both ulnar and median nerves. In the dominant-hand median nerve of participants with current exposure, the SNCV was 41.4 m/s (SD 8.0) for the wrist-palm segment, 50.8 (SD 9.5) for the palm segment, and 42.1 m/s (SD 9.3) for the digital segment. Temperature had an important effect on nerve conduction velocity but not equally across segments. Other explanatory variables had modest effect on SNCV. CONCLUSIONS: Reduced SNCV in the digits may be a consequence of industrial exposure to vibration. Each sensory nerve segment appeared to have a different characteristic velocity and different pattern of association with skin temperature. There are differences between median and ulnar nerve segments, with potentially important consequences when standard distances are used to assess wrist-digit velocity.

Carpal Tunnel Syndrome↗
PubMed1997

Association between a quantitative measure of tactile acuity and hand symptoms reported by operators of power tools.

An association between a quantitative measure of tactile acuity at the fingertips and symptoms of reduced manipulative function, as established by responses to a questionnaire, was demonstrated in a population of 81 manual workers from the mining industry (62 power-tool operators and 19 nonusers). Mechanoreceptor-specific vibrotactile thresholds were determined for the slowly adapting type I (SAI) and fast-adapting types I and II (FAI and FAII) receptors at the fingertip of the third digit of each hand. Statistically significant threshold shifts in SAI and/or FAII acuity were found in persons responding affirmatively to questions concerning finger/hand numbness, blanching, and difficulty buttoning clothing. The best predictors of a quantitative change in tactile acuity were questions relating to difficulty manipulating small objects and buttoning clothing, yielding positive predictive values of from 90% to 100% and false positive rates of from 0% to 2.8%. The demonstration of an association between a quantitative measure of tactile acuity at the fingertips and some symptom reports, obtained by means of a questionnaire, provides the basis for the development of a screening procedure for persons at risk of such disturbances in hand function.

Adult↗
PubMed1997

Comparison between subjective and objective measures of active hearing protector and communication headset attenuation.

A masked-threshold and a loudness-balance method have been developed to estimate the attenuation of communication headsets and hearing protectors with built-in active noise reduction (ANR) systems. Both methods are used to estimate the attenuation of the ANR systems and the masked-threshold method is also used to estimate the total attenuation (active plus passive) of the device. The procedures are designed to be used in the presence of environmental noise, and to minimize the noise exposure of subjects during the measurements. For comparison, physical measurements of insertion loss have also been performed using a miniature microphone in the concha. Experiments showed that the masked-threshold methods tends to give increased estimates of the attenuation if the noise reduction of the left and right earcup ANR systems differs, as commonly occurs in practice. In contrast, the loudness-balance method reduces the estimates of the active attenuation. Insertion loss measurements may be influenced by the position of the microphone, owing to the spatial variability of the sound field under an earmuff when the ANR system is operating. Differences between physical and subjective measurements of up to 20 dB have been obtained in this study at frequencies of 250 Hz and below for a device in which the sound pressure varied substantially near, and within, the ear canal.

Adult↗
PubMed1987

Tactile perception in hands occupationally exposed to vibration.

The sensory changes that occur in hands occupationally exposed to vibration have been assessed clinically by conventional neurologic tests and, independently, by improved techniques for the determination of tactile spatial resolution (gap detection) and vibrotactile perception thresholds at frequencies from 2 to 400 Hz. Data from 10 forest workers who were exposed to chain saw vibration and seven laboratory workers of similar age, all of whom were screened to exclude confounding factors, revealed, for the first time, three patterns of response, two of which are associated with a vibration-induced neuropathy. The first appears to be characterized by normal or better than normal thresholds in SAI, FAI, and FAII mechanoreceptor types, while a second, extreme response involves elevated thresholds in all three receptor systems (and abnormal two-point discrimination). The third pattern appears to be characterized by elevated thresholds in SAI and/or FAII receptor types.

Hand↗
PubMed1987

Assessment of impaired tactile sensation. A pilot study.

Three methods are compared for assessing impaired tactile sensation in vibration-exposed workers: a medical examination including traditional neurological tests and refined measures of vibrotactile perception and gap detection. Of 18 subjects only 12 were judged free of confounding factors--five forestry workers exposed to chain-saw vibration, aged 28 (SD 5) years, and seven laboratory workers not exposed to vibration, aged 36 (SD 7) years. Each method identified the same subject as suffering the most from tactile impairment, but they differed in their ranking of the severity of sensory changes. The ranking by gap detection and vibrotactile perception at low frequencies was the most consistent [Spearman rank correlation coefficient (r) = 0.90]. The clinical results, when staged according to the neurological component of vibration-induced white finger, ranked the thresholds for gap detection and low-frequency vibrotactile perception equally well (r = 0.70). In contrast, the Taylor-Pelmear staging of the clinical results poorly represented the ranking of tactile thresholds recorded for these workers (r = 0.00 and -0.20, respectively). It also appeared that improved techniques for measuring vibrotactile and gap perception thresholds can detect sensory changes in the fingers not consistently found by conventional clinical tests.

Adult↗
PubMed1987

Sensorineural stages of the hand-arm vibration syndrome.

Recent work has shown that the vascular signs and neurological symptoms commonly associated with exposure of the hand to vibration may develop independently. A classification for the neurological component of the hand-arm vibration syndrome has been developed for those symptoms dominated by sensory afferent involvement, based on the results of objective tests on 634 hands. The first symptomatic stage (1SN) consists essentially of episodic finger numbness with or without tingling, the second involves, in addition, reduced sensory perception (2SN), while the most severe stage (3SN) focuses on reduced tactile discrimination and/or manipulative dexterity. Consistent implementation of this classification by means of objective tests requires one, or more, precise, quantitative measure of peripheral somatosensory dysfunction, in addition to the traditional neurological tests (fine touch, pain, and temperature). Measurements of tactile function by means of esthesiometry or vibrotactile perception appear suited to this purpose. A procedure for staging individual hands may then be based on combining numerical scores assigned to the results of the traditional neurological tests and, additionally, esthesiometer and/or vibrotactile perception thresholds.

Hand↗
PubMed1987

Vibration-induced neuropathy. Detection by nerve conduction measurements.

An analysis of electroneurographic studies of workers who operate hand-held vibrating power tools reveals that, when controlled for polyneuropathy and the effects of heavy manual work, significantly reduced sensory nerve conduction velocities occur within the hands. This finding is compatible with the available pathophysiological evidence. The detection of this presumed vibration-induced neuropathy and its distinction from compression neuropathies involving a localized primary lesion, such as carpal tunnel syndrome, thus requires a detailed investigation of nerve conduction within the hands. A technique well adapted to the detection of abnormalities in the most peripheral sensory nerve fibers and mechanoreceptors has been developed based on vibrotactile stimulation of a fingertip. The compound action potentials recorded noninvasively at the base of the finger and wrist from healthy male subjects possess peak-to-peak amplitudes of no more than 0.5 and 0.25 microV, respectively.

Action Potentials↗
PubMed1986

Assessing the severity of the neurological component of the hand-arm vibration syndrome.

In view of the observation in epidemiologic studies that the neurological component of the hand-arm vibration syndrome develops first, a conservative measure of the presence and progression of the syndrome may be obtained from the degree of numbness and loss of fine touch. Degraded tactile spatial resolution, as measured by step and gap detection with an esthesiometer, has been found, on the average, in stages 2 and 3 of the Taylor-Pelmear classification for vibration-induced white finger (VWF). Present evidence suggests that this occurrence is due to the degeneration of slowly adapting (type I) and, possibly, fast adapting (type I) mechanoreceptors, and/or their nerve fibers. The apparatus commonly employed for measuring vibrotactile perception thresholds in clinical studies records the sensitivity of fast adapting type II mechanoreceptors (pacinian corpuscles), which play no role in step or gap detection. They may, however, provide early evidence of neurological changes occurring in the syndrome, as a significant degradation in the threshold of fast adapting type II receptors appears to develop, on the average, before stage 2 of VWF.

Fingers↗
PubMed1986

Physiological noise and its influence on vibrotactile perception thresholds.

Vibration of physiological origin (physiological noise) was studied when a small diameter probe, attached to a vibrator and accelerometer for the determination of vibrotactile perception thresholds, was held in contact with a fingertip. The acceleration spectrum consisted of a broad plateau between 0.1 and 10 Hz, where the power spectral density was about -20 dB re 1 (m/s2)2/Hz, and it fell rapidly with increasing frequency above 10 Hz. Substantial contributions from respiration (0.2-1 Hz), blood circulation (1-5 Hz), and hand tremor (6-8 Hz) could be identified. The physiological noise was largely independent of subject, contact force, and probe diameter, and it was approximately equal in amplitude to the threshold of the vibrotactile perception. Current knowledge of the masking and adaptation of vibrotactile signals indicates that vibrotactile thresholds in the frequency range 2-250 Hz may be influenced by the magnitude of this physiological noise under some conditions of flesh stimulation.

Adult↗
PubMed1986

Dose-response relationships for hand-transmitted vibration.

Few dose-response relationships have been reported for signs and symptoms resulting from occupational exposure of the hand to vibration. For population groups whose members operate the same vibrating power tool or industrial process throughout the workday, a simple model may be constructed to provide functional dose-response relationships for the onset of episodes of finger blanching. In such groups, the latency interval for various population percentiles may be expressed in terms of a frequency-weighted, root-mean-square, component acceleration at a surface in contact with the hand. Of the two constitutive equations required by the model, one appears to be supported by epidemiologic data published since its derivation, but the second may require modification to be applicable to very short daily exposure durations.

Fingers↗
PubMed1986

A clinical assessment of seventy-eight cases of hand-arm vibration syndrome.

After the obtainment of an occupational history the following objective tests were carried out: esthesiometry, light touch, pain, temperature appreciation, Tinel's and Phalen's test, grip strength, Allen's test, and cold provocation (10-12 degrees C for 1 min). The 78 subjects were categorized (Taylor-Pelmear classification) according to the number, severity, and extent of the blanching attacks; sensory loss; musculoskeletal complaints; and interference with work and domestic and social activities. Four of the subjects had unequal hand assessments. It was not possible to correlate stage assessment with the objective tests on an individual basis. On a group basis, staging correlated with esthesiometry using the improved designs of Carlson et al. Cold provocation produced white finger attacks in only 50% of the cases. In some work processes (road ripping) of the subjects, damage to digital arteries and nerves was confined to the thumb and index and middle fingers. Four subjects had advanced tissue necrosis of the fingertips resulting from the use of hand-held pneumatic percussive tools. There was no evidence to support the view that the hand-arm vibration syndrome affects the central autonomic nervous system.

Adult↗