Relationship between cutaneous pressure threshold and two-point discrimination.
ABSTRACT The amount of pressure that should be applied when doing the two-point discrimination test has always been a matter of controversy. The Pressure-specified Sensory Devices permits recording the pressure at which two-point discrimination (2 PD) occurs. The purpose of this study was to investigate the relationship between the cutaneous pressure threshold and 2PD in people with normal and abnormal peripheral nerve functions. The Pressure-specified Sensory Devices was used to quantify the cutaneous pressure threshold in the index-finger pulp in each individual, between the range of 2 mm and 8 mm of static 2 PD, using 1-mm intervals. Twenty normal controls were examined; ten patients were less than 45 years of age; and ten patients were greater than 45 years of age. This relationship of pressure to 2PD was also tested in eight patients with abnormal peripheral nerve function (four patients with carpal tunnel syndrome, and four patients with diabetic neuropathy). A curvilinear relationship was identified in which, for the same skin surface in the same individual, regardless of age or presence of nerve compression or neuropathy, the cutaneous pressure threshold was inversely related to static 2PD. This curve shifted upward and to the right with the increasing age of the normal population and with neurologic impairment. The awareness of this neurophysiologic relationship between 2PD and pressure threshold permits the design of strategies for sensibility testing and provides a basis for the interpretation of sensory test results.
- SourceAvailable from: Marisa De Cássia Registro Fonseca03/2012; , ISBN: 978-953-51-0407-0
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ABSTRACT: The spatial resolution of the pain system has not been studied in depth, and results are contradictory regarding the gradient of spatial resolution. Microneurographic recordings have revealed smaller receptive fields and higher density of nociceptors in more distal than proximal leg regions, whereas histological studies report higher density of C-fibers in more proximal than distal body regions. Due to this controversy, we conducted various psychophysical tests in order to examine the nociceptive spatial resolution and its gradient. Heat-pain threshold (HPT), perceived pain intensity, spatial summation (SS) of pain, two-point discrimination (2PD) of pain, and pain localization were measured in four body regions: upper back, thigh, lower leg, and foot. The highest HPT was demonstrated in the lower leg as compared with more proximal regions (P < 0.0001). SS was observed in all the regions and was found to be smallest in the foot (P < 0.05). The smallest 2PD and localization distances were found in the foot (P < 0.01) as compared with the lower leg and upper back. It appears that the nociceptive spatial resolution has a proximal-to-distal pattern of performance, namely that the spatial resolution of pain is finer in more distal than proximal body regions, similar to that of the touch system.Experimental Brain Research 11/2011; 216(2):181-90. · 2.22 Impact Factor
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ABSTRACT: Peripheral neuropathy is the most common neurological complication of human immunodeficiency virus (HIV) infection but is widely under-diagnosed in resource-limited settings. We investigated the utility of screening tools administered by nonphysician healthcare workers (HCW) and quantitative sensory testing (QST) administered by trained individuals for identification of moderate/severe neuropathy. We enrolled 240 HIV-infected outpatients using 2-stage cluster randomized sampling. HCWs administered the several screening tools. Trained study staff performed QST. Tools were validated against a clinical diagnosis of neuropathy. Participants were 65% women, mean age 36.4 years, median CD4 324 cells/μL. A total of 65% were taking antiretrovirals, and 18% had moderate/severe neuropathy. The screening tests were 76% sensitive in diagnosing moderate/severe neuropathy with negative predictive values of 84-92%. QST was less sensitive but more specific. Screening tests administered by HCW have excellent negative predictive values and are promising tools for scale-up in resource-limited settings. QST shows promise for research use. Muscle Nerve, 2013.Muscle & Nerve 01/2013; · 2.31 Impact Factor