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VIBROTACTILE THRESHOLD AND PIN-PRICK SENSITIVITY AS INDICATORS OF SUBCLINICAL CHANGES IN SOMATOSENSORY FUNCTION: EFFECTS OF ENVIRONMENTAL EXPOSURE TO ARSENIC IN DRINKING WATER.
Citation:
Otto, D A. AND H. K. Hudnell. VIBROTACTILE THRESHOLD AND PIN-PRICK SENSITIVITY AS INDICATORS OF SUBCLINICAL CHANGES IN SOMATOSENSORY FUNCTION: EFFECTS OF ENVIRONMENTAL EXPOSURE TO ARSENIC IN DRINKING WATER. Presented at 8th International Symposium on Neurobehavioral Methods and Effects in Occupational and Environmental Health, Brescia, Italy, 6/23-26/2002.
Description:
Peripheral neuropathy is a classical symptom of arsenic poisoning. Nerve conduction velocity (NCV) is the preferred measure for clinical assessment of peripheral neuropathy, but this method is not practical for field studies. Alternative methods available for assessing function in the somatosensory system include vibrotactile thresholds (VTT) and pin-prick sensitivity (PPS).
Elevated VTT has been reported following exposure to solvents, jet fuel, elemental mercury and OP pesticides (D. Mergler, Behavioral Neurophysiology: Quantitative Measures of Sensory Toxicity in Chang LW & Slikker W. Neurotoxicology: Approaches and Methods, Academic Press, 1995). VTT can detect subclinical effects not apparent in NCV.
Two measures of tactile sensitivity (VTT and PPS) were used in a study of 321 residents of the Bamen region of Inner Mongolia exposed to arsenic in drinking water. VTTs were measured in the 2nd and 5th fingers of both hands; PPS was assessed in the arms and legs. Reduced pin-prick sensitivity and elevated vibrotactile thresholds were observed in the high exposure group (As levels of 400-700 ug/L) compared to medium (100-300 ug/L) and low (<20 ug/L) groups. The pattern of effect of arsenic exposure on VTT and PPS was similar, although PPS measures were somewhat more sensitive (smaller p-values) than VTT measures. Possible reasons for differences in the two measures are receptor types (Pacinian corpuscles for vibrotactile vs.different free endings for PPS), diameter of nerves (small unmyelinated free endings vs. large myelinated axons of Pacinian corpuscles) and location in skin (superficial vs. deep). The utility of these two measures in the assessment of chemical exposure in workers will be discussed.
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