Pain
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The nociceptive flexion reflex (NFR) has been used as a psychophysiological tool to study spinal nociceptive processes in numerous clinical and experimental studies. Despite widespread use of the NFR, few attempts have been made to empirically test and compare different scoring criteria to detect the presence/absence of the reflex. The present studies were conducted to address this issue. ⋯ In both studies, receiver operating characteristics (ROCs) analyses were used to evaluate and compare different scoring methods. The results indicate that a number of different criteria were acceptable for defining an NFR threshold based on the area under the ROC curve and its statistical significance; however, NFR Interval z score [(NFR Interval Mean-baseline mean)/baseline SD] emerged as the scoring criterion with the greatest accuracy and with cut-points that are reliable across samples. These findings support the application of a common NFR scoring criterion to enhance direct comparison of results across different research laboratories and study samples.
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Clinical Trial
Functional and structural nerve fiber findings in heterozygote patients with Fabry disease.
Fabry disease is an X-linked inherited lysosomal disorder with dysfunction of the lysosomal enzyme alpha-galactosidase A causing accumulation of glycolipids in multiple organs including the nervous system. Pain and somatosensory disturbances are prominent manifestations of this disease. Until recently disease manifestations in female carriers of Fabry disease have been questioned. ⋯ Sensory nerve action potential amplitude and maximal sensory conduction velocity were not different, whereas there was a highly significant reduction in intraepidermal nerve fiber density. We found no correlation between pain VAS score, quantitative sensory testing and intraepidermal nerve fiber density. Our study demonstrates that careful evaluation of symptoms in female Fabry patients is important as small fiber disease manifestations are present, which in some cases is only detected by skin biopsy.
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Studies in healthy human subjects and patients with irritable bowel syndrome suggest sex differences in cerebral nociceptive processing. Here we examine sex differences in functional brain activation in the rat during colorectal distention (CRD), a preclinical model of acute visceral pain. [(14)C]-iodoantipyrine was injected intravenously in awake, non-restrained female rats during 60- or 0-mmHg CRD while electromyographic abdominal activity (EMG) and pain behavior were recorded. Regional cerebral blood flow-related tissue radioactivity was analyzed by statistical parametric mapping from autoradiographic images of three-dimensionally reconstructed brains. ⋯ Greater activation of the ventromedial prefrontal cortex and broader limbic/paralimbic changes in females suggest greater engagement of affective mechanisms during visceral pain. Greater cortical activation in males is consistent with the concept of greater cortical inhibitory effects on limbic structures in males, which may relate to differences in attentional and cognitive attribution to visceral stimuli. These findings show remarkable similarities to reported sex differences in brain responses to visceral stimuli in humans.