Topic
Somatosensory system
About: Somatosensory system is a research topic. Over the lifetime, 6371 publications have been published within this topic receiving 316900 citations.
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TL;DR: The findings in this study indicate that the thalamic processing of somatosensory information conveyed by the lemniscal system is altered by transection of the spinothalamic tract, which would result in altered cortical processing of innocuous somatoensory inputs following deafferentation and so possibly contribute to the generation of the central pain syndrome.
101 citations
TL;DR: Using quantitative sensory testing, neurophysiology and skin biopsies, Schmid et al. demonstrate that carpal tunnel syndrome affects large fibres and their nodal complexes, but is also associated with a reduction in the number of small sensory axons.
Abstract: Surprisingly little is known about the impact of entrapment neuropathy on target innervation and the relationship of nerve fibre pathology to sensory symptoms and signs. Carpal tunnel syndrome is the most common entrapment neuropathy; the aim of this study was to investigate its effect on the morphology of small unmyelinated as well as myelinated sensory axons and relate such changes to somatosensory function and clinical symptoms. Thirty patients with a clinical and electrophysiological diagnosis of carpal tunnel syndrome [17 females, mean age (standard deviation) 56.4 (15.3)] and 26 age and gender matched healthy volunteers [18 females, mean age (standard deviation) 51.0 (17.3)] participated in the study. Small and large fibre function was examined with quantitative sensory testing in the median nerve territory of the hand. Vibration and mechanical detection thresholds were significantly elevated in patients with carpal tunnel syndrome (P 0.13). A skin biopsy was taken from a median nerve innervated area of the proximal phalanx of the index finger. Immunohistochemical staining for protein gene product 9.5 and myelin basic protein was used to evaluate morphological features of unmyelinated and myelinated axons. Evaluation of intraepidermal nerve fibre density showed a striking loss in patients (P 0.07). However, patients displayed a significant increase in the percentage of elongated nodes (P < 0.0001), with altered architecture of voltage-gated sodium channel distribution. Whereas neither neurophysiology nor quantitative sensory testing correlated with patients’ symptoms or function deficits, the presence of elongated nodes was inversely correlated with a number of functional and symptom related scores (P < 0.023). Our findings suggest that carpal tunnel syndrome does not exclusively affect large fibres but is associated with loss of function in modalities mediated by both unmyelinated and myelinated sensory axons. We also document for the first time that entrapment neuropathies lead to a clear reduction in intraepidermal nerve fibre density, which was independent of electrodiagnostic test severity. The presence of elongated nodes in the target tissue further suggests that entrapment neuropathies affect nodal structure/myelin well beyond the focal compression site. Interestingly, nodal lengthening may be an adaptive phenomenon as it inversely correlates with symptom severity.
100 citations
TL;DR: The present results suggest that a chronic pathological modification of peripheral sensorimotor inputs is associated with changes in neural activity at multiple sites of the somatosensory system.
Abstract: The human somatosensory cortex (S1) is capable of modification after partial peripheral deafferentation, but it is not known whether spinal and brainstem changes contribute to this process. We recorded spinal, brainstem and cortical somatosensory evoked potentials following ulnar nerve stimulation in patients affected by unilateral carpal tunnel syndrome with EMG evidence of chronic alterations in median nerve sensorimotor conduction at the wrist lasting at least 4 weeks, and compared them with those from the unaffected hand and with those obtained in a control group. Amplitudes of spinal N13 and brainstem P14 potentials following stimulation of the ulnar nerve ipsilateral to the deafferented median nerve were greater than those following stimulation of the contralateral ulnar nerve. Side-to-side amplitude differences in N13 and P14 were greater in patients than in the control group. Parietal N20 and P27 potentials, supposedly generated in S1, were also significantly increased. The present results suggest that a chronic pathological modification of peripheral sensorimotor inputs is associated with changes in neural activity at multiple sites of the somatosensory system. Changes in spinal and brainstem structures could contribute to the mechanisms subserving changes in the S1. Changes in synaptic strength and unmasking inputs secondary to disconnection of the normally dominant inputs to the 'median nerve' cortex may be the mechanisms underlying ulnar nerve SEP changes.
100 citations
TL;DR: The occurrence of mislocalizations was correlated with a detailed psychophysical examination in which sensory, motor and autonomic symptoms were assessed and support the concept of pain–induced reorganization in the somatosensory system of CRPS patients.
Abstract: Complex-Regional-Pain-Syndromes (CRPS) are characterized by sensory,motor and autonomic dysfunctions. Patterns of sensory symptoms suggest changes within the central nervous system (CNS). Recently, we could show substantial reorganization of somatotopic maps within the central nervous system of patients with CRPS using functional imaging techniques (Maihofner et al. Neurology, 2003). These changes were predicted by CRPS pain and mechanical hyperalgesia. In the present study we looked for potential psychophysical correlates of cortical reorganization in CRPS. Sequential pneumatic non-noxious tactile stimulation was performed at digits 1 and 5 in 24 patients with CRPS of the upper extremities. Both the unaffected and affected side were examined. Patients were interviewed for tactile induced sensations. The occurrence of mislocalizations was correlated with a detailed psychophysical examination in which sensory, motor and autonomic symptoms were assessed. Eight patients (30 %) reported tactile mislocalizations, which were felt in the affected hand. In four cases the referred sensations spread into other nerve territories (ulnar/median nerve). Presence of mechanical hyperalgesia significantly predicted the occurrence of mislocalizations. In contrast, in a healthy control group, no mislocalizations were found. Thus, our results further support the concept of pain-induced reorganization in the somatosensory system of CRPS patients.
100 citations
TL;DR: The authors studied four hemiparetic patients with large unilateral periventricular brain lesions acquired during the early third trimester of pregnancy, finding that the primary somatosensory representation of their paretic hands was nevertheless located in the contralateral rolandic cortex.
Abstract: The authors studied four hemiparetic patients with large unilateral periventricular brain lesions acquired during the early third trimester of pregnancy. fMRI and magnetoencephalography demonstrated that the primary somatosensory representation of their paretic hands was nevertheless located in the contralateral rolandic cortex. Thus, outgrowing thalamocortical somatosensory projections had apparently bypassed the lesion to reach their original cortical destination. Such somatosensory projections curving around the lesion were effectively visualized by magnetic resonance diffusion tractography.
100 citations