| 2. |
- Perini, Irene, et al.
(författare)
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Rare human nerve growth factor-beta mutation reveals relationship between C-afferent density and acute pain evaluation
- 2016
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Ingår i: Journal of Neurophysiology. - : AMER PHYSIOLOGICAL SOC. - 0022-3077 .- 1522-1598. ; 116:2, s. 425-430
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Tidskriftsartikel (refereegranskat)abstract
- The rare nerve growth factor-beta (NGFB) mutation R221W causes a selective loss of thinly myelinated fibers and especially unmyelinated C-fibers. Carriers of this mutation show altered pain sensation. A subset presents with arthropathic symptoms, with the homozygous most severely affected. The aim of the present study was to investigate the relationship between peripheral afferent loss and pain evaluation by performing a quantification of small-fiber density in the cornea of the carriers, relating density to pain evaluation measures. In vivo corneal confocal microscopy (CCM) was used to quantify C-fiber loss in the cornea of 19 R221W mutation carriers (3 homozygous) and 19 age-matched healthy control subjects. Pain evaluation data via the Situational Pain Questionnaire (SPQ) and the severity of neuropathy based on the Neuropathy Disability Score (NDS) were assessed. Homozygotes, heterozygotes, and control groups differed significantly in corneal C-nerve fiber density, with the homozygotes showing a significant afferent reduction. Importantly, peripheral C-fiber loss correlated negatively with pain evaluation, as revealed by SPQ scores. This study is the first to investigate the contribution of small-fiber density to the perceptual evaluation of pain. It demonstrates that the lower the peripheral small-fiber density, the lower the degree of reported pain intensity, indicating a functional relationship between small-fiber density and higher level pain experience.
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| 3. |
- Sagafors, Dagrun, et al.
(författare)
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Single-Fiber Recordings Of Nociceptive Fibers in Patients With HSAN Type V With Congenital Insensitivity To Pain
- 2016
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Ingår i: The Clinical Journal of Pain. - 0749-8047 .- 1536-5409. ; 32:7, s. 636-642
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Nerve growth factor (NGF) is a protein important for growth and survival, but also for modulation of sensitivity of nociceptors and sympathetic neurons. The purpose of the present study was to investigate the effects of reduced NGF signaling in patients with hereditary sensory and autonomic neuropathies type V, congenital insensitivity to pain, caused by a mutation of the NGF beta gene, including a characterization of single nociceptive fibers using microneurography (MNG).Materials and Methods: One homozygote and 2 heterozygote patients with this mutation were examined with electromyography/neurography, thermal testing, quantitative sudomotor axon reflex test, and electrically induced axon reflex erythema in addition to MNG.Results: Low quantitative sudomotor axon reflex test measurements of 0.02 (left foot) and 0.03 (right foot) mL/cm(2) and elevated thermal thresholds for warmth and cold detection testing showed clear impairment of small nerve fibers, both sudomotor efferent and somatic afferent fibers, in the patient homozygote for the mutation. MNG from one of the heterozygote patients revealed changes in the small nociceptive fibers in skin, including abnormally low conduction velocity, spontaneous activity in A-delta fibers and C-nociceptors and abnormal or lacking response to heat.Discussion: The findings of grossly intact pain thresholds compared with anamnestic insensitivity of pain in deep somatic tissue such as bone suggest a gradient of impairment dependent on different NGF availability in various tissues. Even though these patients in some aspects report insensitivity to pain, they also report chronic spontaneous pain as their main symptom, strikingly highlighting differential mechanisms of insensitivity to evoked pain versus spontaneous pain.
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