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PubMed1997

Cutaneous norepinephrine application in complex regional pain syndrome.

Patients with complex regional pain syndrome (CRPS) (n=20) were examined in order to evaluate cutaneous reactions to norepinephrine (NE) on both the affected and the unaffected limb in comparison to healthy controls. Sixteen female and four male patients suffering from very acute and therefore untreated CRPS with a mean duration of 5.5 weeks were included in this study. Two groups of healthy volunteers served as control groups: the first group (n=18) according to the same study protocol as CRPS patients, and the second group (n=10) after warming up one limb. Norepinephrine was iontophoresized (0.2 mA, 120 s) and vasoconstriction was recorded by laser-doppler flowmetry. Pain sensations were simultaneously rated on a visual analogue scale (VAS). Five patients underwent a second trial with higher intracutaneous NE concentrations in order to study possible dose-dependent effects of NE on pain sensation. After acclimatization, skin temperature was recorded by infra-red thermography. The NE-induced reduction of skin blood flow was significantly higher in the affected limb in the patient group (33.0 vs 11.2%, p<0.005). None of the patients reported pain or hyperalgesia. The skin temperature of CRPS patients was significantly higher in the affected limb (34.7 vs 32.5 degrees C, p<0.001). The first control group did not show any difference between left and right sides concerning NE-induced vasoconstriction or skin temperature. The second control group had an increased unilateral skin temperature after warming up (35.0 vs 34.3 degrees C, p<0.006) and demonstrated a significantly increased vasoconstriction on the warmer side (52.0 vs 20.2%, p<0.03) corresponding to findings in patients with acute CRPS. The present study proves that there are signs of decreased sympathetic activity in the affected limb in very acute CRPS. However, no indication was found for increased sensitivity of vascular alpha-receptors in the very acute stages of CRPS, and there was also no indication for a significant direct contribution of the sympathetic nervous system to pain in very acute CRPS.

Journal Article↗

PubMedDate not supplied

Cardiac autonomic involvement and peripheral nerve function in patients with diabetic neuropathy.

The aim of our study was to investigate the relationship between cardiac autonomic neuropathy and dysfunction of myelinated and unmyelinated nerve fibres in the peripheral nerve. We measured nerve conduction velocities, warmth/cold perception thresholds at the foot dorsum, sympathetic skin response (SSR), and performed the quantitative sudomotor axon reflex test (QSART). Forty-three diabetic patients with distal-symmetric polyneuropathy were included. According to the results of heart rate variation, 20 patients had cardiac autonomic neuropathy (CAN+). Apart from motor nerve conduction velocities, all tests were more often abnormal in CAN+ patients. Warmth thresholds (afferent C-fibres) and reduced compound muscle action potentials (CMAPs) of the tibial and peroneal nerve, indicating axonal damage, were more often abnormal in CAN+. Cold threshold and sural nerve conduction velocity were indicators of involvement of myelinated small and large nerve fibres, but not of the cardiac autonomic system. Ninety-four percent (94%) of patients with absent SSR and 78% of patients with abnormal QSART had CAN+. SSR and QSART may be useful for assessment of autonomic neuropathy in diabetic patients with cardiac arrhythmia where direct measurement of heart rate variability is not possible. In the majority of our patients with CAN+, the vagal-cardiac and the sudomotor-sympathetic systems were involved simultaneously, although two entirely different systems were tested. This may reflect a C-fibre directed selectivity of the pathological process in autonomic diabetic neuropathy. In conclusion our results show that diabetics with and without cardiac autonomic neuropathy have a different profile of involvement of peripheral nerve fibres.

Adult↗