Validation of the composite autonomic symptom scale 31 (COMPASS-31) in patients with and without small fiber polyneuropathy.

BACKGROUND AND PURPOSE: The recently developed composite autonomic symptom score 31 (COMPASS-31) is a questionnaire that assess symptoms of dysautonomia. It was distilled from the well-established Autonomic Symptom Profile questionnaire. COMPASS-31 has not yet been externally validated. To do so, its psychometric properties and convergent validity in patients with and without objective diagnosis of small fiber polyneuropathy (SFPN) were assessed. METHODS: Internal validity and reliability of COMPASS-31 were assessed in participants with or without SFPN spanning the full range of severity of autonomic symptoms. Convergent validity was assessed by comparing results of the COMPASS-31 with the "gold standard" autonomic function testing that measures cardiovagal, adrenergic and sudomotor functions. Additionally, relationships between COMPASS-31 and the Short Form McGill Pain Questionnaire, Short Form Health Survey and 0-10 numeric pain scale were measured. COMPASS-31 and all other questionnaire results were compared between patients with or without evidence of SFPN, objectively confirmed by distal-leg PGP9.5-immunolabeled skin biopsy. RESULTS: Amongst 66 participants (28 SFPN+, 38 SFPN-), COMPASS-31 total scores had excellent internal validity (Cronbach's α = 0.919), test-retest reliability (r(s) = 0.886; P < 0.001) and good convergent validity (r(s) = 0.474; P < 0.001). COMPASS-31 scores differed between subjects with or without SFPN (Z = -3.296, P < 0.001) and demonstrated fair diagnostic accuracy. Area under the Receiver Operating Characteristic curve was 0.749 (P = 0.01, 95% confidence interval 0.627-0.871). CONCLUSIONS: COMPASS-31 has good psychometric properties in the population of patients being evaluated for SFPN and thus it might be useful as an initial screening tool for the more expensive SFPN objective tests.

Endoneurial pathology of the needlestick-nerve-injury model of Complex Regional Pain Syndrome, including rats with and without pain behaviors.

Current rodent models of neuropathic pain produce pain hypersensitivity in almost all lesioned animals and not all identified experimental effects are pain specific. 18G needlestick-nerve-injury (NNI) to one tibial nerve of outbred Sprague-Dawley rats models the phenotype of Complex Regional Pain Syndrome (CRPS), a post-traumatic neuropathic pain syndrome, leaving roughly half of NNI rats with hyperalgesia. We compared endoneurial data from these divergent endophenotypes searching for pathological changes specifically associated with pain-behaviors. Tibial, sural, and common sciatic nerves from 12 NNI rats plus 10 nerves from sham-operated controls were removed 14 days post-surgery for morphometric analysis. PGP9.5(+) unmyelinated-fibers were quantitated in plantar hindpaw skin. Distal tibial nerves of NNI rats had endoneurial edema, 30% fewer axons, twice as many mast cells, and thicker blood-vessel walls than uninjured tibial nerves. However the only significant difference between nerves from hyperalgesic versus non-hyperalgesic NNI rats was greater endoneurial edema in hyperalgesic rats (p < 0.01). We also discovered significant axonal losses in uninjured ipsilateral sural nerves of NNI rats, demonstrating spread of neuropathy to nearby nerves formerly thought spared. Tibial and sural nerves contralateral to NNI had significant changes in endoneurial blood-vessels. Similar pathological changes have been identified in CRPS-I patients. The current findings suggest that severity of endoneurial vasculopathy and inflammation may correlate better with neuropathic pain behaviors than degree of axonal loss. Spread of pathological changes to nearby ipsilateral and contralateral nerves might potentially contribute to extraterritorial pain in CRPS.