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Abstract
Objective To test whether contralateral sensory abnormalities in the clinically unaffected area of patients with unilateral neuropathic pain are due to the neuropathy or pain mechanisms.
Methods We analyzed the contralateral clinically unaffected side of patients with unilateral painful or painless neuropathy (peripheral nerve injury [PNI], postherpetic neuropathy [PHN], radiculopathy) by standardized quantitative sensory testing following a validated protocol. Primary outcome was the independent contribution of the following variables on the contralateral sensory function using generalized linear regression models: pain intensity, disease duration, etiology, body area, and sensory patterns in the most painful area.
Results Among 424 patients (PNI n = 256, PHN n = 78, radiculopathy n = 90), contralateral sensory abnormalities were frequent in both painful (n = 383) and painless (n = 41) unilateral neuropathy, demonstrating sensory loss for thermal and mechanical nonpainful stimuli and both sensory loss and gain for painful test stimuli. Analysis by etiology revealed contralateral pinprick hyperalgesia in PHN and PNI. Analysis by ipsilateral sensory phenotype demonstrated mirror-image pinprick hyperalgesia in both mechanical and thermal hyperalgesia phenotypes. Pain intensity, etiology, and affected body region predicted changes in only single contralateral somatosensory parameters. Disease duration had no impact on the contralateral sensory function.
Conclusion Mechanisms of sensory loss seem to spread to the contralateral side in both painful and painless neuropathies. Contralateral spread of pinprick hyperalgesia was restricted to the 2 ipsilateral phenotypes that suggest sensitization; this suggest a contribution of descending net facilitation from supraspinal areas, which was reported in rodent models of neuropathic pain but not yet in human patients.
Glossary
- CI=
- confidence interval;
- CPT=
- cold pain threshold;
- DFNS=
- German Research Network on Neuropathic Pain;
- DMA=
- dynamic mechanical allodynia;
- HPT=
- heat pain threshold;
- MDT=
- mechanical detection threshold;
- MPS=
- mechanical pain sensitivity;
- MPT=
- mechanical pain threshold;
- PHS=
- paradoxical heat sensations;
- PPT=
- pressure pain threshold;
- QST=
- quantitative sensory testing;
- TSL=
- thermal sensory limen;
- VDT=
- vibration detection threshold;
- WDR=
- wide-dynamic-range;
- WDT=
- warm detection threshold;
- WUR=
- wind-up ratio
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
- Received January 2, 2021.
- Accepted in final form April 19, 2021.
- © 2021 American Academy of Neurology
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