Complex regional pain syndrome (CRPS) impairs visuospatial perception,whereas post-herpetic neuralgia does not: possible implications for supraspinal mechanism of CRPS.
BACKGROUND
Complex regional pain syndrome (CRPS) patients show impaired visuospatial perception in the dark, as compared to normal patients with acute nociceptive pain. The purpose of this study is 2-fold: (i) to ascertain whether this distorted visuospatial perception is related to the chronicity of pain, and (ii) to analyse visuospatial perception of CRPS in comparison with another neuropathic pain condition.


METHODS
We evaluated visual subjective body-midline (vSM) representation in 27 patients with post-herpetic neuralgia (PHN) and 22 with CRPS under light and dark conditions. A red laser dot was projected onto a screen and moved horizontally towards the sagittal plane of the objective body-midline (OM). Each participant was asked to direct the dot to a position where it crossed their vSM. The distance between the vSM and OM was analysed to determine how and in which direction the vSM deviated.


RESULTS
Under light condition, all vSM judgments approximately matched the OM. However, in the dark, CRPS patients, but not PHN patients, showed a shifted vSM towards the affected side.


CONCLUSIONS
We demonstrated that chronic pain does not always impair visuospatial perception. The aetiology of PHN is limited to the peripheral nervous system, whereas the distorted visuospatial perception suggests a supraspinal aetiology of CRPS.
Uematsu
Hironobu
H
Department of Acute Critical Medicine (Anesthesiology), Osaka University, Graduate School of Medicine, Osaka, Japan.
Sumitani
Masahiko
M
Yozu
Arito
A
Otake
Yuko
Y
Shibata
Masahiko
M
Mashimo
Takashi
T
Miyauchi
Satoru
S
D000328:Adult; D000368:Aged; D020918:Complex Regional Pain Syndromes / Q000150:complications* / Q000209:etiology; D003624:Darkness; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D051474:Neuralgia, Postherpetic / Q000150:complications*; D010468:Perceptual Disorders / Q000209:etiology* / Q000503:physiopathology; D017933:Peripheral Nervous System / Q000503:physiopathology*; D013647:Task Performance and Analysis