Dynamic mechanical allodynia & evoked peripheral neuropathy pain

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Pain. 2005 Jun;115(3):264-72.

Dynamic mechanical allodynia: On the relationship between temporo-

spatial stimulus parameters and evoked pain in patients with

peripheral neuropathy.

sson M, Leffler AS, Hansson P.

Section of Clinical Pain Research, Department of Surgical Science,

Karolinska Institute and Pain Center, Department of Neurosurgery,

Karolinska University Hospital Solna, SE-171 76 Stockholm, Sweden.

The relationship between temporo-spatial stimulus parameters and

evoked pain intensity as well as duration was examined in patients

with peripheral neuropathy and brush-evoked allodynia, i.e. dynamic

mechanical allodynia. Brush-evoked allodynia was induced in the

innervation territory of the lesioned nervous structure in 18

patients by lightly stroking different distances of the skin (20, 40,

60mm) two or four times with brushes of different widths (4, 8,

16mm). Pain intensity and duration of brush-evoked allodynia was

recorded using a computerized visual analogue scale. The total brush-

evoked pain intensity, including painful aftersensation was

calculated as the area under the curve.

Following each stimulus, the patients selected pain descriptors from

a validated instrument. Significantly increased total brush-evoked

pain intensity was demonstrated with increased brushing length and

number of strokes (P<0.001), but not while altering brush width. Lack

of influence of brush width was further underlined by the finding

that activation of equivalent areas (e.g. 160mm(2)) resulted in

higher total brush-evoked pain intensity if brushing the skin with a

thin brush (4mm) over a longer distance (40mm) than a thick brush

(8mm) over a shorter distance (20mm). Significantly increased

duration of aftersensation was demonstrated only following increased

brushing length (P<0.008).

The most commonly used sensory-discriminative pain descriptors were

pricking, burning and sore and for the affective descriptors,

annoying and troublesome. This is the first study demonstrating a

relationship between evoked pain and some temporo-spatial stimulus

parameters during brush-evoked allodynia.