Allodynia is a well-known component of
neuropathic pain resulting from injury to the nervous system. Clinical
pain states with
allodynia in connection with longstanding superficial
wounds have, however, not been reported in the literature. In this case a
chronic pain state developed in a previously healthy 17-year-old girl in and around a persistently suppurating
appendectomy wound. There was no spontaneous
pain but pronounced
allodynia in the
wound and in the surrounding skin. Quantitative thermal tests showed abnormal thresholds for several sensory modalities confirming abnormal processing of sensory input from the involved area. The pattern of sensory abnormalities evaluated with thermal testing changed transiently and the
allodynia diminished during a
phentolamine block. Since the
pain responded poorly to
opioids and
ketamine has been reported to reduce
allodynia, it was administered in a sub-dissociative bolus dose during
wound dressing. The
wound was essentially unchanged
after treatment for 3 months but the
allodynia and sensory aberrations had decreased significantly. We interpret these results as a de-sensitizing effect in the long term of repeated
NMDA-receptor blockade by
ketamine in a
chronic pain state, with indications of central sensitization, partially maintained by sympathetic activity.