Problems of pain and paresthesia in the healed wounds of burn patients are an understudied and poorly documented phenomenon. This descriptive study was designed to examine the prevalence and characteristics of these chronic sensory problems 1 year or more postburn. Four hundred and thirty patients were sent questionnaires which assessed the frequency and intensity of the problems, influencing factors and impact on patients' lives. These problems were assessed by rating scales (visual analogue and categorical scales) and the McGill Pain Questionnaire (MPQ). The response rate was 67%. Over one-third of the participants (36.4%) complained of pain while the prevalence of paresthetic sensations was 71.2%. More than half of the symptomatic patients experienced sensory problems every week sufficient to interfere with daily living. No relationships were found between these sensory problems and the patients' age or sex, burn etiology, or length of time elapsed since injury. Burn severity was related to the frequency of the problems. Discussion emphasizes the need for adequate treatment of these problems and suggests further research issues.

Abnormal return of cutaneous sensibility is common after burn injuries and many patients complain of painful and/or paresthetic sensations in their healed wounds. However, little is known about the exact nature and severity of these problems. The present study was designed to provide a quantitative evaluation of the cutaneous sensibility in burned patients. Tactile, thermal and pain thresholds were measured in 121 patients with healed burns paired-matched to 121 control healthy subjects more than 18 months after the burns. Testing was confined to both upper limbs and was performed in a healed burn area and its contralateral burned or unburned counterpart. The tested sites were also divided into symptomatic and asymptomatic ones, depending on the presence or not of pain or paresthesia at the site. The results showed significantly higher sensory thresholds in burned patients than control subjects. Severity of the deficits of the various sensory modalities was, however, a function of burn depth. Deep burn injuries which had required skin grafts to heal were more seriously affected than superficial burns which had healed spontaneously. Significant sensory losses were found not only in burn sites but also in the non-injured areas suggesting changes in the central nervous system. When symptomatic and asymptomatic sites were compared, significant deficits were observed in the tactile modality (touch-pressure). Other significant predictors of chronic sensory problems were burn depth and patients' age. Pathophysiological mechanisms of diminished sensibility in burned and unburned skin as long as several years after the injury are discussed along with those implicated in pain and paresthesia problems reported by the patients.

Results on a mirrow drawing task showed that a deafferented patient had no problem completing the pattern, whereas normal subjects needed more than four trials to attain a similar performance. The results suggest the presence of integrated visual and proprioceptive maps. The inversion of visual coordinates requires the need for a recalibration. Without proprioception, the task is more like a simple visual tracking task.

It has previously been established that muscles become active in response to deviations from a threshold (referent) position of the body or its segments, and that intentional motor actions result from central shifts in the referent position. We tested the hypothesis that corticospinal pathways are involved in threshold position control during intentional changes in the wrist position in humans. Subjects moved the wrist from an initial extended to a final flexed position (and vice versa). Passive wrist muscle forces were compensated with a torque motor such that wrist muscle activity was equalized at the two positions. It appeared that motoneuronal excitability tested by brief muscle stretches was also similar at these positions. Responses to mechanical perturbations before and after movement showed that the wrist threshold position was reset when voluntary changes in the joint angle were made. Although the excitability of motoneurons was similar at the two positions, the same transcranial magnetic stimulus (TMS) elicited a wrist extensor jerk in the extension position and a flexor jerk in the flexion position. Extensor motor-evoked potentials (MEPs) elicited by TMS at the wrist extension position were substantially bigger compared to those at the flexion position and vice versa for flexor MEPs. MEPs were substantially reduced when subjects fully relaxed wrist muscles and the wrist was held passively in each position. Results suggest that the corticospinal pathway, possibly with other descending pathways, participates in threshold position control, a process that pre-determines the spatial frame of reference in which the neuromuscular periphery is constrained to work. This control strategy would underlie not only intentional changes in the joint position, but also muscle relaxation. The notion that the motor cortex may control motor actions by shifting spatial frames of reference opens a new avenue in the analysis and understanding of brain function.