Biomedical subjects

R Forget

Publications and source records attributed to R Forget.

At least 19 recordsLinked to original sources

PubMed2002

Long-term adjustment in burn victims: a matched-control study.

BACKGROUND: To date, there is little information about how severely burned patients compare to unburned healthy individuals in terms of psychological profile and quality of life. As part of a larger study on the sensory consequences of burns, we assessed psychological functioning and quality of life in burned patients and unburned healthy control subjects. We also examined whether burn patients experiencing pain and/or paresthetic sensations (i.e. symptomatic patients) present a profile that is different from those who are asymptomatic. METHODS: Forty-nine burned patients (% total body surface area = 34 59 % +/- 13.40; 82% males/18% females) were evaluated 63 59 +/- 28.1 months post-burn. They were matched with 49 unburned healthy volunteers on age, sex, and education level. All subjects were administered the Symptom Checklist 90-Revised (SCL-90-R) to assess psychological functioning and the 36-item Short-Form Health Survey (SF-36) to assess quality of life. RESULTS: Approximately 25% of the burn patients presented clinically-significant psychological disturbances compared to 12% in the control group. Burn patients enjoyed a quality of life comparable to that of the control subjects, although they perceived some deterioration in their general health. More symptomatic than asymptomatic patients suffered from clinically-relevant somatization and obsessive-compulsive disturbances. CONCLUSIONS: Severely burned patients adjust relatively well, although some develop clinically-significant psychological disturbances such as somatization and phobic anxiety. Burn patients experiencing abnormal sensations in their healed wounds (i.e. symptomatic patients) do not suffer from maladjustment to a greater extent than their asymptomatic counterparts, although more symptomatic patients experience somatization and obsessive-compulsive behaviours.

Adaptation, Psychological↗

PubMed2001

Prolonged orbicularis oculi activity: a major factor in apraxia of lid opening.

BACKGROUND: Apraxia of lid opening (ALO) is a nonparalytic inability to open the eyes at will in the absence of visible contraction of the orbicularis oculi (OOc) muscle. OBJECTIVE: To test the hypothesis that sustained activity of the OOc is a major factor in the difficulty in opening the eyes in this condition. METHODS: Lid movement detected in an electromagnetic field and electromyogram activity of the septal and pretarsal portions of the OOc were recorded in 12 healthy control subjects and 12 patients with a clinical diagnosis of ALO. The latencies to onset and to complete eye opening and the time during which eye opening was sustained were measured and analyzed in relation to OOc activity. RESULTS: The lid opening latencies and the lid movement duration were significantly increased in patients compared with control values. An abnormal persistence of OOc activity was present in 10 of the 11 patients with a delay in complete lid opening. The complete lid opening delay showed a strong positive correlation with the time it took to inhibit the OOc activity. This relationship fit the same linear regression in both groups. CONCLUSIONS: Patients with ALO show significant delays in eye opening. An abnormal persistence of OOc activity, detectable electromyographically but not clinically, could be the main factor contributing to the delay in lid opening in these patients.

Aged↗

PubMed2001

Balance findings in a child before and after a mild head injury.

OBJECTIVE: This case study reviews the preinjury and postinjury balance performance of an 11-year-old child who sustained a mild head injury. DESIGN: A prospective design was used to document balance 5 days before injury and 1, 4, and 12 weeks after injury. OUTCOME MEASURES: The assessments used were the balance subtest of the Bruininks-Oseretsky Test of Motor Proficiency, the Pediatric Clinical Test of Sensory Interaction for Balance, and the Postural Stress Test. RESULTS: One week after the trauma, balance deficits were observed in the three tests. The deficits improved 4 weeks after the injury, and performance remained stable over the following 2 months for two of the evaluations except for the Postural Stress Test performance, which failed to improve in the 3-month period after trauma. CONCLUSIONS: The good recovery of balance skills observed over the first month after injury seems to validate the current activity restrictions imposed on children after a mild head injury. However, the persistence of poor performance in the area of reactions to external perturbations indicates that some deficits may persist beyond what is expected with this population.

Child↗

PubMed1998

Muscle strength in individuals with healed burns.

OBJECTIVE: To quantify the long-term effects of burns on muscle strength and to investigate the impact of the initial severity of the trauma on muscle strength. DESIGN: Cross-sectional study comparing individuals with healed burns to nonburned control individuals matched for age, gender, body mass index, and physical activity level. SETTING: Subjects were selected from the data bank of a burn center of a large Montreal teaching hospital and tested in a university laboratory. PATIENTS: Thirty subjects (mean age, 36.3 +/- 11.5 yrs) with second- and third-degree burns covering 15% to 75% of total body surface area (TBSA) (mean, 35.5% +/- 15.9%) were evaluated more than 1 year after discharge (mean, 37.3 +/- 20.4 months; range, 15 to 92 months). Thirty unburned subjects were recruited from the community at large. MAIN OUTCOME MEASURE: Maximal torque, work, and power developed by the elbow and knee flexors and extensors. RESULTS: Subjects with burns of > 30% of TBSA produced significantly less torque, work, and power in the quadriceps than control subjects (15.2% to 20.5% depending on velocity [p < .05]). The ability to develop muscle power at the elbow was also compromised in the severely burned subjects (19.2% in extension and 18.7% in flexion [p = .07]) at the faster velocities. No differences were observed between controls and patients with small burn injuries (TBSA of < 30%). CONCLUSION: Patients who had severe burns (TBSA of > 30%) had weaker muscles even years after the trauma, suggesting either an inability to fully recover or insufficient rehabilitation.

Adult↗

PubMed1998

Motor performance following a mild traumatic brain injury in children: an exploratory study.

Mild Traumatic Brain Injury (TBI) is a common occurrence in the paediatric population and, as the concept of motor performance has not been assessed specifically in this population, the purpose of this study was to determine if motor performance deficits are present and can be objectively identified in a sample of children having sustained a mild TBI (Glasgow Coma Scale score 13-15). Twenty-eight children aged between 5 and 15 years were recruited immediately post-trauma. Subjects were considered normal on standard neurological exam at the time of discharge. They were assessed 13-18 days post-trauma using the Bruininks-Oseretsky Test of Motor Proficiency, a norm referenced clinical standardized assessment tool. Compared to published norms, motor performance was significantly lower in domains of balance, response speed and running speed an agility (t-test p < 0.01), and significantly higher in domains of upper extremity coordination and visual motor control (t-test p < 0.01). Although excellent performance can be observed in domains requiring upper limb coordination, motor planning and execution of motor tasks, deficits in balance and response speed can be identified in a significant number of children even after mild TBI. More specific and sensitive evaluations are necessary to identify the exact nature of the problems and evaluate their functional impact on daily activities.

Adolescent↗

PubMed1996

Control of single-joint movements in deafferented patients: evidence for amplitude coding rather than position control.

Two deafferented patients and several control subjects participated in a series of experiments to investigate how accurate single-joint movements are programmed, spatially calibrated, and updated in the absence of proprioceptive information. The deafferented patients suffered from a permanent and severe loss of large sensory myelinated fibers below the neck. Subjects performed, with and without vision, sequences of forearm supinations and pronations with two temporal delays between each movement (0 s and 8 s). Overall, the lack of proprioception did not yield any significant decrease in movement accuracy when vision was available. Without vision, the absence of proprioceptive afferents yielded (1) significantly larger spatial errors, (2) amplitude errors similar to those of control subjects, and (3) a significant drift when an 8-s delay was introduced between two successive movements. Subjects also performed, without vision, a 20 degrees supination followed by a 20 degrees pronation that brought back the wrist to the starting position. On some trials, the supination was blocked unexpectedly by way of a magnetic brake. When the supination was blocked, subjects were already on the second target and no pronation was required when the brake was released. The deafferented patients, unaware of the procedure, always produced a 20 degrees pronation. These data confirm that deafferented patients were not coding a final position. It rather suggests that they coded an amplitude and translated the spatial distance between the two targets in a corresponding force pulse. Overall, the results highlight the powerful and key role of proprioceptive afferents for calibrating the spatial motor frame of reference.

Adult↗

PubMed1996

Prevalence and characteristics of chronic sensory problems in burn patients.

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.

Adolescent↗

PubMed1996

Evaluation of two-point discrimination in children: reliability, effects of passive displacement and voluntary movements.

Two-point discrimination (2-PD) thresholds were studied at three sites (tip of index finger, thenar eminence, external malleolus) and under various testing conditions (dynamic vs static, with and without displacement of instrument on skin; and active vs passive, with and without voluntary movement of subject) in 47 healthy children between 6 and 13 years of age. Reliability was fair to moderate, with slightly better perception (learning effect) during the second testing session. The threshold values of these children were similar to those of adults. For the passive conditions, the threshold values were lower for dynamic than for static tests at all sites. For the active condition at the index finger, there were no differences between dynamic and static values and there was no active/passive main effect. It is concluded that: (1) the hand is more sensitive than the ankle, with the finger being the most sensitive area, (2) the 2-PD test procedure used was most reliable at the index finger and least reliable at the external malleolus and (3) displacement of the instrument on the skin can improve 2-PD threshold values in children but the discrimination thresholds are not changed by active movement of the subject.

Adolescent↗

PubMed1996

Gait of a deafferented subject without large myelinated sensory fibers below the neck.

We evaluated the gait pattern of a deafferented subject who suffered a permanent loss of large sensory myelinated fibers below the neck following an acute episode of purely sensory neuropathy 21 years ago. The subject has developed several strategies to achieve a secure gait, namely: (1) a reduction of the degrees of freedom by freezing the knee articulations during the stance phase, (2) a preservation of body balance by enlarging his base of support, and (3) visual monitoring of his step by stabilizing the head-trunk linkage together with a characteristic forward tilt. As a result, the gait of the deafferented subject lacks the fluidity of normal gait. Compared with normal subjects, the gait pattern of the deafferented subjects is characterized by a shorter cycle length, a longer cycle duration, a slower speed, and a lower cadence. Using a dual-task paradigm, the attentional demands for walking were particularly important (as indexed by longer probe reaction times) during the double-support phase, suggesting that the deafferented subject uses the double-support phase as a transitory stable phase to update cognitively the postural features necessary for generating his next step.

Denervation↗

PubMed1995

Is proprioception important for the timing of motor activities?

This study tested whether a deafferented patient demonstrates impaired timing ability compared with four control subjects. By comparing normal subjects with the deafferented patient, some insight was expected on the importance of proprioception in timing of motor behavior. The protocol was set to enhance the strategy of the subjects in using feedbacks. Subjects had to synchronize finger taps with a sound produced at regular intervals. Once synchronized, the bips were muted and the subjects had to continue the tapping at the same pace. Interresponse interval (IRI) variability was measured under two feedback conditions: with and without vision and auditory feedback. The Wing and Kristofferson model (A.M. Wing and A.B. Kristofferson. Percept. Psychophys. 13(3): 455-460, 1973) was used to segment IRI variance into separate components: a central clock and a peripheral motor delay. When the deafferented patient saw and heard the outcome of her tapping movements, there was a greater variability in successive intervals between taps than when vison and hearing were blocked. We interpret this variability as indicating that the subject used auditory and visual feedback to maintain a correct overall rhythm. The patient may easily substitute visual and (or) auditory feedback for her defective proprioception for movement timing. However, this substitution proved to be inefficient in the limited training period provided in this experiment. The results suggest that the proprioceptive contribution to the time-keeping mechanism presumably depends on the presence of an efference copy signal.

Efferent Pathways↗

PubMed1995

Postural adjustments associated with different unloadings of the forearm: effects of proprioceptive and cutaneous afferent deprivation.

Postural adjustments to imposed (passive) and voluntary (active) unloading conditions of the forearm were studied in normal subjects and a deafferented patient. The latency of the postural behaviour (deactivation of the biceps supporting the weight) was linearly related to the displacement amplitude of the unloaded forearm, independent of the unloading conditions. The postural behaviour consisted of an anticipatory postural adjustment (APA) occurring prior to active unloading (in both normals and the patient) and conversely in an unloading reflex response following passive unloading (only in the normals). In both the deafferented and the normal subjects, the amplitudes of the displacement during active unloadings were much smaller (3x) than in the passive conditions and an APA was present in both the deafferented and the normal subjects. The APA could not be triggered by some types of active movement and was absent when the movement was not directly producing the unloading. The EMG latencies of the APA and of the contralateral muscles used to unload were tightly coupled. However, the latency would sometimes be decoupled, particularly when a temporal delay was introduced between the active movement and the unloading in normal subjects. In contrast to the normal subjects, who were able to adapt quickly to an unusual unloading condition (produced by voluntary knee flexion), the deafferented patient did not show an APA in this task. It was concluded that, although the APA is of central origin, it cannot be generated only on the basis of internal timing cues and must rely on afferent information for its generation during unfamiliar unloading conditions.

Adult↗

PubMed1994

A re-examination of the effects of instruction on the long-latency stretch reflex response of the flexor pollicis longus muscle.

We re-examined the issue of how a subject's intention to react to a joint perturbation may modulate the long-latency M2 stretch reflex response. The experiments were done on the flexor pollicis longus muscle (FPL) of the human thumb, for which there is evidence that its M2 reflex response is mediated, at least in part, by a pathway that traverses the motor cortex. The participation of the cerebral cortex in the genesis of the M2 reflex response may allow for a modulation of its amplitude, based on the intention of the subject. To test whether the M2 response is genuinely modulated by the subject's intention, we examined the magnitude of this response as a function of the FPL background level of activation, measured by the surface rectified and filtered EMG. The subject was instructed either to oppose the perturbation as quickly as possible, not to react, or to relax as quickly as possible after the onset of the perturbation. The time integral of the long latency FPL EMG response, computed between 40 and 70 ms following the onset of stretch, was plotted against the mean torque produced by the distal inter-phalangeal joint of the thumb, or against the mean background FPL EMG. There were no significant differences in the FPL M2 EMG responses for different instructions. The amplitude of the reflex response was dependent only--in an approximately linear manner--on the background level of muscle activation. The total joint stiffness (intrinsic plus reflex) was also calculated for each combination of instruction and background torque.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Production of short timing responses: a comparative study with a deafferented patient.

How far can proprioception contribute to time keeping? To answer this question, a deafferented patient and neurologically normal subjects produced 1- or 5-sec durations in a sustained (continuous finger press) or discrete (two successive finger taps) manner, with and without Knowledge of Results. The findings were that: (1) proprioceptive afferents contribute to timing regulation in motor production of short durations; (2) this role can be rapidly compensated by Knowledge of Results; (3) the proprioceptive contribution is more important for sustained than for discrete performances; (4) stable performances are produced even when KR is withdrawn, suggesting familiarization with KR leads to the establishment of a mnemonic trace.

Adult↗

PubMed1994

Evaluation of cutaneous and proprioceptive sensation in children: a reliability study.

Forty-three healthy children aged between six and 12 years were tested to determine the intra-rater reliability of four clinical cutaneous and proprioceptive sensory assessment tools: touch pressure, vibration perception, thermal discrimination and kinaesthesis. The tests were carried out bilaterally on proximal and distal upper- and lower- extremity sites. The mean intraclass coefficients represented good to excellent reliability, which suggests that these assessment tools allow objective and reproducible measurements of cutaneous and proprioceptive sensation in children. The results were compared with existing data in the literature: in general, children and adults obtain similar sensory scores, and sex, age and laterality have no significant effect on the results for any test. However, the touch-pressure and vibration scores were significantly influenced by the site tested, the index fingerpad being the most sensitive area in both tests.

Child↗

PubMed1993

Reference systems for coding spatial information in normal subjects and a deafferented patient.

To produce accurate goal-directed arm movements, subjects must determine the precise location of target object. Position of extracorporeal objects can be determined using: (a) an egocentric frame of reference, in which the target is localized in relation to the position of the body; and/or (b) an allocentric system, in which target position is determined in relation to stable visual landmarks surrounding the target (Bridgeman 1989; Paillard 1991). The present experiment was based on the premise that (a) the presence of a structured visual environment enables the use of an allocentric frame of reference, and (b) the sole presence of a visual target within a homogeneous background forces the registration of the target location by an egocentric system. Normal subjects and a deafferented patient (i.e., with an impaired egocentric system) pointed to visual targets presented in both visual environments to evaluate the efficiency of the two reference systems. For normals, the visual environment conditions did not affect pointing accuracy. However, kinematic parameters were affected by the presence or absence of a structured visual surrounding. For the deafferented patient, the presence of a structured visual environment permitted a decrease in spatial errors when compared with the unstructured surrounding condition (for movements with or without visual feedback of the trajectory). Overall, results support the existence of an egocentric and an allocentric reference system capable of organizing extracorporeal space during arm movements directed toward visual targets.

Adult↗

PubMed1993

The role of proprioceptive information for the production of isometric forces and for handwriting tasks.

A patient showing a total loss of all the large sensory myelinated fibers but intact peripheral motor system produced simple isometric force pulses and more complex tasks like handwriting and drawing. Overall, the patient was able to perform the isometric force task with an accuracy that approached that of normal subjects. The writing tasks, however, proved to be more challenging. In absence of vision, the different forms and cursive trajectories forming letters (morphocinetic components) were preserved but their localization within the constraints of the graphic space (topocinetic components) were severely impaired. These results demonstrate that, in absence of visual information, proprioceptive information is necessary to calibrate the hand in space.

Adult↗

PubMed1992

Role of afferent information in the timing of motor commands: a comparative study with a deafferented patient.

The accuracy of the motor system in synchronizing simultaneous movements initiations was tested in two conditions: (1) when the motor commands were triggered by an external signal (reactive condition), and (2) when subjects self-paced their movement onsets (self-paced condition). The task consisted of initiating simultaneously ipsilateral finger extension and heel raising. Eight normal subjects and a deafferented patient were tested. In the reactive condition, both normal subjects and the deafferented patient exhibited a precession of finger initiation over heel raising. This delay corresponds to the difference observed in the reaction time of the two limbs when measured independently. It reflects the difference in conduction times of the efferent pathways, as if the two motor commands were released simultaneously through a common triggering signal in the motor cortex. In contrast, in the self-paced condition normal subjects showed precession of heel over finger onsets, suggesting that synchrony is based upon the evaluation of afferent information. Unlike normal subjects, the patient showed no heel precession in the self-paced condition. These findings suggest that reactive and self-paced responses are produced through two different control modes and that afferent information contributes to the timing of motor commands in the self-paced mode.

Adult↗

PubMed1992

Mirror drawing in a deafferented patient and normal subjects: visuoproprioceptive conflict.

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.

Adult↗