Biomedical subjects
Publications and source records attributed to Birgitta Rosén.
Functional magnetic resonance imaging (fMRI) was used to study the cortical integration of an osseointegrated prosthetic thumb that had been attached to the amputee's hand 13 years ago. We found that tactile stimuli applied to the prosthesis activated the primary somatosensory cortex on both sides.
To explore whether contralateral deafferentation by tourniquet-induced anaesthesia can improve function in a nerve-injured hand, we investigated 14 patients with median or ulnar nerve injuries at wrist level. Deafferentation of the contralateral forearm and hand resulted in significantly improved tactile discrimination, threshold for perception of touch in the injured nerve area and in the area corresponding to the intact nerve in the injured hand, and significantly increased grip strength. Improvements lasted at least 15 min. The results show that hand function after peripheral nerve injury can be temporarily enhanced by manipulation of the process of brain plasticity. Our results may have practical applications in the rehabilitation of peripheral nerve-injured patients.
The capacity of the central nervous system for plastic alterations is the base for our ability to adapt to environmental needs. The crossmodal capacity of the brain makes interaction between senses possible, and deprivation of one sense leads to compensatory changes in other senses. We have recently shown how hearing can substitute for sensation in a transplanted insensitive hand by using a sensor glove equipped with small microphones that pick up the sound of friction, which is elicited by active touch. Here we have used functional magnetic resonance imaging (fMRI) in healthy people to illustrate their capacity for cortical audiotactile interaction with activation of the somatosensory cortex induced by auditory stimuli. The phenomenon occurred only in subjects trained to substitute sensibility by hearing, and no audiotactile interaction was found in untrained subjects.
Treatment with a mirror gives an illusion of function in a missing or non-functioning hand. The method is based on the concept that the central representation of phantoms and body image can change rapidly, and has been described in the treatment of phantom pain and stroke. We show in three pilot cases new applications for the use of the mirror in rehabilitation after hand surgery.
Acute improvement of sensory functions in the contralateral hand during experimental, tourniquet-induced anaesthesia has been described. Tourniquet compression over an extended time period, however, may be painful - which may influence the result. To study the effects of deafferentation of the upper extremity with the pain factor eliminated, we investigated 100 patients with anaesthetised axillary plexus for perception of touch and tactile discrimination in the contralateral (unanaesthetised) hand. Anaesthesia induced a rapid, significant, improvement in tactile discrimination in the contralateral hand, compared with before anaesthesia, measured as two-point discrimination (p=0.0001), and perception of touch, measured with Semmes-Weinstein monofilament (p=0.0005). The improvement lasted as long as the arm was anaesthetised. Understanding the mechanisms of brain plasticity, including interhemispheric plasticity, is essential for designing appropriate strategies for upregulation and downregulation of cortical reorganisational changes to promote sensory relearning after nerve injury.
To study cortical reorganisation after acute hand deafferentation, we investigated 10 experimental subjects and 10 controls for function in the left hand, before, during and after tourniquet induced anaesthesia of the right hand. fMRI was performed in three experimental subjects. Right hand anaesthesia resulted in rapid significant improvement in grip strength, tactile discrimination and sensibility in the left hand. Tactile discrimination and grip strength improvements lasted at least 15 mins after anaesthesia. fMRI showed increased activation in the right primary motor cortex after anaesthesia. We conclude that tourniquet induced anaesthesia is an easy way to induce rapid and significant improvement in contralateral hand function. This finding may have a potential clinical application for evolving sensory relearning strategies after nerve repair.
BACKGROUND: The primary sensory cortex (S1) in the postcentral gyrus is comprised of four areas that each contain a body map, where the representation of the hand is located with the thumb most laterally, anteriorly and inferiorly and the little finger most medially, posteriorly and superiorly. Previous studies on somatotopy using functional MRI have either used low field strength, have included a small number of subjects or failed to attribute activations to any area within S1. In the present study we included twenty subjects, who were investigated at 3 Tesla (T). We focused specifically on Brodmann area 3b, which neurons have discrete receptive fields with a potentially more clearcut somatotopic organisation. The spatial distribution for all fingers' peak activation was determined and group as well as individual analysis was performed. RESULTS: Activation maps from 18 subjects were of adequate quality; in 17 subjects activations were present for all fingers and these data were further analysed. In the group analysis the thumb was located most laterally, anteriorly and inferiorly with the other fingers sequentially positioned more medially, posteriorly and superiorly. At the individual level this somatotopic relationship was present for the thumb and little finger, with a higher variability for the fingers in between. The Euclidian distance between the first and fifth finger was 17.2 mm, between the first and second finger 10.6 mm and between the remaining fingers on average 6.3 mm. CONCLUSION: Results from the group analysis, that is both the location of the fingers and the Euclidian distances, are well comparable to results from previous studies using a wide range of modalities. On the subject level the spatial localisation of the fingers showed a less stringent somatotopic order so that the location of a finger in a single subject cannot be predicted from the group result.
A long-term study in adults at a public dental clinic in Sweden was initiated to evaluate the relative effectiveness of prophylactic treatments on the progression of dental caries and periodontal discase. With treatments scheduled every 3rd, 6th, 12th or 18th month, this report presents results on caries for the 3-month, 6-month and 18-month groups, and evaluates the impact of various caries-related risk factors. Caries increment over approximately 5 years was determined by adding clinical and radiographic findings of manifest primary and secondary caries during the study. Overall caries activity among all 105 participating individuals was low to moderate. No significant differences for caries on any of the various tooth surfaces or for total caries were observed among the three groups. Multiple regression analysis with 5-year caries increment as dependent variable showed that the following factors had a statistically significant association with caries increment: percentage filled surfaces at baseline examination, dietary score, plaque score, and number of mutans streptococci and lactobacilli in saliva. Non-significant factors included number of preventive treatments provided during the 5-year interval. The results of this long-term trial suggest that preventive treatments as often as every 3 6 months may not be justified in the case of patients with low to moderate caries activity.
Hands were transplanted from brain-dead donors for the treatment of two male unilateral amputees, aged 35 years and 32 years, involved in the Italian Hand Transplantation Programme. Each had lost his right dominant hand, in a farming accident and an explosion, respectively. In one case artificial sensibility was applied postoperatively using a Sensor Glove that transformed vibrotactile stimuli induced by touch, to stereophonic vibroacoustic stimuli perceived through earphones. The principle is based on the brain's capacity for multimodal plasticity, implying that deprivation of one sense (somatosensory) can be compensated for by another sense (auditory). Functional magnetic resonance images (fMRI) taken at regular intervals showed that cortical remodelling of the transplanted hand within the sensory-motor maps occurred early in the patient who used the artificial sensibility regimen compared with the one who did not. We conclude that postoperative use of a device using hearing as a substitution for sensation in hand transplantation may have considerable potential value for speeding up cortical integration of a transplanted hand.
The cortical representation of body parts is constantly modulated in response to the afferent input, and acute deafferentation of a body part results in bilateral cortical reorganization. To study the effects on hand function of right forearm anaesthesia, we investigated ten human subjects (group 1) for perception of touch, tactile discrimination and grip strength in the right (ipsilateral) and left (contralateral) hand before, during and 24 h after forearm skin anaesthesia with a local anaesthetic cream (EMLA). Ten age-matched controls (group 2) were investigated in the same way but received placebo. In group 1 a significant improvement was seen in tactile discrimination in the ipsilateral hand compared to base line (P = 0.009) and compared to group 2 (P = 0.006). The improvement in tactile discrimination remained for at least 24 h after anaesthesia. Perception of touch, was improved during anaesthesia compared to baseline values in group 1 (P = 0.046) and remained for at least 24 h. Grip strength did not change. These findings suggest that transient selective deafferentation of an extremity results in enhanced sensory functions of the functionally preserved parts of the same extremity, presumably as a result of expansion of adjacent cortical territories. Such rapid functional changes suggest unmasking of pre-existing synaptic connections as the mechanism underlying the acute modulation of sensory functions in the hand. Our findings open new perspectives for sensory re-education and rehabilitation following injury to the peripheral and central nervous system.
The Model instrument for outcome after nerve repair has so far proved valid and reliable. It supports the authors' hypothesis that the summary of specific limitations of body function agrees with patients' opinions on the impact of the nerve injury on ADL. These features together with its flexibility make the Model instrument for outcome after nerve repair a psychometrically sound and clinically useful diagnosis-specific outcome instrument for routine evaluation after nerve repair. An optimal choice in the future when assessing the outcome after nerve repair may be a combined use of this model and a more generic outcome instrument. Such a protocol would take into account specific body functions and well being in a wider perspective.
Artificial sensibility based on use of a "tactile glove" which substitutes for lack of sensory afferent inflow with acoustic feedback, was used early after repair of the median and ulnar nerves in a 21-year-old man. After six and 12 months the functional outcome exceeded what is expected in adults, and analysis with calculations for the minimal detectable change (MDC) in tactile gnosis showed a true change. This case highlights the timing of sensory re-education after nerve repair and also emphasises the importance of early restitution of afferent inflow from a denervated hand during rehabilitation.