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- Fornander, Lotta, et al.
(författare)
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Age- and time-dependent effects on functional outcome and cortical activation pattern in patients with median nerve injury: a functional magnetic resonance imaging study Clinical article
- 2010
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Ingår i: Journal of Neurosurgery. - : American Association of Neurological Surgeons. - 0022-3085 .- 1933-0693. ; 113:1, s. 122-128
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Tidskriftsartikel (refereegranskat)abstract
- Object. The authors conducted a study to determine age- and time-dependent effects on the functional outcome after median nerve injury and repair and how such effects are related to changes in the pattern of cortical activation in response to tactile stimulation of the injured hand. Methods. The authors studied 11 patients with complete unilateral median nerve injury at the wrist repaired with epineural suture. In addition, 8 patients who were reported on in a previous study were included in the statistical analysis. In the entire study cohort, the mean age at injury was 23.3 +/- 13.4 years (range 7-57 years) and the time after injury ranged from 1 to 11 years. Sensory perception was measured with the static 2-point discrimination test and monofilaments. Functional MR imaging was conducted during tactile stimulation (brush strokes) of Digits II-III and IV-V of both hands, respectively. Results. Tactile sensation was diminished in the median territory in all patients. The strongest predictor of 2-point discrimination was age at injury (p less than 0.0048), and when this was accounted for in the regression analysis, the other age- and time-dependent predictors had no effect. The activation ratios (injured/healthy hand) for Digit II-III and Digit IV-V stimulation were positively correlated (rho 0.59, p less than 0.011). The activation ratio for Digit II-III stimulation correlated weakly with time after injury (p less than 0.041). The activation ratio of Digits IV-V correlated weakly with both age at injury (p less than 0.048) and time after injury (p less than 0.033), but no predictor reached significance in the regression model. The mean ratio of ipsi- and contralateral hemisphere activation after stimulation of the injured hand was 0.55, which was not significantly different from the corresponding ratio of the healthy hand (0.66). Conclusions. Following a median nerve injury (1-11 years after injury) there may be an initial increase in the volume of the cortical representation, which subsequently declines during the restoration phase. These dynamic changes may involve both median and ulnar nerve cortical representation, because both showed negative correlation with time after injury. These findings are in agreement with animal studies showing that cortical plasticity is an important mechanism for functional recovery after peripheral nerve injury and repair.
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| 2. |
- Fornander, Lotta, et al.
(författare)
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Inter-hemispheric plasticity in patients with median nerve injury
- 2016
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Ingår i: Neuroscience Letters. - : Elsevier. - 0304-3940 .- 1872-7972. ; 628, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- Peripheral nerve injuries result in reorganization within the contralateral hemisphere. Furthermore, recent animal and human studies have suggested that the plastic changes in response to peripheral nerve injury also include several areas of the ipsilateral hemisphere. The objective of this study was to map the inter-hemispheric plasticity in response to median nerve injury, to investigate normal differences in contra- and ipsilateral activation, and to study the impact of event-related or blocked functional magnetic resonance imaging (fMRI) design on ipsilateral activation. Four patients with median nerve injury at the wrist (injured and epineurally sutured amp;gt;2 years earlier) and ten healthy volunteers were included. 3T fMRI was used to map the hemodynamic response to brain activity during tactile stimulation of the fingers, and a laterality index (LI) was calculated. Stimulation of Digits II-III of the injured hand resulted in a reduction in contralateral activation in the somatosensory area SI. Patients had a lower LI (0.21 +/- 0.15) compared to healthy controls (0.60 +/- 0.26) indicating greater ipsilateral activation of the primary somatosensory cortex. The spatial dispersion of the coordinates for areas SI and SII was larger in the ipsilateral than in the contralateral hemisphere in the healthy controls, and was increased in the contralateral hemisphere of the patients compared to the healthy controls. There was no difference in LI between the event-related and blocked paradigms. In conclusion, patients with median nerve injury have increased ipsilateral SI area activation, and spatially more dispersed contralateral SI activation during tactile stimulation of their injured hand. In normal subjects ipsilateral activation has larger spatial distribution than the contralateral. Previous findings in patients performed with the blocked fMRI paradigm were confirmed. The increase in ipsilateral SI activation may be due to an interhemispheric disinhibition associated with changes in the afferent signal inflow to the contralateral primary somatosensory cortex.
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| 3. |
- Lundborg, Göran, et al.
(författare)
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Artificial sensibility of the hand based on cortical audiotactile interaction : A study using functional magnetic resonance imaging
- 2005
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Ingår i: Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery. - : Informa UK Limited. - 0284-4311 .- 1651-2073. ; 39:6, s. 370-372
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Tidskriftsartikel (refereegranskat)abstract
- 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. © 2005 Taylor & Francis.
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