Effects of Temporary Functional Deafferentation in Chronic Stroke Patients: Who Profits More?

Temporary functional deafferentation (TFD) by an anesthetic cream on the stroke-affected forearm was shown to improve sensorimotor abilities of stroke patients. The present study investigated different predictors for sensorimotor improvements during TFD and indicated outcome differences between patients grouped in subcortical lesions only and lesions with any cortical involvement. Thirty-four chronic stroke patients were temporarily deafferented on the more affected forearm by an anesthetic cream. Somatosensory performance was assessed using von Frey Hair and grating orientation task; motor performance was assessed by a shape-sorter-drum task. Seven potential predictors were entered into three linear multiple regression models. Furthermore, effects of TFD on outcome variables for the two groups (cortical versus subcortical lesion) were compared. Sex and sensory deficit were significant predictors for changes in motor function while age accounted for changes in grating orienting task. Males, patients with a stronger sensory deficit, and older patients profited more. None of the potential predictors made significant contributions to changes in threshold for touch. Furthermore, there were no differences in sensorimotor improvement between lesion site groups. The effects of TFD together with the low predictability of the investigated parameters suggest that characteristics of patients alone are not suitable to exclude some patients from TFD.

Cortical reorganization after macroreplantation at the upper extremity: a magnetoencephalographic study.

With the development of microsurgical techniques, replantation has become a feasible alternative to stump treatment after the amputation of an extremity. It is known that amputation often induces phantom limb pain and cortical reorganization within the corresponding somatosensory areas. However, whether replantation reduces the risk of comparable persisting pain phenomena as well as reorganization of the primary somatosensory cortex is still widely unknown. Therefore, the present study aimed to investigate the potential development of persistent pain and cortical reorganization of the hand and lip areas within the sensory cortex by means of magnetoencephalographic dipole analyses after replantation of a traumatically amputated upper limb proximal to the radiocarpal joint. Cortical reorganization was investigated in 13 patients with limb replantation using air puff stimulation of the phalanges of both thumbs and both corners of the lower lip. Displacement of the centre of gravity of lip and thumb representations and increased cortical activity were found in the limb and face areas of the primary somatosensory cortex contralateral to the replanted arm when compared to the ipsilateral hemisphere. Thus, cortical reorganization in the primary somatosensory cortex also occurs after replantation of the upper extremity. Patients' reports of pain in the replanted body part were negatively correlated with the amount of cortical reorganization, i.e. the more pain the patients reported, the less reorganization of the subjects' hand representation within the primary somatosensory cortex was observed. Longitudinal studies in patients after macroreplantation are necessary to assess whether the observed reorganization in the primary somatosensory cortex is a result of changes within the representation of the replanted arm and/or neighbouring representations and to assess the relationship between the development of persistent pain and reorganization.

Differences in somatosensory and motor improvement during temporary functional deafferentation in stroke patients and healthy subjects.

Temporary functional deafferentation is of interest to become an additional tool in neurorehabilitative treatments. Temporary functional deafferentation is known to improve sensory and motor outcomes in chronic stroke patients and healthy subjects. The present study soughts to indicate differences in the efficiency of pharmacologically induced temporary functional deafferentation between chronic stroke patients and matched healthy subjects. 46 chronic stroke patients and 20 age- and gender-matched healthy subjects were deafferented on one forearm by an anesthetic cream. Somatosensory performance was assessed using von-Frey Hair testing and Grating orientation task; motor performance was assessed by means of a shape-sorter-drum task. Grating orientation task and shape-sorter-drum task were significantly improved during temporary functional deafferentation in stroke patients but not in healthy subjects. Von-Frey Hair testing revealed no improvement of absolute tactile thresholds during temporary functional deafferentation in both groups. Furthermore, the stroke patients showed deficits at baseline measurement in all assessments except the von-Frey Hair test. Temporary functional deafferentation of a forearm by an anesthetic cream results in improvements of motor performance and somatosensory discrimination in stroke patients but not in healthy subjects. Therefore, it is reasonable to test in a next step whether temporary functional deafferentation might become an additional tool in motor rehabilitation of post stroke patients.

Effects of temporary functional deafferentation on the brain, sensation, and behavior of stroke patients.

Following stroke, many patients suffer from chronic motor impairment and reduced somatosensation in the stroke-affected body parts. Recent experimental studies suggest that temporary functional deafferentation (TFD) of parts of the stroke-affected upper limb or of the less-affected contralateral limb might improve the sensorimotor capacity of the stroke-affected hand. The present study sought evidence of cortical reorganization and related sensory and motor improvements following pharmacologically induced TFD of the stroke-affected forearm. Examination was performed during 2 d of Constraint-Induced Movement Therapy. Thirty-six human patients were deafferented on the stroke-affected forearm by an anesthetic cream (containing lidocaine and prilocaine) on one of the 2 d, and a placebo cream was applied on the other. The order of TFD and placebo treatment was counterbalanced across patients. Somatosensory and motor performance were assessed using a Grating orienting task and a Shape-sorter-drum task, and with somatosensory-evoked magnetic fields. Evoked magnetic fields showed significant pre- to postevaluation magnitude increases in response to tactile stimulation of the thumb of the stroke-affected hand during TFD but not following placebo treatment. We also observed a rapid extension of the distance between cortical representations of the stroke-affected thumb and little finger following TFD but not following placebo treatment. Moreover, somatosensory and motor performance of the stroke-affected hand was significantly enhanced during TFD but not during placebo treatment. Thus, pharmacologically induced TFD of a stroke-affected forearm might improve the somatosensory and motor functions of the stroke-affected upper limb, accompanied by cortical plasticity.

Deafferentation of the affected arm: a method to improve rehabilitation?

BACKGROUND AND PURPOSE: Reduced somatosensation is a common impairment after stroke. This somatosensory deficit is known to be a reliable predictor of poor rehabilitation outcome. Several methods of physical therapy have addressed this problem, but with only moderate success. Here, we used a new neural plasticity-based approach, ie, a simple, inexpensive, pharmacologically induced temporary functional deafferentation (TFD) of the forearm to investigate whether TFD might result in beneficial effects on the somatosensory sensibility and motor capacity of the stroke-affected hand. METHODS: Examination was performed over 2 consecutive days of an efficient rehabilitation program for stroke patients referred to as constraint-induced movement therapy. Patients were deafferented on one of these days but not on the other (placebo session). The order of deafferentation and nondeafferentation was counterbalanced across patients. TFD of the stroke-affected forearm was realized using an anesthetic cream. Somatosensory abilities were assessed by a Grating orienting task, and a shape-sorter drum task was used to test motor performance. Both tests were performed each day before and after the constraint-induced movement therapy training session. RESULTS: We found significantly better outcomes for Grating orienting task and shape-sorter drum task after TFD on the forearm as compared to placebo, indicating increased somatosensory abilities and motor performance in stroke patients using the simple TFD procedure. CONCLUSIONS: The improvement was achieved during the course of one of the best established poststroke rehabilitation programs, suggesting that TFD on the more affected forearm might become an efficient additional tool in stroke rehabilitation.