Long-term sensory stimulation therapy improves hand function and restores cortical responsiveness in patients with chronic cerebral lesions. Three single case studies

Abstract

Rehabilitation of sensorimotor impairment resulting from cerebral lesion (CL) utilizes task specific training and massed practice to drive reorganization and sensorimotor improvement due to induction of neuroplasticity mechanisms. Loss of sensory abilities often complicates recovery, and thus the individual's ability to use the affected body part for functional tasks. Therefore, the development of additional and alternative approaches that supplement, enhance, or even replace conventional training procedures would be advantageous. Repetitive sensory stimulation protocols (rSS) have been shown to evoke sensorimotor improvements of the affected limb in patients with chronic stroke. However, the possible impact of long-term rSS on sensorimotor performance of patients with CL, where the incident dated back many years remains unclear. The particular advantage of rSS is its passive nature, which does not require active participation of the subjects. Therefore, rSS can be applied in parallel to other occupations, making the intervention easier to implement and more acceptable to the individual. Here we report the effects of applying rSS for 8, 36, and 76 weeks to the paretic hand of three long-term patients with different types of CL. Different behavioral tests were used to assess sensory and/or sensorimotor performance of the upper extremities prior, after, and during the intervention. In one patient, the impact of long-term rSS on restoration of cortical activation was investigated by recording somatosensory evoked potentials (SEP). After long-term rSS all three patients showed considerable improvements of their sensory and motor abilities. In addition, almost normal evoked potentials could be recorded after rSS in one patient. Our data show that long-term rSS applied to patients with chronic CL can improve tactile and sensorimotor functions, which, however, developed in some cases only after many weeks of stimulation, and continued to further improve on a time scale of months.

Keywords: chronic cerebral lesion; repetitive sensory stimulation; sensorimotor hand function; single case.

Figure 1

(A) Postischemic cranial CT of subject AA showing extensive postischemic necrosis in the pericentral right MCA distribution. (B) Postoperative cranial MRI of subject CC demonstrating a focus of gliosis in the left thalamus with discreet hemorrhagic residua on a T2w image. Incidental finding of single subcortical microangiopathic gliosis in the right centrum semiovale on FLAIR image. Coronal FLAIR image (left), transverse T2w image (right).

Figure 2

Absolute touch thresholds of the index fingers (IF) for subject AA. While no sensation was reported prior and after 2 weeks of intervention at the paretic limb using forces of 294 mN (crossed out bars), touch thresholds were substantially reduced and thus measurable after 5 (117.78 mN) and 8 (52.62 mN) weeks of intervention. Touch thresholds of the unaffected limb were only assessed prior to the intervention.

Figure 3

Absolute touch thresholds of the index fingers (IF) for subject BB (note split ordinate). While no assessment was possible prior to the intervention using maximal forces of 294 mN (crossed out bar), touch thresholds were markedly reduced to 1.09 mN after 24 weeks and to 0.63 mN after 76 weeks of intervention.

Figure 4

Time to complete the aiming test for subject BB. Total time decreased after 24 and 76 weeks of intervention.

Figure 5

Absolute touch thresholds of the index fingers (IF) for subject CC. While no assessment was possible prior and after 9 and 22 weeks of intervention at the paretic limb using forces of 294 mN (crossed out bars), touch thresholds were reduced and thus measurable after 36 weeks (46.28 mN) of intervention.

Figure 6

Total time to complete the pin-plugging test using long pins for subject CC. Improvements were found after 9 weeks of intervention for the affected hand.

Figure 7

Multiple-choice reaction times of all fingers averaged for each hand for subject CC. Considerable reaction time speeding up was found for the affected hand after 22 and 36 weeks of intervention.

Figure 8

Percentile rank of the hand-dominance-test (HDT) for subject CC at baseline, after 7 weeks and after 36 weeks of intervention. Extreme left-handedness (PR = 1.7) was found at baseline, changing to left-handedness (PR = 4.2) after 7 weeks of rSS intervention resulting in right-handedness (PR = 24) after 36 weeks of intervention.

Figure 9

Somatosensory evoked potentials (SEPs) obtained from high-density EEG recording at electrode C3 made in subject CC during tactile stimulation of the little finger (d5) of the affected hand. SEP source waveforms were analyzed using brain electrical source analysis (BESA), MEGIS Software GmbH, Munich, Germany. Vertical red line represents stimulus onset. While prior to intervention no SEP was detectable (A), a clear P50, N80, and P200 indicative of normalized tactile somatosensory cortex processing could be obtained after 22 weeks of intervention (B).