INTENSIVE REHABILITATION CHANGES CORTICOSPINAL EXCITABILITY AMONG ADULTS WITH SUBCORTICAL STROKE: EVIDENCE FROM TRANSCRANIAL MAGNETIC STIMULATION.

Abstract

PURPOSE/HYPOTHESIS: Use-dependent cortical reorganization within both the ipsilateral (IH) and contralateral hemispheres (CH) to the hemiparesis have been implicated mechanisms for recovery after sensorimotor stroke. In this pilot study, we hypothesize that in subacute (< 9 months) subcortical stroke, improved function of the affected limb is mediated through changes in bilateral corticospinal excitability associated with two weeks of constraint induced therapy (CIT). NUMBER OF SUBJECTS: Three adults with stroke participated (S1: Fugl-Meyer (FM): 45, subcortical lesion: post-limb internal capsule; S2: FM: 39, subcortical lesion: tail of caudate nucleus, periventricular, part of corona radiata; S3: FM: 33, lesion: pons). S1 and S3 received CIT but S2 did not. MATERIALS/METHODS: Functional capacity of hemiparetic upper limb was assessed using movement time (MT) of 6 fine motor items from the Wolf Motor Function Test (WMFT). Corticospinal excitability (CE) over bilateral motor cortex pre- and post 2-week CIT (no CIT: control) was examined with transcranial magnetic stimulation. CE was characterized using slope of input-output recruitment regression line (RLSlope) during active contraction (10% max voluntary contraction). RLSlope change scores (pre, post) were normalized to the baseline maximal amplitude of motor evoked potential for each hemisphere. RESULTS: Total MT of selected WMFT items decreased for S1 and S3 (76%, 8%, respectively), but increased 13 % for S2. For S1, CE efficiency (RLSlope) increased for both hemispheres with greater changes in CH (52% greater than IH). In contrast, for S3 RLSlope decreased in both hemispheres with greater changes in CH (69% greater than IH). For S2 (control), RLSlopes of both hemispheres decreased slightly with a greater decrease in IH (30% greater than CH). CONCLUSIONS: The WMFT results (SI, S3) suggest functional improvements in response to CIT. The corresponding greater RLSlope changes in CH (S1, S3) suggest ipsilesional corticospinal reorganization in response to CIT. For the control (S2), however, the greater RLSlope changes were in the III and this may reflect compensation from the contralesional hemisphere. The different RLSlope change patterns between S1 and S3 might be associated with baseline impairment levels and/or lesion locations. More data is necessary to understand if baseline impairment and/or lesion locations influence the corticospinal reorganization in response to therapy. CLINICAL RELEVANCE: This pilot study propses a measurement to detect the changes occur in corticosipnal level in response to intensive rehabilitation.