The unsolved role of heightened connectivity from the unaffected hemisphere to paretic arm muscles in chronic stroke

Ulrike Hammerbeck

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Objective
    Ipsilateral connectivity from the non-stroke hemisphere to paretic arm muscles appears to play little role in functional recovery, which instead depends on contralateral connectivity from the stroke hemisphere. Yet the incidence of ipsilateral projections in stroke survivors is often reported to be higher than normal. We tested this directly using a sensitive measure of connectivity to proximal arm muscles.

    Method
    TMS of the stroke and non-stroke motor cortex evoked responses in pre-activated triceps and deltoid muscles of 17 stroke survivors attending reaching training. Connectivity was defined as a clear MEP or a short-latency silent period in ongoing EMG in ≥ 50% of stimulations. We measured reaching accuracy at baseline, improvement after training and upper limb Fugl-Meyer (F-M) score.

    Results
    Incidence of ipsilateral connections to triceps (47%) and deltoid (58%) was high, but unrelated to baseline reaching accuracy and F-M scores. Instead, these were related to contralateral connectivity from the stroke hemisphere. Absolute but not proportional improvement after training was greater in patients with ipsilateral responses.

    Conclusions
    Despite enhanced ipsilateral connectivity, arm function and learning was related most strongly to contralateral pathway integrity from the stroke hemisphere.

    Significance
    Further work is needed to decipher the role of ipsilateral connections.
    Original languageEnglish
    Pages (from-to)781-788
    Number of pages6
    JournalClinical Neurophysiology
    Volume130
    Issue number5
    DOIs
    Publication statusPublished - 26 Mar 2019

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