Neurorehabilitation and Neural Repair

Randomized Controlled Trials (RCTs) are essential to underpin the superiority of novel interventions affecting upper extremity capacity post-stroke. However, many RCTs are underpowered, due to heterogeneity in recovery. Prognostic targeting may help reduce sample sizes while maintaining sufficient power.

This study investigates the effects of prognostic targeting on the required sample size to achieve 70% to 90% power in early post-stroke RCTs with upper extremity capacity measured with the Action Research Arm Test (ARAT) as the outcome.

Serial data from 4 prospective cohort studies (N = 372 stroke patients) were pooled, with assessments from week 1 to 6 months post-stroke. Using this dataset, we generated synthetic 6-month ARAT outcomes and analyzed data cross-sectionally and longitudinally, with and without prognostic targeting based on a pre-existing prognostic model predicting 6-month outcome. We then calculated power for different sample sizes and assessed trial efficiency, determined by the estimated sample size and inclusion rate.

Prognostic targeting within 3 weeks post-stroke theoretically reduced the required sample size by up to 56% and improved trial efficiency by 40 to 45% for detecting a 6-point ARAT difference at 6 months. The targeted trials needed 220, 270, and 360 patients vs. 470, 560, and 820 in non-targeted trials for 70% to 90% power. Benefits persisted in longitudinal analyses.

This study demonstrates the benefits of prognostic targeting for improving power and efficiency in early post-stroke upper extremity trials using ARAT as outcome. We strongly recommend its use in future stroke rehabilitation and recovery studies.

Action observation (AO) has emerged as a potentially powerful therapeutic tool to improve stroke rehabilitation. What remains unclear are the underlying visual attention mechanisms that inform gaze strategies during AO. Further, it is unclear whether visual attention is sustained during AO or influenced by the severity of residual functional impairments following stroke.

This study seeks to explore eye gaze patterns and vigilance during a single session of AO in stroke survivors with varying levels of impairment.

Twenty stroke survivors with upper limb impairment (Fugl-Meyer Scores ranging 23-54) engaged in AO by watching an actor performing a disc placement task (observation phase), followed by the participant performing the task (execution phase) with their more affected, then less affected limb. Gaze patterns during the observation phase were evaluated for areas of most prominent gaze and compared between varying levels of severity of residual limb impairment.

Gaze during AO prior to movement on the more affected side is focused on hand and object while AO prior to movement on the less affected side is focused on the overall action in the video. These patterns are prevalent for all levels of severity.

This suggests that participants are developing gaze patterns in line with optimal approaches to encode action specifics, especially on the more affected side. This presents valuable understanding of perceptual patterns of AO that may be optimal for studies evaluating AO in stroke.

Clinical practice guidelines for walking recovery post-stroke recommend high aerobic intensity training, which usually involves walking at fast speeds. However, the acute effect of fast speeds on the neuromuscular control of walking is unclear.

(1) Assess the criterion validity of the Dynamic Motor Control Index (WalkDMC) as a measure of coactivation post-stroke. (2) Assess acute speed-dependent coactivation post-stroke. (3) Assess how clinical characteristics shape the speed-dependent coactivation response. (4) Assess the relationship between heart rate and coactivation post-stroke. We hypothesized that WalkDMC is correlated with function and impairment measures. We also hypothesize that coactivation measured via the WalkDMC increases for speeds above or below self-selected speeds (SSS).

32 chronic stroke survivors and 17 age and sex-matched controls walked at SSS, fast, and slow speeds. EMGs were measured bilaterally on 7 lower extremity muscles. We used non-negative matrix factorization to calculate WalkDMC. We used regression to assess the relationship between WalkDMC, speed, heart rate, and clinical outcomes.

WalkDMC was correlated with clinical outcomes, supporting its criterion validity. We observed a quadratic relationship between speed and coactivation: for the paretic extremity, the predicted speed that would lead to the lowest coactivation was ~120% higher than SSS. Slow speeds consistently increased coactivation in controls and participants post-stroke. Coactivation in the paretic extremity was significantly predicted by speed, balance, and impairment.

Our results suggest that increased speeds lead to differential improvements in coactivation in the paretic and non-paretic extremities. These results may inform speed prescriptions for HIT interventions.

Short-term maintenance of phonological information is critical for language production and comprehension, and is often impaired in stroke survivors with aphasia.

In this pilot study, we investigated whether brain oscillatory activity underlying phonological short-term memory (pSTM) can be influenced by transcranial alternating current stimulation (tACS) in stroke survivors with aphasia (SWA).

In a within-subject, single-blinded, sham-controlled study, 13 SWA received theta-tACS (4-7 Hz) targeting left temporoparietal and inferior frontal regions across 3 tACS conditions (in-phase, anti-phase, and sham; 20 minutes each). Participants completed an adaptive delayed match-to-sample task with spoken consonant-vowel strings (2-8 syllables) before, during, and after stimulation. The primary outcome was change in pSTM capacity (ie, number of syllables maintained over a 5-second delay), estimated using a linear interpolation approach. We hypothesized that in-phase tACS would enhance, and anti-phase tACS would disrupt, pSTM capacity relative to sham.

LME analyses reveal significant interactions between tACS condition and block (F(4, 91.9) = 2.65, P = .038), and post-hoc estimated marginal means comparisons show increased pSTM capacity during in-phase tACS versus sham (estimate = 0.71, t(92) = 2.26, P = .040) and anti-phase (estimate = 0.75, t(92) = 2.44, P = .040) conditions, only during the stimulation period. Differences between anti-phase and sham-tACS were not significant (estimate = −0.04, P = .901). Individual response to tACS was variable, with only 60% of SWA responding.

This study supports in-phase theta-tACS positively impacts pSTM. Larger studies are needed to confirm these findings and evaluate lasting effects to increase clinical relevance.

Spoken language and environmental sounds hold rich and nuanced meaning for the listener, but depend on accurate hearing of the soundscape, including the timing, volume, and contrasts of its component pitches. Sensorineural hearing loss with aging degrades these properties, leading to progressive disability.

This case study and review describe my experience and behavioral accommodations to progressive bilateral hearing loss, limited compensation with hearing aids, and the stuttering evolution of gains after a unilateral cochlear implant (CI).

Despite increasingly powerful hearing aids over 25 years, spoken phonemes and words became increasingly muffled, misheard, and often dissipated into ambient background noise. The cognitive effort to extract meaning and mask my disability grew exhausting. I gradually eliminated many of my usual family, medical career, and social roles. To try to recover some communication-dependent activities, I sought a bionic solution. A right-sided CI initially carried an ambiguous, fizzling code and unrecognizable synthetic voices. With 8 months of auditory rehabilitation, I better deciphered conversational speech and ambient sounds. By audiological testing, I improved from 10% hearing accuracy of single words to 65%, typical of post lingual adult users. Better hearing in ambient noise and for what had been excessively rapid speech evolved out to 18 months, allowing me to re-engage in many of my daily roles.

Hearing loss beyond the compensation of aids deeply challenges quality of life. Auditory rehabilitation after cochlear implantation engages neuroplasticity to re-establish functional communication.

Functional electrical stimulation (FES) may enhance the impact of locomotor training on walking impairments following spinal cord injury (SCI).

This systematic review (PROSPERO: CRD42023435210) evaluated the therapeutic effectiveness of FES-assisted locomotor training (FALT) on improving walking speed and endurance for individuals with motor incomplete SCI (iSCI).

Databases (MEDLINE, EMBASE, CINAHL) were searched for interventional studies of FALT in iSCI that assessed the therapeutic effects on walking speed and/or endurance when the FES was not active. Study characteristics and findings were extracted, summarized, and narratively synthesized. Risk of bias was assessed using the Cochrane tools for interventional studies. Random effects meta-analyses were conducted to generate standardized pooled effect sizes for both outcomes.

Thirteen studies were identified: 4 randomized controlled trials (RCTs) and 9 pre-post tests. RCTs scored low (n = 1 study), intermediate (n = 1), and high (n = 2) on the RoB2, and all pre-post tests studies (n = 9) scored high on the ROBINS-I. Meta-analyses of 3 RCTs found that treadmill-based FALT was associated with a small, non-significant effect on walking speed (n = 76 participants; Hedge’s g: −0.01; 95% CI: −0.46, 0.43; P = .96) and a small, non-significant effect on walking endurance (n = 71; Hedge’s g: 0.20; 95% CI: −0.25, 0.65; P = .39) when compared to control conditions.

This review did not find evidence that FALT improves walking speed or endurance for people with iSCI relative to other types of locomotor training. Future trials of FALT for SCI should aim to better standardize and report training dose and stimulation parameters to improve comparability.